COSTA RICA FOREST RESEARCH PROGRAMME

Carate, Osa Peninsula, Costa Rica

CRF Phase 184 Science Report

Emma Korein, Lynn Pallemaerts, Harriet Alice Taberner, RebeccaJarrett, Matthew Clark, Varvara Vladimirova. Photos by Loris Capria

18th September 2018 - 18th December 2018

Contents

1 Introduction 51.1 Natural History of Costa Rica and its Wildlife Conservation . . . . . . . . . . . . . . . . . 51.2 Osa Peninsula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.3 Aims and Objectives of Frontier CBP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2 Training 72.1 Briefing Sessions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.2 Science Lectures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.3 Field Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3 Research Work Programme 83.1 Survey Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4 Projects 94.1 Assessing primate habitat preferences and the effects of disturbance on behaviour . . . . . 9

4.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.1.2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.1.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.1.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.1.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.2 Mammal Diversity Outside Corcovado National Park . . . . . . . . . . . . . . . . . . . . . 204.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.2.2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.2.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234.2.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264.2.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.3 A study of the habitat preference of selected bird species in the Osa Peninsula . . . . . . 284.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.3.2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294.3.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.4 Temporal and Spatial Variations in the Abundance of Amphibians and Reptiles . . . . . . 324.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324.4.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324.4.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354.4.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394.4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

4.5 Sea Turtle Predation and Hatching Success Study along Playa Carate . . . . . . . . . . . 424.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424.5.2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434.5.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474.5.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494.5.5 Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.6 The importance of Ara macao feeding ecology in promoting early social structuring inreleased birds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524.6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524.6.2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534.6.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544.6.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554.6.5 Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

5 Projects in Progress 595.1 Assessing the degree of disturbance and secondary succession on forest habitats in Carate,

Osa Peninsula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595.1.2 Literature Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595.1.3 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605.1.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

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5.2 The effect of vegetation structure on bat activity and species variation on forest trails androads in Carate, Costa Rica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645.2.2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645.2.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

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Field Staff

Staff Member RoleLaura Exley (LE) Project Manager (PM)Emma Korein (EK) Principal Investigator (PI)Francesca Standeven (FS) Research Officer (RO)Matthew Clark (MC) Assistant Research Officer (ARO)Rebecca Jarrett (RJ) Assistant Research Officer (ARO)Lynn Pallemaerts (LP) Assistant Research Officer (ARO)Harriet Alice Taberner (HAT) Assistant Research Officer (ARO)Varvara Vladimirova (VV) Assistant Research Officer (ARO)

Foreword

It is with great pleasure that I present this document which contains the results of the scientific studiesundertaken by the Frontier Costa Rica Forest (CBP) project. This report contains all the data collectionmethodologies, results, analyses and conclusions of the avian, herpetological, mammalian, primate, andsea turtle studies, as well as background information on the biodiversity of the Osa Peninsula and futuredevelopment ideas for the project.Like many tropical countries, Costa Rica lost a significant portion of its forests to agriculture in the20th century (Stan and Sanchez 2017). With an increase in global demand for meat in the late 1950s,Costa Rica became a large exporter of beef to the United States, supported by loans from the WorldBank and other international development organizations (Parsons 1983). As a result, large areas offorest were converted into farmland and pasture, leading to the destruction and fragmentation of manyforest habitats (Arroyo-Mora, Snchez-Azofeifa, et al. 2005; Solorzano, Camino, et al. 1991). Habitatfragmentation causes isolated areas to become overcrowded and inhibits animals from moving to breedwith other populations. This leads to inbreeding, which decreases the heterozygosity and therefore theoverall genetic fitness of a population (Keyghobadi 2007).Measures are being taken in Costa Rica to restore and conserve forest habitats, such as the implemen-tation of payments for environmental services (PES) and a government ban on deforestation (Fagan,DeFries, et al. 2016). Despite such conservation efforts, the long-term damaging effects of deforestationon ecosystem processes can be widespread, and it is still unknown whether regenerating (i.e. secondary)forests are able to effectively sustain wildlife populations as well as forests untouched by human distur-bance (i.e. primary forests) (Fagan, DeFries, et al. 2016; Dent and Wright 2009; Klimes, Idigel, et al.2012; Mackey, Della Sala, et al. 2015; Ribeiro, Metzger, et al. 2009). Furthermore, ecosystems in re-generating forests continue to suffer from human activities such as hunting, logging, and cattle grazing(Stan and Sanchez 2017). It is therefore important to conduct baseline comparison studies in areas thathave been anthropogenically disturbed, as a means to determine the full extent of damage caused bydeforestation and how effectively regenerating forests can support wildlife.In addition to forest dwelling species, Costa Ricas marine fauna have also suffered from population de-clines due to human-induced threats, including fishing, poaching, coastal development, pollution, andclimate change (Wehrtmann and Corts 2008; Chacn-Chaverri and Eckert 2007; “Marine turtle nesting,nest predation, hatch frequency and nesting seasonality on the Osa Peninsula, Costa Rica”; Tomillo,Saba, et al. 2008). Sea turtles are particularly vulnerable to such threats, as their behaviours naturallytraverse a variety of ecosystems throughout their lifespan (e.g. migration across marine ecosystems,nesting on coastal ecosystems), exposing them to a range of threats in all stages of their development(Fish, Cote, et al. 2005). Though efforts have been made to conserve turtle populations in Costa Rica,such as increased egg and turtle harvesting regulations, long-term studies are needed to determine theeffectiveness of such conservation policies and to monitor population trends over time (Campbell 1998;Rees, Alfaro-Shigueto, et al. 2016).The research we conduct on this project is aimed to improve our knowledge of various animal groups onthe Osa Peninsula in order to better understand how conservation policies can be developed that promotesustainable biodiversity conservation in this region and reduce the negative impact of increasing humandevelopment. An equally important aspect of our research program is the participation of volunteers,who come from all over the world to learn and contribute to environmental conservation efforts. Byproviding this experience for eager volunteers, we hope to spread awareness and knowledge about the

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importance of this region as a biodiversity hotspot. Lastly, our project works with local communitymembers and organizations to improve research techniques and promote conservation strategies that areboth beneficial to local businesses and respectful of cultural values.I would like to thank the other staff on the project, including; Project Manager Laura Exley, AssistantResearch Officers Joseph Hamm, Loris Capria, Grace Bond, Samantha Earl, and Sarah Johnson-Gutirrez.I would also like to thank all the previous staff who have worked on the project, all of whom contributeda great deal to the running and development of our research. I owe a great deal of gratitude to membersand organisations of the local community for helping us integrate our work programme here. Finally, Iwould like to thank the staff at Frontier HQ in London, as well as all the current and previous volunteersfor their hard work and invaluable contribution towards the research programme.

Sincerely,

Emma Korein, Principal Investigator

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1 Introduction

1.1 Natural History of Costa Rica and its Wildlife Conservation

Costa Rica is situated between Nicaragua to the North and Panama to the South on a southern stretchof the North American continent. It is one of the seven Central American nations and covers an area ofapproximately 51, 100km2. It is enveloped by the Pacific Ocean on the west and the Caribbean Sea onthe east, creating coastlines of 1103 km and 255 km respectively. Even though this small country coversonly 0.01% of the Earth’s surface, it contains more than 4% of our planet’s biodiversity. This greatvariety and abundance is shared across many taxa, with around 12,000 plant species, 1,239 butterflyspecies, 838 bird species, 440 reptile and amphibian species, and 232 mammal species hailing from thiscountry (Sanchez-Azofeifa, Rivard, et al. 2002; Bulter 2006; IUCN 2006). There are two main factorsthat have led to this impressive biodiversity; the geographical location and the climatic conditions ofCosta Rica. The fact that Costa Rica is situated between the main bodies of North and South Americameans it can serve as a species corridor between the two continents. It also lies halfway between theTropic of Cancer and the equator, leading to an annual average temperature of 27oC, with very fewfluctuations throughout the year. The dry season starts around December or January and continuesthrough to April or May, after which time the rainy season begins. The southern Pacific lowlands receivea particularly high level of average annual rainfall at approximately 7,300 mm per year (Eye WitnessTravel Costa Rica). The consistent high temperature and rainfall both contribute to the richness of lifehere. Although Costa Rica is praised for having one of the most successful protected area systems in theworld (Andam, Ferraro, et al. 2008; Sanchez-Azofeifa, Daily, et al. 2003), further action must be takenin order to raise, or at the very least sustain, the current level of biodiversity.Costa Rica is a global frontrunner in environmental sustainability and conservation (Fagan, DeFries,et al. 2013). However, this has not always been the case. Like many other countries throughout theworld, Costa Rica has been the site of extensive deforestation over recent centuries. Up until the 1960s,activities such as logging and hunting seriously threatened the biodiversity of the region, resulting inover half of the country’s forests being cut down and many species being driven to the verge of extinction(Field guide to the wildlife of Costa Rica). In particular, the hunting of Costa Rica’s wild cat species,peccaries, and tapirs for their meat, skin and other body parts has significantly reduced wild populations.Human disturbance is also having a negative impact on marine fauna. The poaching of turtles for thefatty calipee and the collection of turtle eggs has severely depleted populations of endangered Greenturtles (Chelonia mydas) and vulnerable Olive Ridley turtles (Lepidochelys olivacea), both of which useCosta Rica’s coastlines as nesting sites (Tomillo, Saba, et al. 2008; Chacn-Chaverri and Eckert 2007).Since the 1960s, some of these issues have been controlled through the implementation of several refor-estation programs, legislation, education, and the creation of protected areas, which now represent almost27% of the country’s surface area (Andam, Ferraro, et al. 2008). Costa Rican law currently protects166 species from being hunted, captured, and traded, yet illegal hunting still occurs even in protectedareas (Eye Witness Travel Costa Rica). Deforestation and habitat fragmentation outside of protectedareas and national parks is still a significant problem due to an expanding human population and therelated increases in economic pressure (Carrillo, Wong, and Cuarn 2000; Sanchez-Azofeifa, Daily, et al.2003). Additionally, the projected impacts of climate change are likely to have significant adverse effectson Costa Rican biodiversity (Eye Witness Travel Costa Rica). Due to the high levels of biodiversityand the multitude of threats facing Costa Rica, it is important to conduct research to determine thehealth of the ecosystem and its species. Massive deforestation and the resulting biodiversity crisis havealready increased awareness and interest in the conservation of tropical habitats worldwide (Krupnickand Knowlton 2017). However, the actual implementation of conservation practices requires a basicunderstanding of native fauna and flora. Tropical forests are not single, homogeneous, biotic formations,and therefore the biodiversity of these areas must be understood on both a local and regional level(Gentry 1988).

1.2 Osa Peninsula

The Osa Peninsula is located in the southwest of Costa Rica and covers an area of 1093km2 (figure 1)(Field guide to the wildlife of Costa Rica). The peninsula contains the last remnants of tropical broadleaved evergreen lowland rainforest on the Central American Pacific slope and has a very high speciesrichness, containing approximately 50% of Costa Rica’s biodiversity (Kappelle 2016). Furthermore,this area contains several endemic species such as the Cherrie’s Tanager (Ramphocelus costaricensis),the Red-backed squirrel monkey (Saimiri oerstedii), and the Golfo Dulce poison dart frog (Phyllobates

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Figure 1: Map of the Osa Peninsula showing Carate (red circle), our area of study (VivaCosta Rica, 2003)

vittatus). The presence of these endemic species and the overall high density of biodiversity in this regionmakes the Osa Peninsula an ideal location for conservation research (Larsen and Toft 2010).Three types of forest can be found in the Osa Peninsula: Tropical Wet, Premontane Wet and TropicalMoist forest, with elevations ranging between 200 m and 760 m Sanchez-Azofeifa, Rivard, et al. 2002.The variation in topography allows for a highly variable climate, with an average annual rainfall of 5,500mm, a mean temperature of 27oC, and humidity levels almost never dropping below 90% Cleveland,Wieder, et al. 2010.There are about 12,000 people living on the Osa Peninsula, most of whom are located in small andscattered villages. The most important sources of income in this region are agriculture (rice, bananas,beans and corn), livestock (cattle), gold mining, logging and, more recently, the expanding eco-tourismindustry (Carrillo, Wong, and Cuarn 2000). The population in the region is increasing at a rate of 2.6%annually, which is incredibly high compared to the 1.3% growth in the rest of the country and the globalgrowth rate of 1.14% (Sanchez-Azofeifa, Harriss, and Skole 2001). As a result of the growing popularityof ecotourism since the 1990s, there has been a rise in the number of hospitality businesses along theroad from Puerto Jimenez to Carate (Minca and Linda 2000). This has caused growing concern forthe sustainability of the regions environmental resource demands (Sanchez-Azofeifa, Harriss, and Skole2001).Frontiers Costa Rica Forest Research (CBP) programme began in July 2009 in collaboration with thelocal NGO Osa Conservation, based in Piro (N08o23.826, W083o20.564) in the southeast of the peninsula.In October 2015, Frontier moved to Carate, located in the southwest of the Osa Peninsula (figure 1). Thesite is a prime location for carrying out both forest and shoreline surveys, as there is relatively easy accessto both primary and secondary forests, as well as pristine beach habitats. The long-term objective ofthis project is to investigate the effects of climate change, deforestation and other anthropogenic impactson the terrestrial communities of Costa Rica. Our research will provide information on the dispersal anddiversity of faunal communities in the Golfo Dulce Forest Reserve, with the aim of increasing protectionand connectivity in the area. There are five core faunal study groups within CBP: primates, sea turtles,mammals, herpetofauna and birds.The Osa Peninsula has undergone irreversible deforestation and fragmentation (Sanchez-Azofeifa, Rivard,et al. 2002), and more research is needed on how this is affecting species movement throughout thepeninsula. The Ministry of Agriculture and Environment (MINAE) in Costa Rica is exploring ways toincrease landscape connectivity in the region, and our project will contribute to decisions regarding thedesignation and location of habitat corridors and protected areas.

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1.3 Aims and Objectives of Frontier CBP

Under the umbrella of the research program, there are two main study aims and five objectives of FrontierCBP:

• Study aim 1: Identify the habitat preferences of various animal groups in Carate to help informconservation decisions made by MINAE, especially regarding habitat protection policies and theimplementation of wildlife corridors.

• Study aim 2: Participate in global efforts to conserve threatened sea turtle populations throughresearch and in-field conservation.

• Objective 1: Estimate the population density, distribution and feeding preferences of the fourprimate species present in Carate and compare these among habitats with varying levels of distur-bance.

• Objective 2: Assess mammal species richness and abundance along various forest transects bysearching for tracks and setting up camera traps.

• Objective 3: Determine the habitat preference of 10 endemic and/or data deficient bird speciesby conducting point counts surveys in forest of varying levels of disturbance.

• Objective 4: Compare amphibian and reptile abundance and species richness in habitats ofvarying levels of disturbance by conducting 30-minute visual encounter surveys along trails inCarate.

• Objective 5: Collect data on adult sea turtle nesting patterns, hatching success rate, and nestpredation by conducting morning and night patrols along Playa Carate.

2 Training

All volunteers, Assistant Research Officers (AROs) and newly appointed staff members receive a numberof briefing sessions on arrival (table 1), followed by regular science lectures and field training (table2) throughout their deployments. The CBP research program also supports candidates completing theAdvanced Diploma in Tropical Habitat Conservation.

2.1 Briefing Sessions

Everyone newly arriving to CBP receives an introduction to the aims of the research program, themethodologies used, and the research output of the individual projects. Furthermore, they get anupdate on the achievements of CBP through a general science presentation; this is an introduction tothe Frontier Costa Rica Forest Research Program in Carate. Additionally, all volunteers and staff aregiven a health, safety and medical briefing, of which they are tested on before participating in any fieldactivity. Volunteers undertaking the Advanced Diploma in Tropical Habitat Conservation certificate aregiven an introductory briefing before they begin the assessments.

Table 1: Briefing sessions conducted during Phase CBP 182.

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2.2 Science Lectures

A broad program of science lectures is offered at CBP, providing information and training on the differentaspects of research happening in our study area. Lectures are presented using PowerPoint and give abetter understanding about the biology and ecology of the studied species. Furthermore, they give aninsight in the methods and data analysis used by CBP and considerations made when planning researchprojects. Attendance of lectures is compulsory.

Lectures are scheduled with the following objectives:

• To allow every volunteer and member of staff to attend each presentation at least once duringdeployment, regardless of length of stay.

• To avoid conflict with other activities to maximize attendance.

• To provide detailed training on specific software and applications used in conservation, such asGPS.

Table 2: Science lectures delivered during Phase CBP 184.

2.3 Field Training

All volunteers and newly appointed staff members receive field training. Training is hands-on andprovides an opportunity to become familiar with the field equipment used during surveys. These sessionsare held before starting every survey to inform volunteers and new staff members about the way thesurvey is carried out and to assure accurate data collection. Identification books are present both in thefield and on the camp site to help teach participants how to identify flora and fauna species.

3 Research Work Programme

3.1 Survey Area

Since November 2015, fieldwork has been carried out in Carate, located in the southwest of the OsaPeninsula. The landscape is heterogeneous, composing of lowland moist primary, secondary and coastalforest, and disturbed forest. Dominant tree species include: Ficus insipida, Ceiba pentandra, Attaleabutyracea, Carapa guianensis, Castilla tunu, Spondias mombin, Hyeronima alchorneoides, Chimarrhislatifolia, Fruta dorada, Caryocar costaricense, Ocotea insularis, Pouteria torta, and Inga allenii.Mean annual rainfall and temperature for the area are 5,000-6,000 mm and 26 − 28oC respectively,with the dry season extending from the end of December until March (Cleveland, Wieder, et al. 2010).Different trails have been selected that encompass a range of different habitat types and varying degreesof usage and disturbance (table 3, figure 2). These trails are used as survey transects for each of ourstudies. Most of the trails are narrow and machete-cut. The exact habitat types present on the trails isnot yet known; for example, it is highly possible that Luna ridge contains a mix of primary and secondaryforest. In order to assess this in more depth, GIS work and phenological surveys are being undertakenwith the prospective use of drones in the future. This will allow the project to gain more knowledgeabout the different habitat types present in and around Carate.

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Table 3: Current trails used for all research projects carried out in Carate. Trail lengthrepresents the distance of the full trail, though specific surveys may use only part of a trail foreach transect. Codes represent trails displayed on the map below.

4 Projects

4.1 Assessing primate habitat preferences and the effects of disturbance onbehaviour

4.1.1 Introduction

Primates play an important role in the ecosystem with monkeys constituting an important proportionof the diet of some apex predator species. As an example, the African crowned hawk-eagle has a dietof which up to 88% consists of monkey (Mitani, Sanders, et al. 2001). Similarly, in Costa Rica mon-keys have been shown to make up a significant proportion of the harpy eagle, one of the largest extanteagles (Aguiar-Silva, Luz, and Sanaiotti 2014). Primates that are omnivorous such as capuchins - playa role in controlling populations of species which they prey upon (Lambert, Kays, et al. 2009). Evenleaf predation pressure, such as that exhibited by mantled howler monkeys, can have dramatic effectson the forest (Glander 1975). In addition to their predator-prey interactions, primates often act as seeddispersers. In the tropics up to 95% of all seeds are thought to be dispersed by animals, with primatesbeing particularly important due to their size, abundance and large home ranges (Lambert, Kays, et al.2009).Over half of the world’s primate species are currently threatened by extinction due to disease and anthro-pogenic activities such as hunting, the pet trade, and habitat alteration for agriculture and development(Cropp and Boingki 2000; Cowlishaw and Dunbar 2000; Nunn and Altizer 2006). Several common prac-tices, such as logging, building roads, and clearing for telephone and electric power lines directly lead totropical forest fragmentation and restrict populations to smaller forest patches. This inhibits primates’ability to find food during times of the year when food abundance is lowest (e.g. dry season), which inturn leads to a decline in genetic diversity and thereby population health and stability (Boinski, Jack,et al. 1998). Arboreal primates appear to be particularly sensitive to these effects, as their ability tomove between forest patches becomes more limited when the surrounding matrix is composed of cattlepastures or croplands (Estrada and Coates-Estrada 1996; Arroyo-Rodrguez and Mandujano 2006).Despite the extensive literature analysing the effects of habitat fragmentation and disturbance on pri-mates, no clear patterns have yet been identified. Understanding the population density of primates cangive an indication of the ecological and social processes affecting group size and composition, which canbe a crucial tool for conservation (Plumptre 2013). The present study focuses on the four species of CostaRican primate present in Carate, Osa Peninsula; the Central American squirrel monkey (Saimiri oerste-

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Figure 2: A map of the study region and project trails, with the Frontier campsite labelled in redas FC. This map was created using QGIS version 2.18.15. Map shapefiles were downloaded fromINOGO Iniciativa Osa y Golfito at Stanford University and Stanford Woods Institute for theEnvironment. Available at: http://inogo.stanford.edu/resources/INOGOMapas?language=en.

dii), the mantled howler monkey (Alouatta palliata), the Geoffreys spider monkey (Ateles geoffroyi) andthe white-faced capuchin (Cebus capucinus). The Osa Peninsula is the only part of Costa Rica wherethese four New World primate species occur together, providing us with a unique opportunity to studythe effects of varying degrees of forest degradation on multiple species of primates (Carrillo, Wong, andCuarn 2000).Since this study commenced in November 2015, Frontier CBP has been surveying for the presence ofthese four primate species on trails in primary forest, secondary forest, and anthropogenically disturbedareas throughout the study region. During this time period, we have monitored the effects of foresttype on primate group composition and energy budgets, as well as developing trends or changes in groupcomposition over time. The overall research aim is to gain more knowledge about the population density,distribution, and feeding preferences of the four primate species in this region of the Golfo Dulce Reserve,and to compare these among different habitat types present in this area. As humans continue to developprimate habitat, it is becoming increasingly more important to understand the ecology and behaviourof primates in human-dominated environments. By comparing the richness and abundance of primatespecies between the different habitat types, we can gain more information regarding management andpolicy decisions at a local level.

4.1.2 Materials and Methods

Study Species:MANTLED HOWLER MONKEY (ALOUATTA PALLIATA):Mantled howler monkeys can be found in Costa Rica, Nicaragua, Panama, and Guatemala (figure 3), andtend to be found in the older areas of evergreen primary forest as well as secondary and semi-deciduousforest. They are classified as Least Concern by the IUCN (Cuarn, Shedden, et al. 2008), with their mainthreats being habitat loss and fragmentation. Howler monkeys are a diurnal, arboreal species with a dietthat mainly consists of leaves, giving them low energy, which results in a lethargic behaviour. They havean average group size of 13, but groups can reach up to 40 individuals (Chapman 1990). The males arecharacterized by having a white scrotum when they reach sexual maturity and having an enlarged hyoidbone which allows them to create a loud howling noise, usually displayed at dawn and dusk (Cuarn,Shedden, et al. 2008; Zaldvar, Rocha, et al. 2004).

GEOFFROY’S SPIDER MONKEY (ATELES GEOFFROYI ):Spider monkeys are native to Central America and are currently classified as Endangered with a decreas-

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ing population (Cuarn, Morales, et al. 2008; Zaldvar, Rocha, et al. 2004; figure 3). This primate speciesis mainly threatened by habitat loss, hunting for bush meat, and the pet trade. They are a diurnal andarboreal species, mainly inhabiting the upper layers of the forest, and have a diet of fruits, leaves andsometimes insects, seeds, barks and flowers. Spider monkey group sizes range from 20 to 40 individuals(Chapman, Chapman, and Wrangham 1995). They operate in a fission-fusion society, splitting into sub-groups during the day and congregating again during the night. The females are characterised as havinga pendulous clitoris (Cuarn, Morales, et al. 2008; Zaldvar, Rocha, et al. 2004).

WHITE-FACED CAPUCHIN (CEBUS CAPUCINUS):The white-faced capuchin, also known as the white-headed or white-throated capuchin, ranges fromHonduras to Ecuador. They are classed as Least Concern by the IUCN. Capuchins are a diurnal andarboreal species, with a diet of mainly fruits and insects (Cunha, Vieira, and Grelle 2006). They are ahighly adaptive species, meaning they can occupy various habitats but usually occur in tropical evergreenand dry deciduous forests. They are a sociable species, with group sizes ranging from 4 to 40 individuals(Zaldvar, Rocha, et al. 2004).

CENTRAL AMERICAN SQUIRREL MONKEY (SAIMIRI OERSTEDII ):Squirrel monkeys inhabit the lowland rainforests of Pacific Costa Rica towards Western Panama (figure3). They are currently listed as Vulnerable, with decreasing populations on the IUCN red list (Wong,Cuarn, et al. 2008). The main threat to squirrel monkeys is habitat loss due to logging and agriculture.They are an arboreal and diurnal species, depending on a diet of insects, leaves, fruits, barks, flowersand nectar. They forage in the low and middle levels of primary and secondary forests. They tend totravel between 2.5 and 4.2 km per day and their group size ranges from 20 to 75 individuals, with anaverage of 41 individuals per group (Wong, Cuarn, et al. 2008; Zaldvar, Rocha, et al. 2004).

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Figure 3: Distribution of three of the primate study species across Central America.

Survey Site:

Data was collected by walking seven different pre-determined trails (Beach trail, Road, Attalea loop,Luna Ridge, Leona Loop, Shady Lane, Camp trail; figure 2) and conducting total counts of all theprimates encountered. The surveys were conducted at least twice per week, starting in the morningbetween 05:50 and 06:00, and in the afternoon between 15:50 and 16:00 to cover peak primate activity,thus increasing detection probability. This is important because squirrel monkeys have been shown tobe more active during the afternoon Baldwin and D. 1972. A minimum of two observers walked at aconstant speed of 2 km/h while scanning the canopy for primates. Additional stops would be takenevery 100 meters to minimise the likelihood that an observer would miss seeing a primate while walking.The seven trails were divided into three main habitat types: primary forest (Luna ridge, Leona loop),secondary forest (Beach trail, Shady lane) and disturbed area (Road, Attalea loop, Camp trail) forests.Each trail was walked in one direction, no more than once a week and at the same time of day.

Study Area:

Data was collected by walking 11 different predetermined trails and conducting single observer linesurveys, with total counts of all the primates encountered. The surveys were conducted twice a week,starting either at 06:00 in the morning or at 16:00 in the afternoon; both times are known to show peakprimate activity, so surveying at these times of day will increase the detection probability. A minimumof three observers walked at a constant speed of 2 km/h while scanning the canopy for primates. Every100 m, the observers stopped to listen for any sounds of primates that would otherwise be missed whilewalking. Each trail was walked in one way, and not more than once a week at the same time of day. Iftwo consecutive surveys were held on the same trail, this did not happen any earlier that 48h after thefirst survey.

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Survey Protocols:

When a troop of monkeys was encountered, observers would attempt to count them over the courseof a 10 minute observation time. All individuals seen at the same time and exhibiting the same generalbehaviour were considered to be part of the same group (Chapman, Chapman, and Wrangham 1995).The following data was then recorded: the number of individuals in the group, behaviour, compass bear-ing, GPS coordinates, direction of travel (if travelling), the height at which they were found, and theperpendicular distance from the path to the tree in which the primates were first spotted. Using a digitalrangefinder, both these measurements can now be taken exactly and no longer need to be estimated.When possible, data on group composition (i.e. gender and age distribution) were also recorded. Thisis easily done for howler and spider monkeys, where one sex has a distinct trait; for the capuchins andsquirrel monkeys, however, the only possible distinction to be made between adult males and femalesdepended on the presence of infants, i.e. if an infant was carried around by an individual, this individualwas assumed to be a female.The three behaviours classified for this study were (1) travelling, (2) foraging, and (3) resting. Restingwas defined as a group of monkeys that were sitting, lying, scratching, grooming and/or playing. For-aging was defined as monkeys that were moving around in the same general area, climbing from onetree to the next, stopping and munching, picking at leaves and fruits, using tools, and peeling, biting orlicking bark. A group was considered to be travelling when the majority of the members were movingin a distinct direction, climbing, or running from one tree to the next without stopping at any time toforage.This study was non-invasive and according to the legal requirements of Costa Rica (Costa Rica 2003).Any kind of abnormal or aggressive behaviour towards the observers by individual primates was re-sponded to by moving away as quickly as possible.

Analysis:

All data on encounters, species, group size and composition, behaviour, location, was all analysedusing R Studio version 1.1.463(R Core Team 2018) and Microsoft Excel.

4.1.3 Results

There were a total of 523 primate encounters during phase 184, however, only 230 encounters producedGPS coordinates due to GPS failure. Figure 4 displays the locations of each encounter for each species.

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Figure 4: Map showing some of the primate encounters. NOTE: Due to GPS failure, 230 outof our 523 encounters do not have any GPS coordinates associated with them

Encounters and group size and composition:

An encounter was defined as a group of monkeys spotted during a survey. Spider monkeys were byfar the most commonly encountered species with 268 encounters, followed by howler monkeys (145),capuchins (65), and squirrel monkeys (40). This resulted in an encounter rate (i.e. the proportion ofencounters of each species found on survey, compared to the total number of encounters) of 0.52, 0.28,0.13, and 0.08, respectively (figure 5).

Figure 5: Encounter rate for the four different study species across Carate.

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Figure 6: Number of encounters for each species on each trail. NOTE: the trails Los Avesand Waterfall have so far been surveyed only once, and so are not represented in this picture.

Across trails, we found different encounter rates for all four species (figure 6). On all but one trail(i.e. Camp), we found mostly spider monkeys. Second most common species on all trails was the howlermonkey, with the exception of Camp trail, where they were most common. The highest number of squirrelmonkeys were spotted on Camp trail, followed closely by Attalea; on all other trails, their numbers arelow, with no encounters on Luna. Capuchin monkeys are found on all trails, except on Camp trail.

Group size varied a lot between species. The largest groups were found for squirrel monkeys (8.82 ±2.06 individuals), followed by capuchin monkeys (6.17 ± 1.07 individuals), spider monkeys (4.32 ± 0.41individuals), and howler monkeys (3.70 ± 0.68 individuals; figure 7). Maximum group sizes for eachspecies were 31, 24, 20, and 15, respectively.

Sex and age ratios vary across species (figure 8). While groups of howler monkeys were most likelymade up of a higher proportion of males, spider monkey groups tended to contain a higher proportionof females, and capuchins were roughly even. No such conclusions can be drawn for squirrel monkeys,due to the low number of encounters as well as the difficulty of sexing animals without the presence ofinfants.

Activity Budgets:Activity budgets also varied between the species (figure 9). Spider and squirrel monkeys were most oftenspotted while travelling, while capuchins would most often be found while foraging. Howler monkeyswere most often heard, but when spotted, they would most often be found eating or resting.

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Figure 7: Mean group size for each species.

4.1.4 Discussion

Encounter rates and group sizes

Of the four species monitored, spider monkeys are the ones most often encountered while on survey,with a total of 268 encounters. This is good news, as it is the only species of Costa Rican monkey tobe classified as Endangered by the IUCN (Cuarn, Morales, et al. 2008). This finding tells us that theregion of Carate, and possibly the larger Osa Peninsula, is a very important area for A. geoffroyi. If thearea harbours a large population of this species, the Osa Peninsula could function as a population sourceand/or refuge, should the overall global population of A. geoffroyi continue to decline. The peninsulawould then have to be a conservation priority, and as much of its natural habitat protected for thelong-term survival of spider monkeys. However, before any management decisions can be made, a robustestimation of population size and density is required.Howler monkeys were the second most common species encountered on survey, followed by capuchins andsquirrel monkeys. This is probably an interaction between each species status and body size. Mantledhowler monkeys are considered Least Concern (Cuarn, Shedden, et al. 2008), indicating a relatively largepopulation, and are large, easily spotted animals (especially in combination with their calls). As such,they are more likely to be spotted on surveys. Capuchins are smaller, and squirrel monkeys even smaller,and so will be more difficult to spot, leading to a gradually declining encounter rate across species.Spider monkeys can form big loose communities of up to 40 individuals (Cuarn, Morales, et al. 2008),but are most often spotted in smaller groups of around four individuals during the day while foraging.Our mean group size of approximately four individuals per group reflects those smaller foraging groups.Our mean group size for squirrel monkeys is in line with previous literature (e.g. Wong, Cuarn, et al.2008), although the groups around Carate tend to be smaller than in other areas. Squirrel monkeyscan easily form groups up to 100 individuals, although generally 20 to 75 individuals are more common(Wong, Cuarn, et al. 2008). In Carate, the largest group recorded was of 31 individuals. For howler

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Figure 8: Group composition per species. Abbreviations: F = female, M = male, J&I =juveniles and infants, U = unknown.

Figure 9: Activity budgets for each species.

monkeys, our average of less than four individuals per group is much lower than any previous estimates(e.g. Cuarn, Shedden, et al. 2008).

Across trail comparisonThe environments in which primate species live influence social structures, feeding ecology, body sizeand cognition (Rode 2013). In a time when habitat loss is occurring at an alarming rate, it is importantto understand the effects of habitat disturbance on the ecology and behaviour of primates, and if they

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are capable of surviving in human dominated or disturbed areas. The long-term survival of primatespecies depends on particular habitat requirements and the ability to adapt to altered habitats (Kulpand Heymann 2015).Spider monkeys were most frequently detected on the trails Luna (70 encounters), Leona (52), andAttalea (49). The first two are the oldest and least disturbed forest habitats, which shows the spidermonkeys are particularly sensitive to habitat destruction. Attalea trail, however, has so far been clas-sified as disturbed forest, with broad, well-used trails, and much human activity. The spider monkeyspresence on this trail may indicate that this part of the forest holds abundant fruit supplies, and so forthe spider monkeys the benefit of abundance of food would outweigh the cost of human disturbance.Howler monkeys and capuchins were more often found on Road (36 and 19 encounters, respectively),followed by the trails Beach, Attalea, and Shady. All of these, except the latter, are used frequently bypeople and contain forest that is more disturbed than e.g. the trails Luna and Leona. This indicates thatboth species are more adaptable and rely less on pristine, undisturbed forest. Such behaviour is goodnews towards their conservation, as it would give them more leeway to cope with human disturbance ifhabitat loss is not countered.A similar pattern can be found for squirrel monkeys, which have been encountered most on the trailsAttalea (18) and Road (12). In addition, they were almost entirely absent on Luna and Leona. Previousliterature has found that squirrel monkeys are tolerant of habitat disturbance and can in some caseseven benefit from habitat disturbance. Many primates, particularly generalist species such as squirrelmonkeys (Kulp and Heymann 2015), utilise disturbed areas for their rapid fruit regeneration and surplusof young leaves (Johns and Skorupa 1987). However, disturbed habitats are preferred only to a point;e.g. squirrel monkeys are greatly inhibited by agricultural monocultures (Wainwright 2007). This sug-gest that Carate is a very important site for squirrel monkeys, as this region has been mildly disturbedby gold mining and tourism, but not agriculture. Just outside of Carate, however, most of the land isused for farming, which emphasises the need to build natural corridors that connect fragmented foresthabitats.From this, we can assume that howler monkeys, capuchins, and squirrel monkeys, are more likely tomaintain stable population for the short-term, while spider monkeys will be most affected by habitatdisturbance, loss, and fragmentation.

Activity Budgets

Howler monkeys spent a large portion of their time foraging and resting, but very little time travelling.The diet of howler monkeys varies seasonally, but primarily consists of very low-energy food sources suchas leaves and flowers. Because of this, howler monkeys tend to be more lethargic and less active thanother primate species (Wainwright 2007). Our data supports this information; with a low energy diet,howlers would be required to spend most of their time resting and foraging and would not be inclinedto travel frequently.While capuchins also spent most of their time foraging, they spent a lot less time resting than howlermonkeys. Capuchins have an omnivorous diet; in addition to feeding on fruits and leaves, they havealso been found to eat insects, birds, small mammals, lizards, frogs and crabs. Studies have also foundcapuchins to have home ranges extending from 30 to 160 hectares (Wainwright 2007). Their large homerange and higher energy diet could explain why we found capuchins to be more mobile than howlermonkeys.Spider and squirrel monkeys on the other hand spend the largest portion of time traveling and the leastamount of time resting. Previous literature has found that primates are likely to change their behaviourbased on the availability of food in a particular environment (A.I. 2007). Spider monkeys have a specialistdiet consisting primarily of fruit, though in forest fragments where fewer resources are available they willsupplement their diet with leaves (Gonzalez-Zamora, Arroyo-Rodriguez, et al. 2009). This suggests thatleaves are the lesser preferred food source, and when possible, spider monkeys may travel long distancesto find areas where fruit is most abundant.

4.1.5 Conclusion

Carate and its surrounding area has been found to be an important habitat for primates. Despitedifferent degrees of human disturbance outside Corcovado National Park, the four study species seem tobe present in large populations. The endangered spider monkey has been found to be most sensitive tohuman disturbance, while howler monkeys, capuchins, and squirrel monkeys have been found to be more

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adaptable and tolerant to human activity. For all species, the presence of humans in their environmenthas not influenced their activities to any large extent. All this highlights the importance of the OsaPeninsula for primate conservation.

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4.2 Mammal Diversity Outside Corcovado National Park

4.2.1 Introduction

One of the major threats to wildlife populations is human disturbance. Two thirds of the world’s plantand animal species are found in the tropics, where deforestation is a frequent occurrence due to loggingand agriculture (DeFries, Hansen, and Hansen 2005). Areas that separate species from these threateningdisturbances are known as protected areas (Margules and Pressey 2000) and are a vital conservation strat-egy for safeguarding species and their habitats (Hansen and DeFries 2007). Anthropogenic mortality offauna is most common when species’ home ranges extend beyond protected areas (Balme, Slowtow, andHunte 2010). Large carnivore species often have wide individual home ranges which frequently extendbeyond protected areas, leading to increased movement in unprotected areas where human disturbance ishigh (Balme, Slowtow, and Hunte 2010; Revilla, Palomares, and Delibes 2001). In addition, high levelsof competition and reduced prey availability threaten protected areas that are reaching their carryingcapacity, resulting in many species moving outside protected areas (Balme, Slowtow, and Hunte 2010).Unfortunately, there is often little connectivity between protected areas that would allow safe movementbetween habitats (Sanchez-Azofeifa, Rivard, et al. 2002). This movement is necessary for foraging andreproductive behaviours and protects populations from genetic isolation ((Crooks, Burdett, et al. 2011;Wainwright 2007)).Costa Rica is known to be one of the most biodiverse places in the world (Harvey, Komar, et al. 2008),representing 0.03% of the worlds land surfaces yet containing 6% of its mammal species (Baltenspergerand Brown 2015). Following mass deforestation in the 1970s, a national park system was created, lead-ing to 187 protected areas that make up 27.6% of the country (UNEP-WCMC 2019). However, manyreserves are reaching their carrying capacity and there is little connectivity between the protected areas(Sanchez-Azofeifa, Rivard, et al. 2002).Corcovado National Park, located on the Osa Peninsula in Costa Rica, has one of the largest populationsof jaguars and white-lipped peccaries in the country (Carrillo, Saenz, and Fuller 2002). Corcovado hasreached its carrying capacity, which adds pressure to the interspecific and intraspecific competition forprey and habitat space. Thus, mammals are migrating outside Corcovado National Park to unprotectedareas in the Osa Peninsula. With no protected corridor to another reserve, mammal populations in thepark are at risk of inbreeding, genetic isolation, and human predation (Carrillo, Wong, and Cuarn 2000;Carrillo, Saenz, and Fuller 2002; Salom-Prez, Carrillo, et al. 2007).This study monitors mammals that are migrating out of Corcovado National Park and into the surround-ing area of Carate. Costa Rican cats have suffered a major decline due to habitat loss and poaching(Wainwright 2007; Baltensperger and Brown 2015), while prey species such as pacas and Central Ameri-can agoutis are hunted for their meat (Wainwright 2007). Historically, human wildlife conflict has takenplace between farmers and big cats. This is due to felines preying on livestock if prey availability islimited, however, cats would rather eat their natural prey species (Zimmermann, Walpole, and Leader-Williams 2005). Therefore, keeping prey populations elevated will help to reduce this conflict.Establishing corridors between reserves requires evidence of habitat use outside protected areas. Cor-ridors are strips of land that aid the movement of organisms through landscapes, reducing the amountof designated protected area required for their home ranges (Puth and Wilson 2001). For example, anisolated population of pumas would need 220 000 hectares of land, but the introduction of a corridorreduces this number to 110 000 hectares (Wainwright 2007). Thus, one goal of this study is to provideevidence that big cats and their prey are migrating out of Corcovado National Park, facilitating thecreation of a corridor to the nearest protected area.Forest type is an important feature of corridors because species vary in their habitat preference. Forexample, the white-lipped peccary will disperse from an area as soon as disturbance is detected (Wain-wright 2007; M. 2006), while other species can cope with minor disturbance. In addition, the presenceof certain habitat features, such as a water source, can increase species diversity (Redford and Fonseca1986). The second aim of this study is to assess the abundance of big cats and their prey across varyinghabitats outside Corcovado National Park to ensure a proper corridor is constructed.

4.2.2 Materials and Methods

Survey Area:

Carate is located along the Pacific Coast of Costa Rica, bordering Corcovado National Park on theOsa Peninsula. The study area has a mixture of forest types, with varying levels of succession and habitat

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features. The climate is hot and humid; the annual average temperature is 25oC with average rainfallof 450 mm per month in the dry season and 800 mm per month in the wet season (Carrillo, Saenz, andFuller 2002). Carate is composed of privately owned land (mostly eco lodges) and community buildings,with a main road running along the coast. It is adjacent to Corcovado National Park and part of theGulfo Dulce Forest Reserve. Trails used in the study are composed of early, mid, and late successionalforests, some with rivers, lagoons, and steep changes in elevation.

Species:

This study focuses on 18 of the 236 mammal species that are currently present in Costa Rica. Table4 gives an overview of the 18 selected mammal species. Previous study species, like the crab-eatingraccoon (Procyon cancrivorus) and the water opossum (Chironectus minimus), were removed from thestudy, because there is no conclusive evidence of them being a prey species to any of the big cats.

Table 4: List of study species in Carate. Abbreviations: C= common, R = rare, U =uncommon, DD = data deficient, LC = least concern, NT = near threatened, VU = vulnerable,EN= endangered.)

Mammal tracks:

One of the oldest known methods of identifying mammal presence in an area is by identifying printsand tracks left in substrate (Silveira, Jacomo, and Diniz-Filho 2003; Bider 1968). Track surveys areefficient and usually low in cost, but they do depend on suitable field conditions and trained observers(Smallwood and Fitzhugh 1995; Burnham, Anderson, and Laake 1980).Surveys were conducted along nine trails: Beach, Camp, La Leona, Los Aves, Luna, Puma, Rio Carate,and Shady. Surveys began at 6:00 am to ensure prints were fresh from night activity. Staff and volun-teers walked at a slow pace along the trails, recording any mammal tracks seen. The length and width oftracks were measured at the widest point of the print (as shown in figure 10), to allow for more precisespecies identification for similar prints (e.g. between the two species of peccary). All measurements andprints were then compared to a mammal track sheet for definite species identification. GPS coordinates

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Figure 10: Standard measurements taken at the widest point (A) and vertical distance fromtoes to pad (B) for each observed print.

and direction of travel were also recorded for each set of prints. To avoid redundant counts and thereforean overestimation of individuals, tracks of the same species within 100m were not taken into account forfuture analysis.Previously our mammal study also included the use of camera traps and sand traps in the dry sea-son. Camera traps have been taken down due to heavy rains that could damage equipment. They willbe used again in late January when the dry season begins. Sand traps are most useful in dry seasonwhen substrates are not wet enough to capture clear footprints. These will also likely be used again indry season. Regardless, all data previously collected through either method was included in this analysis.

Analysis:

Three common biodiversity indices were calculated from the data collected by mammal tracking,sand trapping, and camera trapping: (1) species richness, (2) Shannon’s diversity, and (3) Simpson’sdiversity. Species richness refers to the number of species present in the study area. Shannon’s diversityis an index that weighs all species equally, while Simpson’s diversity index weighs common species moreheavily.

All diversity indices were calculated using the vegan package for R Studio (Oksanen, GuillaumeBlanchet, et al. 2019).

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4.2.3 Results

Mammal tracking :

From the 11th of November 2015 to the 12th of November 2018, a total of 163 mammal trackingsurveys were conducted across nine trails: Attalea, Beach, Camp, Leona, Los Aves, Luna, Puma, RoCarate, and Shady. Mammal tracks were observed on 148 of those surveys, resulting in a total of 430sightings.Out of the 18 study species, 17 were observed during our current study period. The jaguar is the onlystudy species that we have not encountered during our surveys. The least common species tracked werethe jaguar (0 sightings), margay (1 sighting), and white-lipped peccary (3 sightings), while the white-nosed coati, Bairds tapir, and the Central American agouti were spotted most often (46, 71, and 115sightings, respectively; see table 5, figure 11).

Table 5: Number of encounters and encounter rate for all study species in Carate, fromNovember 2015 until November 2018.

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Figure 11: Encounter rate of the different study species in Carate during phase 184.

Figure 12: Locations of mammal encounters across Carate.

Most species were found on Rio Carate, with 15 out of 18 study species spotted along these trails.The lowest number of species was found on Leona (1), Shady (3), and Luna (4) (figure 12). However,

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this is due to the low sampling effort on these specific trails, and the diversity indices are expected tobecome more representative with more surveys. The Shannon diversity was highest on Beach and loweston Leona (although, again, this is due to the low sampling effort). The Simpson diversity is again higheston Beach trail(table 6).

Table 6: Diversity measures for our study area and each specific trail.

To analyse yearly trends, the data was split into four time categories: (1) from November 2015 untilOctober 2016 (a.k.a. ’year A’), (2) from November 2016 until October 2017 (a.k.a. ’year B’), (3) fromNovember 2017 until October 2018 (a.k.a. ’year C’), and (4) from November 2018 until October 2019(a.k.a. ’year D’; as of yet unfinished).There was an overall increase in the number of mammals detected over each year; there were 118individual mammals encountered in year A, 126 in year B, and 172 in year C (note that year D isdisregarded for lack of completion). However, when looking at biodiversity indices, we note an overalldecrease in mammal biodiversity across Carate (figure 13).

Figure 13: Changes in biodiversity indices over our study period.

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4.2.4 Discussion

The collective results from our mammal tracking, camera trapping, and sand and mud trapping resultedin the capture of 17 out of our 18 study species over a three-year period. The most common speciestrapped in Carate is the Central American agouti, with a total of 115 encounters. Agoutis play an im-portant role in their respective ecosystems, most notably as seed dispersers. Being small animals, theyare more likely to disperse seeds towards areas that might not be reached by larger seeds dispersers (e.g.primates). Moreover, agoutis are unlikely to collect all buried seeds, giving neglected stashes the perfectconditions to germinate and grow (Wainwright 2007).The order of Rodentia, along with the order of Primates and Chiroptera (i.e. bats), are the most note-worthy mammalian seed dispersers (Stiles, 1992), especially in the area around Carate and CorcovadoNational Park. Such a distinction is well reflected in their ecology, as agoutis are often spotted follow-ing troops of monkeys around for any seeds that the latter drop from the canopy (Wainwright 2007).Unfortunately, seed dispersers across the world are under threat (Farwig and Berens 2012), and theirdecreasing populations will result in an overall lower plant biodiversity (Farwig and Berens 2012). How-ever, agoutis are widespread across Mesoamerica, and their population is considered stable, leading inthe IUCN status of Least Concern (Emmons 2016). This means that, as of yet, there is no immediatethreat to the agouti’s seed dispersing abilities, and this is good news for the larger ecosystem of the OsaPeninsula.The capture of felids outside of Corcovado National Park is also good news towards their conservation.For large carnivores, survival is often lower outside of protected areas (e.g. leopards Panthera pardusin South Africa; (Balme, Slowtow, and Hunte 2010), resulting in lower population densities outsideprotected compared to the cores of these areas. Because of this, individuals of threatened populationswill first settle in protected areas, and only start dispersing outside of the borders of the PAs when thepopulation has reached a higher density. The presence of jaguarundis, margays, and ocelots in Carateindicates still high population sizes inside protected areas like Corcovado National Park, which also re-flects in their IUCN status (i.e. Least Concern for jaguarundis and ocelots, and Near Threatened formargays).The presence of pumas outside of Corcovado National Park relates the same story but can be considereda slightly bigger conservation success because of the felid’s size. Big cats are generally restricted toPAs, where they are the least persecuted by humans. The dispersal of pumas out of the national parkindicates a high population density inside the park, and so an increasing or stable population. However,this success story cannot be extrapolated to jaguars. No sightings have yet been reported outside of Cor-covado’s borders, which indicates a low dispersion rate, despite a generally high estimated populationdensity (approx. 7 individuals per 100km2; Salom-Prez, Carrillo, et al. 2007). Some explanations havebeen offered for this, notably (1) the risk of persecution is still too high outside of the park’s borders,and (2) the low density of white-lipped peccaries outside of the park. The latter would mean decreasedprey availability for jaguars, since white-lipped peccaries are a very important prey species (Carrillo,Saenz, and Fuller 2002; Carrillo, Wong, and Cuarn 2000).Out of all the trails used in this survey, Beach and Ro Carate have the highest biodiversity accordingto both Shannon’s and Simpson’s diversity indices. Out of all our trails, these two are the closest inproximity to Corcovado National Park, indicating that mammal diversity decreases the further awayfrom park boundaries. The lowest biodiversity could be found on La Leona, Shady, and Luna, but thisis mostly due to low surveys efforts on all three trails (La Leona: N=2; Shady: N=4; Luna: N=8).We noted an increase in mammal encounters across the three survey years. This is mostly due to anincreased survey effort for each year. A larger amount of surveys conducted will generally lead to moretracks being found. The increased survey effort is probably also the reason for the noted decrease in bio-diversity across Carate. A low survey effort can easily result in over- or underestimations of biodiversity,while a higher survey effort will lead to more precise estimations.

4.2.5 Conclusion

Our study has detected that species are present in the area of Carate, located on the borders of CorcovadoNational Park. This means that wildlife, including big cats, are moving out of the national park. However,despite the area being part of the Gulfo Dulce Forest Reserve, there is not enough protection for speciesfrom hunting, resulting in lower biodiversity estimates and the absence of the jaguars. Moreover, despiteits status as a forest reserve, the Carate-Matapalo corridor is still subject to deforestation, resulting inthe fragmentation of forest on the Osa Peninsula. This will limit the movement of species outside thenational park. This study therefore highlights the need to upgrade the management level of the Gulfo

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Dulce Forest Reserve, which would provide better protection for mammals by allowing a safe passagebetween national parks (i.e. Corcovado NP and Piedras Blancas NP). A long-term study of five yearswould benefit this project by providing enough data to make suggestions regarding conservation andprotected area connectivity.

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4.3 A study of the habitat preference of selected bird species in the OsaPeninsula

4.3.1 Introduction

The highly heterogeneous environments of Costa Rica give rise to many species-rich communities, partic-ularly those within the bird families (Herzog, Kessler, and Cahill 2002). Costa Rica hosts approximately850 bird species, 160 of which are endemic (Henderson and Adams 2010). This high bird species richnessmeans that Costa Rica has a relatively long history of studies focusing on bird community structure (e.g.Young, Derosier, and Powell 1998; Blake and Loiselle 2001; Sigel, Sherry, and Young 2006) and demog-raphy (e.g. Ruiz-Gutierrez, Gavin, and Dhondt 2008; Young, Sherry, et al. 2008; Woltmann and Sherry2011). Birds provide various important ecological functions, including seed dispersal and pollination,and as such are an integral factor in the maintenance of plant communities, even contributing towardsthe reforestation of fragmented habitats (Pejchar, Pringle, et al. 2008).The majority of bird studies, however, have been carried out in pristine habitats with very little attentionpaid to degraded or fragmented areas (Wilson, Collister, and Wilson 2011). To ignore these habitats isto ignore a large and important aspect of biodiversity conservation. For conservation approaches to beeffective, there has to exist an appreciation of the importance of degraded habitats. The rapid rate ofworldwide habitat degradation necessitates a corresponding increase in their assigned importance.It is equally pertinent for researchers to understand the current status of chosen study species in thesehabitats, as well as their prevalence and their potential to adapt to increasing human pressures and achanging climate. This, in combination with its remoteness, means that little is known about the birdcommunities of the Osa Peninsula, despite its extraordinary species diversity and high levels of endemism(Wilson, Collister, and Wilson 2011).Home to approximately 375 species of birds, including many migratory birds and 18 endemic species(Sanchez-Azofeifa, Rivard, et al. 2002), the Osa Peninsula comprises one of the largest remaining tractsof intact lowland rainforest in Mesoamerica (Barrantes 1999). This provides important habitats for amyriad of bird species. While 39% of the region is under the protection of Corcovado National Park, thesignificant recent development has resulted in deforestation and forest fragmentation occurring outsideand along the periphery of the reserve (Sanchez-Azofeifa, Rivard, et al. 2002).Deforestation and fragmentation are considered the primary threats to birds in the Osa Peninsula (Birds- Osa Conservation). Due to a human population growth rate of 2.6% (Sanchez-Azofeifa, Harriss, andSkole 2001) and a large drive towards attaining status as a prime ecotourism location, large areas offorest have been cleared to make space for agricultural practices and the hospitality industry (Minca andLinda 2000). Studies have found that in the period between 1979 and 1997, the percentage of forestedarea in the peninsula decreased from 97% to 89% (Sanchez-Azofeifa, Rivard, et al. 2002). Furthermore,the authors found that in 1997, the majority of the remaining forest outside of Corcovado National Parkhas been altered, with only 44% of the region representing mature forest; this figure is likely to havedecreased over the intervening two decades.Today, the tropical forest exists as a patchwork of varying size, age, and connectivity within a human-dominated landscape (Wilson, Collister, and Wilson 2011). Such fragmentation is not conducive torobust ecosystem dynamics, or to viable bird populations (Simberloff 1995). Indeed, the pejorative ef-fects of habitat fragmentation have been argued to be more detrimental than the loss of sizeable portionsof the habitat itself (Bender, Contreras, and Fahrig 1998). Particular bird groups, such as understoryinsectivores (Canaday 1996; ekerciolu, Ehrlich, et al. 2002; Sigel, Sherry, and Young 2006), can be verysensitive to habitat fragmentation, whilst others are more able to adapt to and effectively utilise degradedand fragmented habitats (Fahrig 2003).The Osa Peninsula has undergone a large amount of development, and it can be argued that the ratewill likely increase (Sanchez-Azofeifa, Rivard, et al. 2002). It is therefore of the utmost importance tounderstand how the birds outside of the protective sphere of Corcovado National Park are affected byfragmentation and deforestation. In addition to the very tangible issues of deforestation and fragmen-tation, the birds of the Osa Peninsula face the more subtle, omnipresent, and perhaps more dangerousthreat of climate change. Whilst far from unique to the region, changes in temperature, precipitation,and more pronounced climatic extremes are likely to have significant and pejorative - impacts on theavifauna present in the peninsula (Crick 2004).Increased temperatures are likely to result in greater energy expenditure on thermoregulation due tobirds’ endothermic nature (Wormworth and Mallon 2006). Temperature changes can also indirectly af-fect bird reproduction, timing of breeding, and migration (Wormworth and Mallon 2006). This climate-induced, temporal discordance risks shifting key bird behaviours out of synchrony with other species,

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notably those plants and insects necessary for their survival (Wormworth and Mallon 2006). Such changesmay significantly impact species’ reproductive fitness, which could ultimately result in the decimation ofbreeding populations in the long-run (Wormworth and Mallon 2006).Precipitation changes are also expected to negatively affect bird populations; periods of low or zerorainfall are correlated with decreasing bird populations, due to reduced food availability (Wormworthand Mallon 2006). Furthermore, it is believed that climate change is likely to increase extreme weatherevents such as drought or flooding (Wormworth and Mallon 2006). Extreme conditions can alter im-portant habitats and reduce the survival rates of both young and adult birds. Drought or floods incritical stopover areas along bird migration routes can impair migratory birds’ ability to reach their finaldestination (Wormworth and Mallon 2006). Altogether, the effects of climate change and bird species’response will likely be highly variable, but with a dearth of research into their plight comes a lack ofpredictability. It is therefore critical that the different bird species of the Osa Peninsula are monitoredin order to determine how they are being affected by long-term environmental changes.Overall, the wealth of diversity and endemism of avifauna in the Osa Peninsula, when coupled withthe threats of deforestation, fragmentation and climate change, highlights the need for increased qualityresearch in this location. Frontier’s primary objective is to compare species abundance and evenness be-tween disturbed, secondary, and primary forest habitats using point count surveys, whereby bird speciesare identified by sound and sight. Temple and Wiens 1989) argue that due to bird species’ sensitivity to-wards environmental changes, they are good indicators of habitat health. Monitoring such trends in birddiversity levels may help to identify species at risk of severe population decline due to human-inducedchanges, such as habitat fragmentation and loss, climate change, pollution, and the pet trade (Pejchar,Pringle, et al. 2008).

4.3.2 Materials and Methods

The present study contains some adjustments to the methodologies and study aims outlined by Fron-tier CBP’s previous study on birds in Carate. We believe that these adjustments (outlined throughoutthis proposal) allow us to focus our efforts and time on research that can have an impact on the widerscientific understanding of the species we study. The following sections describe the methodology of ournew study, along with descriptions of how and why it has changed compared to our previous methodology.

Species:

The previous methodology of studying 44 bird species has been reduced to 10 species, as it is verydifficult and impractical for short term staff members to accurately identify this quantity of calls (assis-tant research officers rarely stay longer than six months and it usually takes a year for bird experts to betrained in such a high quantity of calls, as most birds have more than one call and differences betweensounds can be very subtle). Instead, our study will assess the habitat preferences of 10 bird species inthe Osa Peninsula to contribute to scientific understanding of these species.The species were chosen because they are data deficient and very little is known about either their habitatpreference or feeding ecology. The majority (7) of these species are also endemic to the area. This is thebest way to contribute to the literature on birds in the Osa, taking into account the inherent limitationsof our project (e.g. lack of equipment and expertise to perform genetic testing, no access to mist nets,rate of turnover of staff and volunteers, etc.). A contributing factor in our choice of study species wasour ability to identify them, particularly by their calls and songs. One of the key goals of this study is toresearch the habitat of the Riverside Wren, Cantorhilus semibadius, as it is poorly described in currentscientific literature, a species we encounter frequently, and one which we can identify (both by sight andits numerous calls) with a high degree of accuracy. By studying the habitat preferences of select speciesabout which little is known, we have the potential to collect high quality data with the aim of publishingseveral papers that will advance the scientific understanding of these species and possibly form the basisof future studies.There are a number of species in the area whose ecology is very poorly understood. One such bird isthe riverside wren, about which very few studies have been published. The majority of the few exist-ing papers which concern the riverside wren are more broad studies on neotropical birds (e.g. Price etal., 2008; Skutch, 1985), and there are almost no studies which focus solely on the riverside wren, andno published research that describes its habitat preference. While this species will be a major focusof the study, we will also include nine other species: Bicolored Antbird, Gymnopithys bicolor, BairdsTrogon, Trogon bairdii, Golden Naped Woodpecker, Melanerpes chrysauchen, Black Hooded Antshrike,

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Thamnophilus brigesi, Black Cheeked Antanager, Habia atrimaxillaris, Scarlet-rumped Tanager (Cher-rie’s), Ramphocelus passerinii costaricensis, Blue Crowned Manakin, Lepidothrix coronata, Red CappedManakin, Ceratopipra mentalis, Orange- Collared Manakin, Manacus aurantiacus. These species arealso poorly described in the literature in terms of habitat preference and we think we can collect highquality data on them which will be a useful contribution to scientific understanding.

Survey Protocols

Surveys are conducted using point counts to estimate bird abundance and species richness. Pointcounts are a widely used method to assess distribution patterns and relative abundance of birds in trop-ical habitats (Bradford, Franson, et al. 1998; Sanchez-Azofeifa, Harriss, and Skole 2001; Henderson andAdams 2010). Each point count survey is conducted from a fixed place, and target species are noted bysight and/or call for a fixed period of time (C.J. 1999; Gibbons, Donald, et al. 2007; Greene and Pryde2012). The methodology is straightforward and enables observers to gather the required data by simplywalking a trail and stopping at designated points to record target bird species. All birds seen and heardare noted down with their respective detection mode (seen: S; heard: H), and grouped into one of threedistance bands (010 m, 1030 m and > 30 m) (figure 14). Recording time is 15 mins and is preceded by a3 min settling period to allow the birds to settle after any disturbance caused by walking to the points.Point counts are conducted on seventeen of our trails (table 7), each point located at 200 m intervalsalong the trail (unless a trail is shorter than 200 m long, in which case one point count will take place100 m in from the trail). There is a total of 57 locations for point count surveys, a high enough numberfor accurate data analysis to be conducted and to ensure sufficient habitat variation across points. Birdsurveys will take place at three different times throughout the day: to coincide with the dawn chorus,9:00 and 14:00. We conduct our surveys at least twice, ideally thrice, a week, visiting one point per sur-vey. The points will be assigned a number and a random number generator will be used at the beginningof each week to determine what points will be used that coming week.This methodology differs from our previous survey methodology in several ways. First, we used to onlyconduct surveys with the dawn chorus, but this does not give us any information on patterns of bird ac-tivity throughout the day. Second, we used to conduct three point counts per survey rather than one. Wefind two flaws with this methodology: 1) each point count would be conducted at a different time (someat the dawn chorus, some after), which would leave us unaware as to whether the presence of a particularspecies was due to its location or the amount of time that has passed since the dawn chorus. 2) We wouldonly cover three bird points on every trail, which only allows us to study a small fraction of each habi-tat. Our new study method allows us to conduct surveys at a higher quantity of points along longer trails.

Figure 14: A diagram visually depicting how bird calls will be categorized into bands based onthe distance of the bird, which was estimated by sight or sound (image not to scale).

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Table 7: The name of each trail being used, along with the trail length and number of pointcounts that will be conducted on each trail.

Analysis

Data will be analysed in terms of presence and absence, thus answering the question; are certainspecies more likely to be present in one particular type of habitat? A generalized linear regression witha binomial error structure will be calculated to answer this question. All analysis will be carried outusing RStudio version 1.1.463 (R Core Team 2018) and Microsoft Excel. Analysis will be carried outseparately for each bird species.

4.3.3 Results and Discussion

Between 1st June 2018 and 3rd December 2018, 40 bird point counts have been conducted. In this timeperiod the following has been heard or seen: 16 riverside wrens, 15 black-hooded antshrikes, 1 bicoloredantbird, 3 golden naped woodpeckers, and 3 blue-crowned manakins. Because data collection for thisstudy has only recently commenced, there is not enough data for further analysis.

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4.4 Temporal and Spatial Variations in the Abundance of Amphibians andReptiles

4.4.1 Introduction

Amphibians and reptiles play vital parts in the world’s food chain and life cycle. Amphibians are cur-rently one of the most threatened vertebrate groups on the planet (Puschendorf, Carnaval, et al. 2009),with over 43% of species facing population decline (Folt and Reider 2013). Reptiles, although being un-derstudied (only 35% of described species have been evaluated by the IUCN), are believed by some to befacing a similar decline in terms of taxonomic breadth and geographic scope (Bhm, Collen, et al. 2013).Despite the global biodiversity crisis these animals are facing and their extreme ecological importancewithin tropical ecosystems, very little is known about what is causing these severe declines (Collins andStorfer 2003; Whitfield, Bell, et al. 2007). It is believed that herpetofauna, due to their very specifichabitat requirements and narrow distribution ranges, are especially at risk from anthropogenic distur-bance and habitat fragmentation (Whitfield, Bell, et al. 2007; Bell and Donnelly 2006; Bhm, Collen, et al.2013). However, decreases in amphibian populations have also been witnessed in apparently undisturbedhabitats which seemingly lack any harmful human activity (Puschendorf, Carnaval, et al. 2009).On a smaller scale, Central America is known to be one of the most biologically diverse hotspots foramphibians, inhabiting 6.8% of the world’s species in 0.36% of total land area (Myers, Mittermeier, et al.2000). Unfortunately, it has also witnessed one of the most drastic declines in amphibian populationsand overall mass mortality events than any other world region (Whitfield, Lips, and Donnelly 2016).Costa Rica became at the forefront of mass amphibian decline events when researchers recorded theextinction of the nationally treasured Golden Toad in the late 1980s, as well as massive reductions inspecies numbers throughout the 1990s and 2000s (Lips 1998). Despite such setbacks, Costa Rica is knownfor having high levels of anuran diversity and endemism. The Golfo Dulcean lowlands of the southwestcontain the highest amphibian species richness, with 53 single-country endemics (Whitfield, Lips, andDonnelly 2016). While there are numerous studies (Whitfield, Bell, et al. 2007; Lips 1998; Mendenhall,Frishkoff, et al. 2014) on the status of Costa Rica’s amphibian and reptile species, very rarely are theGolfo Dulcean lowlands or the Osa Peninsula used as a study area.Reptiles and amphibians play a major role in supporting Costa Rica’s highly biologically diverse ecosys-tem, therefore it is crucial to understand what the principal causes are behind their biodiversity loss.Amphibians and reptiles are integral parts of the food chain as both predators and prey, and amphibiansin particular act as indicators of the health of terrestrial and freshwater habitats (Bell and Donnelly 2006;Bhm, Collen, et al. 2013). Because of their ecological importance, continued declines in herpetofaunapopulation numbers could have negative consequences for a variety of species at an ecosystem-wide level.However, it can be especially difficult to analyse changes in amphibian populations as these tend tofluctuate greatly on an annual basis due to variations in rainfall, temperature, and other environmentalfactors that influences their behaviour and physiology (Collins and Storfer 2003).The study that we are undertaking attempts to catalogue species abundance of amphibian and reptilesthroughout the seasons and in particular forested areas. Only once we have collected a sufficiently largedatabase can we investigate the causes of population decline, if in fact there are any, and the extent towhich certain factors play a role. Our investigation is twofold with one already underway and reportedin previous science reports and a current one presented for the first time here.The aim of the first part of the study is to analyse the abundance of the two taxa across the year. Herewe hope to track peaks and drops in animal numbers and be able to identify the causes of each. Thisis deemed important as it will help dramatically in mapping any climatic shifts throughout the years.The second part of the investigation aims to look at the abundance of taxa in a variety of different foresttypes: primary, secondary and disturbed. By doing this we are able to see how and whether particularspecies prosper in other environments and not in others, and whether they are able to adapt to shifts inhabitat or not. It is important to note that our data regarding forest type is not completely watertightas of yet, and as a result we have not included any definite description of each trail in this paper, justa general description. This data deficiency is being dealt with in our habitat study which should befinished by the next science report and then promptly integrated into this research.

4.4.2 Methodology

Survey Area Surveys were carried out on eleven different trails: Attalea Loop, Camp Trail, Catappa,Laguna Vista, Leona, Los Aves, Luna, Puma Creek, Road Shady Trail, and Waterfall. Visual encountersurveys (VES) were used, as this is the most efficient and one of the most widely used methods for

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surveying tropical herpetofauna (Doan 2003; Laurencio and Malone 2009; Folt and Reider 2013; Doanand Ariaga 1998).Costa Rica has two seasons: the dry (verano) and the wet (inverno). The driest months of the year in theOsa Peninsula are January, February and March, with the wetter ones being May through to November,with September and October generally being the wettest months of the year. Temperatures are alwayshigh: the hottest month tending to be March where temperatures can reach mid-thirties; the coolerones October and November where they hover just over 30. On average, March is the sunniest time ofthe year; while June experiences the least sunshine. Figures 15a, 15b and 15c depict the temperature,precipitation and sunshine hours of the Osa Peninsula.

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Figure 15: A) Average minimum and maximum temperatures in Puntaneras, the Costa RicanProvince where our study takes place. B)Average precipitation rates in Puntaneras, the CostaRican Province where our study takes place. C) Average minimum and maximum monthly sunhours in Puntaneras, the Costa Rican Province where our study takes place. These graphs weretaken from www.weather-and-climate.com.

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Survey Protocols

Surveys began from 19:00 onwards and consisted of 30 minutes total search time, with the timerpaused at each amphibian or reptile sighting for data recording. At least two individuals participatedon each survey; half of the surveyors took the left side of the trail to search for amphibians and reptiles,while the other half looked to the right. All surveyors walked slowly to avoid disturbance, scanning fromthe ground to eye level and then to tree tops for any herpetofauna. Upon encounter, the following datawas recorded: species; substrate found on; adult or juvenile; sex; and height above ground level the spec-imen was found on. Any animal that could not be identified in the field was photographed and identifiedusing field manuals on camp following the survey. Since the last report, the data collection methodologyhas been corrected to include the name of the survey leader, the number of people involved in eachsurvey, the initial and end weather as well as initial and end temperature and humidity readings. Thelatter three categories are incredibly pertinent to our investigation of the effect of changing seasons forthe following reasons: firstly, in identifying the seasonal preferences of each taxa and individual species;and secondly in confirming that higher temperatures and lower humidity rates are changing habitats, orindeed, diminishing numbers.

Analysis

For this study amphibians and reptiles were analysed separately, as their ecology, physiology, be-haviour and habitat preference are sensibly different. For the amphibians taxa we considered only Anuraspecies (frogs and toads). For reptiles we considered only Squamata species (snakes and lizards). Themean encounter rate (i.e. number of encounters per survey), species richness, and Simpsons diversityindex were calculated for each of the trails and each taxa (amphibians and reptiles separated). Speciesrichness was measured by the number of different species found within a survey. A Simpsons diversityindex is a method of calculating species diversity that takes into account both the number of speciespresent and the relative abundance of each species (Morris, Caruso, et al. 2014). It is calculated usingthe formula D = Σ(n/N)2, where n is the number of individual species found, N is the total number ofall encounters, and D represents a diversity index. D can take any value between 0 and 1, where zerorepresents lower levels of diversity and 1 represents complete diversity (there is an equal number of allspecies detected). These values were taken across all surveys of a particular forest or group and used forstatistical analysis. All data analysis was completed using Microsoft Excel.

4.4.3 Results

Over the study period a total of 529 amphibians were sited, and a total of 456 reptiles were (397 lizardsand 59 snake sightings respectively). Figure 16 illustrates the number of the anuran taxa sightings, whereCraugastor fitzingeri at 215 sightings was the most common anuran species; followed by Leptodactylussavage at 92 and Rhinella marina at 41.

As regards to reptiles, the anole Norops polylepsis were the most frequently spotted reptile, accountingfor more than half of all encounters at 252 (figure 16). Iguana iguana and Basiliscus basiliscus werethe second and third most frequently sighted reptile at 53 and 50 respectively. A total of 19 individualspecies were encountered.

As the majority of reptilian sightings are lizards (figure 17), figure 18 demonstrates the breakdownof snake encounters. As can be seen in this chart, only seven species of snake were encountered over thecourse of two and a half years from June 2016 to December 2018. Leptodeira septentrionalis was seenthe most by far, with 40 sightings, followed by Imantodes cenchoa at 13. The other species displayedwere seen once, apart from Bothrops asper which was encountered twice.

Encounter rates per month

Figure 19 displays the abundance of amphibians throughout the year, broken down by month. Marchhad the highest number of anuran sightings, with just over eight encounters per survey, whereas themonths with the fewest encounters were January, May, October and December.The values fluctuate quite distinctly over the year: the first part of the graph, from December throughto May, experiences a rapid and steep peak with a 6.5 difference in sightings per survey. The secondpoint is reached in August after a climb of 3.6 from almost two sightings per survey to 5.7. After that,in the final three months of the year, there are sightings ranging from 1.7 to 2.7.

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Figure 16: A bar chart displaying the anuran species sighted throughout the survey period andthe relative frequency of each species seen

Figure 17: A bar chart displaying the reptilian species sighted throughout the survey periodand the relative frequency of each species seen.

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Figure 18: A bar chart displaying the snake species sighted throughout the survey period andthe relative frequency of each species seen.

Figure 19: Average amphibian sightings on each survey per month.

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Figure 20: Average reptile sightings on each survey per month

Figure 20 displays the average number of reptile sightings: reptiles showed a different pattern fromamphibians with the peak occurring during October with 6.2 average reptile sightings- a period in whichthe presence of anuran is relatively low. November and December experienced the lowest number ofsightings at 1.8 and 1.5 respectively. Reptile encounters did not fluctuate as much as amphibian sight-ings.

Encounter rate per trail

For this part of the study, the individual taxa were sorted into separate trails which is useful for ourinvestigation into the abundance of amphibian and reptiles in different forest types. Encounter rate isdefined as the average number of sightings per survey. Figure 21 shows the average encounter rate acrossall surveys was where 2.2 was the average for amphibians and 1.8 for reptiles. Catappa had the highestoverall amphibian encounters at 6, followed closely by Puma at 5.8. In addition, Puma was the trail inwhich more reptiles were sighted (5.4), followed by Attalea (4.2). The trails with least sightings wereLaguna Vista, Leona, Los Aves and Luna; Laguna Vista and Los Aves showed an average of 0 sightingsfor amphibians, whereas Los Aves was the only one where the average was 0. It is important to note,however, that the number of times we have frequented the trails differs considerably and thus affects theresults. This discrepancy will be seen to in future months.

A Simpsons diversity index was also calculated for each of the trails and found that Shady (0.85),then Waterfall (0.79), were the most diverse locations for amphibians. Reptiles, on the other hand, weremore diverse on Catappa (0.65) and Leona (0.63). Table 8 illustrates the Simpson Diversity indices foramphibians and reptiles across trails.

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Figure 21: Average abundance of taxa per trail.

Table 8: Simpsons Diversity index for Amphibians and Reptiles on different trails.

4.4.4 Discussion

The most notable data collected is the difference in abundance between the two taxa; amphibians andreptiles. The results clearly show a temporal variation in the presence of species - one occurring morefrequently during the dry season (amphibians) and one more frequently during the wet (reptiles). Thepeak for amphibians is in the hottest, driest and sunniest month of the year; whereas reptiles are moreabundant during the wettest month of the year. The results, therefore, seem to illustrate the fact thatstandard weather variables such as temperature, humidity, precipitation, sunlight, moonlight, and atmo-spheric pressure, which are all linked to the seasons, play a part in the abundance of anura and squamatain Carate.

Amphibians

Amphibians were most frequently encountered during the driest months of the year. Encounter ratesin amphibians can be associated with reproductive seasonality, food availability, hibernation and mating(Brown and Shine 2002). One hypothesis for the result relates seasonal fluctuations in water availability.In drier seasons bodies of water become smaller and more scarce. During this time period, amphibiansare compelled to congregate in the few sites where water is present, causing them to ’cluster’ and, as aresult, become more easily spotted (Watling and Donnelly 2002). Therefore, our results do not neces-sarily represent a growth in population size but a decrease in preferred habitat.Another theory that has been discussed in previous literature, is that a spike in amphibian abundance

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during the dry season is linked to reproduction. Reproduction is linked to prey abundance (for themost part arthropods), which is often highest during the dry season. Therefore, many amphibians’species mate during the rainy season so that juveniles are born in the dry season during months of peakarthropod abundance (Watling and Donnelly 2002). They are able to do this even in circumstances ofdiminished rainfall, and one way to adapt to shallow ponds with high temperatures and low dissolvedoxygen is foam nests which itself supplies the oxygen needed for the eggs (Arzabe 1999). This methodof conserving juveniles is seen here near the Corcovado National Park when the land dries up and thewater bodies shrink. The increased amphibian encounters in dryer months found in the presents studycould therefore be due to the increased presence of juveniles.Further data collection is needed to fully understand the temporal variations in amphibian encountersfound in our study. However, based on previous studies by others, possible explanations are the ’clus-tering’ of animals near scarce water supplies and the growth of juveniles to correlate with the highabundance of arthropods during the dry season. Or even, a mix of the two.

Reptiles

In contrast to amphibians, reptiles were encountered most frequently during the wetter months ofthe year. This taxa is particularly linked with their environments thanks to specific regulatory charac-teristics such as abiotic (temperature and humidity for example) and biotic (competition and predation)features (Brown and Shine 2006). Reptiles warm their bodies via the environment - sun to heat; andsubsurface sites to either insulate from the cold or to cool down. One would expect therefore, not to seea particularly high abundance during the summer months as the sunlight could risk desiccation. Thebalance between needing the sun to warm the bodies and avoiding desiccation results in a relativelymoderate abundance level towards the beginning of the year, however this changes towards the end.An explanation as to why there is such a peak during October, Osas rainiest month of the year, is thatexcessive rains force animals (especially snakes) out of their underground nests to avoid drowning in theirflooded nesting sites (Delia, Ramirez-Bautista, and Summers 2013), and therefore can be more easilyspotted.Studies have found that most reptilian species breed in periods of high precipitation (Brown and Shine2006) which in Carate is towards the end of the year. A moist environment is incredibly important in thebreeding process as they better sustain embryogenesis. Wetter nests produce larger hatchlings which areconsequently more likely to survive (snakes reproduce seasonally). However, there is danger in excess,and too heavy a rain will result in the nests becoming completely waterlogged and destroying the chancesof survival. The link between precipitation and abundance seems to be greater than temperature andabundance as the temperature in tropical climates is relatively stable compared to the highly fluctuatingprecipitation rates.

Encounter rates per trail

AmphibiansAmphibians showed the highest average encounter rate on Catappa followed by Puma. Both trails con-tain water supplies which are both fast-flowing during the rainy season. Road, which had the next highestabundance, accumulates stagnant water in the ditches in the wet months which attracts breeding popu-lations (Curado, Hartel, and Arntzen 2011). Attalea, which had the fourth highest abundance, is near tothe lagoon. A surprising result in the data is that Leona, which in the previous reports was reported asshowing the highest average encounter rate of all, came back with a Simpson’s diversity index of zero. Infurther inspection, this is due to the fact that the vast majority of amphibians spotted on this trail weregreen and black poison dart frogs (Dendrobates auratus). This shows that the high encounter rate onthis trail is largely attributed to one species, resulting in a low diversity index. This is not to say howeverthat there is not a high abundance of other species; very few surveys have been conducted after 19:00on Leona, so many nocturnal amphibian species were not accurately represented in our data collection.Nevertheless, the fact that Leona trail is at a high elevation and very far from any significant body ofwater should be considered in future analysis. A zero sighting on Los Aves may at first seem surprisingas it contains a body of water good for breeding, however this could be because very few surveys havebeen conducted on this transect, as it was only recently added to our study. Furthermore, surveys onthis trail did not commence until the end of the year when, as our other investigation into temporalvariation shows, encounter rates with amphibians are at their lowest. We therefore conclude that someof our low trail encounters are expected to have more to do with deficient data rather than a scientific

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reasoning.Shady had the highest reptile diversity. This is unexpected as this trail is furthest away from a watersource, yet one explanation could be that Shady is one of a larger network of trails that covers an exten-sive forested area including Luna which also has a high diversity index. Previous literature has foundthat habitat fragmentation can be damaging to amphibian populations, as isolated habitats limit juve-nile dispersal (Cushman 2006). The high habitat connectivity of Shady and Luna trails could thereforecontribute to the increased diversity of amphibians encountered here.

ReptilesReptiles were found to have the highest encounter rate on Puma, Attalea, Catappa and Road respec-tively. The majority of all sightings, as can be seen by figure 17, were Norops polylepsis,Iguana Iguanaand Basiliscus basiliscus. Previous studies have found that specialist species are more sensitive to hu-man disturbances in landscape than generalist species (Devictor, Julliard, and Jiguet 2008), and thusgeneralist species tend to be more abundant in disturbed environments close to roads and open areas.All the aforementioned species are generalist, and two out of the four most abundant trails for reptilesare disturbed.As regards to diversity, most of the trails exhibit more or less a diversity index of around 0.5 apart fromLos Aves and Road. The latter has diminished since the last report when we incorporated day sightingsinto the database, which leads to the question of whether particular species use the trail diurnally ratherthan nocturnally. The only reptile species encountered on Los Aves was Norpos polylepsis, which wasin general the most common reptile species spotted during our study. The fact that the trail is mostlyundisturbed and close to a body of water should predict a higher rate of abundance, but further datacollection on this trail is needed to test this hypothesis.

4.4.5 Conclusion

In conclusion, we can see that there is a difference in abundance rates across the seasons: amphibiannumbers peak during the dry season; whereas reptile encounters spike during the wet. Possible explana-tions regarding amphibian activity are 1) that the individuals congregate near scarce water bodies andare therefore easier to spot in these sites 2) that breeding coincides with abundance of prey (arthropodsfor the most part) which occurs during the dry season. Reasons for a higher abundance of reptiles in therainy season are both dependent on rainfall: 1) that due to hard rains, reptiles are forced out of theirnests to avoid drowning and seek dry sites to stay until the rain abates. This increases the likelihood ofhuman encounters as humans are relatively adept at creating dry sites. 2) The successful breeding of rep-tiles depends upon moist, damp, wet earth to optimize embryonic development too much rain however,results in water-logged nests and higher mortality rates. These two reptile hypotheses, however, appearto be unable to coexist for if there is too much rain, situation A occurs; if moderate but not excessive rainoccurs, situation B happens. It would be pertinent, therefore, to conduct further investigation into bothtaxa’s seasonal abundances and behaviors. All surveys in the future need to report the temperature,humidity, precipitation, sunshine and moonshine so that a reliable and thorough analysis can be made.As regards to abundance per trail, a major point that needs to be rectified is the unequal number ofsurveys done on each trail. This problem creates skewed results and incorrect analysis, so it is vitalthat readers understand that the results displayed here are those in progress and that our studies willcontinue in the future, hopefully giving a more faithful presentation of the facts as they are. The presentconclusions to be drawn are that trails with water bodies present attract the presence of amphibians;whereas reptiles are seen more often on frequently used trails. Explanation for the former result is linkedto breeding possibilities, and that for the second is ease of sighting.

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4.5 Sea Turtle Predation and Hatching Success Study along Playa Carate

4.5.1 Introduction

Sea turtles are a fundamental part of both marine and terrestrial ecosystems. They maintain the healthof sea grass beds, which are important breeding grounds for a variety of marine fauna (Lutz, Musick, andWyneken 2002; Thayer, Bjorndal, et al. 1984), and the nutrients in eggs laid on the beach promote soilfertility in coastal habitats (“Sea turtles as biological transporters of nutrients and energy from marine toterrestrial ecosystems”). While sea turtles are a highly adaptive species and have historically withstoodlarge environmental changes (Honarvar, OConnor, and Spotilla 2008), recent increases in anthropogenicinterferences have taken a great toll on sea turtle populations worldwide. Sea turtles face a range ofhuman-induced threats, including poaching, climate change, pollution, beach development, and artificiallighting. These threats negatively impact their growth and reproduction, and thus threaten their overallsurvival (Honarvar, OConnor, and Spotilla 2008; Fuentes, Limpus, and Haman 2011; Tripathy andRajasekhar 2009; Dudley and Porter 2014; Camacho, Luzardo, and Ors 2017). Worldwide, all sevensea turtle species are listed as Endangered, Vulnerable or Data deficient (IUCN 2017). As a migratoryspecies, changes in sea turtle populations have the potential to affect marine ecosystems on a global scale(Heithaus, Alcoverro, et al. 2014). Green turtles help to mitigate against the impacts of eutrophicationto sea grass beds due to the nutrients they uptake while grazing. It is therefore important that sea turtlepopulations are restored to historic levels to ensure healthy seagrass ecosystems against subsequenthypoxia (Jackson, Rowden, et al. 2001).One of the greatest threats facing sea turtle population’s world-wide is climate change. Rising sea levelsencroach on shorelines where turtles lay their eggs, thus limiting the amount of space that a mother turtlehas to lay her eggs a safe distance from the high tide line (Fish, Cote, et al. 2005). As a result, turtles arenesting in locations with a high risk of tide inundation, which exposes eggs to predation and unfavourableweather conditions (Burger and Gochfeld 2014). Rising temperatures affect sea turtles as well, as the sexof a hatchling is temperature-dependent (“High pivotal temperature in the sex determination of the oliveridley sea turtle, Lepidochelys olivacea, from Playa Nancite Costa Rica”). As temperatures rise, there isan increasing female-bias in the sex of sea turtles, creating an uneven balance of genders and thereforemaking it more difficult for female turtles to find a mate (Hawkes, Broderick, et al. 2007; Valverde,Wingard, et al. 2010). Increasing sand temperatures can also negatively impact the development andhatching success rate of a nest, and in extreme cases can lead to egg mortality (“Turtle hatching successas a function of the microbial abundance in nest sand at Ostional, Costa Rica”; Wood, Booth, andLimpus 2014; Lalo, Cozens, et al. 2017; Santos, Livesey, et al. 2017; Howard, Bell, and Pike 2014; Pike2014).In addition to climate change induced-threats, poaching and predation have a major negative impact onturtle populations. In Central America, many communities permit their domesticated dogs and cats torun free in coastal villages. This is a problem, as dogs will often dig up turtle nests and attack nestingfemales (Fowler 1979; RuizIzaguirre, Woersem, et al. 2015). Even when dogs only partially dig up aturtle nest, they expose the turtle eggs to further threats from other predators, such as vultures (Burgerand Gochfeld 2014).Poaching and the illegal trade of eggs, hatchlings and turtles have further reduced turtle populations inCosta Rica (Tomillo, Saba, et al. 2008; Chacn-Chaverri and Eckert 2007). As an example, in ParqueNacional Marino las Baulas, leatherback turtle nesting populations declined from 1,500 nesting seaturtles per year to around 100 (Tomillo, Saba, et al. 2008). A number of conservation strategies havebeen established in Costa Rica to reduce the negative impact of poaching on turtle populations. The Fish& Maritimes Law of 1948 prohibits the commercial capture and sale of marine turtles and eggs and thedestruction of turtle nests. The Promotion of Agricultural Production Law states that in Ostional duringthe arribadas (mass turtle nesting event) eggs are able to be commercially harvested, but restrictionsare in place to minimize the negative impact this could have on turtle populations (Campbell, 1998).Additionally, the growing ecotourism industry in Costa Rica, as well as increased funds being allocatedto turtle research and conservation projects, have provided locals with an alternative source of incomeand have promoted conservation throughout the country (Fennell and Eagles 1990; Chacn-Chaverri andEckert 2007). As an example, Frontier has trained local gold miners to help conduct beach patrols andrun the turtle hatchery on our research site in Carate, Osa Paninsula. To evaluate the effectiveness ofsuch strategies, it is imperative that monitoring programmes are long term as it can take decades forspecies with late maturity to show a population response (“Twenty Six Years of Green Turtle Nestingat Tortuguero, Costa Rica: An Encouraging Trend”; Trong and Rankin 2005).Costa Rica is an important nesting area for four sea turtle species: green turtles (Chelonia mydas),

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hawksbills (Eretmochelys imbricata), olive ridleys (Lepidochelys olivacea) and leatherbacks (Dermochelyscoriacea) (“Marine turtle nesting, nest predation, hatch frequency and nesting seasonality on the OsaPeninsula, Costa Rica”). All four species have been recorded nesting at our research site on the OsaPeninsula, on the southern Pacific slope of Costa Rica. The olive ridley is the most commonly foundsea turtle nesting on Playa Carate beach, while the green, and to an even greater extent the hawksbillsand leatherbacks, only nest here rarely (Trong and Rankin 2005; Honarvar, OConnor, and Spotilla 2008;IUCN 2013). Under the IUCN list, hawksbill and leatherback turtles are listed as Critically Endangered,Pacific green turtles as Endangered, and olive ridleys as Vulnerable (IUCN 2013). On the Osa Peninsula,turtles are threatened primarily by predation by dogs, coastal development, and the illegal trade of eggs(“Marine turtle nesting, nest predation, hatch frequency and nesting seasonality on the Osa Peninsula,Costa Rica”). The primary aim of this project is to monitor the frequency of predation and the healthof the nesting turtle populations on Playa Carate beach.There is currently a shortage of studies focusing on the effects of climate change on sea turtle populations(Rees, Alfaro-Shigueto, et al. 2016). Frontier is in the unique situation of running a continuous and on-going project, providing the perfect opportunity to collect baseline data for a long-term study on theimpact of climate change on marine biodiversity. A second project aim is therefore to monitor theongoing effects of rising sea levels and temperatures on the health of turtle populations on Playa Caratebeach.

4.5.2 Materials and Methods

Species

This study focused on the two most common sea turtle species present in this area: the Pacific greenturtle (Chelonia mydas) and the olive ridley sea turtle (Lepidochelys olivacea). The Pacific green turtlehas a circumglobal distribution, occurring in tropical and subtropical waters. They are migratory speciesand undertake complex movements and migrations through geographically different habitats. Nestingtakes place in more than 80 countries worldwide (Hirth 1980). Their movements within the marine envi-ronment are less understood, but it is believed that they inhabit the coastal water of over 140 countries(Groombridge and Luxmoore 1989). The olive ridley sea turtle has a circumtropical distribution, withnesting occurring in tropical waters and migratory circuits occurring in tropical and subtropical areas.They nest along the beaches of nearly 60 different countries (Pritchard and Plotkin 1973).

Survey Protocol

Surveys are carried out on Playa Carate beach in both the early morning and night. The survey areaencompassed a 2.6 km stretch on Playa Carate, with labelled posts splitting the beach into numberedsectors every 25 m. Morning patrols began at 5:00 am or earlier (depending on the tides) to minimisesurveyor exposure to direct sunlight and high temperatures. Night patrols took place when the tide wasmid-level (in between high and low tide) anytime between 19:00 and 23:00, ideally when the tide wasdropping from mid-tide to low tide to avoid the risk of high tides inhibiting the survey effort. To minimisethe disturbance to nesting females, survey teams were limited to six people and only red lights were usedduring night patrols. Gloves were always worn when directly touching the turtle to prevent diseases orharmful substances being transferred from peoples hands to the turtles and vice versa. To reduce the useof one-use plastic, we have started using reusable plastic gloves. In order to avoid cross-contamination,all gloves were washed thoroughly with biodegradable disinfectant before each subsequent use.

Night Patrols

For every turtle track encountered, the following data was collected during night patrols:

• Patrol date.

• Name of the patrol leader.

• The time the track was encountered.

• Beach sector number, always taking the lowest number (e.g. if observers are in between sector 11and 11.25, they will write down sector 11).

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• Location of nest on the beach: either zone 1 (tidal inundation zone), zone 2 (beach area, still withinreach of the high tide) or zone 3 (vegetation area, safely away from the high tide).

• Sea turtle species: olive ridley turtle or Pacific green turtle, determined either by sight of the turtleor by the size and symmetry of the tracks (small asymmetrical tracks indicate an olive ridley andlarge symmetrical tracks indicate a green turtle). If a hawksbill or leatherback turtle was sightedin person, this was identified as well.

• Whether a nest was present or whether it was a false crawl (when the turtle returned to the seawithout attempting to nest) or false nest (when the turtle attempted to dig but did not lay anyeggs).

• Whether or not a bamboo nest cover was placed on the nest.

• GPS coordinates of the nest.

• Distance from the nest to the vegetation line, estimated to the nearest meter.

When possible, nests were covered with a mesh bamboo nest cover to prevent dogs and other predatorsfrom digging up the nest (see figure 22). Bamboo nest covers were built at the hatchery by frontier staffand volunteers, as well as local community members and volunteers of partnering organizations. Coverswere constructed using fourteen 1 meter bamboo sticks, woven together and secured at the ends withhessian twine to create a 7x7 mesh cage. These cages were placed at every whole numbered sector alongPlaya Carate to be put on any nest when possible, with a priority to nests that had been partiallypredated or when predators were nearby. Whether or not the nest was covered with a bamboo coverwas also recorded in the data. If a nest cover was not available, logs were placed on top of a nest in acriss-cross fashion (to mimic the bamboo cover design) as an alternative method of preventing predation.

Figure 22: A) Image of a bamboo nest cover. B) A bamboo nest cover placed on top of a turtlenest, with the edges of the nest buried in sand and sticks dug into the corners of the cover tostabilize it and prevent dogs from moving it to dig up a nest. The small wooden block tied tothe stick in the right hand corner indicates the nest number.

If we came across a turtle while she was emerging from the sea, searching for a location to lay, ordigging up a nest, we waited quietly at the bottom of the beach so as not to disturb her. We only

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approached a turtle when we were sure that she had started laying her eggs, during which she goes intoa ’nesting trance’ and does not notice or change her behaviour in response to human activity (Dutton1996).When approaching the turtle, all surveyors were extremely quiet and interacted with the turtle asminimally as possible. If a turtle was found laying eggs, we collected the following additional data:

• The size of her shell (width and length).

• If she has any damage on her shell (scars or barnacles).

• If she has a tag, and if so, what number it is.

After writing down the data, the track was crossed out by drawing a line in the sand to avoid thetrack being recorded again in subsequent patrols. The exact location of the nest was then confirmed byinserting a stick into the sand to locate the egg chamber (indicated by a marked change in resistancewhen pressure was applied). A ”false crawl” was identified when it was clear that the turtle returned tosea without digging a nest. A nest was identified as a ”false nest” if was clear the turtle had dug but noeggs were laid, and the nest had no evidence of covering (Eckert, Bjorndal, et al. 1999). Because eggscan be difficult to find even by experienced staff members, if there was ever any doubt regarding thepresence of eggs we took a conservative approach and assumed that eggs were present and covered andmarked the nest accordingly. Every nest found was given an identification number, which was writtenon a small piece of bamboo tied to a sturdy stick that was placed sticking up one meter behind the nest,or on the right upper hand corner of the bamboo nest cover (figure 22). If the nest was identified asneeding relocating and the turtle was in the process of laying, a tape measure would be placed into thenest chamber, so the eggs could be easily found once covered back up by the turtle.Nests were only relocated if they were laid in an area of the beach we identify as extremely dangerous,meaning we believe the benefits of relocating the nest to a more secure location are worth the inherentrisks of relocating a nest. These dangerous locations include:

1. Nests in zone 1 or zone 2. This is because high tides frequently wash away the sand coveringany nests located in zones 1 and 2, making them more exposed and vulnerable to predation andextreme heat (Burger and Gochfeld 2014)

2. Nests located in areas where local dogs are more abundant (outside the lodges for example)

3. Nests located near a river or cliff edge, as these regions are particularly prone to sand erosion andthus increased risk of a nest being washed away.

Nests located near the lagoon on the east side of Playa Carate, as in the wet season the lagoon oftenopens up into the ocean, leading to nest damage or exposure.In order to relocate a nest, the eggs were first dug up and carefully placed one by one into a plasticbag-lined bucket. The depth and width of the nest chamber were noted so that the hole dug in therelocation location would mimic the natural hole dug by the mother turtle. For every relocation, werecorded the number of relocated eggs, what time the original nest was dug up, and what time the nestwas relocated to a new area. Nests were either relocated to a safe location on the beach or to the hatchery.Relocations only took place on night turtle surveys to ensure that eggs were moved shortly after beinglaid, thus reducing the potential damage done to eggs during relocation (Limpus, Baker, and Miller 1979).

Morning Patrols

During morning patrols, the beach was scanned for adult turtle tracks, hatchling tracks, and predatednests. If adult turtle tracks were found, the same procedure was followed for tracks encountered on nightsurveys as described above.Predated nests were identified based on the presence of animal prints, signs of digging (soft, recentlydisturbed sand around the nest), and the presence of broken or shredded egg shells around the nest.Hatched nests were identified by the presence of hatchlings or a large number of hatchling tracks. Ifonly a few hatchlings or hatchling tracks were present, the nest would be left for 48 hours, ensuringall hatchlings have been given a chance to emerge naturally. When a predated or hatched nest wasencountered, it was excavated. This process involved digging up the nest and recording the followinginformation:

• Patrol date.

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• Name of patrol leader.

• Time the nest was encountered.

• Beach sector number, always taking the lowest number.

• Location of the nest on the beach: zone 1, zone 2, or zone 3

• Sea turtle species: olive ridley turtle or Pacific green turtle. If tracks were present, identificationwould be based on the size and symmetry of the tracks. If hatchlings were present, the species couldbe identified by the hatchlings. If no tracks or hatchlings were present, the species was recorded as”unknown”.

• ”Nest type”, indicating whether a nest was hatched, fully predated, semi-predated or a falsecrawl/false nest.

• Number of predated eggs.

• Number of hatched eggs.

• Number of live hatchlings.

• Number of dead hatchlings.

• Number of unhatched eggs and their stage of development (recorded only in the case of a hatchednest, not a predated nest).

• Presence of animal tracks, if possible, identifying the predator based on the tracks.

• Whether or not the nest was covered with a bamboo nest cover.

• Depth of the nest.

• Presence of fungus, bacteria, or overheating in unhatched eggs.

Predation

Only freshly predated nests were recorded, as animals would often dig up previously predated orhatched nests for which data had already been collected. Freshly predated nests were identified based onthe shape and colour of the egg shells, as newly predated eggs were still soft and white, while old eggswere drier and had a yellow tint. If a new predated nest was found, the pieces of egg were put togetherto determine the number of eggs that were predated. If more than 50% of the shell was intact, it wascounted as one whole egg. Any smaller fragments were pieced together to make up an entire shell. Ifthe nest was only partially predated and some remaining intact eggs were found in the chamber, thepredated eggs were counted and the whole eggs were left in the nest to be reburied. In these scenarios,any eggs and pieces of shell that were predated on were reburied at a different location in the sand toavoid predators smelling the open eggs and re-digging up the nest. When possible, a bamboo nest coverwas then placed on the nest to prevent further predation.

Hatched Nests

Hatched nests were identified by the presence of hatchling tracks and a small crater in the sand atthe sight of the nest, caused by soft sand collapsing into the nest when the eggs hatched. After a nestwas identified as hatched, and additional 48 hours was waited before excavating a nest to ensure it wasfully hatched before digging it up. To excavate a nest, gloves were used to gently dig until egg shellswere found. The egg shells were then carefully scooped out of the nest and counted to determine thenumber of hatched eggs. As with the predated nests, if more than 50% of the shell was intact it wascounted as one whole egg, while smaller fragments were pieced together to make up an entire shell. Anyun-hatched eggs and dead hatchlings were placed to the side and counted separately.If either a live hatchling or a large number of unhatched eggs (> 10) were found in the nest, we re-coveredthe nest and waited for another 24 hours to give the hatchlings a chance to hatch and emerge naturally.If less than 10 unhatched eggs were present, or if the unhatched eggs were still present after waitingthe additional 24 hours, they were broken open to determine their stage of development. Five differentstages of egg development in unhatched eggs were recorded. These were:

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• No visible embryo: only an egg yolk can be seen; it somewhat resembles the inside of a chickenegg.

• Stage One: you can see signs of an embryo but it is just a tiny white dot within the embryonicsack.

• Stage Two: A small hatchling has begun to develop which may be either white or just starting toturn black.

• Stage Three: The hatchling has begun to visibly take shape and is dark in colour. The hatchlingwill be hugging the embryonic sack, but the embryonic sack remains larger than the hatchling.

• Stage Four: A fully developed hatchling the embryonic sack that it is hugging is noticeably smallerthan the hatchling.

Fungus often occurs in sea turtle eggs and is characterized by the yolk having a slightly solidifiedtexture, almost like cottage cheese. Bacteria is most easily identified from the strong odour it gives off,as well as a purple or black coloration on the egg shell. Eggs that have been overheated appear to be”cooked” on the inside; their yolk almost resembles that of a hard-boiled egg.After an excavation was completed, all shells, eggs and dead turtles were placed back into the nest andreburied. Alternatively, if unhatched eggs or live turtles were placed back into the nest, a separate holewas dug away from the nest to bury egg shells and dead turtles. This prevented the spread of fungusand bacteria to unhatched eggs and live turtles, and also prevented animals from smelling open eggs anddigging up the nest.

Tide Level

Tide measuring transects were conducted on Playa Carate at every full moon and new moon to ensurethat the influence of the moon cycle on tide measurements was as consistent as can be controlled for,and thus comparisons of measurements over time can be made. During the initial phase of this research,both a tape measure and GPS (later analysed in QGIS) were used to measure the distance between thehigh tide line and the sector post. After collecting five months of data we compared these two methodsand found there was an average of less than 0.2 m difference between measurements. This margin oferror is comparable to subtle measurement errors that can occur when using a measuring tape, such ashigh winds or uneven sand. We therefore decided that using the GPS method of measuring high tidedistance was sufficient.GPS coordinates of the tide line, sector post, and vegetation line were recorded, and the distance be-tween the tide line and both the vegetation line and sector post for each sector was measured using QGIS.Tide-measuring sessions would take place 15 minutes after high tide, when the high tide line was easilyidentifiable by observing lines in the sand. Tide-measuring sessions will be conducted on a monthly basisover the coming years in order to track long-term changes in tide-levels and thus the availability of suit-able beach habitat for sea turtles to lay their eggs without risking their nests being inundated by the tide.

Analysis

All statistical analyses were conducted using Microsoft Excel and R Studio version 1.1.463 (R CoreTeam 2018). A generalized linear model (GLM) with a binomial error structure was calculated to testwhether there was a significant relationship between a nest having a bamboo cover and the likelihood ofit being predated. A result was considered statistically significant if p ≤ 0.05. The risk ratio with 95%confidence intervals was also calculated to determine the relative probability of a nest being predatedwith versus without a nest cover. A risk ratio of 1 would indicate no difference in probability of predationacross the two conditions, so a result was considered statistically significant if the confidence interval didnot straddle 1.

4.5.3 Results

Nesting Patterns

This section describes results from data collected during the current turtle nesting season, from 2ndJune 2017 until 12th November 2018. During this time period, 2,068 adult turtle tracks were found on

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Playa Carate, with a total of 1646 identified as nests. Of these nests, 40 were identified as Pacific Greenturtles, one was identified as a hawksbill, one was identified as a leatherback, and the remaining nestswere identified as olive ridley turtles.Of these nests, 1,329 nests were left in situ (80.7%), 56 were relocated to a different location on thebeach (3.4%), 79 were relocated to a hatchery (4.8%), 80 were poached (4.9%), 95 were predated onthe same night that they were laid (5.7%), and 7 were washed away by the sea immediately after beinglaid (0.4%). Added together, these figures show that 6% of nests were destroyed through either naturalor anthropogenic causes on the same day that they were laid. Another 422 false crawls were recorded,meaning that 20.4% of turtles that came up onto Carate beach did not lay a nest.Nests were laid an average of 8.6 meters from the vegetation and false crawls/nests were identified asbeing an average of 8.3 metres from the vegetation.

Predation and bamboo nest covers

A total of 375 numbered nests experienced some level of predation over the course of the season, givinga predation rate of 22.8%. An additional 71 of these nests did not have a nest number and thus couldnot be included in predation rate calculations; however, this data still contributes to our understandingof how frequently predation can occur on Playa Carate beach. In the cases where identification of apredator was possible, 127 predators were identified as dogs (33.9%), 128 as vultures (34.1%) or otherbirds of prey, 6 as raccoons (1.6%), 1 as a coati (0.3%) and 71 as crabs (18.9%). Dogs predated anaverage of 45 eggs per nest, birds of prey 40 eggs per nest, racoons 41 eggs per nest, and crabs 2.6 eggsper nest.Bamboo nest covers were placed on 529 nests, 27 of which were predated. This shows that the presenceof a bamboo cover reduced the predation rate from 22.8% to 13.8%, thus almost cutting in half therisk of predation on turtle nests. A total of 217 nests had logs placed on them this season, 8 of whichwere predated. The data collection for logs only commenced this quarter so the predation rate of logs incomparison to bamboo nest covers can therefore not be compared in statistical analysis. A total of 67bamboo nest covers were placed on nests after they had already been predated, and logs were placed on18 nests in the absence of bamboo nest covers.A generalized linear model (GLM) with a binomial error structure revealed that nests without a bamboocover were significantly more likely to be predated than nests with a bamboo cover (Z = 5.21, P < 0.001)(see table 9 for GLM regression outputs). A calculation of the risk ratio found that the probability of anest being predated without a bamboo nest cover was 2.30 (95% CI: 1.63, 4.48) times greater than theprobability of predation with a nest cover.

Table 9: Outputs for the estimates, standard errors, confidence intervals, z-values and p -values of the coefficients for the generalized linear model (GLM) describing the effect of bamboonest covers on predation.

The outputs in table 9 are reported in the logistic scale, as a binomial error structure was applied forthe GLM. ”No bamboo” is a categorical variable representing nests that did not have bamboo covers onthem, while the intercept represents the ”yes bamboo” variable where nests did have covers on them.

Hatching success

So far this season we have excavated 586 hatched nests on Playa Carate, seven of which were iden-tified as Pacific green turtles and 540 of which were olive ridley turtles. For Olive Ridleys the averagehatchling success rate, defined as the percentage of turtles that fully hatched from their shell, was 82%.The seven hatched nests identified as green turtles had an average hatchling success rate of 84%. Theaverage distance from the vegetation of a nest was 8.8 meters for olive ridley turtles and 5.5 meters forPacific green turtles. The average nest depth was 44.2 cm for olive ridley turtles and 57 cm for greenturtles. For all species combined, 40 nests were found with bacteria, 78 were found with fungus and 7

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contained overheated eggs.

Effect of zone and relocation on hatching success rate.

A total of 57 nests were found in zone 1. In zone 1, one nest was excavated after hatching and foundto have an average hatchling success rate of 88%. 955 nests were located in zone 2,161 of which wereexcavated to find an average hatchling success rate of 82% for zone 2 nests. Zone 3 had a total of 789nests, 169 of which were excavated to find an average hatchling success rate of 84% for zone 3 nests. Notall nests are excavated due to nest numbers getting lost by extreme weather (heavy rain), or throughcages or logs getting washed away by the tide, making it impossible to locate the nest A Kruskal Wallacetest showed that there was no statistically significant difference between average hatching success rateacross zones (p=0.87). A Kruskal Wallace test also revealed that hatching success rate was not statisti-cally significantly different between nests that had and had not been relocated (p=0.42).

Development of unhatched eggs.

360 (97%) hatched nests contained some unhatched eggs, with an average of 6.5 unhatched eggsper nest (minimum = 0, maximum = 92). The majority of hatched nests (67%) contained unhatchedeggs that had no visible embryo. Unhatched eggs at stages 1-4 were less frequent but still occurred fairyregularly, especially eggs in stages 3 and 4 (figure 23). Unhatched eggs were also assessed for the presenceof fungus and bacteria; 78 (20.7%) nests contained unhatched eggs infested with fungus and 40 (10.6%)infested with bacteria.

Figure 23: A graph displaying the percentage of nests containing unhatched eggs in each of 5categorized stages of development on Playa Carate. See methodology section of this report fora full description of each stage.

4.5.4 Discussion

Predation and bamboo nest covers

Our data indicates that predation is a large threat to turtles in this region, as 22.8% of nests on PlayaCarate experienced some level of predation. The most common predators were dogs, crabs, and birds ofprey, which in the majority of cases were vultures. This is consistent with previous studies, which have

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found dogs and vultures to be the most prominent predators of both green and olive ridley turtles inother regions of Costa Rica (Fowler 1979; Burger and Gochfeld 2014).Crabs would often only predate a few eggs in any given nest (average = 2.6 predated per nest), andthus the damage was negligible. Vultures and other birds of prey predated on a large number of nests,however rather than digging up nests, birds would often scavenge eggs that had already been dug up byanother animal (Burger and Gochfeld 2014). Because of these factors, in addition to the fact that dogshave been anthropogenically introduced to this area and therefore do not play a natural role in localfood chains, we focus our conservation efforts on protecting nests from hunting dogs using bamboo nestcovers.Our data shows that nests without bamboo covers were 2.3 times more likely to be predated than nestswithout nest covers, and that this increased likelihood is statistically significant. This result shows thatbamboo nest covers are an effective method of keeping turtle nests safe from predation. In the scenarioswhere nests with bamboo covers were predated on, it was often the case that the bamboo cover was noton the nest when the surveyor found the nest to be predated. We suspect that in these cases the tidewashed the bamboo cover away from the nest and thus re-exposed the nest to predators. In order toprevent this, we anchor the bamboo covers to the sand by digging sticks into the corner of the nest coverand burying the edges of the bamboo cover in sand. This also prevents dogs and other animals frommoving the cover to the side in order to dig at the nest.The success of bamboo nest covers at preventing predation has very promising implications for sea turtleconservation worldwide. Predation on sea turtle nests by both wild and domestic animals has beenreported on a global scale (Fowler 1979; Burger and Gochfeld 2014; RuizIzaguirre, Woersem, et al.2015; Witherington, Peruyero, et al. 2017; O’Connor, Limpus, et al. 2017; Lei and Booth 2017). Otherstudies have reported similar success with using nest covers to prevent predation (O’Connor, Limpus,et al. 2017; Lei and Booth 2017). These studies, however, have used covers made of plastic, which ifwashed away into the sea are likely to have adverse effects on marine fauna, especially sea turtles (Mas-carenhas, Santos, and Zeppelini 2004). The placement of nest covers on the beach inevitably puts themat risk of being washed away by the tide. Therefore, the use of natural materials such as bamboo andbiodegradable twine rather than plastic is more sustainable and environmentally friendly in the long term.

Hatching success

Pacific green turtles had a slightly higher average hatching success rate (84%) than olive ridley turtles(82%). Many nests with a high number of unhatched eggs were infested with fungus or bacteria. Previousliterature has found that nests closer to the tide line are placed under a high level of continuous stressfrom repeated inundation by the sea, which results in increased egg mortality. Dead eggs have a higherchance of being infested by fungus and bacteria, which can then more easily spread to healthy eggs inthe nest (Sarmiento-Ramirez, Abella-Perez, et al. 2014). Green turtles tended to lay their nests closer tothe vegetation (5.5 m average) than olive ridley nests (8.8 m average), so it is possible that olive ridleyturtles’ lower hatchling success rate is in part a function of their tendency to lay nests closer to the tidethan green turtles. However, we did not find a statistically significant difference in hatchling success ratebased on the zone a nest was laid in, so it is likely that multiple factors influence hatchling success. Themajority of these unhatched eggs were found to have no visible embryo, indicating that egg mortality ismost likely to occur prior to the earliest stage of development.

4.5.5 Future Research

Our study has statistically shown that the use of bamboo covers on turtle nests have decreased predationrates on Carate beach by nearly half. There is not yet sufficient data to analyse the effectiveness of placinglogs on predation rates but this will be included in our next science report. Previous studies have shownthat the relocation of eggs is also an effective method to increase hatchling success rates. A study byGarcia, Ceballos, and Adaya 2003, found that relocated nests had a higher survival rate than nests leftin situ due to in situ nests experiencing high levels of predation and beach erosion. With the hatcherynow running, we therefore aim to relocate more nests on night patrols when we identify them as beingin a dangerous location; which will hopefully increase hatchling success rates and decrease the numberof nests experiencing predation on Carate beach. This study is therefore important for future researchas it will help increase hatching success rates. The shading placed in the hatchery also aims to mitigatethe effects of increased nest temperatures (due to a global climate change) and therefore reduce skewsex ratios in hatchlings and decrease egg mortality (Wood, Booth, and Limpus 2014). The analysis of

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hatchling success of nests relocated to the hatchery will be included in future science reports once moredata can be collected.

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4.6 The importance of Ara macao feeding ecology in promoting early socialstructuring in released birds

4.6.1 Introduction

In addition to our long-term bird monitoring program, we have started a study focused specifically on thescarlet macaw (Ara macao) population found in Carate, which has the highest density of scarlet macawsightings in Central America (Dear, Vaughan, and Polanco 2010). The iconic scarlet macaws of theNeotropics once ranged from Mexico to Bolivia but have been subject to recent declines in both spatialdistribution and population numbers (Snyder and Beissinger 1992). Primary drivers behind this trendof tropical biodiversity loss include deforestation and human disturbance; however intense poaching ofchicks for the pet trade continues to be a limiting pressure on populations of scarlet macaws in CostaRica (Vaughan, N., and Marineros 2003; Sehgal 2010; Brook, Sodhi, and Ng 2003).There exist only two viable populations of scarlet macaw in Costa Rica (Dear, Vaughan, and Polanco2010). One population, the subject of over 15 years of research, is located in the Central Pacific Con-servation Area and numbers approximately 400 individuals; and the second population is found on theOsa Peninsula Conservation Area (ACOSA) and numbers in the region of 800-1200 individuals (“ScarletMacaws of Carara”). This population has been described as genetically isolated and virtually unstudied(Nader and Wink 1999). For these reasons, we have recently implemented a study examining Ara macaofeeding ecology so as to better inform conservation strategies targeted towards this charismatic species,including reintroduction efforts.The environmental impact of scarlet macaws is multi-faceted and not to be underestimated. Like mostpscittacines it is an ecologically important species with a high rate of seed-dispersal (Renton 2006). Ithas immense cultural value, with regional ties going back as far as the Aztecs (Riedler, Pearlstein, andGleeson 2012). As the largest population in Central America, Ara macao assumes a significant flagshiprole for ACOSA, in particular Corcovado National Park (Guittar, Dear, and Vaughan 2009).The present study examines the validity of captive and hand-reared Ara macao release schemes, pri-marily the choice of release location in regard to the presence and abundance of foraged tree species.The available literature is examined to determine whether a heavy dependency on a small number oftree species constitutes a threat to Ara macao populations, and the significance of this on the choice ofrelease site. Further questions examine whether the presence of a relationship between average foragingflock size and tree species directly correlates to increased levels of early social structuring in released Aramacao.

Informing release programmes

As on-going local and international efforts to curb the pejorative effects of increasing human pressureon tropical forests and their psittacine inhabitants have had little in the way of tangible results, con-servation efforts, for better or worse, have increasingly turned to captive-bred release projects (Collar2000). There exist at least four of such projects within in the Osa & Golfito region.For release programmes to establish successful Ara macao populations, core flocks of macaws must beestablished early on (Brightsmith, Hilburn, et al. 2005). As scarlet macaws do not roost communally,group feeding activities make up a large proportion of social structuring opportunities (Brightsmith,Hilburn, et al. 2005). To this end, comprehensive data of foraging patterns is required in potentialrelease sites, particularly regarding the foraging group size of macaws in respect to their choice of treespecies.Scarlet macaws are a social species, and previous Ara macao releases within Costa Rica have witnessedthe slow formation of core flocks, resulting in lower survival rates; the selection of release sites withsufficient suitable foraging species is likely to facilitate more cohesive social structuring and subsequentlyincrease survival rates (Brightsmith, Hilburn, et al. 2005).Data from Olah, Smith, et al. 2017 suggests that both elevation and anthropogenic effects act as lim-iting factors of physical and genetic dispersal in scarlet macaw populations, and therefore the effectiveselection of suitable release sites is of utmost importance in securing and establishing viable populationsof scarlet macaws. This is particularly pertinent in regions of low genetic connectivity, such as the OsaPeninsula (Nader and Wink 1999).

Key Research Questions:

• How selective is the Ara macao population of Carate in their foraging choices? Is this selectivity

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weighted equally, or are specific species heavily depended upon?

• Is there a correlation between foraging group size and choice of tree species?

• Do foraging choices change seasonally?

• Are this populations foraging choices similar to other Costa Rican and Central American popula-tions of Ara macao?

4.6.2 Materials and Methods

Gilardi and Munn 1998 argue that visual observations using point surveys or transects can be utilised aseffective and accurate data-gathering techniques for Psittacine feeding ecology. Indeed, they state thatscarlet macaws ”can be reliably counted to a distance of 300 m”. This may be true of flying macaws;however, for increased accuracy in data collection on foraging birds, this study has reduced Gilardi &Munns chosen distance value and includes macaws only within 100 m of transect lines.This study used three 1 km transects for surveying foraging scarlet macaws. The first was a road transect;a route that partially runs parallel to a freshwater lagoon, before dissecting a localised lowland palmforest. This transect serves as a useful indicator of how resilient Ara macao populations are to a disturbedrainforest habitat with significant human presence, an important factor in determining suitable futurerelease sites.The second survey location was a 1 kilometre survey of the beach front, enabling the study of this coastalfacet of the regional lowland pacific rainforest habitat, an important factor in peninsular conservationareas, such as Corcovado National Park and its periphery.The third and final transect was the river mouth and lower course of Rio Carate, where the wide viewingangle permitted by the watercourse allows for greater quantity of data collection. This transect isparticularly useful it runs perpendicular to the coast, demonstrating a cline of habitats, from disturbedthrough to enclosed primary forest, and from sea-level to surrounding higher elevations. This allowedfor greater heterogeneity of possible Ara macao habitats to be surveyed. It is hoped that this choice oftransects resulted in habitat sampling that is representative of lowland Pacific rainforest, inclusive of arange of disturbance levels and a variety of coastal and freshwater biogeographical factors.Surveys were conducted at various times between 05.00 and 18.00 approximately two to three timesper week. This variation helped to mitigate against biases that could skew the data towards selectivelyforaged morning- or afternoon-feeding groundsWhen perched Ara macao were observed, data was collected on the following variables:

• Number of Ara macao present on each tree

• The time of the observation

• Whether foraging is occurring

• The species of tree foraged from (if not foraging, the species of tree sat in)

• Date and time of survey

• Number of people conducting the survey

When Ara macao are observed, but are not seen actively feeding, a timeframe of five minutes is takento confirm the absence of foraging behaviours. Their presence and relevant other data continue to benoted, but the foraging variable is marked as a negative. Tree species are identified with reference toGargiullo, Magnuson, and Kimball 2008.

Limitations

The selected forest transects, whilst heterogeneous, may not be entirely representative of lowlandpacific forest. Freshwater (as opposed to coastal) lagoon systems, whilst not commonly an importantrole in the ecology of lowland Pacific rainforests. It is not known how dependent scarlet macaws areupon these biogeographic habitats, however their relative rarity and inaccessibility are not conducive toobtaining accurate, reliable transect data, and have therefore been omitted from this study.Human interference along transects, particularly in disturbed forest areas, cannot be quantified, andthere is a strong likelihood that individuals with vested interests in promoting eco-tourism in the area

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are providing supplementary feeding for the purpose of attracting scarlet macaws. This is likely to leadto inaccuracies in the data but is an inevitable consequence of conducting real-time research on a flagshipspecies in an area actively undergoing ecotourism-focused development.

4.6.3 Results

Data has been regularly collected for this study since November 2017. Encouragingly, during times ofthe year where volunteer participation was highest, data collection had occurred at a rate more than fivetimes faster than a comparable study in Costa Rica (see Vaughan, N., and Marineros 2003).

Table 10: Summary of the total count and number of macaws detected in each transect.

The data was analysed to assess the frequency of macaw detection on transects (figure 24). Therewas a significant difference in detection rate between transects (Kruskal-Wallis test: X2= 34.896, df= 2,P < 0.001), with higher chances of detecting macaws on beach transect in comparison to river and road(Kruskal-Wallis test: X2= 49.786, df= 2, P < 0.001).

Figure 24: Summary of the detection rate (number macaws per survey) of macaws on surveysfrom 2017 to 2018.

The average group size was calculated for macaws in each transect type (figure 25). There wasa significant difference in group size between the transects (Kruskal-Wallis test: X2= 8.2141, df= 2,P < 0.01), with beach transect having the highest ratio of small to large group of macaws in comparisonto other transects. Moreover, majority of macaw groups had less than five individuals with an averageof three individuals per sighting.

Choice of tree species

Difference in preference of tree species in macaws was calculated (figure 26). Although there was nosignificant difference between choice of tree species in macaws, the largest proportion of the time macawswere found spending on Terminalia catappa tree (51.6%), followed by Ochroma pyramidae (19.1%).There was a significant difference in group size across different species of trees (Kruskal-Wallis test: X2=

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Figure 25: Summary of group size of macaws between the transects

34.109, df= 17, P < 0.01). Group number was lower in Ochroma pyramidaie and Terminalia catappa andonly three other species of trees, including the ones mentioned, had groups of larger than five individualsof macaws found. The other tree species are Anacardium excelsum, Astronium graveolens and Attalearostrata.

Seasonal changesChoice of tree species was recorded monthly in macaws (figure 27). Seasonal changes significantlyinfluenced the choice of tree species in macaws (Kruskal-Wallis test: X2= 61.564, df= 12, P < 0.01), withTerminallia catappa being predominant choice of tree species for macaws during most seasons, exceptfor May, June and July, with Astronium graveolens, Anacardium excelsum and Ochroma pyramidalerespectively being the predominant choice of tree species.

4.6.4 Discussion

Feeding and tree preferences

Studying parrots in the wild is notoriously difficult due to various characteristics, such as a lack ofterritoriality, migration and dwelling on tree tops (Casagrande and Beissinger 1997; Marsden and Field-ing 1999; Masello, Pagnossin, et al. 2006). Since Costa Rican Pacific Coast scarlet macaw populationis the largest nationally, yet the least studied (Dear, Vaughan, and Polanco 2010), it is important toevaluate the reason behind the success of the population.Scarlet macaws have been shown to have a high variety of diet, including seeds, ripe and unripe fruit, andflowers (Renton 2006; Forshaw and Cooper 1989). The variety spans from 15, 32, 42 to 52 plant speciesin Belize; Nicoya Peninsula, Costa Rica; Carara, southern Nicoya, Costa Rica; and Peru, respectively(Renton 2006; Gilardi 1996; Vaughan, Nemeth, and Marineros 2006; Matuzak, Bezy, and Brightsmith2008). However, most studies suggest that scarlet macaws are mainly seed eaters (Matuzak, Bezy, andBrightsmith 2008; Renton 2001; Desenne 1994).In this study, similarly to other reports, scarlet macaws foraged heavily on T.catappa (Matuzak, Bezy,and Brightsmith 2008; Vaughan, Nemeth, and Marineros 2006). This could be due to the tree producingseeds all year round, as well as macaws predominantly preferring beaches and coastal areas, which iswhere Indian almond trees are found (Matuzak, Bezy, and Brightsmith 2008). Moreover, the Indianalmond tree is also a low growing tree, which increases the chance of spotting the animal. Interestingly,other studies also found high use of C.nucifera by macaws (Matuzak, Bezy, and Brightsmith 2008),

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Figure 26: Preference of tree species in macaws

Figure 27: Seasonal preferences in tree species in macaws. Trees that were least visited bymacaws were grouped into a category ”others”.

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whilst in this study they were only seen using this tree species only once. Other studies also foundmacaws predominately feeding on Teak (T.grandis), melina (G.arborea) (Dear, Vaughan, and Polanco2010) and D.regia (Matuzak, Bezy, and Brightsmith 2008). In this study macaws were seen on G.arboreaonly twice and none on T.grandis or D.regia. This is due to these trees being uncommon on the transectsselected for the study.Most species used by scarlet macaws in this study were non-native and cultivated plant species, whichis consistent with other studies of scarlet macaws in Costa Rica (Dear, Vaughan, and Polanco 2010;Matuzak, Bezy, and Brightsmith 2008). This result lead to a debate on whether high use of non-nativetree species in macaws is beneficial for the population (Pitter and Christiansen 1995; Moegenburg andLevey 2003; Matuzak, Bezy, and Brightsmith 2008; Dear, Vaughan, and Polanco 2010). Some stud-ies argue that with high habitat destruction observed in Costa Rica, with up to 70% of the originalforest cover removed (Kleinn, Corrales, and Morales 2002; Matuzak, Bezy, and Brightsmith 2008), cul-tivated tree species could potentially sustain the population of Scarlet Macaws (Pitter and Christiansen1995; Moegenburg and Levey 2003; Matuzak, Bezy, and Brightsmith 2008), similarly to how cultivatedsunflowers (Helianthus annus) were shown to sustain population of Orange-bellied Parrots (Neophemachrysogaster) in Australia (Eckert 1990; Vaughan, Nemeth, and Marineros 2006). However, high depen-dency of scarlet macaws on particular species, like T.catappa, as seen in this study could be detrimentalfor the population, as species with specialised diets are more vulnerable to environmental changes suchas climate change. Moreover, it was suggested that investing in increasing population of native plantspecies, thus reducing dependency of scarlet macaws on the non-native species would be more beneficialfor the population of scarlet macaws (Matuzak, Bezy, and Brightsmith 2008).Similarly to other studies, seasonal changes have been shown to have an effect on the feeding preferencesin scarlet macaws in this study (Brightsmith, Hilburn, et al. 2005; Matuzak, Bezy, and Brightsmith2008) due to changing food availability depending on the seasonal rainfall patterns (Schaik, Terborgh,and Wright 1993). These results are in agreement with previous findings that suggest a decrease in varietyof food plants used in scarlet macaws during dry season (Renton 2006; Matuzak, Bezy, and Brightsmith2008), although the difference is not large (n=11 dry season, n=16 wet season). Moreover, in this study,the use of T.catappa increased drastically in January and February, just as seen in majority of otherstudies (Schaik, Terborgh, and Wright 1993; Brightsmith 2006; Matuzak, Bezy, and Brightsmith 2008).Most fleshy fruits are produced in the beginning of wet season due to abundance in water, which allowsfor better growth (Schaik, Terborgh, and Wright 1993; Brightsmith 2006). However, since T.catappa hasseeds all year round, it would be the main source of food during the times where other trees do not havecrops. Interestingly, in this study, A.rostrata was highly used in October in comparison to other months,however the fruiting season is known to be from April to July. Moreover, scarlet macaws were morecommonly seen on trees such as O.pyrimidala and A.excelsum in comparison to other months and thisis possibly due these tree species starting to fruit in beginning of wet season. This result has not beenreported previously, possibly due to low abundance of these trees in other studies of scarlet macaws.Breeding season is known to correlate with the period of highest food abundance (Lack 1968; Brightsmith2006). However, this study did not show any correlation of mating season and choice of tree species. InCosta Rica, breeding season extends from late November to May in Scarlet Macaws (Forshaw and Cooper1989; Renton 2006). Ceibra pentandra (Ceiba) was a predominant nesting tree for scarlet macaws insome studies (Dear, Vaughan, and Polanco 2010). In this study, macaws did not use Ceiba tree due toits absence on the transects chosen. Incorporating more transects in future studies would allow for amore in-depth use of tree species during mating season in macaws. For example, Dear, Vaughan, andPolanco 2010 found a high use of Ceiba and Schizolobium parahybum (Gallinazo) close to a Look OutInn hotel, which was not used in this study. Other studies show common use of Caryocar costaricense,Schizolobium parahyba, Ceiba pentandra and Ficus during mating season (Guittar, Dear, and Vaughan2009).

Population Status

It is true that scarlet macaws are widely distributed, and their population is not considered to beunder threat (Snyder and McGowan 2000). Moreover, reintroductions of these species had a success rateof 70% after 2-3 years, with high survival rate (Forbes 2006; Boyd and McNab 2008; Raigoza Figueras2014). However, scarlet macaws once ranged from Mexico to Bolivia (Snyder and Beissinger 1992), whichmeans that they have undergone a drastic population decline at some point. This in combination withincreased habitat destruction rate and high dependency on selected tree species could have a negativeeffect on the population of scarlet macaws. Moreover, high population success rate of scarlet in Costa

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Rica could be used as a guide to support populations with a drastic reduction, such as Mexico, wherethe population is thought to be extinct in 10 years (Raigoza Figueras 2014). The main hypothesis fromother studies suggest reduced poaching as a reason for a success rate (Vaughan, Nemeth, et al. 2005),which was reduced due to increased profit tourists being attracted to wild scarlet macaws, thus makinglocals to protect the species (Vaughan, Nemeth, et al. 2005; Dear, Vaughan, and Polanco 2010).

4.6.5 Future Research

Future research should concentrate on evaluating nesting sites and habitat preference during matingseason in scarlet macaws, where apart from recording visual encounters of the individuals, feathersand eggshells found on the ground should be recorded. In addition, analysing preference for certaincharacteristics in trees as seen in other studies such as preference for high and deep hollows with relativelylarge entrances in emergent canopy trees (Brightsmith, Hilburn, et al. 2005; Olah, Vigo, et al. 2014)would further allow to understand the social structure of macaws. In addition, high success rate ofscarlet macaws in Osa peninsula should be further examined. It should include interviewing localsas seen in Dear, Vaughan, and Polanco 2010, as they could provide with valuable information on thepopulation increase and behaviour of the macaws as well as roosting sites. Moreover, our results wereshown to be inconsistent with the previous studies and have certain bias, which is why future studyshould concentrate on incorporating more transects to include more trees. Furthermore, habitat analysisof the transects where macaws are spotted should be carried out. This should include the species foundin the area and their stage (e.g. if they have crops, leaves etc), site elevation (as seen to have an effecton the population (McReynolds 2012)) and other factors that could affect the choice of certain transectin scarlet macaws.

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5 Projects in Progress

The following section describes projects that are currently being implemented into the project, but forwhich not enough data has been collected for proper analysis. Each section describes the justification,study aims, methodology, and current status of the study.

5.1 Assessing the degree of disturbance and secondary succession on foresthabitats in Carate, Osa Peninsula

5.1.1 Introduction

Secondary forests, defined as forested habitats regenerating from previous disturbance, have the potentialto hold important ecological value. They provide atmospheric carbon fixation, protection from erosion,and can support a diversity of fauna and flora in fragmented landscapes (Fearnside and Guimaraes 1996;“Tropical Forest Remnants: Ecology, Management, and Conservation of Fragmented” 1997). Therefore,despite often being cited as less diverse than primary forests (Barlow, Gardner, et al. 2007), secondaryforests should still be considered important for conservation. Forests classed as ”secondary” can containa large range of diverse characteristics which affect the level of biodiversity; factors such as geographiclocation, taxonomic group and disturbance type make it difficult to generalize the findings of any onestudy (Gibson, Lee, et al. 2011). Studies show biodiversity can in fact thrive in forests recovering fromdisturbance (Berry, Phillips, et al. 2010), and as the matrix surrounding forested habitats has beenshown to influence species composition within them (Dent and Wright 2009). Despite their potential asa conservation tool, secondary forest patterns of disturbance and succession are poorly understood dueto the complexity of the subject, the large range of both biotic and abiotic factors at play, and issuesrelating to accessibility and resources.In this study, we aim to perform an initial habitat assessment of a number of trails in Carate, OsaPeninsula, Costa Rica, on which our research is based for primates, mammals, amphibians and reptiles,insects and other related projects. This initial assessment is crucial for helping us understand patternsof abundance, diversity and behaviour of all our study species, as well as to help understand wildlifepopulation trends in the Osa Peninsula on a wider scale. This study is additionally important as theresearch area has received little scientific attention and the habitat quality remains unassessed thusfar. Furthermore, there is scope to develop this project further into a long-term monitoring studyto investigate rate of regeneration of tropical forests in the context of succession after anthropogenicdisturbance.Carate is situated just outside of Corcovado National Park, a 424 km2 protected area established in 1975to combat degradation caused by rapid changes in land use. Corcovado and its adjacent areas containthe last remnants of tropical broadleaved evergreen lowland rainforest on the Central American Pacificslope (McHargue and Hartshorn 1983). This region is also home to approximately 50% of Costa Ricasflora and fauna (Kappelle 2016), many of which are endemic (Salom-Prez, Carrillo, et al. 2007; Soto-Quiros, Bustamante, et al. 1994; Naranjo-Pinera 1995). This makes this study highly relevant to theconservation of vulnerable biodiversity in Costa Rica, and potentially useful to conservation in tropicalhabitats recovering from disturbance all over the world.

5.1.2 Literature Review

Secondary succession is defined as the long-term directional change in community composition followinga disturbance event (Chazdon 2008). In the case of our study site Carate, as with most of the world’ssecondary forests, human impacts are responsible for these disturbances (Brown and Lugo 1990; Guar-iguata and Ostertag 2001). The area of Carate has previously been cleared for agricultural purposes,and now faces new pressures from the growing tourism industry in the area.Successional changes in tropical vegetation structure have been studied extensively from a theoreticalstandpoint, however, observational and experimental studies to corroborate theory have produced variedresults. This is due to the complexity and interplay of a wide range of factors which affect vegetationdynamics during secondary tropical forest succession. These include type and intensity of previous landuse, soil fertility, and the surrounding landscape matrix (Guevara, Purata, and Maarel 1986; Hughes,Kauffman, and Jaramillo 1999; Johnson, Zarin, and Johnson 2000; Moran, Brondizio, et al. 2000; Pas-carella, Aide, et al. 2000; Ferguson, Vandermeer, et al. 2003; Myster 2014).In this study, we will investigate the differences between a set of parameters which have been used inprevious studies to define degree of succession in tropical forests. Firstly, the presence or absence of

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disturbance favoring or avoiding species can be indicators of successional stage (Guariguata, Chazdon,et al. 1997; Bognounou, Morton, et al. 2011; Herwitz 1981; Myster 2014). For example, light demanding’pioneers’ of the genus Cecropia, Ochroma, Solanum and species of Melastomataceae and Rubiaceae indi-cate early successional forest (Myster 2014), in contrast to members of the genus Andirma, Brosium andSymphonia, which indicate climax conditions (Herwitz 1981). Fast-growing early successional colonizerstend to increase rapidly in basal area and height, leading to a decrease in understory light availability.These changes are associated with a decrease in density of woody and shade-intolerant species of shrubs,lianas and canopy trees (Capers, Chazdon, et al. 2005). Therefore, in addition to indicator species, veg-etation composition and structure can inform degree of succession. Early successional stands predictedto be characterized by higher tree densities, lower basal areas and shorter canopy heights (Guariguataand Ostertag 2001), as well as lower canopy cover (Myster 2014). Lastly, vegetation composition will bean indicator of succession, where younger stands will have less frequently encountered lianas, large logssand large trees compared with older stands (Oliver and Larson 1996; Guariguata and Ostertag 2001).

Aims of study

This study aims to collect data on the structure and level of secondary succession of forests in thisregion to attempt to quantify and better understand the level and impact of disturbance present on sixforest trails in Carate.

1. To provide baseline data on the structure and degree of succession of habitats in Carate so thatour studies can assess how these characteristics affect wildlife populations in this region.

2. To provide MINAE (Ministerio de Ambiente y Energa de Costa Rica) with an assessment ofhabitats surrounding Corcovado National Park that will help inform policy decisions regarding theprotection and conservation of these areas, particularly with regards to the maintenance of bufferzones surrounding Corcovado National Park.

5.1.3 Materials and Methods

Study Sites

Habitat surveys will be conducted on Attalea, Golden Ridge, Luna, Shady road, Puma, Road, Campriver, Rio Carate, Catappa Ridge, Leona, Shady Trail, Beach Trail, Miners Trail, Los Aves, LagunaVista, Waterfall Trail, and Trail Verde. These trails will be examined as transects, to be sampled at 200m intervals on 5x5m quadrats.For each plot, the following parameters will be recorded:

Indicator species present

The presence and abundance of plant species, which indicate level of succession, will be identifiedusing dichotomous keys and local guide interviews. Species will be identified to the species level wherepossible; however, due to limitations in our current field knowledge of plant species, genus level willbe accepted (table 11). Whether a species indicates pristine, successional or disturbed forest will bebased on interviews and previous vegetation studies on the Osa Peninsula, including (Herwitz 1981;Vaughan 1981; Bognounou, Morton, et al. 2011; Myster 2014); as well as inventory data provided by theUniversidad de Costa Rica.

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Table 11: Species indicating level of succession taken from previous studies, with references.

Structure of vegetation

The vegetation structure, also an important indicator of forest succession, will be characterized withineach plot by recording a) canopy cover; b) mean canopy height; c) herb and shrub layer; and d) stemdensity of 4 plant size classes; e) ground cover, f) flatness.a) Canopy cover will be calculated by taking photos at 10 points to be analysed with the mobile phoneapplication GLAMA (Gap Light Analysis Mobile Application), which previous research has found to bean efficient yet accurate measure of calculating canopy cover (Tichy 2016), to produce a canopy coverindex.b) Mean canopy height will be recorded using a TONOR laser rangefinder. All trees will be recordedper plot, and the average height calculated.c) Herb and shrub layer measured with a banded meter stick at each corner of the plot and in the centreof the plot. The person standing at the top left corner will start by holding the meter stick parallelto their body, while the person on the bottom left corner states (without moving their head to adjustposition) how many bands on the meter stick they can see.d) Stem density will be calculated for all free-standing woody vegetation (including palms and lianas)categorized into four plant size classes, following methodology adopted from Guariguata, Chazdon, et al.1997. Plant sizes will be categorized as follows: trees (stems ≥ 10cm DBH), treelets (stems ≥ 5cm DBHand ¡ 10 cm DBH), saplings (stems ≥ 1m tall and < 5cm DBH), and seedlings (stems ≥ 0.2m tall and< 1m tall). We will also measure the DBH (diameter breast height) of the largest tree in the plot.

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e) Ground cover will be measured as a percentage; what percentage of the ground is made up of leaflitter, bare ground, coarse woody debris, grass, water, swamp/mud (adding up to 100%). The leaf litterdepth at every corner of the plot will also be taken.fFlatness is a measure of the undulation in any given plot. The measurements are F (flat), MU (mildlyundulated, U (undulated), SL (slope), SSL (super slope).

Vegetation composition

The composition of all vegetation, including of the undergrowth, will be characterized by recordingthe abundance per 5x5 m plot of the following:

• Stumps;

• Large logs;

• Emergent trees;

• Very large trees (DBH > 2m);

• Lianas, epiphytes and stranglers.

Data Analysis

Data will be analysed using a 2-way Analysis of Variance on RStudio (R Core Team 2018) to de-termine whether there are significant differences in the biotic and abiotic parameters recorded betweentrails, which will correspond to the successional stage of the forest and explore the interactions betweenthese factors.

Limitations

The main limitation of this study will be accessibility to certain plots along the transects which aretoo densely vegetated, or too steep to safely and accurately sample. In these scenarios, we will walkanother 25 meters along the transect and analyse the plot at this point, repeating this step again ifthe second plot is also too steep to safely take measurements. Secondly, the size of plots are limitedby the manpower and resources available to us, so the representativeness of our sample will be affected.Furthermore, abiotic factors such as soil quality will not be measured in this initial study, again dueto limitations in resources. The last main limitation, again related to our resources, is our speciesidentification knowledge, which will improve as the study progresses, but is not at an expert level. Theselimitations will be improved as we develop our study, as we learn more through our data and what itneeds to be improved.

Equipment

• Tape measures

• Species identification book

• Smartphone and GLAMA application

• TONOR laser range finder

Status of project

Habitat surveys have currently been completed for 4 of our trails: Attalea, Camp trail, Puma Creek,and Beach Trail.

5.1.4 Conclusion

This study is an excellent opportunity to diversify the range of activities and experiences available tovolunteers on this project, as habitat survey skills are a crucial part of ecological fieldwork. Furthermore,our current vertebrate studies rely on habitat classification; however, these trails have not properly beencategorized. Thus, this study will improve the accuracy of all other projects taking place on-projectwhich assess the health of animal populations outside Corcovado National Park. In addition, this study

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can inform MINAE policy and ultimately contribute to the improvement of the habitat connectivity ofCorcovado National Park. Furthermore, there is scope to develop this project further into a long-termmonitoring study, continuing the data collection on a yearly basis to investigate rate of regeneration inthe context of succession after disturbance.

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5.2 The effect of vegetation structure on bat activity and species variationon forest trails and roads in Carate, Costa Rica

5.2.1 Introduction

Bats are highly important for a functioning ecosystem, particularly in tropical and subtropical habitatswhere they preserve biodiversity through services such as pollination and seed dispersal (Fleming 1988;Patterson, Willig, and Stevens 2003). As high trophic flyers bats are highly sensitive to environmen-tal changes and can therefore act as a bioindicator species, helping us understand how environmentalstressors are impacting a variety of taxa (Jones, Jacobs, et al. 2009). Insectivorous bats also hold greateconomic importance by acting as a natural form of pest control (Wanger, Darras, et al. 2014; Maine andBoyles 2015). For example, Boyles, Cryan, et al. 2011 estimated that the loss of bats in North Americawould cost the United States more than 3.7 billion USD per year from losses in agricultural productivity.Costa Rica contains over 109 known bat species, which is more than twice the amount of bat speciesfound in the United States and Canada combined and represents over 10% of all bat species in the world(Reid, Leenders, et al. 2010). Despite the ecological significance of Costa Rica for bats, relatively fewstudies have examined bat activity in this region, and only a handful of studies could be identified thattook place on the Osa Peninsula. Given the ecological significance of bats as a promotor of floral andfaunal biodiversity, it is important to build an understanding of what habitat types bats are most likelyto thrive in.As most bat species rely on echolocation to gather information about their surroundings, the structureand shape of features in a habitat can greatly influence bat activity. For example, previous studies haveshown that many bat species prefer linear rows and alley ways of vegetation (e.g. hedgerows or treelines) to open areas (Frey-Ehrenbold, Bontadina, et al. 2013; Kalda, Kalda, and Liira 2015). Studieshave shown a similar pattern in neotropical region, finding that bats prefer forest and riparian habi-tat to open landscapes (Pena-Cuellar, Benitez-Malvido, et al. 2015). The particular characteristics ofvegetation structure within a habitat can be important as well, such as density of vegetation presentwithin a forest area. While some species of bat are more commonly found foraging in areas of sparse,uncluttered vegetation (open-adapted species), others are more well adapted to densely cluttered habi-tats, using detailed short-range echolocation calls to navigate. However, the specific habitat preferencesof a bat can vary greatly depending on the species (Ford, Menzel, et al. 2005; Rainho and Palmeirim2011; Brigham, Grindal, et al. 1997; Brooks 2009; Crome and Richards 1988). It is therefore importantto examine a variety of structural features within a habitat to best understand what characteristics aremost accommodating to different species.Forest trails and roads have the potential to serve as an important conservation tool, as they form alinear alley way in an otherwise densely forested area. These pathways can act as corridors for bat speciesto facilitate movement through the forest, which is important as some species will travel up to 3.4 km insearch for food each night (Wainwright, 2007). Few studies however have specifically analysed patternsof bat activity on trails and roads, and thus their value as a conservation tool is not fully understood.Given that bat activity can vary greatly based on the shape of particular features in a habitat, it isespecially important to know how bats are influenced by the structural characteristics of trails and roadsin forest habitats.The present study will fill this gap of knowledge by assessing bat activity and species variation on 15trails and roads in Carate, Osa Peninsula, Costa Rica. The central aim of this study is to determinehow various structural characteristics of a forest path or road affect the number of bat passes and thepresence or absence of bat species with varying echolocation strategies (open-adapted versus clutter-adapted). The results could also have implications for the conservation of bat species by evaluating theeffectiveness of using trails as bat corridors, and by evaluating what structural characteristics on thesetrails will facilitate the movement of various bat species. This is particularly important in the studyregion, as Carate has been subject to a large amount of development over the past decade due to a risein the ecotourism industry, and as a result roads and forest trails frequently occur.

5.2.2 Materials and Methods

Survey Area

Surveys will take place on 15 trails within Carate, Osa Peninsula, Costa Rica: Waterfall Trail, Wa-terfall Road, Shady Lane Road, Shady Lane Trail, Attalea Loop, Road, Los Aves, Camp Trail, UpperGreen Trail, Lower Green Trail, Catappa Trail, Catappa Ridge, Luna Trail, Beach Trail, and Puma

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Creek. These trails all represent a diversity of characteristics to ensure that all variables are representedequally amongst survey sites.

Habitat characteristics

For every trail, the following variables will be recorded: width of path, proximity to water, canopycover, elevation, canopy height, vegetation density, and linearity of path. Path width, canopy cover,elevation, vegetation density and canopy height are continuous variables that will be measured at 10 mintervals on every path, taking the average to determine the overall value for each trail. Proximity towater and linearity will be categorical variables: whether or not the path is adjacent to a body of water,and whether the path is linear or curved.Canopy cover will be measured using a canopy cover index. This will be calculated by taking photos tobe analysed with the mobile phone application GLAMA (Gap Light Analysis Mobile Application), whichprevious research has found to be an efficient yet accurate measure of calculating canopy cover (Tichy2016). Vegetation density is measured by one surveyor going five meters away from the path and directlyinto the vegetation with a meter ruler which has highly visible markings at ten-centimetre intervals. Thenumber of markings that are visible from the trail itself can then be used as an indicator of vegetationdensity. Canopy height will be measured as two variables; mid canopy (the height of vegetation coverageimmediately above each interval on the trail), and maximum canopy (the height of the highest visibletree on either side of the trail). Tree height will be measured using a range finder; one person will standa given distance from a tree and use a range finder to measure their distance to the bottom of the treeand to the top of the tree. Pythagorean theorem can then be used to calculate the height of the tree.Elevation will be measured using a Global Positioning System (GPS).

Survey Protocol

Surveys will commence 15 minutes after sunset and at midnight, as these two times cover the peakactivity periods of a wide variety of Neotropical bat species (Hayes 1997). While conducting surveys atonly two times of night may exclude some information about species whose peak activity occurs at otherperiods during the night, the present methodology will still allow for a general comparison between ourindependent variables. Surveys will last for 20 minutes and take place over a 200 m transect, walkingthe transect twice with 10 minutes walking one direction and 10 minutes in the opposite. The start timeand finish time of the survey will be written down, as well as the trail the survey is taking place on andthe leader of the survey.Surveyors will walk at a slow pace (20m/min) holding a bat detector in front of them pointing at a 45o

angle upwards in such a way that there is nothing preventing the device from picking up bat activity.The bat detector functions by converting ultrasonic echolocation calls into a sound audible to humans.The detector also produces a sonogram image of the recorded bat call that can be analysed to determinebat activity, defined as the total number of bat passes occurring within the survey period (Thomas,West, and Portland 1989; Walsh and Harris 1996). Specific bat species can also be identified based onthe length of the call, the peak frequency of the echolocation call, the time between echolocation pulses,and the slope of the pulse ((London) and Hundt 2012). This will enable us to determine the presenceand absence of open-adapted versus clutter adapted species in post-analysis by comparing our data tosonograms of known bat species.

Equipment

Surveys will be conducted using an Echo Meter Touch 2, a bat detector that can be plugged into aniPhone and used in conjunction with the Echo Meter Touch app to record all conducted surveys. Therecordings can be played back for auditory and visual analysis in the form of a sonogram image.The Echo Meter Touch 2 contains a function that classifies bat calls into different categories and suggeststhe most likely species of a particular call. Given the vast number of bat species present in Costa Rica,this feature will help us more easily develop a catalogue of the various species we hear. Because the datais recorded on an iPhone, it is easily shareable and transferable to other devices. The app also has aGPS feature to record the exact location of each transect.

Status of Project

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Bat transect surveys have been conducted twice a week since February 2018. Data analysis willbe possible when habitat variables have been measured on each trail, and when a catalogue of callparameters has been collated.

5.2.3 Conclusion

This project will contribute to Frontier’s Costa Rica project aims by researching the effects of habitatstructure and human disturbance on one of the most species rich animals in Costa Rica, thus progressingefforts to conserve the vast biodiversity present in this region. This project will additionally providebaseline information on the bat species that are present on the Osa Peninsula, as this data is currentlylacking. Furthermore, this project will diversify the skills that volunteers can learn on our program bygiving them experience collecting data with new technological equipment (the Echo Meter Touch 2 is avery new product to the market) and teaching them scientific protocols for bat surveys (skills that canbe easily transferable to research projects in other areas of the world, as bats have a wide geographicalrange).

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