orangutan behaviour in captivity: activity … · orangutan behaviour in captivity: activity...

O R A N G U T A N B E H A V I O UR IN C APT I V I T Y :

A C T I V I T Y BUD G E TS, E N C L OSUR E USE A ND

T H E V ISI T O R E F F E C T

C H O O Y U A N T IN G

B.Sc. (Hons.), NUS

A THESIS SUBMITTED FOR THE DEGREE OF

MASTER OF SCIENCE

DEPARTMENT OF BIOLOGICAL SCIENCES

NATIONAL UNIVERSITY OF SINGAPORE

2011

ii

A C K N O W L E D G E M E N TS

Just as I was thinking that my affair with the hairy creatures would never end, I finally found

myself having to bid them farewell. The following thanks are kept brief, as no words adequately

express the relationships between people. I had fun and much chance to grow during my research,

and to everyone listed here, I hope I have made just a bit of difference in your life as well.

As with any routine done regularly over time, one starts to develop what I call specialized quirks.

Some people call them occupational hazards. Being in the unique situation of watching apes in a

zoo setting, where I have both hairy as well as hairless ones to watch, I cannot help but draw

comparisons between the two.

During the first few months of watching orangutans, I started seeing orangutans everywhere I

went. The way my dad sat with his leg up on the sofa looked like an orangutan. The way a

stranger on the street scratched himself reminded me of a certain old orangutan in the zoo. The

crowning touch came one day when after exiting the zoo washroom, I passed through a crowded

restaurant on the way back to the orangutan exhibit. To my horror/amazement, I saw Bento, one

of the 2 year old (orangutans) rolling around on the floor! How on earth did he get out, and there

he was, frolicking in the midst of humans! I was stunned. But on taking a second look, I realized

that it was actually a very tanned human child in an orange singlet, rolling around on the floor.

That incident proved really hilarious, even to myself.

Other humou s of time include

hearing the zoo show jingle, in the toilet. And once, I thought I heard

the mating/territorial call of a mature male orangutan in my house. I wondered: Why is Charlie

long-calling in my house??

The following thesis is a summary and analysis of my past months with these apes. They have

brought me only fun, laughter and constant opportunities to self-introspect. On the other hand, the

heartache and sweat came solely from the efforts of this human, to want to watch them in order to

write a long report that humans call a thesis. For all of this, I am grateful, and would like to thank

the following people.

iii

Dr Li, my ever present source of advice and support. Thank you for taking in the young and

inexperienced girl back then, and nurturing her into the competent, confident researcher she is

today.

Dr Todd, my grammar master. Always ready to pick up where I have left off, and pushing me that

extra step to do a better job. Thank you.

Of course, with any captive animals, come their ever faithful keepers. Jack, Kumaran, Gabriel,

Prakash, Md Noor, Arshad and Marzuki. I sincerely thank you for all you have taught me and I

hope your lives have been at least somewhat enriched,

rt and advice you have given

me, I have really enjoyed knowing you!

Eunice. I felt that choosing to go on with Masters, rather than working after my B.Sc, was made

in part worthwhile because I got to know you ^^

My labmates with them, I understand why humans are truly social creatures. Even the intensely

focused task of analyzing data or writing a thesis re

company better to revel in, than those of my ever fun, ever game fellow researchers. Thank you

Huishan, Diego, Stanley, Junhao, Seok Ping, Shichang, Mindy, Joelyn, Ganison and my other

Spider Lab colleagues who make me look forward to going to lab.

Giam, Dr Chan Yiong Huak, Kia Chong, Yangchen and Lainie. Thank you for your invaluable

statistical advice and comments on my project.

My father, who paces me both in life, and as a researcher. He, who I must attribute much of who I

am today to. My family, always supportive, despite my regular crankiness. Thank you.

And last but definitely not least, myself.

best and grown lots through this experience. Well done.

And to you, dear reader, I hope you enjoy the following account of my time spent with the hairy,

as well as not so hairy apes of the Singapore Zoo.

iv

T A B L E O F C O N T E N TS

Page

Acknowledgements ii

Table of Contents iv

Summary vii

L ist of Tables ix

L ist of F igures x

Chapter 1: General Introduction 1

Orangutans 1

Zoos then, and now 4

Singapore Zoo 6

Study objectives 8

Chapter 2: Activity Budgets of O rangutans in Two Naturalistic Enclosures and Comparisons to Wild O rangutans

11

Introduction 12

Materials and Methods 15

Results 23

Overall activity budgets and activity budgets across age groups 23

Comparing activity budgets across enclosures 27

Comparing captive to wild activity budgets 28

Discussion 29

Comparing activity budgets across age groups 29

Comparing activity budgets across enclosures 31

Comparing captive to wild activity budgets 33

Recommendations 37

v

Chapter 3: Use of Enclosure Structures and Vertical Space in Two Naturalistic O rangutan Exhibits

39

Introduction 40


Results 50

Overall structure use 50

Structure use across age groups in both exhibits 51

Behaviours at each structure type 53

Use of vertical space in enclosure 56

Discussion 57

Use of enclosure structures across age groups and exhibits 57

Behaviours at each structure type 61

Use of vertical space in enclosure 64

Limitations of study 67

Recommendations 68

Chapter 4: V isitor effects on zoo orangutans in two novel, naturalistic

enclosures

71

Introduction 72


Results 82

Effect of visitors on orangutan behaviour in the Boardwalk exhibit 83

Effect of visitors on orangutan behaviour in the Island exhibit 83

Discussion 87

Effects of visitor number 87

Effects of visitor activity 88

Effects of visitor proximity 90

Other influences on the visitor-animal interactions 91

Limitations of study 92

Recommendations 96

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Chapter 5: General Discussion 98

Common factors across the three chapters 99

Recommendations on enclosure design 102

Recommendations on husbandry routine 104

Other considerations and recommendations 106

Study limitations and future directions 109

References 111

Appendix 124

vii

SU M M A R Y

Orangutans are great apes that are found in the forests of Borneo and Sumatra. In the wild, they

live in complex rainforest habitats, and travel great distances daily for food. As a result of habitat

destruction and poaching, these apes are now endangered. In captivity, orangutans become obese

if not provided with sufficient arboreal stimulation. They are also known for their intelligence,

and keeping them mentally occupied is a challenge. For captive orangutans, little is known about

their activity budgets, enclosure use and how zoo visitors affect them. Hence, more knowledge is

required to maintain the welfare of these intelligent apes.

In zoos, there is a current and ongoing interest for naturalistic exhibits, as such exhibits may

provide greater stimulation for captive animals. Using features such as vegetation and rockwork,

naturalistic enclosures are designed to increase species-specific behaviours by simulating wild

habitats. Such exhibits have also been found to improve visitor appreciation of captive animals. In

Singapore Zoo, the presence of two naturalistic orangutan exhibits provides the chance to study

the behaviour of this ape in such enclosures. Hence, the activity budgets, enclosure use, and

visitor effects on Singapore Zoo orangutans were investigated.

The results showed that captive orangutan activity budgets were age-specific, differed across

enclosures, and were not dissimilar from that of wild orangutans. Exhibit use was influenced by

both biological and environmental factors. Biological factors included age and dominance

hierarchy in orangutans, and environmental factors included the availability and arrangement of

structures within an exhibit, as well as features surrounding the exhibit. For visitor effects, large

crowds, visitors with food, visitors who were looking or taking photographs, and visitors who

were close by, all affected orangutan behaviour. On the whole however, the effects of visitors on

viii

Interestingly, possible

sources of visitor stress appeared to be alleviated by the large, naturalistic enclosure designs and

the unusual husbandry routines implemented at Singapore Zoo. Being the first study on structure

use in a naturalistic orangutan exhibit, and amongst the few existing studies on orangutan activity

budgets and visitor effects, this research provides useful information for zoo management, and

sets possible direction for future studies.

ix

L IST O F T A B L ES

Table 2.1.

Individual details of study animals. 20

Table 2.2.

Definitions for orangutan behaviours.

20

Table 3.1.

Individual details and age groups of study animals. 49

Table 3.2.

Definitions for orangutan behaviours. 49

Table 4.1.

Individual details of study animals. 78

Table 4.2.

Definitions for orangutan and visitor variables.

79

Table 4.3.

Definitions and levels of variables for multinomial logistic regression 81

Table 4.4. Likelihood ratio test results for both enclosures.

82

Table 4.5. Results from multinomial logistic regression testing effects of visitor number, activity and proximity on orangutan behaviour in the two exhibits.

85

Table 4.6. Effects of visitor variables on likelihood of each orangutan behaviour for both exhibits.

86

x

L IST O F F I G UR ES

Fig 1.1. Top: adult female orangutan. Bottom: juvenile and adolescent males feeding on leaves.

3

Fig. 2.1. Schematic diagram of Boardwalk Free-ranging exhibit.

16

Fig. 2.2. Schematic diagram of Island Free-ranging exhibit.

17

Fig. 2.3. Plan diagram showing proximity of Boardwalk and Island exhibits to surrounding features.

18

Fig. 2.4. Overall activity budgets for all orangutans in Boardwalk exhibit and Island exhibit.

23

Fig. 2.5. Activity budgets for different age groups in Boardwalk exhibit.

24

Fig. 2.6. Activity budgets for different age groups in Island exhibit.

25

Fig. 2.7. Activity budgets for Boardwalk and Island exhibits.

27

Fig. 2.8. Activity budgets for wild and captive orangutans.

28

Fig. 3.1. Schematic diagram of Boardwalk Free-ranging exhibit

45

Fig. 3.2. Schematic diagram of Island Free-ranging exhibit.

46

Fig. 3.3. Plan diagram showing proximity of Boardwalk and Island exhibits to surrounding features.

47

Fig. 3.4. Overall structure use for all orangutans in Boardwalk and Island exhibits.

50

Fig. 3.5. Structure use for different age groups in Boardwalk and Island exhibits.

51

Fig. 3.6. Behaviours of different age groups at structures in the Boardwalk and Island exhibits.

54

Fig. 3.7. Use of vertical space by different age groups in Boardwalk and Island exhibits.

56

Fig. 4.1. Island exhibit and Boardwalk exhibit showing possible locations of visitor-orangutan interaction.

77

Fig 5.1. Log that facilitates entry into Island orangutan exhibit.

109

1

C H APT E R 1

G E N E R A L IN T R O DU C T I O N

O rangutans

The orangutan (Pongo pygmaeus, Pongo abelii) is an enigmatic ape which lives in the forests of

Southeast Asia. It belongs to the family Hominidae, and is the only great ape found outside of

Africa (Groves et al., 2005). Orangutans are currently distributed on the islands of Borneo and

Sumatra (P. pygmaeus, P. abelii respectively), and from fossil records, were thought to

previously range through Java, Vietnam and Southern China (Delgado and Van Schaik, 2000;

Rijksen and Meijaard, 1999). These apes show sexual dimorphism, where adult females weigh an

average of 36 kg, and males, 78 kg (Smith and Jungers, 1997). Males come in two forms, mature

flanged males with disc-like cheek pads (Kingsley, 1988), and unflanged subadult males, which

weigh approximately the same as adult females (Galdikas, 1985b).

In the wild, orangutans are mostly arboreal, and have home ranges spanning several kilometers

(males: 0.6 25 km2, females: 0.4 9km2) (Utami Atmoko et al., 2009). Because they are highly

adapted to life in the trees, orangutans have relatively longer upper limbs and shorter lower limbs.

Hook-like hands and opposable toes in combination with extremely mobile hip joints allow all

four limbs to grip tree branches, providing ease of movement in the spatially complex tree canopy

(see Fig 1.1) (Morbeck and Zihlman, 1988; Rodman and Mitani, 1987). These slow moving

creatures are frugivores, and feed opportunistically according to seasons in the rainforest. When

fruits are abundant (e.g. during masting season), orangutans spend more time feeding, and are

thought to store fat reserves for seasons of unpredictable fruit availability. When fruits are less

2

abundant, orangutans compensate by increasing the amounts of bark and leaves in their diet

(Delgado and Van Schaik, 2000). Because their food sources tend to be distributed irregularly

throughout the forest, these apes spend more than half of their time foraging and travelling

(Morrogh-Bernard et al., 2009)

Besides being physically adapted to life in the rainforest, orangutans are also intelligent creatures

with distinct cognitive abilities. As mentioned, orangutan food sources are located patchily in the

forest (Oates, 1987). Before an orangutan can feed, it has to first recall where the nearest food

source is, whether it is currently in season, and the shortest way to get there through the spatially

complex tree canopy. All these requirements point to capacities for higher mental abilities (Wich

et al., 2009). Orangutans in the wild also have distinct cultures and are known to innovate in their

behaviour and food extraction techniques (van Schaik et al., 2009). Although not as well studied

as in chimpanzees (Pan troglodytes), tool use is present in orangutans; more than twenty different

tool types have been fashioned for a variety of purposes (van Schaik et al., 2003). Captive

orangutans are also known to be expert tool users, and have been anecdotally reported to use tools

in escaping from zoo enclosures (Marks, 2009; Pope, 2009; Sonti, 2009). In captivity, orangutans

consistently score amongst the highest for primates in cognition tests (Tomasello and Call, 1997).

Together with the other great apes, they are capable of abilities seldom found in other primates,

such as mirror self-recognition, intentional deception and proto-language (Russon, 1998; Russon

and Bard, 1996). Studies have also shown that orangutans are capable of communicating their

intention to human observers and are able to modify their gestures to match the understanding of

the person (Cartmill and Byrne, 2007). Lastly, anecdotes from orangutan caretakers illustrate how

animals under their care actively observe their surroundings and show great interest in the

3

happenings beyond their enclosure (Hebert, 2011, pers. comm.1; Nantha, 2009, pers. comm.2). All

these poi

F ig 1.1. Top: adult female orangutan. Hand-like feet and mobile hip joints allow arboreal flexibility in orangutans. Bottom: juvenile and adolescent males feeding on leaves. Feeding typically occurs in pronograde suspension; the orangutan is suspended by one arm and one leg, and its body is horizontal to the ground.

1 Patricia Hebert, Orangutan Researcher, Fort Wayne Children's Zoo. 2 Gabriel Nantha, Orangutan Keeper, Singapore Zoo

4

In the 1700s, when wild orangutans were first discovered and captured by explorers, little was

known about their behaviour or ecology. As a result, captive animals rarely survived for long

(Maple, 1979). With present knowledge gained from wild populations, the reproductive success

and welfare of captive orangutans has improved greatly (Markham, 1990). Because orangutan

populations in the wild are declining rapidly due to habitat loss and poaching, much effort has

been turned to captive rehabilitation and release (Delgado and Van Schaik, 2000). Many zoos

have also started captive orangutan breeding programs to ensure the survival of this endangered

ape. As pointed out by Maple (1979) and Gippoliti (2000), orangutan exhibits still suffer from the

difficulties of creating suitable habitats for a large, arboreal primate. This is in comparison to

gorilla and chimpanzee exhibits, where excellent enclosures exist in a number of zoos. The main

challenges of keeping orangutans in captivity are providing adequate physical and mental

stimulation (Markham, 1990). Because orangutans tend to become obese if not given sufficient

climbing opportunities (Maple, 1979; Maple, 1980), and their intelligence and immense strength

lends to great investigative and destructive capabilities (Maple, 1980); it is essential to have good

understanding of both wild and captive orangutan behaviour for their welfare in zoos to be

optimized (Snowdon, 1989).

Zoos then, and now

Since olden times, zoos (and their historic equivalents) have been a source of fascination for

people of all cultures. The earliest records of exotic animals in captivity stem from 2500 BC,

where ancient Egyptians kept many species of birds and mammals as pets or in royal gardens

(Kisling, 2001; Strouhal, 1992). Menageries were also common in China and Greece where

animals were housed in private collections (Hosey et al., 2009; Schafer, 1968). During mediaeval

times, zoos (or their equivalents) did not feature as prominently in the historical records (AD 600

1450). However, in the seventeenth century, they proliferated again. A turning point came in

5

the eighteenth century when growth of European empires encouraged travel to distant places.

Enthused explorers returned from faraway lands, bringing with them an influx of exotic animals

and stimulating a subsequent interest in natural history. With the growing public interest, zoos

were no longer private menageries for the rich, but started opening to members of the public. By

the late nineteen century, the creation of zoological parks had also spread to the USA, and zoos

began to be seen as places of conservation and education. Nowadays, zoos are perceived as

conservation parks with missions to conduct research and create awareness on captive animal

welfare (Hosey et al., 2009).

With changes in the philosophy and mission statements of zoos, the way animals are housed has

also evolved. The mid-eighteenth century saw the use of first-generation exhibits which were

barren cages with steel bars and concrete floors. Subsequently, second-generation exhibits, still

prevalent today, are often cement enclosures surrounded by dry or wet moats. And as animal

welfare came under scrutiny in the 1970s, third-generation, and the most recent exhibits, came

into being (Hosey et al., 2009; Shettel-Neuber, 1988). Such exhibits are enclosures of greater

complexity which make use of naturalistic features to improve the welfare of captive creatures.

-nat

visitor appreciation of animal behaviour and ecology (Maple and Stine, 1982; Shettel-Neuber,

1988). Existing variants of naturalistic displays include free-ranging and immersion

(walkthrough) exhibits, as well as ecosystem zoos, wildlife parks, and bioparks (Hosey et al.,

2009).

Even though the shift towards naturalistic enclosures has proliferated worldwide, rigorous studies

on the benefits of such exhibits are still underway. To date, it is known that naturalistic exhibits

benefit both animals and zoo visitors, but scientific understanding is currently limited.

6

Naturalistic exhibits have been found to decrease abnormal behaviours and increase species-

specific behaviours in a variety of primates (Brent et al, 1991; Maple and Stine, 1982, Little and

Sommer, 2002). They can also improve visitor understanding of animal behaviour, increase

positive feelings towards the animals (Finlay et al., 1988; Ford and Burton, 1991) and have

greater visitor holding power (Ogden et al., 1994; Price et al., 1994). In addition, potential stress

from visitors is thought to be dampened in a large exhibit with natural features (Davey, 2007).

Despite the overall positive benefits of naturalistic enclosures, how animals interact with

individual features in their environment is poorly understood (Ogden et al., 1990) and the study

of visitor-animal interactions in such enclosures is still in its infancy (Davey, 2007; Ogden et al.,

1990). Hence, the following work will focus on addressing existing gaps in zoo ecology.

Singapore Zoo

Singapore Zoo, opened in 1973, is a local zoo under the management of the Wildlife Reserves

Singapore. Set in tropical surroundings, the zoo spans 28 hectares and holds 315 animal species

in its collection (website, Singapore Zoo) - ed for many of

the species, including the orangutans, Pongo pygmaeus and Pongo abelii.

In 2006, Singapore Zoo introduced two -

design from the older island-style exhibit, these enclosures each comprise a row of tall trees,

joined by artificial vines, nets, platforms and logs. Using trees which were originally situated next

to main visitor tracks, the orangutan enclosures were constructed by adding vines and structures

to the tree canopy and pruning tree foliage to maintain a minimum gap from surrounding trees.

Low-current electrical wires were also installed at the base of tree canopies to prevent orangutans

from descending to the ground.

7

- -ranging

(see Chapter 2, page 16). The former enclosure has an elevated boardwalk, so visitors

can view orangutans from both the main track (road), and the boardwalk. Visitors to the Island

exhibit, however, can only view orangutans from the main track below. These enclosures were

designed to encourage species-specific behaviours,

- website, Singapore Zoo). The enclosures are unique in

several ways and these include possible effects on both orangutans and visitors. The following are

several examples.

First, the majority of orangutan enclosures worldwide have animals displayed in exhibits at the

eye level of visitors, and climbing structures provided are often made of timber or inanimate

materials. Singapore Zoo orangutan exhibits are unique because orangutans are displayed on live

trees, under which visitors walk. Because the height at which animals are viewed has been found

or she is looking down at an animal, looking up instead at orangutans may instead evoke different

responses (Coe, 1985). Personal observation has shown that visitor responses range from one of

pleasant surprise, to obliviousness of the large apes moving overhead, and most comically of all,

sudden realization as the unsuspecting visitor is showered by excrement from an orangutan

above! In addition, it has also been suggested that viewing an animal amidst a natural backdrop of

greenery may promote a different viewing experience, because visitors gain a greater appreciation

of t and how it moves about in its natural environment (Shettel-Neuber,

1988).

Secondly, orangutans at Singapore Zoo have been observed to move from tree to tree using

species-specific behaviours which may not be possible in traditional orangutan exhibits. One

-

8

weight is used to bend tree branches to decrease the distance and cross gaps between

neighbouring trees (Thorpe et al., 2007). The presence of live trees in the exhibits may in this way

provide additional physical and mental stimulation for this group of orangutans.

Last but not least, when the effects of enclosure design on visitor-animal interactions are

considered, the elevated boardwalk in one of the exhibits allows visitors to come very close, up to

a distance of 3 m, from the orangutans. This close proximity permits animal observation in great

detail, and has been seen to evoke many excited responses from visitors. As a result, visitor-

animal interactions, such as food solicitation, are believed to occur more frequently in the exhibit

with the elevated boardwalk. For these reasons, Singapore Zoo orangutan exhibits are thought to

be unique.

Study objectives

Having discussed the presence of a unique study site, and the need for more information on

certain aspects of captive orangutan welfare, my study will focus on three areas of captive

orangutan behaviour, specifically, activity budgets, enclosure use and visitor effects.

Activity budgets

To date, published studies on captive orangutans have focused on cognition, play,

communication, plus a few on enrichment and enclosure modification (Cartmill and Byrne, 2010;

Leavens, 2007; Pizzutto et al., 2008; Tripp, 1985; Zucker et al., 1986). Although data are

available for many basic aspects of orangutan biology, there is a lack of information on captive

orangutan activity budgets. The activity budget of an animal can be defined as an adaptation to its

environment (Daan and Aschoff, 1975; Jaman and Huffman, 2008). For example, captive animals

9

are known to vary their activity budgets when changes are made to their enclosure or husbandry

routine (Hoff et al., 1997; Shepherdson et al., 1993). By comparing activity budgets between two

captive conditions, or between wild and captive populations, behavioural data can be used to

gauge if the welfare of the animals has been adequately provided for (Hosey et al., 2009). Such

data can also be used to ensure that behavioural diversity has not been lost through generations of

captive breeding (Hosey et al., 2009). Because orangutans are slow moving and are known to be

less expressive than other primates (Maple, 1980), specific indicators of stress in these captive

apes may be more difficult to identify. Hence, the proportion of time spent on different activities

can serve as a broad index of welfare. To date, there are only a few instances of published activity

budgets in orangutan literature (Forthman et al., 1993; Pearson et al., 2010; Pizzutto et al., 2008).

comparisons to wild conspecifics as well as those in other zoos, is the first objective of this thesis.

Enclosure use

As mentioned previously, there is a current trend worldwide to build naturalistic zoo exhibits.

These enclosures, with their greater complexity and more natural features, have been found to

improve the general welfare of captive animals. Aggressive and abnormal behaviours have been

reported to decrease, and species-specific behaviours increase, in naturalistic, complex,

enclosures (see review in Stoinski et al., 2001). However, specific interactions of animals with

features in the enclosure are not well understood, and more knowledge is required to optimize

exhibit use. Hence, the second objective of this study is to learn more about how captive

orangutans interact with structures in a naturalistic exhibit. The presence of two novel,

naturalistic enclosures at Singapore Zoo presents a good opportunity to research this topic.

10

Visitor effects

One factor that is common to all zoos is the presence of visitors. The effects of visitors on

animals have been studied since the 1970s (Oswald and Kuyk, 1977; Thompson, 1976) and have

been found to have positive, neutral or negative effects on animal welfare (Hosey, 2000). Such

welfare indications include: increases in active behaviour (positive) (Hosey, 2000), increases in

aggressive behaviour (negative) (Chamove et al., 1988; Sellinger and Ha) or no response to

varying visitor conditions (neutral) (see review in Davey, 2007). Most visitor research has

focused on simple presence-absence or visitor numbers. The limited knowledge on other aspects

of visitor presence, the lack of detailed definitions for some visitor variables, and the study of

visitor effects in isolation from other exhibit variables, all need to be addressed (Davey, 2007).

Hence, the third objective of this study is to investigate the visitor effects on orangutans in two

naturalistic, novel enclosures. The study will include a relatively wide range of visitor variables,

as well as investigate how visitor effects may interact with exhibit design.

11

C H APT E R 2

Activity Budgets of O rangutans in Two Naturalistic Enclosures

and Comparisons to Wild O rangutans

Abstract. Activity budgets can be used as indices of welfare, and also to check if captive animals

possess the behavioural diversity of their wild counterparts. Because keeping orangutans both

physically and mentally occupied in captivity is challenging, knowledge of their basic behaviour

is essential. However, detailed activity budgets for captive orangutans are currently lacking in zoo

literature. This study was designed to provide baseline data on orangutan activity budgets in two

naturalistic, novel enclosures. Activity budgets were collected for animals of different ages, and

compared against that of wild orangutans and animals from other zoos. A comparison of activity

budgets across two different enclosures was also made. Activity budgets differed significantly

across age groups, with younger animals showing more play and movement, and older animals

idling and paying more attention to their surroundings. Enclosure design and surrounding features

also appeared to influence activity budgets. Interestingly, activity budgets of this group were

similar to that of other orangutans, and also wild orangutans, especially those in masting

forests. The findings of this study are discussed in relation to captive welfare, and relevant

recommendations are made for zoo management.

K eywords: orangutan, activity budget, welfare, wild-captive, enclosure design, naturalistic

12

IN T R O DU C T I O N

The activity budget of an animal is the proportion of time it spends on different behaviours, such

as feeding, resting, and travelling. In captivity, many factors like restricted space, husbandry

practices or social grouping may affect an anima (Hosey et al., 2009). For

example, gorillas which were kept in an indoor enclosure showed more aggression, lay down

more, and had significantly different activity budgets from animals kept in outdoor naturalistic

enclosures (Hoff et al., 1997). Similarly, when feeding routines of leopard cats were changed to

include multiple feedings of hidden food, the cats paced less and their exploratory behaviour and

movement increased (Shepherdson et al., 1993). Because the activity budget of an animal can be

considered as an adaptation to its environment (Daan and Aschoff, 1975; Jaman and Huffman,

2008), a creature in captivity may have a budget that differs from that of the wild. In order to

provide optimal welfare, animal keepers have to understand how the species under their care may

respond to different captive conditions (Kleiman, 1994).

In the wild, orangutans are arboreal creatures which travel great distances daily (Galdikas, 1988;

Singleton and van Schaik, 2001). Because their food sources tend to be temporally and spatially

separate, free-living orangutans have to make their way through complex forest environments

(Oates, 1987) in search of food (Wich et al., 2009). Wild orangutans have distinct cultures in

different populations (van Schaik et al., 2003), and their ability to use and fashion tools for a

variety of purposes suggests a high level of intelligence (Parker and Gibson, 1977; van Schaik et

al., 1999). However, due to habitat loss and poaching, both Bornean and Sumatran orangutans are

endangered in the wild (IUCN, 2010). As a result, much effort has been focused on ensuring

welfare and reproductive success in captive populations (Gould, 1983; Mallinson, 1984;

Markham, 1990).

13

In captivity, orangutans are inclined towards obesity due to protein-rich diets (Delgado and Van

Schaik, 2000; Gippoliti, 2000) and a lack of physical activity (Maple, 1979; 1980). Orangutans

tend to become inactive and confined to the ground if not provided with adequate structures for

arboreal activity (Gippoliti, 2000; Pizzutto et al., 2008). Coupled with their curious nature which

lends to their destructive propensity, it is agreed that keeping orangutans both physically and

mentally occupied in captivity is challenging (Markham, 1990). Hence, it is important to have

sufficient knowledge about captive orangutan behaviour, to ensure adequate welfare for this

intelligent ape (Snowdon, 1989).

To date, behavioural studies on captive orangutans tend to focus on cognition (Leavens, 2007),

communication (Cartmill and Byrne, 2010), social behaviour (Poole, 1987; Tobach et al., 1989),

or the effects of enrichment or enclosure modification (Perkins, 1992; Pizzutto et al., 2008; Tripp,

1985). Detailed activity budget studies are rarely published; of the few available studies, the

majority are internal zoo reports or unpublished student projects which are not easily accessible

by the zoo or research community. So far, there have only been a few published papers which

detail the activity budgets of captive orangutans (Forthman et al., 1993; Pearson et al., 2010;

Pizzutto et al., 2008). As behavioural data can be used to gauge if animals have adequate welfare,

as well as ensure that behavioural diversity has not been lost through generations of captive

breeding (Hosey et al., 2009), it is essential to have records of captive orangutan activity that can

be used for further evaluation (Snowdon, 1989). In addition, even though many existing

environmental enrichment and management routines attempt to simulate wild-type behaviour in

captive primates (Britt, 1998; Honess and Marin, 2006; Marriner and Drickamer, 1994), there

have been surprisingly few comparative studies on wild versus captive primates (Melfi and

Feistner, 2002; Todd et al., 2008). Hence, by comparing captive orangutan activity budgets with

those of wild animals, we can shed light on how the zoo environment has affected orangutan

behaviour (Hosey et al., 2009). Therefore, this study is designed to elucidate the activity budgets

14

of captive orangutans as well as provide baseline data for future comparisons. The activity

budgets of two captive orangutan groups were studied in Singapore Zoo, and comparisons were

made against wild orangutan data as well as orangutans from other zoos. The activity budgets of

animals in different age groups were also compared.

In addition, there is currently a trend in zoos worldwide to provide naturalistic exhibits for

animals. , are designed

to encourage wild-type behaviours in captive animals, as well as educate visitors by fostering an

appreciation of animals in their natural setting (Coe, 1989; Hosey et al., 2009). Although such

exhibits have burgeoned worldwide; to date, there have been only a handful of studies (mostly on

primates) on how such enclosures influence animal behaviour (Stoinski et al., 2001). There is a

need to learn how these naturalistic and often, more structurally complex enclosures (Ogden et

al., 1990) may affect the behaviour of animals (Stoinski et al., 2001). Currently, only a few

published studies exist on orangutan behaviour in naturalistic exhibits (Forthman et al., 1993;

Hebert and Bard, 2000; Pearson et al., 2010). The orangutan exhibit in Singapore Zoo is not only

naturalistic, but also novel in that there is no physical barrier between animals and visitors;

visitors can walk directly under the trees on which the orangutans are found. As a result, the

presence of two novel, naturalistic treetop exhibits in Singapore Zoo, as well as a unique

husbandry routine in which two groups of animals are rotated regularly between two enclosures,

allows us to study not only orangutan behaviour, but also shed light on how naturalistic exhibits

may influence animal behaviour. Hence, this study also investigated the differences in activity

budgets between apes in two naturalistic enclosures.

15

Objectives of study

1. What is the activity budget of the orangutans? How does it differ for animals of different

ages?

2. Does activity budget differ between two naturalistic enclosures?

3. How does the activity budget of Singapore Zoo orangutans compare to that of wild

orangutans and orangutans in other zoos?

M A T E RI A LS A ND M E T H O DS

Study site and data collection

The study was conducted at orangutan enclosures in Singapore Zoo. The zoo introduced two

- naturalistic exhibits in 2006, - (Boardwalk

exhibit) - (Island exhibit) (Raj, 2009, pers. comm.3). Each

exhibit was situated next to main tracks in the zoo, and consisted a row of tall trees joined by

vines, nets, logs, and platforms. Some differences were present between the exhibits. In the Island

exhibit, visitors could only view the orangutans from the main road next to the trees, but in the

Boardwalk exhibit, visitors could see the orangutans from both the main road and an elevated

boardwalk in the exhibit. This boardwalk allowed visitors to come into much closer proximity (up

to 3m) from the animals (see Figs. 2.1, 2.2).

3 Jackson Raj, Head orangutan keeper, Singapore Zoo

16

F ig. 2.1. Schematic diagram of Boardwalk Free-ranging exhibit. (a) Vine, (b) Horizontal log between two trees, (c) Net, (d) Platform on a tree. Visitors walk along the road, and orangutans move about in the trees and structures above. Some foliage omitted for purposes of clarity. (Figure not drawn to scale; however human silhouettes convey a sense of proportion)

17

F ig. 2.2. Schematic diagram of Island Free-ranging exhibit. (a) Large net, (b) Vine, (c) Horizontal log, (d) Platforms. Visitors walk along the road, and orangutans move about in the trees and structures above. Some foliage omitted for purposes of clarity. (Figure not drawn to scale; however human silhouettes convey a sense of proportion)

18

The other main difference between the enclosures was that visual stimulus from surrounding

features was greater for orangutans in the Boardwalk exhibit than in the Island exhibit. Features

in the vicinity of both exhibits were generally closer to the Boardwalk exhibit (Fig. 2.3). The

latter was situated directly alongside a third orangutan enclosure and a busy restaurant. On the

other hand, the Island exhibit was further from the restaurant and there were trees between the

Island exhibit and the third enclosure, which obstructed the view of the latter from the Island

exhibit. Hence, orangutans when in the Boardwalk exhibit, received more visual stimuli than

when in the Island exhibit.

Busy restaurant with outdoor dining area

ISL

AN

D E

xhib

it

T hird orangutan exhibit

B O ARDWA L K Exhibit

Main track for visitors and vehicles

Tree

F ig. 2.3. Plan diagram showing proximity of Boardwalk and Island exhibits to surrounding features. Orangutans received greater visual stimuli from surrounding features when in the Boardwalk exhibit.

19

Two groups of orangutans were rotated daily between the free-ranging exhibits. The groups were

made up of individuals of varying ages, and each group had one mother-infant pair (Table 2.1).

As the infants were still dependent on their mothers, they were excluded from the observations.

The composition of the groups remained the same throughout the study period. This display

arrangement presented a unique opportunity: usually, studies that compare animal behaviour

across different enclosures use data from different animals; however, in Singapore Zoo, because

the same animals were regularly rotated between two exhibits, I had the rare chance to study the

same subjects in different enclosures, simulating a manipulative experiment.

Data was collected on both weekdays and weekends from October 2009 to February 2010,

between 09:30 h to 17:00 h. Instantaneous scan sampling, with the aid of binoculars, was used for

taken at 10 min intervals were sufficiently far apart enough to avoid autocorrelation. A total of

192 hours of observations (48 hours for each group-exhibit combination) were made. As regular

feeding sessions were held twice daily, at 11:30 h and 15:30 h for the Island exhibit and 14:15 h

and 16:30 h for the Boardwalk exhibit, data collection was paused 15 min before each session

started and only resumed 15 min after the feeding ended. During each scan, the behaviour and

location of individual orangutans was recorded (see Table 2.2 for behaviour categories). All

observational procedures in this study complied with the guidelines of the Institutional Biosafety

Committee (National University of Singapore, NUS) and the NUS Institutional Animal Care and

Use Committee, risk assessment number OSHE/RA/03/04/ FOSo-152.

20

Table 2.1 Individual details of study animals. All individuals were born in Singapore Zoo except Anita who was donated to the zoo at one year of age. Name Sex Age

(yr) Species Allocated age group

Group A

Ah Meng Jnr Female 1 Pongo pygmaeus NA Bento Male 3 Pongo pygmaeus 1 - Juvenile Budi Male 7 P. pygmaeus/ P. abelii cross 2 - Adolescent Gunta Male 7 Pongo pygmaeus 2 - Adolescent Chomel Female 13 Pongo abelii 3 Sub-adult Anita (with infant Ah Meng Jnr)

Female 24 Pongo pygmaeus 4 Adult

Group B Saloma Female 0.5 Pongo pygmaeus NA Merlin Male 5 Pongo pygmaeus 1 - Juvenile Vira Male 9 Pongo pygmaeus 3 Sub-adult Labu Male 11 Pongo pygmaeus 3 Sub-adult Binte (with infant Saloma)


Table 2.2 Definitions for orangutan behaviours Orangutan Behaviour Definition

Idle Orangutan is motionless, with unfocused gaze, or performing any of these behaviours: autogrooming, expelling bodily waste.

Look Orangutan is looking at an object/keeper/another orangutan in surroundings, face and eyes are oriented towards that location.

Move Orangutan is travelling from one location to another; can be brachiating, bi/quadrupedal walking, or any other form of locomotion.

Feed Orangutan is engaged in searching for, preparation of, or ingestion of food.

Play/Social Orangutan is engaged in object use, solitary play, social play, or social interaction.

Regurgitate Orangutan is engaged in retrograde movement of food from its oesophagus or stomach to its mouth, hand or floor, and subsequent reingestion of the food.

Human Interaction (Look visitor or Beg)

Orangutan is looking at visitor(s), face and eyes are oriented towards visitor(s), or is soliciting food by stretching out hand towards visitor(s).

21

Data processing and analysis

The data from both orangutan groups were pooled for each exhibit. The activity budgets for

individual orangutans were calculated by counting the number of scan samples for each

behaviour and converting it to a percentage of the total number of scans. A total activity budget

was calculated for each enclosure by averaging across all orangutans.

To compare behaviour between animals of different ages, the orangutans in the study were

grouped into four age groups based on classifications from Mackinnon (1974) (see Table 2.1).

To investigate if there was any relationship between age group and activity budget (i.e. proportion

of time spent on different activities), a chi-square test of independence was run for age

group against counts of behaviour in each activity. Separate chi-square analyses were run for both

enclosures. Subsequent chi-square tests of independence were then run for each behaviour to see

if the amount of that behaviour different significantly across age groups.

When comparing activity budgets between the Boardwalk and Island exhibits, a Pe -

square test of independence was run for exhibit versus behaviour. Again, individual chi-square

tests were conducted for each behaviour.

For the comparison of captive to wild orangutan behaviour, data was gathered from orangutan

studies which had been conducted in other zoos (Jersey Zoo, UK, Cleveland Metroparks Zoo,

USA, and Zoo Atlanta, USA). Both published (Pearson et al., 2010) and unpublished data

(Cassella, 2010; Marchal, 2004) were used. Captive orangutan behaviour was recategorized for

comparison against the wild orangutan data. The data for wild orangutans came from Morrogh-

Bernard et al. (2009), which was a compilation of orangutan activity budgets from various study

sites in Borneo and Sumatra. The study sites comprised two types of forests, one with regularly

22

fruiting trees, and one with irregularly fruiting trees (masting forests). One activity budget was

calculated from the data for each forest type by averaging across all sites in that forest type. These

data were then used for qualitative comparisons of the captive and wild orangutan groups.

23

R ESU L TS

Overall activity budgets and activity budgets across age groups

The overall activity budgets for each enclosure showed that most time was spent on idling (28-

31%), feeding (19-25%), and looking (17-25%) (Fig. 2.4). The rest of the time was spread

between moving, playing/socializing, interacting/looking at visitors (human) and regurgitating.

s

Idle28%

Look25%

Move11%

Feed19%

Play/social8%

Human interaction

3%

Regurgitate7%

Idle31%

Look17%Move

15%

Feed25%

Play/social 7%

Human Interaction

1%

Regurgitate5%

F ig. 2.4. Overall activity budgets for all orangutans in Boardwalk exhibit (left) and Island exhibit (right).

24

In the Boardwalk exhibit, activity budgets differed significantly for animals in different age

groups ( 2= 214.964, df = 18, p < 0.001) (Fig. 2.5). The individual chi-squares for each behaviour

showed that the following behaviours differed significantly across age groups: idling ( 2= 22.44,

(3) p < 0.001), looking ( 2= 80.90, df = 3, p < 0.001), moving ( 2= 20.99, df = 3, p < 0.001),

playing/socializing ( 2= 72.43, df = 3, p < 0.001) and regurgitation ( 2= 48.62, df = 3, p < 0.001).

0

10

20

30

40

50

Perc

enta

ge

of a

ctiv

ity b

udge

t (%

)

Age gp 1

Age gp 2

Age gp 3

Age gp 4

*** ***

*** *** ***

F ig. 2.5. Activity budgets for different age groups (gp) in Boardwalk exhibit (*** = p < 0.001).

Specifically, there was more idling and looking in older animals, and more moving,

playing/socializing and regurgitation in younger animals. Orangutans in age group 1 (ages 3, 5)

spent 15% of their time moving, which was almost double that of the 8% spent on moving by

animals in age group 4 (ages 24, 25). Similarly, age group 1 orangutans spent 16% of their time

playing/socializing, which was more than that of all other age groups. Regurgitation at 10% in

age groups 1 and 2 was more than double of that in groups 3 and 4. On the other hand, looking in

age groups 2, 3, 4, ranged from 25-31%, which was more than double the amount of looking in

25

group 1 (12%). Similarly, idling was highest in age groups 3 and 4 at around 30%. Feeding ( 2=

2.90, df = 3, p = 0.407) and human interaction ( 2= 5.27, df = 3, p = 0.153) did not differ

significantly across the age groups (Fig. 2.5).

Similarly for the Island exhibit, the overall chi-square analysis was significant ( 2= 196.88, df =

18, p < 0.001), which indicated a significant relationship between age group and behaviour (Fig.

2.6). Subsequent chi-square analyses showed that the amount of idling ( 2= 61.42, df = 3, p <

0.001), looking ( 2= 26.82, df = 3, p < 0.001), moving ( 2= 19.65, df = 3, p < 0.001), feeding

( 2= 32.61, df = 3, p < 0.001), playing/socializing ( 2= 46.61, df = 3, p < 0.001) and regurgitation

( 2= 44.44, df = 3, p < 0.001) differed significantly across the age groups. Human interaction did

not differ across the age groups ( 2= 5.10, df = 3, p = 0.165).

0

10

20

30

40

50

Perc

enta

ge

of a

ctiv

ity b

udge

t (%

)

Age gp 1

Age gp 2

Age gp 3

Age gp 4

*** ***

*** *** ***

***

F ig. 2.6. Activity budgets for different age groups (gp) in Island exhibit (*** = p < 0.001).

26

Again, older orangutans idled and looked more while younger animals moved, played/socialized

and regurgitated more. Feeding was highest in age groups 2 and 3. These results are similar to

that from the Boardwalk exhibit, except for feeding.

Although there were trends in behaviour across age groups, it is also interesting to note that some

orangutans in the same age group differed greatly in their behaviour. See the Appendix for more

information on individual orangutan behaviour.

27

Comparing activity budgets across enclosures

Activity budgets were significantly different between the two enclosures (Fig. 2.7), ( 2= 142.39,

df = 6, p < 0.001). Individual chi-squares showed that looking, human interaction, and

regurgitation were significantly greater in the Boardwalk exhibit; and idling, moving and feeding

were significantly higher in the Island exhibit. However, idling and regurgitation were only

significantly different across the exhibits for 1 age group each (groups 4 and 3 respectively).

Playing/socializing did not differ significantly across the exhibits.

Idling: ( 2= 4.71, df = 1, p = 0.030), looking ( 2= 47.33, df = 1, p < 0.001), moving ( 2 = 26.69,

df = 1, p < 0.001), feeding ( 2= 30.28, df = 1, p < 0.001), play/social ( 2= 2.71, df = 1, p = 0.100),

human interaction ( 2= 40.47, df = 1, p < 0.001), regurgitation ( 2= 13.27, df = 1, p < 0.001).

0

10

20

30

40

50

Idle Look Move Feed Play/social Human Interaction

Regurgitate

Perc

enta

ge o

f act

ivit

y bu

dget

(%

)

Boardwalk exhibitIsland exhibit

****

***

***

******

F ig. 2.7. Activity budgets for Boardwalk and Island exhibits (* = p < 0.05, *** = p < 0.001).

28

Comparing captive to wild activity budgets

Compared to the wild activity budgets, the captive activity budgets resembled each other more

closely (Fig. 2.8). Captive orangutans spent the least time feeding (18-25%), orangutans in forests

with irregular supply of fruits spent almost 40% of the time feeding, and orangutans in forests

with a regular supply of fruits spent the most time ( - 55%) feeding. Captive orangutans and

orangutans with irregular food supply spent approximately 50% of their time resting but

orangutans with regular food supply spent only about 27% of the time resting. Travelling was

similar across all orangutan groups; captive animals moved 9-14% of the time, animals with

irregular food supply spent 12% in travel, and those with regular food supply spent 15%

comprised social and other behaviours which were not resting, travelling or feeding, whereas wild

animals spent only 1-

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Perc

enta

ge o

f act

ivity

bud

get (

%)

OthersTravelRestFeed

F ig. 2.8. Activity budgets for wild and captive orangutans. The two leftmost columns are from wild orangutans in regularly and irregularly fruiting forests, and the three columns on the right are for zoo orangutans (n = number of data sets).

29

DISC USSI O N

This study investigated orangutan activity budgets across age groups, enclosure designs, and

between wild and captive orangutans. Because it is challenging to keep orangutans in captivity,

and detailed activity budget data for captive animals are rare, activity budget data were collected

on a group of captive orangutans to improve existing knowledge and provide baseline data for

future comparisons. The results showed that orangutan activity budgets differ across age groups,

and are affected by enclosure design. Even though captive activity budgets were not exactly the

same as wild activity budgets, the data from captive animals were surprisingly similar to that of

wild orangutans in irregularly fruiting forests.

Comparing activity budgets across age groups

When comparing behaviours across age groups, the younger orangutans in this study played and

moved significantly more than older animals. Specifically, juveniles (aged 3 and 5) spent the

most amount of time moving and playing, as compared to older animals which tended to idle and

look more at their surroundings. Comparing this study to the few existing captive studies with

detailed activity budgets (Cassella, 2010; Marchal, 2004; Pearson et al., 2010), we see the same

general trends: idling and looking is generally predominant in the older groups, and movement

and play is greater in younger orangutans.

In the wild, adult orangutans are semi-solitary. They have wide home ranges which may

sometimes overlap with that of conspecifics. Therefore, social contact is irregular between mature

animals (Mackinnon, 1974; Rijksen, 1975) and they are not known to play (Mackinnon, 1974).

However in captivity, adult orangutans have been found to engage in social behaviour under

group settings (Poole, 1987; Zucker et al., 1978; 1986). On the other hand, sub-adult orangutans

30

are known to play under free-living conditions (Galdikas, 1985b), and play generally allows

young animals to develop motor and social skills important for survival (Fagen, 1981; Smith,

1978). Hence, we would expect more play and social interactions in immature orangutans

(Mackinnon, 1974). Conversely, alertness to surroundings (looking) was more prevalent in older

animals, and at very low levels in the juvenile orangutans. This is similar to what has been found

in a variety of other species. Dominant wild vervet monkeys in several studies were found to scan

their surroundings more than subordinate animals. This was thought to be a consequence of

having a greater need to protect their kin, as well greater involvement in intergroup resource

competition (Isbell and Young, 1993). Such age-related patterns may explain why attentiveness to

surroundings was found to be lowest in the youngest age group of the present study.

The findings from this study mirror that of previous investigations on wild orangutans, as well as

sociality and play in captive apes. It has been found that younger orangutans are generally more

active, under both captive (Marchal, 2004; Perkins and Bradfield, 1989) and wild settings

(Davenport, 1967; Morrogh-Bernard et al., 2009). Immature animals are also more gregarious

(Galdikas, 1985a; Mackinnon, 1974; Rijksen, 1975) and spend more time playing (Edwards and

Snowdon, 1980; Mackinnon, 1974; Zucker et al., 1986). On the other hand, older orangutans tend

to play less in captivity (Edwards and Snowdon, 1980; Poole, 1987; Zucker et al., 1986) and are

less active both in captivity (Marchal, 2004) and in the wild (Morrogh-Bernard et al., 2009).

The results presented here show that the orangutans in Singapore Zoo display age-specific levels

of behaviour, which reflects positively on the quality of management in this zoo. Such results will

be useful for comparisons with other captive populations to see if captive behaviour deviates

significantly from wild-type behaviour. Such comparisons can be used as welfare indicators for

captive animals (Hosey et al., 2009; Melfi and Feistner, 2002).

31

Comparing activity budgets across enclosures

For this group of orangutans, activity budgets seem to be influenced by two types of factors:

structures within the exhibit, as well as features surrounding the exhibit. Comparing activity

budgets across the two exhibits, orangutans seem to interact more with their surroundings in the

Boardwalk exhibit. As mentioned previously, the Boardwalk exhibit was directly alongside a

(busy) restaurant and a third orangutan exhibit.

further from the restaurant, and the view of the third orangutan exhibit was obscured by several

trees. Because the same environmental features, i.e. the restaurant and the third exhibit were

closer to the Boardwalk than Island exhibit, this resulted in more visitor traffic and orangutan

activity (from the third exhibit) around the Boardwalk exhibit. Hence, the significantly higher

incidences of looking and human interaction when orangutans were in the Boardwalk enclosure

appear to be responses to this particular environment. In addition, the presence of the elevated

visitor boardwalk in this exhibit, which allowed closer proximities between orangutans and

visitors, may also have contributed to the higher human interactions here. Similar results have

been found in other primate studies, where cages nearer the exit and main paths had higher visitor

attendance than cages further from the exit or off the main paths (Mitchell et al., 1990). Also, the

presence of more visitors has been associated with responses from primates which manifest as

greater incidences of aggression (Chamove et al., 1988; Wells, 2005) or the increased use of

enclosure areas near visitors . Not only does enclosure design affect animal behaviour,

environmental features seem to have an effect as well. Information of this nature is especially

useful when designing exhibits for species which may be vulnerable to high levels of noise, or are

easily affected by visitors.

Besides environmental features, the differing arrangement of structures within each exhibit also

seems to have contributed to the dissimilar activity budgets. The higher amounts of regurgitation

32

in the Boardwalk exhibit were most likely due to the location of the platform in this enclosure.

Orangutans in this zoo almost always regurgitated on platforms. The platform in the Boardwalk

exhibit was at the centre, whereas the same structure in the Island exhibit was at one end of the

60m long enclosure. Hence, ease of accessing the platform would have had a strong influence on

amount of regurgitation in each exhibit. Regurgitation occurred more in the Boardwalk exhibit

possibly because the platform was at the centre of the enclosure. Similarly, the spacing and

availability of structural features in the Island exhibit may have contributed to why more

movement was present in that exhibit. The Island exhibit consisted of a straight row of trees, and

the nets, platforms and log in this exhibit were located only at either ends of the exhibit (see Fig.

2.2). In addition, the trees in the centre of the row had less branches and foliage, as compared to

trees at both ends which had larger crown diameters and more foliage and branches. As a result,

the orangutans were observed to spend more time at the sides of the exhibit. Because the row of

trees spanned a good 60m in length, we would expect the orangutans to move more in this exhibit

when getting from one end to the other. In contrast, structural features in the Boardwalk exhibit

were spread more evenly throughout. Similarly, because a huge net was present in the Island

exhibit, but not in Boardwalk exhibit, and heavy utilization of this net was observed, it is possible

that the presence of this structural feature contributed to higher rates of idling (for only age group

4) in the Island exhibit. Lastly, the only plausible reason for more feeding in the latter exhibit, is

that, as compared to the Boardwalk exhibit, the relative lack of environmental stimuli in the

Island exhibit may have resulted in a decrease in other behaviours and a subsequent increase in

feeding behaviour.

It is known that the availability and arrangement of features in an exhibit can affect animal

behaviour. Many studies have found that great apes are more active and display more species-

specific behaviours when in structurally complex enclosures with climbing features, as compared

to barren exhibits (Clarke et al., 1982; Maple and Stine, 1982; Pfeiffer and Koebner, 1978). The

33

location of enclosure features, though not well understood, has also been found to affect how

heavily a feature is used; for example, caimans predominantly used pools in their enclosures and

areas further from the pools were used significantly less (Verdade et al., 2006). From this, we can

see how animal behaviour can be modified providing certain structures or arranging features in a

certain way within an exhibit. This knowledge can be used by zoo management to encourage or

discourage certain behaviours, such as increasing movement or decreasing regurgitation (an

undesirable behaviour, Akers and Schildkraut, 1985, see Chapter 5), or to promote greater use of

the entire exhibit in the species on display (Stoinski et al., 2001). Similarly, features in the

surrounding of an exhibit can be either enrichment or a form of stress for animals. Orangutans are

known to be inquisitive animals, and are often very interested in their surroundings (Hebert,

2011, pers. comm.4; Nantha, 2009, pers. comm.5; pers. obs.). Many anecdotes from zoo keepers,

as well as a study by Bloomfield et al. (2010) suggest that these apes do not actively avoid, and in

fact often spend time watching visitors, as well going-ons outside their enclosure. Hence, features

in the vicinity of an orangutan enclosure could be both enrichment and sources of stress for

captive animals.

Comparing captive to wild activity budgets

Interestingly, the activity budgets of orangutans in captivity were more similar to that of animals

in irregularly fruiting forests than regularly fruiting forests. The amount of time spent feeding

ranged from 18 to 25% in captive animals, as compared to 38% in orangutans of irregularly

fruiting forests and 55% in orangutans of regularly fruiting forests. In the wild, foraging and

ity budget (see review

in Morrogh-Bernard et al., 2009). Orangutans have to locate food sources which are spread

4 Patricia Hebert, Orangutan researcher, Fort Wayne Children's Zoo 5 Gabriel Nantha, Orangutan keeper, Singapore Zoo

34

patchily throughout the forest, and many fruits in the wild require extensive preparation to

separate out the edible from inedible portions (Mackinnon, 1974). However, in captivity, foraging

is reduced to concentrated bouts of feeding during mealtimes where provided foods can usually

be ingested with little preparation. Therefore, it is reasonable to expect that, because orangutans

in Singapore Zoo received only sporadic feedings of leaves and small fruit snacks while on

exhibit, the time spent feeding would be considerably lower than that of wild animals. Also,

because orangutans in the other three zoo studies received only one main meal and sometimes

fresh leaves (browse) during observation periods (Cassella, 2010; Marchal, 2004, Pearson, 2010,

pers. comm.6), feeding behaviours may also be expected to decrease. These results are analagous

to those from another study which compared wild to captive Sulawesi macaques (Macaca nigra),

in which the authors also found that zoo macaques spent less time feeding and more time resting

(Melfi and Feistner, 2002).

Conversely, the amount of resting behaviour in animals from all captive groups, as well as those

from irregularly fruiting forests, was higher than the amount of resting behaviour in animals from

regularly fruiting forests. Due to the lack of foraging opportunities, it is understandable that

captive orangutans spent more time inactive than their wild counterparts (Zucker et al., 1986).

However, what is interesting is that the amount of inactive rest in orangutans with irregular food

supply was not significantly different from that of captive animals. In fact, the main differences in

activity budgets between captive orangutans and wild orangutans with irregular food supply

greater in captive animals and lesser in wild animals. Hence, it appears that the time not spent on

vities such as social and solitary play.

Because all of the captive orangutans in this study were kept in groups of two or more, there were 6 Elissa Pearson, Orangutan researcher, Adelaide Zoo

35

regular opportunities for social interactions which may not be present for wild animals (Zucker et

al., 1986). As a result of this inactivity brought about by the lack of foraging opportunities, as

well as the presence of social partners in captivity, there is a corresponding change in captive

orangutan activity budgets, i.e. less feeding and more play in captive animals. Such reallocation

of activity budgets has been observed in the comparison of provisioned and unprovisioned

primate groups. Savannah baboons (Papio cynocephalus) and vervet monkeys (Cercopithecus

aethiops) which had access to human sources of food spent only about 20% of the time feeding,

and about 50-60% of the time resting. This was in contrast to unprovisioned groups which spent

40-60% of the time feeding, and 10% of their time resting (Altmann and Muruthi, 1988; Brennan

et al., 1985; Lee et al., 1986). Because human food sources such as tourists or garbage dumps

provide easily accessible, spatially concentrated, and relatively nutrition-rich sources of food; as a

result, provisioned animals spend less time procuring the same amount of nutrition. Naturally,

provisioned groups had reduced feeding times, and could afford more time on other activities

such as socializing and resting. Social stimulation may serve as an alternative to reduce inactivity

in captive animals (Perkins, 1992; Wilson, 1982) and may compensate for the lack of captive

environmental complexity relative to that of free-ranging conditions (Poole, 1987).

Lastly, it is encouraging to see that the amount of time spent travelling in captivity was

comparable to that of wild conditions. Although animals in captivity have restricted living space,

these results show that captive orangutans may still have the opportunity to maintain similar

levels of movement as wild counterparts. One possible factor could have been the naturalistic

design of the orangutan enclosures under study. All the orangutan enclosures were large, between

700-1500 m2 in area, and had structures which provided arboreal opportunities (Cassella, 2010;

Marchal, 2004; Pearson et al., 2010). It is known that the presence of complex enclosures, social

partners, and manipulatable objects can increase activity in captive orangutans (Perkins, 1992;

Tripp, 1985; Wilson, 1982), and my results also support this. Because captive apes have a

36

propensity for inactivity and obesity in captivity (Gippoliti, 2000), such findings are encouraging

for zoo managers. Hence, systematic research on the influence of factors such as enclosure usage

may be an important next step to take in optimizing captive animal welfare. The following

chapter investigates the relationship between enclosure structures and animal behaviour to shed

further light on this topic.

Overall, the activity budgets of the captive orangutans seem to be comparable to that of the wild,

which is a good indication for captive orangutan management. Activity budgets give a broad,

although simplistic overview of behavioural expression, which can be used to determine if

captive individuals are deviating from the wild-type pattern, as well as serve as indices of captive

welfare (Hosey et al., 2009).

37

R E C O M M E ND A T I O NS

It should be possible to increase desirable behaviours, and reduce undesirable behaviours

by manipulating the location of structures in an exhibit. For example, placing a platform

at a far end of an enclosure may reduce regurgitation. Also, placing structures far apart in

an enclosure may encourage more movement and less inactivity in captive animals.

It may be feasible to use features surrounding the exhibit as a form of enrichment, and

factor this into exhibit design when deciding where to locate an orangutan exhibit.

Similarly, if the animals are sensitive to noise or visitors, care can be taken in deciding

where to locate an exhibit.

Reduce inactivity by increasing opportunities for feeding, foraging and movement. For

example, increase the complexity, variety and frequency of foods provided. Opportunities

for arboreal movement could also be provided, for example by using live trees in the

exhibit, or providing structures such as sway poles, which allow orangutans to move

between these flexible poles by bending the poles with their body weight. (See next

chapter)

38

C O N C L USI O NS

The activity budgets of the orangutans were found to differ significantly across age

groups. Younger animals were more active and played more, older animals idled and

looked more. Singapore Zoo orangutans show age-specific behaviours, which is a

positive note on orangutan welfare.

Activity budgets differed significantly across enclosures. Both exhibit structures and

environmental features influenced activity budgets.

The activity budgets of zoo orangutans were similar in some ways to that of wild

orangutans. Captive orangutans fed less, rested more, and had comparable amounts of

movement with wild orangutans. Records of captive activity budgets are useful

references for zoo management.

39

C H APT E R 3

Use of Enclosure Structures and Vertical Space

in Two Naturalistic O rangutan Exhibits

Abstract. Animals in captivity are subjected to spatial and behavioural limitations. Research has

examined space use in zoo exhibits, but how animals interact with structures is still poorly

understood. The majority of space use studies have been conducted on chimpanzees and gorillas,

and little is known about the space use of other species. In this study, I investigated the use of

enclosure structures, such trees, vines, nets, platforms and logs in two naturalistic orangutan

exhibits. Proportion of time spent, and behaviours occurring at each structure type were noted.

The time spent by orangutans at different vertical heights in the enclosure was also recorded.

Results showed that structure use varied with age and dominance status. The properties,

availability and location of structures in an exhibit could affect the behaviours which occurred at

each structure type, as well as how frequently the structure was used. Husbandry routines and

features in the surrounding of the exhibits also influenced structure use. Vertical space use was

affected by certain structures, primarily, the properties of tree branches and availability of nets

and platforms at different heights. Recommendations are made on how to encourage behavioural

diversity and optimize exhibit use in captive orangutans.

K eywords: orangutan, naturalistic exhibit, enclosure use, space use, structure use, exhibit design, vertical space

40


Animals in captivity are often subjected to spatial and behavioural limitations. The arrangement

of structural features in a zoo enclosure can determine how animals move or behave (Jensvold et

al., 2001), and biologically relevant environments can only be created when we understand the

requirements of each species (Estevez and Christman, 2006). However to date, knowledge on

space use in many captive species is still lacking (Leighty et al., 2010; Stoinski et al., 2001).

Over the past two centuries, zoos have begun to incorporate the behavioural and psychological

needs of animals in exhibit design. First-generation exhibits of small, barren cages and deep

smooth walled pits have given way to second-generation exhibits which are more spacious, but

still usually cement enclosures surrounded by dry or wet moats. The most recent third-generation

exhibits, however, are more complex, and aim to display animals in naturalistic settings (Shettel-

Neuber, 1988). Such enclosures simulate the natural habitats of the species by making extensive

use of plants and natural features and housing animals in social groups similar to that of their

free-ranging counterparts (Shettel-Neuber, 1988). On the whole, there has been a distinct

movement to increase the size and environmental complexity of zoo exhibits (Hosey et al., 2009).

Complex exhibits have been shown to promote higher levels of activity and species-typical

behaviours, as well as decrease abnormal behaviours in a variety of species. These include

chimpanzees (Brent et al, 1991; Jensvold et al 2001; Pfeiffer and Koebner, 1978), orangutans

(Maple and Stine, 1982, Perkins, 1992; Tripp, 1985; Wilson, 1982), gorillas (Hoff et al, 1994;

Maple and Stine, 1982, Wilson, 1982; Bowen, 1980), hanuman langurs (Little and Sommer,

2002) and Indian leopards (Mallapur and Chellam, 2002). Similarly, naturalistic exhibits also

increase species specific behaviours (Maple and Stine, 1982; Pfeiffer and Koebner, 1978),

decrease stereotypic behaviours (Akers and Schildkraut, 1985; Erwin and Deni, 1979; Gould and

41

Bres, 1986), improve aggression and affiliation in a variety of primates (Clarke et al., 1982;

Maple and Finlay, 1989; Maple and Stine, 1982), and improve visitor appreciation of animal

ecology and behaviour (Price et al., 1994; Stoinski et al., 2001). Although we can see how

naturalistic and complex exhibits benefit both zoo animals and visitors, there is still a lack of

information on how animals interact with individual exhibit features. Because naturalistic exhibits

are often more costly to build and require more maintenance (Shettel-Neuber, 1988; Stoinski et

al., 2001), and with the increase in naturalistic habitats worldwide, there is a need for further

study on this topic (Ogden et al., 1990). Knowledge gained from enclosure use studies can then

be incorporated into future exhibit design to optimize the welfare of captive animals

(Seidensticker and Doherty, 1996; Shettel-Neuber, 1988).

To date, the scientific study of space use is still in its infancy (Ogden et al., 1990; Stoinski et al.,

2001). Of the existing research, the majority has focused on chimpanzees (Bettinger and Carter,

1994; Goff et al., 1994; Ross et al., 2009; 2011) and gorillas (Ogden et al., 1993; Ross et al.,

2009; 2011; Stoinski et al., 2001), with a few on orangutans (Hebert and Bard, 2000; Pearson et

al., 2010). There have also been single studies on a variety of other mammals (wild boars:

Blasetti et al., 1988; sloth bears: Forthman and Bakeman, 1992; manatees: Horikoshi-Beckett and

Schulte, 2006; South American tapir: Mahler , 1984; American bison: Robitaille and Prescott,

1993). Findings have shown that primates have preferences for walls, corners and vertical

structures (James-Aldridge and Gorena, 1991; Ogden et al., 1993) and adult and juvenile animals

have differential space use (Blasetti et al., 1988; Perkins and Bradfield, 1989; Traylor-Holzer and

Fritz, 1985). Certain exhibit structures or areas tend to be associated with particular behaviours,

such as Indian leopards which used enriched areas in their exhibit for active behaviours (Mallapur

and Chellam, 2002) and wild boars which used shaded and muddy areas for resting (Blasetti et

al., 1988). For the majority of species, however, there is still a lack of understanding on detailed

space use and how animals interact with structures (Leighty et al., 2010; Stoinski et al., 2001).

42

In Singapore Zoo, two naturalistic orangutan exhibits of novel design, believed to be the first of

their kind in the world, were established in 2006. Unlike typical exhibits which contain apes by

using indoor enclosures or moated islands, these exhibits are based entirely in the outdoor canopy

of several trees. Orangutans move about in the canopy above the visitors, and low-current

electrical wires at the base of trees as well as large gaps between exhibit and surrounding

vegetation aid in containing the orangutans. Because such a design is new as well as naturalistic,

it provides the unique opportunity to study space use in an orangutan exhibit that is entirely

arboreal. Orangutans are animals with large home ranges in the wild, and they are known to

traverse large distances over tree canopies in search of food (Wich et al., 2009). Correspondingly,

arboreal use of space has been found to be an important factor in captive orangutan enclosures

(Maple, 1979; Maple and Stine, 1982). Because a lack of activity space can lead to lethargy and

obesity (Gippoliti, 2000; Pizzutto et al., 2008), there is a need to provide adequate climbing

opportunities in captive orangutans (Gippoliti, 2000; Hebert and Bard, 2000; Maple and Stine,

1982). However, most studies on enclosure use so far have focused on chimpanzees and gorillas.

Because these apes live in terrestrial habitats, unlike the forest-dwelling orangutans (Wich et al.,

2009); to date, we still have insufficient knowledge on orangutan space use.

Of the few orangutan studies on enclosure use, most have focused on the percentage of enclosure

utilized and time spent off the ground or at certain structures (Manning, 2002; Perkins and

Bradfield, 1989), with no details on what behaviours go on at different structures. Only one study

has systematically observed the behaviour of orangutans at different vertical heights in an

enclosure (Hebert and Bard, 2000). There is a dearth of information on structure use in

orangutans; hence the presence of a naturalistic exhibit with nine animals provides an excellent

opportunity to learn more about space use in captive orangutans. This study is the first to

systematically investigate the use of structures (trees, vines, nets, platforms, logs) in a naturalistic

enclosure, and the behaviours which occur at each type of exhibit structure. The use of different

43

exhibit heights is also elucidated in this novel exhibit to see if there are any preferences for

vertical heights between age groups. Such information will be useful for captive orangutan

management, and can aid in the design of future orangutan enclosures.

Objectives of study

1. What is the proportion of use for different structure types? Does structure use differ

across age groups and exhibits?

2. What activities/behaviours occur at different structures? Does it differ across age groups

and exhibits?

3. What is the proportion of time spent at different vertical heights of the enclosure? Does it

differ across age groups and exhibits?

44


Study site and subjects

The study site and subjects were the same as in the previous chapter. To recap, a group of

orangutans in two treetop, naturalistic enclosures of novel design were studied, to see how they

utilized different structures in each exhibit. The two enclosures, the Boardwalk and Island

exhibits, each consisted trees, vines, nets, platform(s) and a log. However there were differences

in the arrangement of structures within each exhibit, as well as dissimilarities in the

environmental features surrounding the two exhibits (Figs. 3.1, 3.2). The Boardwalk exhibit was

made of an L-shaped row of trees. The structures in this exhibit were spread evenly throughout,

with a log and platform at the centre of the exhibit, and two other small nets spread throughout

the exhibit. On the other hand, the Island exhibit was made up of a straight row of trees. The log

and platforms in this exhibit were located at one end together with a small net, and at the other

end of the exhibit were two other nets, one large, one small. Hence the structures in the Island

exhibit were concentrated at either end of the exhibit, as compared to the Boardwalk exhibit,

which had structures evenly throughout.

45

F ig. 3.1. Schematic diagram of Boardwalk Free-ranging exhibit. Structures are spread throughout the exhibit. (Figure not drawn to scale; however human silhouettes convey a sense of proportion)

46

F ig. 3.2. Schematic diagram of Island Free-ranging exhibit. Structures are clustered on either end of the exhibit. (Figure not drawn to scale; however human silhouettes convey a sense of proportion)

47

Again, the other main difference between the enclosures was that visual stimulus from

surrounding features was greater for orangutans in the Boardwalk exhibit than in the Island

exhibit. Features in the vicinity of both exhibits were generally closer to the Boardwalk exhibit

(Fig 3.3). The latter was situated directly alongside a third orangutan enclosure and a busy

restaurant. On the other hand, the Island exhibit was further from the restaurant and there were

trees between the Island exhibit and the third enclosure, which obstructed the view of the latter

from the Island exhibit. Hence, orangutans when in the Boardwalk exhibit, received more visual

stimuli than when in the Island exhibit.

Busy restaurant with outdoor dining area

ISL

AN

D E

xhib

it

T hird orangutan exhibit

B O ARDWA L K Exhibit

Main track for visitors and vehicles

Tree

F ig. 3.3. Plan diagram showing proximity of Boardwalk and Island exhibits to surrounding features. Orangutans received greater visual stimuli from surrounding features when in the Boardwalk exhibit.

48

Data collection and processing

The data collected in the previous chapter was analyzed to investigate enclosure use patterns in

the same group of orangutans. Orangutans were again classified into four age groups based on

Mackinnon (1974) (see Table 3.1). As mentioned, each exhibit was made up of several structures,

namely trees, vines, nets, platform(s) and a log. Orangutan location was classified according to

the type of structure that each animal was found on. Use of enclosure structures was then

summarized by counting the number of scan samples for each structure type and converting it to a

percentage of the total scans. A summary of overall structure use was done for each enclosure.

Data analysis

Structure use of the different age groups was compared with a hi-square test of

independence, and separate chi-square analyses were run for each enclosure. Following that, the

behaviours at each structure were investigated. For each structure type (tree, vine, net, platform,

or log), the activity budgets of different age groups were plotted. The behaviour categories used

here were similar to those used in Chapter 2, except that the category of play/social was spilt into

two separate categories for more detailed analysis (see Table 3.2).

Lastly, to investigate vertical use of the exhibits, each exhibit was divided vertically into three

leve

the bottom one-

one-

structures at that height. A P -square test was run for age group against height use, for

both enclosures.

49

Table 3.1 Individual details and age groups of study animals. All individuals were born in the Singapore Zoo except Anita who was donated to the zoo at one year of age. Name Sex Age

(yr) Species Allocated age group

Group A

Ah Meng Jnr Female 1 Pongo pygmaeus NA Bento Male 3 Pongo pygmaeus 1 - Juvenile Budi Male 7 P. pygmaeus/ P. abelii cross 2 - Adolescent Gunta Male 7 Pongo pygmaeus 2 - Adolescent Chomel Female 13 Pongo abelii 3 Sub-adult Anita (with infant Ah Meng Jnr)


Group B Saloma Female 0.5 Pongo pygmaeus NA Merlin Male 5 Pongo pygmaeus 1 - Juvenile Vira Male 9 Pongo pygmaeus 3 Sub-adult Labu Male 11 Pongo pygmaeus 3 Sub-adult Binte (with infant Saloma)


Table 3.2 Definitions for orangutan behaviours Orangutan Behaviour Definition Idle Orangutan is motionless, with unfocused gaze, or performing any of these

behaviours: autogrooming, expelling bodily waste. Look Orangutan is looking at an object/keeper/another orangutan in surroundings,

face and eyes are oriented towards that location. Move Orangutan is travelling from one location to another; can be brachiating,

bi/quadrupedal walking, or any other form of locomotion. Feed Orangutan is engaged in searching for, preparation of, or ingestion of food.

Autoplay Orangutan is engaged in object use or solitary play.

Social Orangutan is engaged in social play, or social interactions, inclusive of


Human Interaction Orangutan is looking at visitor(s), face and eyes are oriented towards visitor(s), or is soliciting food by stretching out hand towards visitor(s).

50

R ESU L TS

Overall structure use

The orangutans spent most of their time in trees (~30%) and on nets (28-40%), with the rest of

their time on the platforms (14-16%), logs (8-14%) and vines (8-10%) (Fig. 3.4).

Tree32%

Vine10%Net

28%

Platform16%

Log14%

Tree30%

Vine8%Net

40%

Platform14%

Log8%

F ig. 3.4. Overall structure use for all orangutans in Boardwalk (left) and Island (right) exhibits.

51

Structure use across age groups in both exhibits

Structure use was significantly different across age groups in both exhibits (Boardwalk exhibit:

2= 564.09, df = 12, p < 0.001, Island exhibit: 2=216.51, df = 12, p < 0.001).

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Perc

enta

ge o

f tim

e sp

ent a

t di

ffer

ent s

truc

ture

s (%

)

0%10%20%30%40%50%60%70%80%90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

LogPlatformNetVineTree

F ig. 3.5. Structure use for different age groups (gp) in Boardwalk (left) and Island (right) exhibit.

In the Boardwalk exhibit (Fig. 3.5), animals in group 4 spent the most time (47%) on the net, as

compared to age group 1 (31%), and especially age groups 2 (17%) and 3 (20%). Log use was

also double that in the oldest age group (30%), as compared to the other groups 1, 2, 3 of 9%,

12% and 9% respectively. Conversely, platform and vine use was greater in younger animals.

Groups 1-3 spent 25%, 23% and 13% respectively on platforms, but only 5% by group 4. Vine

use was 9%, 10%, and 15% in groups 1-3 respectively but group 4 only spent 4% of their time on

vines.

For the Island exhibit, structure use was more similar for groups 1 to 3, than group 4. Net use was

highest in group 4 at 57%, as compared to groups 1-3 at 37%, 34% and 36% respectively. Vine

use was lowest in age group 4 (6%), almost half of the other age groups (7-10%). Log and

52

platform use was distributed more evenly across the age groups and utilized less than in the

Boardwalk exhibit, at 6-13% for log and 10-18% for platform use.

53

Behaviours at each structure type

For the trees in the Boardwalk exhibit, the major activities were idling and moving in group 1 and

idling and looking in groups 2, 3 and 4 (Fig. 3.6). In the Island exhibit, idling, moving and

feeding were the major activities in age group 1. Idling, looking and feeding were the major

activities in age groups 2 and 3. Looking and moving were most prevalent in the oldest group 4

animals. Looking was higher in the Boardwalk exhibit, and took between 16-54%, but only

between 12-33% in the Island exhibit. Conversely, feeding was higher in the Island exhibit trees

with from 14-38% but only between 5-20% in the Boardwalk exhibit.

On vines, movement was the major activity across all age groups and exhibits, taking up to 30-

45% in the Boardwalk exhibit and 67-88% in the Island exhibit. More play, human interaction,

and looking were also present on the Boardwalk exhibit vines.

On nets, major activities tended to be idling and feeding in both exhibits. There was slightly more

looking in the Boardwalk exhibit than Island exhibit, double the amount of movement in the

Island exhibit than Boardwalk exhibit, and more play in groups 1 and 2 in the Boardwalk exhibit.

Regurgitation, play and idling were the major activities on platforms. There was human

interaction on the platforms in the Boardwalk exhibit, but none at the Island exhibit platforms.

At the logs, there was an even distribution of behaviours. Movement and feeding made up a

larger proportion of the activity budget in the Boardwalk exhibit than in the Island exhibit. Play

and idling were greater on the Island exhibit log.

54

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Perc

enta

ge o

f act

ivity

bud

get

(%)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Tree

Regurgitate

Human Interaction

Social

Autoplay

Feed

Move

Look

Idle

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Perc

enta

ge o

f act

ivity

bud

get (

%)

0%10%20%30%40%50%60%70%80%90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Vine

Regurgitate

Human Interaction

Social

Autoplay

Feed

Move

Look

Idle

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Perc

enta

ge o

f act

ivity

bud

get

%)

0%10%20%30%40%50%60%70%80%90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

N et

Regurgitate

Human Interaction

Social

Autoplay

Feed

Move

Look

Idle

F ig. 3.6. Behaviours of different age groups (gp) at structures in the Boardwalk (left) and Island (right) exhibits.

55

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Perc

enta

ge o

f act

ivity

bud

get (

%)

0%10%20%30%40%50%60%70%80%90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Platform

Regurgitate

Human Interaction

Social

Autoplay

Feed

Move

Look

Idle

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Perc

enta

ge o

f act

ivity

bud

get

(%)

0%10%20%30%40%50%60%70%80%90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Log

Regurgitate

Human Interaction

Social

Autoplay

Feed

Move

Look

Idle

F ig. 3.6. Behaviours of different age groups (gp) at structures in the Boardwalk (left) and Island (right) exhibits (continued).

56

Use of vertical space in enclosure

The percentage of time spent at different heights differed significantly across the age groups in

both exhibits (Boardwalk exhibit: 2= 91.97, df = 6, p < 0.001, Island exhibit: 2= 94.66, df = 6, p

< 0.001).

In the Boardwalk exhibit, the orangutans generally spent most of their time (59-74%) in the mid

layers of the exhibit (Fig. 3.7). Use of the highest canopy layer was triple that in age groups 1 and

2 at 3-4% as compared to 1% in group 3 and 0% in group 4. Use of the lowest parts of the exhibit

was similar at around 40% in all groups, except age group 3 with 25% use.

In the Island exhibit, vertical use of exhibit was different from that of the Boardwalk exhibit. Use

of the mid canopy was heavier, at 67-83%. Again the youngest age groups 1 and 2 made the most

use of the highest layer, at close to 10%, but only at 3% in group 3 and none in group 4. Use of

the lowest canopy space was around 17-25% in all groups.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

Perc

enta

ge o

f tim

e sp

ent

atdi

ffer

ent e

xhib

it he

ight

s (%

)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Age gp 1

Age gp 2

Age gp 3

Age gp 4

High

Mid

Low

F ig. 3.7. Use of vertical space by different age groups (gp) in Boardwalk (left) and Island (right) exhibits.

57

DISC USSI O N

This study investigated structure use and vertical space use in naturalistic orangutan exhibits to

improve understanding of how captive animals use their enclosures. Previous research suggested

that primates have preferences for certain exhibit structures, but studies have been limited to a

few species only. Here, the time spent by orangutans on the different structure types and their

activity budgets at each structure were investigated. Vertical space use was also elucidated. The

results showed that structure use varied with age and dominance status, as well as the

arrangement and availability of structures within the exhibit. Features surrounding the exhibit as

well as husbandry routine also affected structure use.

Use of enclosure structures across age groups and exhibits

From the results of the structure use study, we can see how two types of factors, i.e. biological

factors, such as age, behavioural profile, dominance hierarchy; and environmental features, i.e.

structure availability and location, can affect structure use (Leuck, 1977).

First, let us consider how biological factors affect structure use. In both exhibits, the largest

amount of time spent on any structure across the age groups was approximately 50% on nets by

age group 4. For net use in the Boardwalk exhibit, age groups 1 and 4 spent double the amount of

time on nets as compared to the other 2 age groups. Considering the results from Chapter 2 on

activity budgets, that age group 4 spent the most (a third of their) time idling and age group 1

spent the most time playing, it makes sense that these two groups had the greatest net use. This is

because idling and playing usually occurred on flat surfaces. Unpublished data by Marchal (2004)

showed that older animals (aged 15 - 40) spent the greatest proportion of their time on the floor, a

large, flat surface, as compared to the arboreal structures in their exhibit. As the nearest

58

equivalent of the floor would be the net in the Boardwalk exhibit, the results from the present

study seem to

been found to spend more time on moveable structures (ropes) than older animals (aged 10 - 32),

and were thought to prefer the moveable structures for play (Perkins and Bradfield, 1989). This is

similar to how the age group 1 orangutans in the Boardwalk exhibit spent more time on the

suspended net as compared to age groups 2 and 3, possibly because group 1 animals played more.

On the other hand, age group 4 dominated use of the log. More than 30% of the time was spent by

age group 4 on the log in the Boardwalk exhibit, whereas other groups only spent about half that

amount of time there. As the log was located in the centre of the exhibit and joined two trees on

which a net and the platform (core areas of activity) were found, this structure may have been a

major route or passageway for movement. It also appears the position of the log allowed the

animal which sat there a good view of the visitors coming up the boardwalk. This may suggest

why the older animals who looked more (see previous chapter), tended to spend a large

proportion of their time there. As a result, similar to what was found in captive bison (Robitaille

and Prescott, 1993) and gorillas (Fischer and Nadler, 1978; 1977; Hedeen, 1982), when older and

-

ranking individuals would actively avoid close interactions with them. Hence, lower rates of log

use are apparent in younger animals. Alternatively, similar to what was found in captive gorillas

(Ross and Lukas, 2006), older animals might also have used their location on the pathway as a

form of control over other individuals in their group.

Conversely, platform use in the Boardwalk exhibit was higher in the younger age groups 1 and 2,

possibly because these age groups played and regurgitated more, and playing and regurgitation

generally are facilitated by flat surfaces. Across both exhibits, vine use was double in all other

age groups, as compared to age group 4. This reflects the relative lack of movement in this age

group. Overall, the oldest orangutans spent more time on nets and logs, and the least on vines,

59

which suggests sedentary activities for these animals. These results mirror those found by studies

on wild (Morrogh-Bernard et al., 2009) and captive orangutans (Cassella, 2010; Marchal, 2004;

Perkins and Bradfield, 1989), which show that older animals generally tend to be less active.

younger animals used all structures more evenly. These results mirrors those from Perkins and

Bradfield (1989) who also found that older orangutans have clumped usage of exhibit and

younger animals were dispersed more evenly throughout the enclosure. Similar findings, although

not statistically significantly, are available for gorillas in a naturalistic exhibit (Stoinski et al.,

2001). From the results, it is clear that age, dominance, and subsequently behavioural profile of

different age groups can affect structure use.

Secondly, the results show how environmental factors, such as the location and availability of

structures within the exhibit, as well as the features in the vicinity of the exhibit can also affect

structure use. This can be seen in the differential use of nets, platforms, and logs across the

exhibits. Unlike the Boardwalk exhibit, net use in the Island exhibit was higher across all age

groups. This may be due to the presence of a huge cargo net which was present only in this

exhibit. Such a finding suggests that the availability of structures can affect choice of orangutan

location. Also, unlike in the Boardwalk exhibit where log and platform use was different across

age groups, we find that use of these structures was more evenly spread, as well as lower across

all groups in the Island exhibit. This was because in the Island exhibit, the log and platforms were

at one end of the exhibit, further away from the other core area of activity (i.e. the large cargo net)

(see Fig. 3.2). Conversely in the Boardwalk exhibit, the log and platform were in the centre.

Hence, orangutans spent more time at the log and platform when in the Boardwalk exhibit.

Finally, vine use was generally higher in Boardwalk exhibit than in Island exhibit. As mentioned,

the two exhibits differed in their proximity to surrounding features, such a restaurant and a third

orangutan exhibit in the vicinity. Orangutans while in the Boardwalk exhibit, had been frequently

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observed to watch other orangutans which were housed in a third exhibit alongside the visitor

boardwalk. This too occurred in the Island exhibit, but to a lesser extent as the view of the third

orangutan exhibit from the Island exhibit was obscured by some trees (see Fig. 3.3). In addition,

have stimulated more looking behaviour. Such behaviour was often carried out from particular

vines in the exhibit.

It is apparent that the arrangement and availability of structures within an enclosure as well as the

presence of features in the surrounding of the enclosure can affect structure use. Manning (2002)

found that orangutans used rope and platform elements in their enclosure more when such

structures were available; similarly, higher rates of structure use were present when gorillas,

orangutans and chimpanzees were moved from barren cages to more complex, naturalistic

habitats (Maple and Stine, 1982; Pfeiffer and Koebner, 1978). The arrangement of features

within an exhibit, although not well studied, has also been found to affect how heavily a feature is

used. For example, caimans, for the most part, used pools in their enclosures; areas further from

pools were used significantly less (Verdade et al., 2006). Also, it has been found that primate

cages nearer the zoo exit and main paths had higher visitor attendance than cages further away or

off the main paths (Mitchell et al., 1990). The presence of more visitors was also associated with

increased aggression from primates (Chamove et al., 1988; Wells, 2005) and increased use of

enclosure areas near visitors (Fa, 1989). From these, we can appreciate how structure

arrangement, availability, and features in the vicinity of enclosures can affect animal behaviour

and subsequently structure use.

Because there is currently very little information available on the use of enclosure space across

many animal species (Stoinski et al., 2001), this knowledge on how different factors affect

structure use will serve as useful baseline data. Such information will come in useful during the

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regular renovations to Singapore Zoo orangutan exhibits, or for the design of future orangutan

exhibits. Specifically, this knowledge can be used to improve animal welfare by ensuring lowest

possible levels of social conflict and sufficient structure availability for all age groups. Also, it

can be used to optimize enclosure use (greater use of entire exhibit), encourage desirable or

discourage undesirable behaviours in animals, or ensure that animals which are more sensitive to

noise or visitors are placed in appropriate locations. Some recommendations are provided at the

end of this chapter.

Behaviours at each structure type

In trees, major activities tended to be idling and looking in older animals, and idling and moving

in younger animals. Hebert and Bard (2000) also found that orangutans in their study (of ages

similar to age group 3 in this study) were solitary inactive (idle and looking) in the upper

canopy. This may be because trees are tall, provide solid surfaces for sitting, and serve as a good

vantage point to observe the surroundings. Therefore, looking and idling were the major activities

there. On the other hand, vines tend to connect structures; hence movement was predominant at

vines. Hebert and Bard (2000) also showed that orangutans in their study were solitary active

(moved and played) for 50% of the time on vines. In the Boardwalk exhibit, some vines were

directly alongside the third orangutan exhibit, with no visual obstructions in between, and some

vines were near the visitor walkway, whereas vines in the Island exhibit were generally higher off

the ground. This might explain why there was more looking and human interaction on Boardwalk

than Island exhibit vines. Feeding was higher at trees in the Island exhibit as fresh leaves

(browse) was always provided at a particular tree, whereas it was not so in the Boardwalk exhibit.

Higher usage of exhibit areas linked to husbandry and feeding has also been found in gorillas

(Stoinski et al., 2001) and tapirs (Mahler, 1984). It was observed that the use of particular exhibit

areas was much heavier when feeding by keepers was carried out there. Such information may be

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useful to know if zoo managements wish to optimize use of exhibit space in captive animals. It is

also interesting to note that orangutans sometimes engaged in species-specific behaviours such as

tree-sway (Thorpe et al., 2007). Tree-

bend the topmost branches of one tree towards the next tree, to enable it to reach out, grab and get

onto the neighbouring tree. Such behaviours could only occur on flexible materials such as the

topmost branches of live trees, which is a positive consequence of having live trees as part of the

exhibit.

The spread of activities in nets was very different from that in trees. Playing, feeding and idling

were the major activities for younger age groups, whereas the older age groups tended to feed,

idle and look more. On the other hand, the platform seemed to facilitate regurgitation and idling

in all age groups. While both surfaces were flat, the nature of the surfaces encouraged different

activities. The orangutans were usually observed to spread browse out on the net and engage in

feeding, whereas the solid surface of the platform facilitated regurgitation and reingestion of

regurgitated material. Both platform and nets encouraged play in animals, as large, flat surfaces

facilitated wrestling and tumbling movements which were characteristic of orangutan play

(Maple, 1980). Again human interaction was more at the Boardwalk exhibit because of the closer

proximities of visitors to the orangutans while on the elevated boardwalk.

Even though there was a more even distribution of behaviours at logs, the log at the Boardwalk

exhibit seemed to be dominated by age group 4. More than 50% of the activities by group 4 at the

log were inactive and longer lasting behaviours such as looking and idling. As discussed

previously, the animals in age group 4 were often observed to sit for long periods at the centre of

the log. Because older animals were dominant in the group, younger animals actively avoided

using the log while older animals were there. Hence, activities in the other age groups at this

structure tended to be more transient, such as movement, feeding, etc. On the other hand, because

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the log in the Island exhibit was not a route between two trees, nor at the centre of the exhibit, use

of the log by all age groups was more even. Idling was the dominant activity here, possibly

because the orangutans would wait at the log in the Island exhibit before feeding times, because

the log was the point of exit from the free-ranging exhibit.

Generally, flat surfaces are used for feeding, playing, idling and regurgitation, vines are used for

movement and looking occurs mainly from trees and vines. It is apparent that behaviour at each

type of structure, other than being dictated by properties of the structure, can also be influenced

by husbandry routine, social factors, location of structures within the exhibit as well as features in

the environment surrounding the exhibit. For example, feeding was more prevalent at trees in the

Island exhibit but the same behaviour occurred more frequently at logs in the Boardwalk exhibit.

This was because browse (fresh leaves) was always provided at a particular tree and at the log in

the respective exhibits. More movement occurred at the log in the Boardwalk exhibit but not the

Island exhibit because the log was a major pathway in the former but not the latter. Also, more

looking took place on vines at the Boardwalk exhibit, but not the Island exhibit because of more

and closer features in the surrounding of the Boardwalk exhibit. Once such knowledge on

behaviours at different structure types is available, this can be used to optimize animal welfare

and improve on future exhibit designs.

In conclusion, a good mix of structure types, at different heights and distances from visitors in an

exhibit, may encourage behavioural diversity in captive orangutans. Some recommendations for

improving orangutan welfare are provided at the end of the chapter.

64

Use of vertical space in enclosure

The results showed that the orangutans favoured the middle layers of the exhibit across both

enclosures. This may have been because the branches in the middle of the canopy were broader

and easier to move on, as compared to thinner branches found at the top of the trees. The results

of this study are similar to another which found that captive marmosets preferred relatively thick

to thin perches (Dettling, 1997). Also, many structures such as nets in both exhibits, and the

platforms in the Island exhibit, were located in the middle layer of the canopy.

The top parts of the exhibit were used mostly by the younger animals (observed to forage there

for seed pods). Although animals from age group 3 also used the topmost layer of the exhibit, it

may have been more difficult for them to move about on the thinner branches, hence, we see less

activity from group 3 animals. The lower usage of the top layer in the Boardwalk than Island

exhibit was because there were more low-current electrical wires to restrict access to the tops of

trees in the Boardwalk exhibit. These wires served to prevent orangutans from escaping the

Boardwalk exhibit as trees there were closer to surrounding trees than those in the Island exhibit.

Hence, access to treetops was limited in the former. Additionally, on occasions that the

orangutans managed to slip past the electrical wires, the presence of more fruiting trees in Island

exhibit than Boardwalk exhibit also encouraged more foraging activity at the top layer.

There was heavier usage of low areas in Boardwalk exhibit as compared to Island exhibit. This

may have been because the log and platform, which were heavily utilized (about 30% of structure

use in total) were both at the low areas in the Boardwalk exhibit, but only the log was at the low

part of the Island exhibit. Similar to the only other study on use of vertical exhibit space (Hebert

and Bard, 2000), the orangutans in that study also used the vertical sections in their exhibit

differently. The exhibit in Hebert and Bard (2000) was divided into four layers. Exhibit skylights

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were the uppermost layer, followed by the upper canopy and lower canopy (of the artificial trees

in the exhibit), and the lowermost layer being a flooded floor which simulated a constantly

flooded peat forest. However, because the vertical sections are defined differently in this study

and the other study, direct comparisons cannot be made.

The animals in Hebert and Bard (2000) spent most of their time (35-40%) in the upper canopy of

their exhibit, which was about 8.5m off the ground. Similarly, the orangutans in this study spent

the most time (60-80%) in the middle layers of the canopy which was 10 to 15m off the ground.

As suggested by Hebert and Bard (2000), this height approximates the height at which wild

orangutans build their day and night nests, i.e. 10 to 20m off the ground (Wich et al., 2009),

hence the vertical level frequented by the captive orangutans can be called day nest sites.

Orangutans in Hebert and Bard (2000) were said to prefer the upper canopy because it afforded

more privacy and greater distance from visitors, as well as being close to where keepers would

drop food into the exhibit. Conversely, orangutans in the Singapore Zoo may have preferred the

middle layer because majority of the structures, such as nets, vines and a platform was found

there.

Use of the lower canopy was about 25-30% in Hebert and Bard (2000), and similar, at about 17-

38% in this study. Across both studies, the lower canopy, although at different heights, provided

places to sit and rest, like a metal ledge leading to the holding area in Hebert and Bard (2000) and

logs and platforms in this study.

The topmost layer in both studies, i.e. the skylights in Hebert and Bard (2000) and the top layer in

Singapore Zoo free-ranging exhibits, had very different purposes. The topmost branches in the

Island and Boardwalk exhibits were thin and only used for foraging purpose by younger

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could be out of public view, be closest to the keepers who were dropping food into the exhibit, as

well as be close to the source of natural sunlight in the exhibit. As a result, we see much less use

of this topmost layer in the free-ranging exhibits (0-10%) as compared to the study by Hebert and

Bard (2000) (16-24%).

Although animals in group 4 of the Singapore Zoo group did not go to the top layer during the

data collection period, one of the adult females, Anita, was once observed to chase a younger

animal to the top layer in an agonistic interaction. This suggests that older animals are still

capable of using thin branches, even in captivity, which is encouraging in terms of species-

specific behaviours. Zoo management can consider encouraging species-specific behaviours, such

- -sway is a method where orangutans rock flexible tree

trunks from side to side with increasing magnitude until they can cross gaps in the canopy

(Thorpe et al., 2007). Only with access to the terminal branches of trees, which are thin and

flexible enough, can this behaviour be performed. Such behaviours require planning and

animals. One method to encourage tree crossings would be to include trees with luxuriant foliage

in the exhibit, or to provide thin, flexible poles which simulate tree-sway in the canopy. Such

sway poles have been implemented successfully at other zoos to simulate arboreal tree-crossing

behaviour in orangutans, and also to foster appreciation for orangutan behaviour in zoo visitors

(Oklahoma City Zoological Park: Grisham et al., 2000; Melbourne Zoo: website, Zoolex).

Overall, all layers of the canopy were utilized in this group of captive orangutans; however, there

was a preference for the middle layer of the exhibit.

67

Limitations of study

The investigation of enclosure use in this study focused on types of structures used, behaviours at

each structure, and vertical space use. It may also have been possible to look at whether

orangutans had differential (horizontal) use of areas in their exhibit. A preliminary study of space

use in this group of orangutans (unpublished data from this study) showed that orangutans spent

more than 70% of their time in half of the exhibit space. This may have been due to the nature of

the exhibit structures or proximity to surrounding features in different parts of the exhibit. A

more detailed analysis may be useful in elucidating how captive orangutans use a treetop,

naturalistic enclosure.

Vines in the exhibit were present in two forms; vines joining neighbouring trees, or vines strung

within the branches of the same tree. There was no distinction made between the location of

orangutans when they were on branches of a tree, or vines in a tree. Both were

for orangutan location. A more detailed categorization may have been useful.

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Animals in age groups 2 and 3 may not be able to access nets as frequently as desired,

due to dominance effects from age group 4 animals. Hence it may be helpful to include

more nets in the Boardwalk exhibit. The presence of more nets may also stimulate play

and social behaviour.

Ensure that there are adequate pieces of each structure to avoid social conflict.

The presence of easily accessible platforms in the Boardwalk exhibit seems to encourage

regurgitation (an undesirable behaviour) in younger animals. It may be good to place

platforms at less accessible parts of the exhibit, or reduce the number of platforms to

reduce regurgitation. Although both play and regurgitation both take place at platforms,

and the platform was more out of the way in the Island exhibit, play was not significantly

lower in the Island exhibit, but regurgitation was. This may have been because of the

large net present in the Island exhibit. Hence, making platforms less accessible may

reduce regurgitation but not play, as long as sufficient net space is provided.

Ensure that there are always alternative routes, and no dead ends in the exhibit pathways

to prevent cornering of less dominant animals by dominant animals. This has already

been done for the free-ranging exhibits (Nantha, 2009, pers. comm.7). Domination of the

log (a major pathway) by older animals may cause frustration in lower-ranking animals if

there is no alternative through route.

7 Gabriel Nantha, Orangutan keeper, Singapore Zoo

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Orangutans in this study do not seem to be adversely affected by proximity to human

establishments (see next chapter), hence close proximity to restaurants and roads may

actually be a source of enrichment. Also, some individuals were observed to actively

watch visitors at the restaurant (pers. obs.; Nantha, 2009, pers. comm.8). An anecdotal

piece of information provided by one of the keepers: Once, when an adolescent orangutan

(Budi) escaped from the exhibit, it was found holding a pair of utensils and sitting at one

of the outdoor tables in the restaurant, which suggests that it had actively observed

visitors at the restaurant beforehand. Hence, the presence of visitors may possibly be a

form of enrichment for this group of orangutans.

Exhibits can be designed with surrounding features in mind, to see whether they can have

potential as enrichment or may disturb the animals.

Enable and provide feeding at varying locations in each exhibit as a form of enrichment.

Provide opportunities for species-specific behaviours, such as tree-sway, by allowing

access to mature trees with thin, terminal branches. Alternatively, thin, flexible poles can

be provided to simulate tree-sway in the canopy.


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C O N C L USI O NS

Structure use can be affected by the following biological and environmental factors:

Age and dominance status of the orangutans

The properties of the structure.

The availability and location of a structure within the exhibit.

The features in the surroundings of the exhibit.

Husbandry routines.

Such information can be used in future exhibit design to maximize animal welfare by reducing

social conflict and encouraging behavioural diversity.

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C H APT E R 4

V isitor effects on zoo orangutans in two novel, naturalistic enclosures

Abstract. Visitors are known to affect zoo animals, and such effects may be stressful, neutral, or

enriching. The majority of research has focused on visitor number or visitor presence-absence,

yet few studies have examined effects of other variables such as sound volume, visitor activity,

and whether visitors interact with animals. In this study, the effects of visitor number, activity and

proximity to animals were investigated on a group of captive orangutans in two t -

relationships between visitor and orangutan behaviours. Results from these analyses revealed a

significant overall effect of the three visitor variables on orangutan behaviour. Interestingly,

visitor number had little effect on the orangutans, except at one of the exhibits where the

likelihood of food soliciting and looking at visitors increased when the number of people was

more than 40. Visitor activity was generally not associated with any obvious signs of stress in the

orangutans; visitors with food could even be a form of enrichment. However, visitors at close

proximity decreased play behaviour and increased the chances of animals looking at the visitors.

Enclosure design and habituation could have alleviated visitor effects for these two groups of

orangutans. This study shows how investigation of a wider range of visitor variables may allow

for more meaningful conclusions about the visitor effect, and that other factors such as enclosure

design and habituation to visitors may also influence captive animal welfare.

K eywords: visitors, captive, welfare, orangutan, behaviour

A modified version of this chapter was submitted to the journal Applied Animal Behaviour Science. Yuanting Choo, Peter Alan Todd, Daiqin Li. (2011) Visitor effects on zoo orangutans in two novel, naturalistic enclosures. Applied Animal Behaviour Science 133, 78 86.

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In the context of captive animal research, the ter

possible influences of visitors on the welfare of zoo animals. Although visitor effect studies have

been conducted since the 1970s (Oswald and Kuyk, 1977; Thompson, 1976), there are still

certain aspects of visitor effects which are relatively unstudied (Davey, 2007; Hosey, 2000).

Here, I will discuss what the visitor effect is, factors which may contribute to it, the consequences

of visitor effects on zoo animals and areas where more research is required.

it is necessary to consider how visitors may impact zoo animals. A visitor crowd can have a

multitude of characteristics. It can be large or small, noisy or quiet. It can comprise of adults

and/or children, who are male or female. They may be near or far away, and may or may not

interact with animals. It has been found that all of these characteristics can affect the behaviour of

zoo animals. Studies have shown that when there are more visitors, animals are found to be more

aggressive (Chamove et al., 1988; Sellinger and Ha, 2005; Simpson, 2004; Wells, 2005), play less

(Glatston et al., 1984; Jones, 2003), and increase their use of enclosure areas near the visitors (Fa,

1989). When visitors are noisier, animals direct more attention towards them (e.g., orangutans:

Birke, 2002). When visitors attempt to interact with the animals, some species of primates display

more visitor-directed behaviours, which can be aggressive, submissive (Chamove et al., 1988;

Hosey and Druck, 1987), or food soliciting behaviours (Cook and Hosey, 1995; Mitchell et al.,

1992a). If visitors appear smaller (by crouching), they appear to create less stress than standing

visitors for some species of primates (Chamove et al., 1988). Interestingly, even the gender of

visitors may play a role in the response of animals. It has found that male mangabeys are more

likely to show aggression towards men, and female mangabeys towards women (Mitchell et al.,

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1992b). From the existing research, it is apparent that many different visitor characteristics can

affect zoo animal behaviour.

? The effect of visitors on

animals has been perceived in one of three ways negative, neutral, or positive (Hosey, 2000). A

negative visitor effect is usually defined by an increase in aggressive and stereotypic behaviours,

and a decrease in affiliative behaviours. A neutral visitor effect indicates that there is no

difference in the behaviour of the animals between varying visitor conditions. A positive effect

providing a source of variability (Davey, 2007). From previous studies, visitors may have one or

more of these effects negative, neutral or enriching.

As reviewed by Davey (2007), gaps in visitor effect studies can be classified into (i) a

disproportionate amount of research across different visitor variables and animal groupings, (ii)

vague and insufficient descriptions of visitor variables, (iii) limitation of conclusions due to

statistical methods used, or (iv) independence from other areas of visitor research. The present

study on orangutans in Singapore Zoo will attempt to address these gaps.

Of the existing visitor effect studies, a wide range of variables have been investigated. These

include variables from visitor presence or number (Anderson et al., 2002; Davis et al., 2005;

Glatston et al., 1984; Mallapur et al., 2005; Mitchell et al., 1990; 1991; 1992a; Shen-Jin et al.,

2010; Thompson, 1989; Wells, 2005), to visitor sound (Birke, 2002; Cooke and Schillaci, 2007),

visitor activity (Hosey and Druck, 1987; Mitchell et al., 1992a), as well as the height (Chamove et

al., 1988), and gender (Mitchell et al. 1992b) of visitors. However, there is an imbalance of

research, with most studies focusing on visitor number or presence, and few on visitor sound,

activity, proximity or crowd composition (Davey, 2007). Therefore, besides the commonly

74

studied variable of visitor number/presence, my study will highlight the less studied effects of

visitor activity and proximity on zoo orangutans.

Visitor activity has been investigated only by Mitchell et al. (1992a) and Hosey and Druck

looking, holding food, etc), more meaningful conclusions may possibly be drawn about the

effects of visitor activity. Similarly, visitor proximity has not been well studied, possibly because

majority of zoo exhibits have limited the distance of visitors from animals using physical barriers

(Hosey et al., 2009) and there is little variation in minimum animal-visitor distance. However, in

an exhibit like the orangutan enclosures in this study, visitor proximity may be of greater concern.

This is because visitors are not separated from the animals by any physical barriers. Instead, the

animals are restricted to a row of trees above the visitors, and people may approach as close as

three metres from the animals. Hence, my study will break down visitor activity into different

sub-categories and also address visitor proximity.

Visitor effect studies usually focus on one or two variables at a time and data is often analyzed

using univariate analyses. This could be due to the practical limitations of collecting several

visitor variables at once or the difficulties of using appropriate multivariate analyses. Other

reasons may be the small sample sizes or lack of independence between subjects, which are

characteristic of zoo studies (Kuhar, 2006; Plowman, 2008). By collecting data on only one or

two aspects, this leaves out the possible effects of other visitor variables. Here, a multivariate

analysis will be used here to simultaneously investigate three visitor variables.

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Visitor effects have traditionally been considered independently from other areas of visitor

research and animal welfare. As reviewed by Davey (2005) and Fernandez et al. (2009), factors

such visitor circulation and responses to exhibit design have rarely been considered. In light of

this, I will investigate visitor effects across two different exhibits, and explain how enclosure

design and captive breeding history could also have influenced visitor effects.

Finally, and of particular relevance to the present study, even though most visitor studies have

focused on primates, there exists only two published reports on orangutans (Birke, 2002;

Bloomfield et al., 2010).

I hypothesized that larger groups of visitors, visitors who were more active (e.g. taking

photographs), and visitors who were closer in proximity would be stressful to the orangutans.

This may lead to lowered incidences of feeding, playing and social behaviours, and increased

incidences of undesirable behaviour such as regurgitation. I also hypothesized that visitors with

food would result in more begging behaviour.

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Enclosure design, subjects and data collection

- orangutans in 2006 (Raj, 2009, pers.

comm.9). These exhibits each comprises a row of tall trees connected by artificial vines,

hammocks and platforms, and are designed to encourage brachiation and other species-specific

behaviour. During the 2009/10 study

and visitors passed by regularly. Visitors on the main track were able to look up into the trees to

view the orangutans. The other free-

Island exhibit but visitors could choose to view the orangutans from the main track, or from an

elevated boardwalk. This boardwalk allowed visitors to come into much closer proximity with the

animals (as close as 3 m).

Two groups of orangutans were rotated daily between the two free-ranging exhibits. The groups

were made up of individuals of varying ages, and each group had one mother-infant pair (Table

4.1). As the infants were still dependent on their mothers, they were excluded from the

observations. The composition of the groups remained the same throughout the study period. This

display arrangement presented a unique opportunity: usually, studies that compare animal

behaviour across different enclosures use data from different animals; however, in Singapore

Zoo, because the same animals were regularly rotated between two exhibits, I had the rare chance

to study the same subjects in different enclosures, simulating a manipulative experiment.


77

F ig. 4.1. Island exhibit (top) and Boardwalk exhibit (bottom) showing possible locations of visitor-orangutan interaction. Island exhibit: (a) large net across trees, (b) ground-to-foliage view of exhibit trees, (c) low vine across main track where orangutans often interacted with visitors. Boardwalk exhibit: (d) low vine across main track where visitor-orangutan interaction often occurred, (e) elevated visitor boardwalk, (f) orangutan platform next to visitor boardwalk, (g) low log next to visitor track where animals would interact with visitors.

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Table 4.1 Individual details of study animals. All individuals were born in Singapore Zoo except Anita who was donated to the zoo at one year of age. Name Sex Age (yr) Species Group A

Ah Meng Jnr Female 1 Pongo pygmaeus Bento Male 3 Pongo pygmaeus Budi Male 7 P. pygmaeus/ P. abelii cross Gunta Male 7 Pongo pygmaeus Chomel Female 13 Pongo abelii Anita (with infant Ah Meng Jnr) Female 24 Pongo pygmaeus Group B Saloma Female 0.5 Pongo pygmaeus Merlin Male 5 Pongo pygmaeus Vira Male 9 Pongo pygmaeus Labu Male 11 Pongo pygmaeus Binte (with infant Saloma)

Female 25 Pongo pygmaeus

In order to capture visitor crowds of varying sizes, I collected data on both weekdays and

weekends from October 2009 to February 2010, between the hours of 09:30 h to 17:00 h.

Instantaneous scan sampling, with the aid of binoculars, was used for both the orangutans and

(1996) protocol, it was calculated that scans taken at 10 min intervals

were sufficiently far apart enough to avoid autocorrelation. A total of 192 hours of observations

(48 hours for each group-exhibit combination) were made. As regular feeding sessions were held

twice daily, at 11:30 h and 15:30 h for the Island exhibit and 14:15 h and 16:30 h for the

Boardwalk exhibit, data collection was paused 15 min before each session started and only

resumed 15 min after the feeding ended. The visitor viewing areas (designated as the areas

directly below the exhibit trees) were divided into arbitrary subsections for the purposes of

specifying visitor location. During each scan, I recorded the behaviour and location of individual

orangutans (see Table 4.2 for behaviour categories). For visitors, I recorded the number of

individuals in each subsection of the viewing area and the activity of which the majority (>50%)

of the visitors in each subsection were performing. The visitor data were then processed to obtain

79

values of total visitor number, visitor activity and visitor proximity per orangutan per scan,

according to the definitions in Table 4.2.

Table 4.2 Definitions for orangutan and visitor variables (also see Table 4.3) Orangutan Behaviour Definition

Idle Orangutan is motionless, or performing any of these behaviours: autogrooming, expelling bodily waste or looking around (excluding looking at visitors).

Look at visitor(s) Orangutan is looking at visitor(s), face and eyes are oriented towards visitor(s).

Move Orangutan is travelling from one location to another; can be brachiating, bi/quadrupedal walking, or any other form of locomotion.

Feed Orangutan is engaged in searching for, preparation of, or ingestion of food.

Play/Social Orangutan is engaged in object use, solitary play, social play, or social interaction.


Beg Orangutan is soliciting food from visitors by stretching out hand towards visitor(s).

Location Each tree/vine/structure in the exhibit was labelled with a name to identify the

location of each orangutan Processed variables Definition

Visitor number Visitor numbers from all subsections were summed to obtain the total number of visitors in the viewing area.

Visitor activity Classified as walking, standing, looking, taking photographs, holding food or no visitors. Only visitors within direct sight of the orangutan were considered. For each scan, I recorded the visitor activity as the activity that the majority (>50%)

visitor behaviours such as looking and taking photographs were thought to draw more attention from the

behaviour was recorded as the activity for that scan sample. The only exception was that visitors with food took precedence over all other visitor activities, regardless of how many such visitors there were, because we noted that food

Visitor proximity Classified into <10 m or >10 m from orangutan. If there were visitors at varying distances from the orangutan, only the closest visitors were considered. Distances were estimated using a rangefinder. Categories were defined as such, because preliminary observations showed that all interactions which involved visitors throwing food occurred at distances of <10 m.

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Data analysis

Multinomial logistic regression was used to investigate possible visitor effects on orangutan

behaviour. Logistic regression was the preferred option as it can analyse dependent variables with

categorical outcomes (Field, 2009, p265). The output from this regression is expressed as the

likelihood (also known as odds ratio, OR) that a particular outcome category (in relation to the

reference category) will occur when a particular independent variable is present. Here, the

analysis provided the OR for each orangutan behaviour when a particular visitor variable was

present. I performed two separate multinomial logistic regressions, one for each exhibit, using

data pooled from both orangutan groups, to assess the associations between the independent

(visitor) and dependent (orangutan) variables. To avoid cells of zero count in the multivariate

analysis, all data points with no visitors were excluded from the analyses. The analysis was run

using PASW Statistics 18 (SPSS Inc. USA) and statistical significance was set at P < 0.05.

The reference categories for all variables are presented in Table 4.3. All levels of total visitor

number were compared agai -

each combination of predictor-dependent variable, multinomial logistic regression assumes that

all other variables are constant. Hence, an OR of more than one meant that the orangutan

behaviour was more likely to occur when a particular visitor variable was present, and an OR of

less than one meant that the orangutan behaviour was less likely to occur when that visitor

variable was present.

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Table 4.3 Definitions and levels of variables for multinomial logistic regression Variable Levels Reference value Visitor number 11-20 visitors 1-10 visitors 21-30 visitors 31-40 visitors >40 visitors Visitor activity Standing Walking Looking Taking photographs Holding food Visitor proximity <10 m from orangutan >10m from orangutan Orangutan behaviour Feed Idle Play/Social Move Regurgitate Look Visitor Beg

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R ESU L TS

Multinomial logistic regressions revealed significant overall effects of the three visitor variables

on orangutan behaviour for both the Boardwalk exhibit ( 2 = 318.902, P < 0.001) and the Island

exhibit ( 2 = 154.435, P < 0.001). For the Boardwalk exhibit, visitor number, activity and

proximity were all significant predictors of orangutan behaviour. For the Island exhibit, visitor

activity and proximity, but not visitor number, were significant predictors of orangutan behaviour

(Table 4.4).

The OR for each of the significant visitor variables in both enclosures are provided in Table 4.5.

For ease of comparison, Table 4.6 presents a summary of the effects of all visitor variables on the

orangutan behaviour decreased (OR < 1), and NS means the visitor variable did not significantly

affect the orangutan behaviour (P

Table 4.4. Likelihood ratio test results for both enclosures Enclosure Variable 2 test

Boardwalk exhibit Visitor number 2 = 37.856, P < 0.05 Visitor activity 2 = 140.222, P < 0.001 Visitor proximity 2 = 114.621, P < 0.001

Island exhibit Visitor number 2 = 34.840, P = 0.071 Visitor activity 2 = 63.059, P < 0.001 Visitor proximity 2 = 39.628, P < 0.001

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Effect of visitors on orangutan behaviour in the Boardwalk exhibit

Only visitor numbers of > 40 increased the likelihood that orangutans would look at the visitors

(OR = 5.936) or beg (OR = 3.799). All other orangutan behaviours were not significantly affected

by visitor number (Table 4.5, 4.6).

Visitors who stood had no significant effect on the likelihood of any orangutan behaviours.

Visitors who looked at the orangutans significantly increased the chances that the orangutans

would feed (OR = 1.676), play/socialize (OR = 1.757), move (OR = 1.569) or beg (OR = 9.521),

but did not affect the other behaviours. Similarly, visitors who were taking photographs of the

orangutans significantly increased the chances that the animals would feed (OR = 1.370),

play/socialize (OR = 2.034) or move (OR = 1.494), but had no significant effect on the other

behaviours. Visitors with food had a significant effect only on the likelihood of begging (OR =

254.754) and looking at visitors (OR = 12.344). No other orangutan behaviours were affected by

visitors with food (Table 4.5, 4.6).

Visitors who were nearer (<10 m away) significantly increased the chances that the orangutans

would regurgitate (OR = 2.610), beg (OR = 3.014) or look at the visitors (OR = 2.924). However,

visitors who were <10 m away significantly decreased the chances that the orangutans would feed

(OR = 0.481) or play/socialize (OR = 0.669) (Table 4.5, 4.6).

Effect of visitors on orangutan behaviour in the Island exhibit

Visitor activity and proximity had significant effects on orangutan behavior in the Island exhibit,

but not visitor number (Table 4.4).

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Visitors who were standing decreased the chances of orangutans feeding (OR = 0.599), but had

no other effects on orangutan behaviour. Visitors who were looking at the orangutans did not

significantly affect any of their behaviours; however, visitors who were photographing the

orangutans significantly decreased the chances of play/social behaviour (OR = 0.218), and

increased the chances of begging behaviour (OR = 31.094). Visitors with food significantly

increased the likelihood that the orangutans would be looking at the visitors (OR = 14.869) or

begging (OR = 256.210) (Table 4.5, 4.6).

Visitors who were <10 m away increased the chances that the animals would feed (OR = 1.544)

or beg (OR = 7.307). Such visitors also decreased the chances that the orangutans would

regurgitate (OR = 0.327) (Table 4.5, 4.6).

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Table 4.5. Results from multinomial logistic regression testing effects of visitor number, activity and proximity on orangutan behaviour in the two exhibits. Odds ratio 95% Cl Odds ratio Lower Upper

Boardwalk exhibit

Orangutan F eed

Visitor activity Looking 1.676 1.294 2.171 Visitor activity Taking photographs 1.370 1.002 1.873 Visitor proximity < 10 m 0.481 0.379 0.611 Orangutan Play/Social Visitor activity Looking 1.757 1.219 2.532 Visitor activity Taking photographs 2.034 1.362 3.039 Visitor proximity < 10 m 0.669 0.494 0.907 Orangutan Move Visitor activity Looking 1.569 1.132 2.175 Visitor activity Taking photographs 1.494 1.029 2.171 Orangutan Regurgitate Visitor proximity < 10 m 2.610 1.868 3.647 Orangutan Look visitors Visitor number > 40 5.936 2.485 14.180 Visitor activity With food 12.344 5.043 30.219 Visitor proximity < 10 m 2.924 1.633 5.238 Orangutan Beg Visitor number > 40 3.799 1.044 13.825 Visitor activity Looking 9.521 1.175 77.153 Visitor activity With food 254.574 30.851 2103.686 Visitor proximity < 10 m 3.014 1.204 7.544

Island exhibit

Orangutan F eed

Visitor activity Standing 0.599 0.459 0.782 Visitor proximity < 10 m 1.544 1.175 2.028 Orangutan Play/Social

Visitor activity Taking photographs 0.218 0.052 0.905 Orangutan Regurgitate

Visitor proximity < 10 m 0.327 0.130 0.820 Orangutan Look visitors

Visitor activity With food 14.869 1.328 166.468 Orangutan Beg

Visitor activity Taking photographs 31.094 3.051 316.920 Visitor activity With food 256.210 19.324 3396.998 Visitor proximity < 10 m 7.307 1.632 32.720

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Table 4.6. Effects of visitor variables on likelihood of each orangutan behaviour for both exhibits.

Orangutan behaviour

Vis no 11-20

Vis no 21-30

Vis no 31-40

Vis no > 40

Vis Standing

Vis Looking

Vis

Vis with Food

Vis <10 m

Boardwalk exhibit

Feed NS NS NS NS NS More More NS Less Play/Social NS NS NS NS NS More More NS Less

Move NS NS NS NS NS More More NS NS Regurgitate NS NS NS NS NS NS NS NS More Look Visitors NS NS NS More NS NS NS More More Beg NS NS NS More NS More NS More More

Island exhibit

Feed NS NS NS NS Less NS NS NS More Play/Social NS NS NS NS NS NS Less NS NS

Move NS NS NS NS NS NS NS NS NS Regurgitate NS NS NS NS NS NS NS NS Less Look Visitors NS NS NS NS NS NS NS More NS Beg NS NS NS NS NS NS More More More

ihood of occurrence of orangutan behaviour; More = likelihood of orangutan behaviour increased when visitor variable was present (OR > 1), Less = likelihood of the orangutan behaviour decreased (OR < 1).

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DISC USSI O N

This study incorporated several variables of visitor number, activity and proximity, in an attempt

to improve our understanding of how visitors affect orangutans. Previous research has suggested

that active visitors elicit more audience-directed behaviours from primates (Hosey and Druck,

1987; Mitchell et al., 1992a), but there has been little research on the effects of specific visitor

activities. Here, visitor activity was broken down into distinct categories. I also exploited the fact

that the two groups of orangutans were rotated daily between two exhibits. This regular rotation

formed a natural experiment and allowed comparison of visitor effects across the different

enclosures while controlling for between-group variation in behaviour. Overall, the results

showed that large crowds, visitors with food, visitors who were looking or taking photographs,

and visitors who were close by, all affected orangutan behaviour. On the whole however, the

hypothesized. The free-ranging exhibit design, habituation to humans, or both, may explain this.

Effects of visitor number

As compared to other studies of visitor effects on orangutans (Birke, 2002; Jones, 2003), my

research reveals little effect of visitor number on orangutan behaviour. The likelihood of begging

and looking at visitors increased only when there were crowds of more than 40 people. No other

behaviours were affected by visitor number, suggesting that human presence induces little or no

orangutans covered themselves with paper sacks more and foraged less when more (> 8) visitors

were present. Visitor-induced stress such as reduced social play and mobile feeding activities has

also been reported in orangutans when there were more than 100 visitors (Jones, 2003). However,

as the visitor numbers in this study rarely went above 80, whether higher visitor numbers (e.g., >

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80) could induce stress on orangutans at Singapore Zoo is unknown. Nevertheless, because the

exhibits were positioned along tracks with heavy human traffic, it is possible that orangutans in

Singapore Zoo have been habituated to large visitor crowds. Also, being at a higher position

(usually in trees) above visitors may have provided a sense of security or dominance (Coe, 1985).

The fact that a large visitor crowd increased the chances of visitor-oriented behaviour only in the

Boardwalk exhibit, where an elevated boardwalk allowed visitors to get closer to the animals,

indicates that exhibit design may influence how visitor numbers affect orangutan behaviour.

Effects of visitor activity

Changes in orangutan behaviour were more strongly associated with active visitors (those looking

or taking photographs) than passive (standing) visitors. Similar results have been reported in other

studies (e.g. Chamove et al., 1988; Hosey and Druck, 1987; Mitchell et al., 1992a), in which

significantly more behaviours were directed towards active than passive audiences. However, in

); whereas in this

study, visitor activity was divided into five categories. It was found that the association between

active visitors and orangutan behaviour was more pronounced at the Boardwalk exhibit than the

Island exhibit, which again suggests that proximity of visitors to animals can affect the visitor-

animal interaction. The greater probability that the orangutans would be feeding,

playing/socializing, or moving when visitors looked or took photographs could be explained by

hypothesis, where active animals attract more attention from visitors

(Hosey, 2000)

visitors in the Boardwalk exhibit who looked at the orangutans, and visitors who photographed

orangutans in the Island exhibit, were linked to a higher chance of begging.

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Overall, the increase in likelihood of feeding, play and social behaviours when visitors were

looking or taking photographs in the Boardwalk exhibit suggests that the visitors were not a

source of stress. At the Island exhibit, visitors standing were linked to lowered incidences of

feeding in orangutans while those taking photographs were linked to lowered incidences of

playing/socializing in the animals. The latter result was the opposite of what we found at the

Boardwalk exhibit but we suggest that, because play/social behaviour in the Boardwalk exhibit

occurred mostly in highly visible locations near the raised visitor walkway, these behaviours were

more likely to attract visitor attention and hence more photography. On the other hand,

playing/socializing at the Island exhibit occurred at less obvious places (i.e. cargo nets in the

upper branches of the trees), hence less photography. The association between visitors standing

and the lowered incidence of feeding was unexpected and cannot be easily explained by either the

visitor attraction or visitor effect hypothesis.

As hypothesized, food was a very strong stimulus of orangutan behaviour, with the likelihood of

begging and looking at visitors increasing significantly in both exhibits when food was present.

This result contributes to the consensus from other studies where apes were also motivated to

interact with visitors for food (Birke, 2002; Cook and Hosey, 1995; Jones, 2003; Wood, 1998).

The lives of zoo animals may often be routine; therefore, novel occurrences of visitors with food

may serve as a source of variability and enrichment (van Rooijen, 1991; Wiepkema and

Koolhaas, 1993). All orangutans would immediately and fixatedly look at visitors who were

holding food; they would also occasionally solicit food by hanging from a branch directly above

and extending their hand towards the visitor. In some cases, the orangutan would clap its hands

repeatedly, then stretch out a hand in request for food. (See video:

http://www.youtube.com/watch?v=L1bU9rHlGZ0 ) Because the orangutans have been trained to

perform certain behaviours for food rewards, repeated personal observations and communication

with the keepers confirmed that this clapping, then hand-out gesture was an active behaviour to

http://www.youtube.com/watch?v=L1bU9rHlGZ0

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solicit food. Food solicitation has also been recorded with other primates (Cook and Hosey, 1995;

Jones, 2003; Wood, 1998). Barring that visitors may throw unsuitable foods such as sweets and

biscuits (pers. obs.), such incidences may otherwise serve as a source of enrichment for the

orangutans.

Interestingly, begging behaviour only occurred consistently with some of the orangutans, namely

Chomel (a 13 year old female) and Labu (a 11 year old male), whereas some individuals, such as

Anita (a 24 year old female) never displayed such behaviour . An obvious difference in individual

begging styles was also observed. Labu would only beg when food was visible; and he was ever

seen scanning passing visitors, and paying more attention to visitors who looked as though they

were holding food. Chomel would sometimes beg regardless of whether food was present, as long

as there were large visitor crowds. She was sometimes observed hang from a branch for up to half

an hour, waving her hands in a presumed attempt to get food. Her begging behaviour sometimes

- . obs.; pers. comm., orangutan keepers). The impression was

given that she did not really care if she got food, she just wanted to occupy herself. It has been

shown previously that personality may influence an o (Uher et al.,

2008) and Fraser (2009) highlighted this phenomenon for further study.

Effects of visitor proximity

I also examined the effects of visitor proximity on orangutans, a rarely studied variable. The

results showed interesting trends between exhibits, and a possibly stressful visitor effect at closer

proximities. The likelihood of both begging and looking at visitors were increased in the

Boardwalk exhibit when visitors were less than10 m away, but in the Island exhibit, only the

chances of begging were increased. This meant that orangutans looked more at visitors when they

were near in the Boardwalk exhibit, but not in the Island exhibit. This difference between

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enclosures may have been due to the elevated boardwalk in the Boardwalk exhibit which allowed

visitor-animal interactions at eye level, and at much closer proximity (3-7 m) between orangutans

and visitors. This was in contrast to the Island exhibit, where the orangutans were always in trees

above the crowds, hence, at least 7 m above the visitors. Consequently, any effects of visitor

proximity may have been reduced in the Island exhibit. When visitors were nearer (less than 10 m

away), regurgitation increased in the Boardwalk exhibit but decreased in the Island exhibit. We

noted that regurgitation almost always took place at platforms; while the platform in the

Boardwalk exhibit was less than 10 m away from visitor viewing areas, the platform in the Island

exhibit was further than 10 m from all visitor viewing areas. Hence, the results for regurgitation

may have been influenced by the location of the platforms where regurgitation usually occurred.

The differences in feeding in relation to visitor proximity can also be explained by where the food

(fresh leaves) was usually provided (closer to visitors at the Island exhibit and further from them

in the Boardwalk exhibit). The association between visitor proximity and decreased

play/socializing in the orangutans was also limited to the Boardwalk exhibit. To date, there has

only been one other study on visitor proximity, Bloomfield et al. (2010), who did not find

evidence that orangutans avoid close visitor contact. In this study, however, visitors at <10 m

proximity decreased the chances of play/socializing, suggesting a stressful effect.

Other influences on the visitor-animal interactions

It has been shown how visitor number, activity, proximity and exhibit design influenced visitor-

orangutan interactions. The relatively low level of visitor effects on these two groups of

orangutans may be due to the large and naturalistic enclosure designs. There are many factors

influencing stress in captive animals, including: a lack of control over their environment,

restricted movement, and forced proximity to humans (Morgan and Tromborg, 2007). The large

and complex design of the free-ranging exhibits possibly reduced stress from visitors by allowing

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for a retreat space, species-specific behaviour, and control over the degree of interaction with

visitors. Generally, the orangutans in this study seem to be habituated to humans, for instance,

active food solicitation by several individuals suggests a lack of fear towards visitors (Hosey et

al., 2009, p. 498). This might be due in part to daily photography sessions, where visitors sit

within one metre of the orangutans; or the regular handling by keepers, during which there is

keeper-animal contact. It has been observed that stimulation during early stages of life enables

some species to cope better with stress when they are older (Moodie and Chamove, 1990). The

orangutans at Singapore Zoo have been handled by keepers up to 12 years of age for males, and

for more than 20 years of age for females, which is not the standard practice at most zoos (Raj,

2008, pers. comm.10). As a result, these captive-born animals have had frequent opportunities to

interact with keepers and observe visitors at close proximity.

Limitations of study

Exclusion of another potential variable

Initially, visitor sound was designed as part of the study. However, preliminary trials showed that

visitor sound died off within 7 m of the source, probably due to the outdoor nature of the exhibit.

Considering that the orangutans could be at a range of distances (3 60 m) from the visitors, this

otherwise potential variable was excluded from the study.


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Definitions of visitor activity

For the definition of visitor activity, the activity that was being performed by most of the visitors

was recorded for each sample point. But for activities of looking and photo taking, they were not

always the majority activities. It was assumed that the effects of looking and photo taking were

dominant over that of walking or st

walking or standing. This assumption was necessary to break down visitor activity into more

detailed categories, however, the specific effects of this assumption are unknown. Further studies

can be carried out to investigate visitor activity in detail.

Limitations of behavioural observations

This study focused on measuring the association between visitor variables and orangutan

behaviour. There are limitations to using only correlational behaviour measurements for welfare

assessment in zoo animals (Davey, 2005; Millman, 2009). It may be possible to supplement

behavioural observations with the collection of physiological indicators, such as measuring

cortisol levels in saliva, urine (Smith, 2004), or any other non-invasive methods to confirm

direction of causality between visitor and orangutan variables. Alternatively, as Bloomfield et al.

(2010) has demonstrated, preference tests in which animals are allowed to choose their level of

interaction with visitors may shed more light into how visitors really affect zoo animals.

Lack of consideration of individual personalities

In many visitor effect studies, the data from several individuals is pooled (Carder and Semple,

2008; Chamove et al., 1988; Fa, 1992; Hosey and Druck, 1987, Mallapur et al., 2005; Mitchell et

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al., 1992b; Shen-jin et al., 2010; Todd et al., 2007). However, it has been shown that individual

orangutans may differ in their responses to stimuli (Uher et al., 2008), and naturally, also to

visitors (Birke, 2002; pers. obs.; orangutan keepers, pers. comm.). It would be interesting to see if

the visitor effect varied between members of this orangutan group, as suggested earlier by the

difference in begging responses between individuals.

A more holistic approach

The design of most visitor effect studies, including this study, focuses only on short term

responses to visitors, and reduces visitor effects to a set of conveniently quantifiable variables

(Fraser, 2009). However, recent discussion in the field has refocused attention on how a more

holistic approach is necessary (Bloomsmith, 2009; Fraser, 2009; Melfi, 2009; Millman, 2009).

Fraser (2009) discussed how animal welfare often involves understanding the affective states of

animals (pain, fear, distress, etc). This understanding requires observation of complex behaviours,

and postulations about intangible entities, such as emotions (Duncan, 1970; Fraser, 1975). But

because philosophical influences in the history of scientific research maintained that science deals

only with tangible, observable phenomenon (Kolakowski, 1968), the development of science over

the mid 20th century has favoured the collection of quantitative over qualitative data (Fraser,

2009). As a result, controlled experiments which attempt to generalize across a species or type

have become commonplace (Fraser, 2009; Millman et al., 2009). However, to answer questions

about animal welfare and behaviour, it may be necessary to adopt a more holistic approach

(Fraser, 2009). As seen in the work of Jane Goodall (1971) and Barbara Smuts (1999), these

scientists collected both quantitative and qualitative data; they described complex behaviours in

addition to isolated phenomenon, and besides pooling data for groups, they also attempted to

consider individual differences (Fraser, 2009). Such adoption of a wide range of measures may

allow a better understanding of animal welfare.

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In addition, a recent conference highlighted the need to use a wider range of responses, in

combination with long term, epidemiological studies to better understand the factors influencing

(Bloomsmith, 2009). However, this type of data collection is understandably more challenging

due to its inter-institutional nature; perhaps that explains why most visitor effect studies choose

instead to focus on subjects from one or few institutions.

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It will be useful for zoo management to know that visitors who were very close to the

animals may have reduced play behaviour. This is especially so, if there are orangutans

with babies in the exhibit group. This is because young orangutans tend to play more than

adults (Nash, 1993; Zucker et al., 1986), and any reduction in play may be detrimental for

their development. Although no observations were made on the two infant orangutans

who accompanied the females, further research could be done to see if visitors have any

stressful effects on the development or behaviour of young orangutans. As shown by

Mather (1999), visitor presence decreased the amount of time orangutan infants spent

suckling from their mothers. The presence of such effects may then be taken into

consideration when deciding which exhibit to display mother-infant pairs in. This would

be important for the captive breeding program which is part of the conservation efforts at

Singapore Zoo.

It is interesting to note how close proximity at certain points in both exhibits allows

visitors to throw food to the orangutans. Regular food soliciting, although possibly

enriching, may or more not be desirable. This is especially so when we consider that

visitors may throw unsuitable foods to the animals.

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C O N C L USI O NS

The results show relatively minor visitor effects on captive-bred orangutans in free-ranging

enclosures at Singapore Zoo. This may be due to enclosure design, or habituation to humans.

However, some visitor effects were observed, for instance large crowds, visitors with food,

visitors who were paying attention to the animals, or visitors who were close by all affected

orangutan behaviour to some degree. Of note, visitors who were close by were associated with

reduced play behaviour. This study highlights how enclosure design and captive history of study

subjects may also influence the visitor effect.

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C H APT E R 5

G E N E R A L DISC USSI O N

The purpose of this study was to investigate the behaviour of captive orangutans in two

naturalistic exhibits. These results represent a substantial cache of information on the activity

budgets, structure use, and possible visitor influences on captive orangutans. This is the first

comprehensive study on orangutan behaviour in a naturalistic exhibit, and can serve as a

reference for zoo management, as well as lay the foundation for future studies.

In summary, the orangutans at Singapore Zoo showed age-specific activity budgets; differing

activity budgets across enclosures, and somewhat similar budgets to that of wild orangutans.

Activity budgets were influenced by husbandry routine, enclosure design, and features in the

vicinity of the exhibit. Structure use and behaviours at each structure varied according to

biological factors and environmental factors. Biological factors included orangutan age,

behavioural profile and dominance hierarchy. Environmental factors consisted of structure

properties, structure availability, location in exhibit, features in exhibit surroundings as well as

husbandry routines. The study on visitor effects showed that large crowds of more than 40,

visitors with food, visitors who were looking or taking photographs, and visitors who were close

by, all affected orangutan behaviour. Of note was the fact that visitor effects may have been

alleviated by the large and naturalistic exhibit design, or habituation to humans.

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Common factors across the three chapters

Across all three studies, enclosure design and husbandry routines seem to have consistent

influence on orangutan behaviour. For enclosure design, the location, availability and

arrangement of structures within an exhibit affected the activity budgets of orangutans by

encouraging or discouraging particular behaviours. These factors also appeared to play a role in

bridging differences between captive and wild orangutan behaviour. The large enclosure design

also possibly alleviated stress from visitors by allowing for retreat space. Likewise, husbandry

routines seemed to improve the welfare of this orangutan group. The provision of regular food

throughout the day lowered inactivity in the animals. Regular keeper-animal contact, in

combination with daily visitor photography sessions, appeared to be a source of enrichment and

helped habituate the animals to visitors.

The importance of exhibit design and keeper interaction on the quality of captive animal welfare

has previously been highlighted by Shepherdson et al. (1998). Unlike their wild counterparts

which are free to roam, animals in captivity have to adapt to and make the best of enclosure

structures. This may result in abnormal (stereotypic) behaviour if there is insufficient stimulation.

One example is a solitary male gorilla which developed regurgitation and reingestion behaviours

when housed in an enclosure with only concrete walls and a wooden structure (Cipreste et al.,

2010). The abnormal behaviours stopped when its exhibit was renovated to become one of greater

complexity, with added vegetation, rockwork and water features. Similarly, many decisions made

by animals in the wild are taken over by keepers in captivity; for example choosing a mate, or

when and what to eat. Free- ver these

-

(Shepherdson, 2010). As a result, increasing feeding activity by varying food presentation or

100

types of food available has been found to promote species-specific behaviours, reduce stereotypic

behaviour and improve captive animal welfare (Young, 2003).

Regurgitation an artefact of captivity

Throughout this study, regurgitation and reingestion behaviour was referred to as an undesirable

behaviour. Regurgitation and reingestion is the voluntary movement of food from the oesophagus

or stomach back into the mouth or substrate. Such behaviour is considered abnormal in primates

because it is observed almost only in captivity. Regurgitation has not been reported in wild

orangutans (Knott, 2011, pers. comm.11, Wich, 2011, pers. comm. 12) or gorillas (Hill, 2009), and

has only been noted in two individual instances in wild primates (proboscis monkeys, Nasalis

larvatus: Matsuda et al., 2011; vervet monkeys, Cercopithecus aethiops: Struhsaker, 1977). On

the other hand, it is found widely in captive primates, including orangutans (Maple, 1980),

gorillas (Akers and Schildkraut, 1985; Gould and Bres, 1986; Lukas, 1999; Lukas et al., 1999),

chimpanzees (Baker and Easley, 1996; Struck et al., 2007), macaques (Bayne et al., 1991),

siamangs (Fox, 1971), as well as in humans, in particular with infants who have undergone

psychological problems such as stress, lack of stimulation or the loss of a parent (Blinder et al.,

1988; Mayes, 1988).

Because orangutans, similar to gorillas, are hindgut fermenters with simple stomachs (Caton et

al., 1999; Knott, 1998), they are not physiologically designed to ruminate food during digestion

(Elftman and Atkinson, 1950). A recent study on gorillas indicates that regurgitated food contains

stomach acid (Hill, 2009). Given that a behaviour similar to regurgitation, the human rumination

syndrome, has been observed in humans, and associated consequences include dental erosion,

11 Dr Cheryl Knott, Field Researcher, Associate Professor, Department of Anthropology, Boston University 12 Dr Serge Wich, Field Researcher, Post-doc, Anthropological Institute & Museum, Universität Zürich

101

oesophagal motor disorders and ulcers (Thame et al., 2000 ), this indicates potential health

consequences for animals that regularly regurgitate. As such, regurgitation and reingestion is

thought to be an undesirable behaviour found only in captive primates (Lukas, 1999).

There are several factors which may contribute to regurgitation in captivity. These include

psychological factors (stress or boredom), housing factors (space restriction or the lack of

environmental/social stimulation), as well as nutritional factors (species-inappropriate diets or

lack of foraging opportunities) (Akers and Schildkraut, 1985; Lukas, 1999; Lukas et al., 1999).

For example, studies on captive gorillas and chimpanzees have shown that increasing the amount

of browse (leafy vegetation) provided throughout the day can reduce regurgitation and reingestion

behaviour (Gould and Bres, 1986; Lukas, 1999; Struck et al, 2007). This may be because in the

wild, gorillas and chimpanzees spend between 47-60% of their time feeding (Goodall, 1986;

Watts, 1988). However in captivity, feeding behaviour often is limited to two or three meals per

day. Hence, regurgitation and reingestion could possibly be an adaptive mechanism to extend

feeding time and approximate more closely the feeding behaviours of wild primates (Lukas,

1999; Lukas et al., 1999). Interestingly, a study on regurgitation in captive gorillas showed that

removing milk from captive diets also resulted in a 28% decrease in regurgitation/reingestion,

which may indicate that appropriate choice of foods by animal management can also reduce this

undesirable behaviour (Lukas et al., 1999). Therefore, regurgitation may be a coping response to

captivity (Lukas, 1999).

In view of the findings from my study, the following are some recommendations for captive

orangutan welfare.

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Recommendations on enclosure design

Structures within the exhibit

It is interesting to note how the availability, and especially location, of structures in an exhibit

may affect structure use and behaviour. Only one study to date has discussed structure location

for a caiman exhibit (Verdade et al., 2006), and little is known about the effects of this factor on

other species. The results of my study suggest that it may be possible to encourage or discourage

particular behaviours simply by rearranging the structures in an exhibit. For example,

regurgitation was less frequent in the Island exhibit than Boardwalk exhibit. This suggests that

orangutans may have regurgitated (an undesirable behaviour) less in the Island exhibit because

platforms, structures where regurgitation normally took place, were at the far end of the

enclosure. Similarly, movement may be increased by placing core areas of activity far apart in an

enclosure, as in the Island exhibit. As there have been almost no studies in this area; such

knowledge should be of use for future enclosure design.

To prevent social conflict for orangutans housed in groups, it is advisable to provide sufficient

pieces of each structure. Alternative routes between structures in each exhibit is also necessary.

This will prevent frustration in less dominant animals when access to a resource/structure is

restricted by dominant animals (Robitaille and Prescott, 1993).

F eatures surrounding the exhibit

Before construction for a new exhibit begins, features surrounding the proposed site should first

be considered. Orangutans are generally known to be intelligent and observant; therefore visitor

establishments or other animal exhibits in the surroundings may serve as enrichment. For

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Singapore Zoo orangutans, there was a restaurant as well as a third orangutan exhibit next to their

enclosures. Constant exposure to visitors and keepers via daily photography sessions and regular

handling is expected to have habituated them to humans; hence, the increased amount of visitor

traffic due to the nearby restaurant may have been less stressful for this group of animals.

Orangutans while in both enclosures were often observed to look at the restaurant; presumably

they were watching the dining visitors. An escaped orangutan was once found seated at an

outdoor restaurant table, holding a spoon and a fork in either hand (Nantha 2009, pers. comm.13).

This suggests that it had previously observed visitors who were using utensils. Hence, the

opportunity to watch visitors may serve as a source of enrichment for these orangutans. Similarly,

the orangutans were often observed to watch some older orangutans which were found in a third

orangutan exhibit between the two free-ranging enclosures (see Fig 3.3). The free-ranging

orangutans showed particular interest when the older orangutans were manipulating objects, or

processing novel foods. Therefore, the presence of the third orangutan exhibit next to the two

free-ranging enclosures is thought to be especially enriching. Such a concept has also been used

in other zoos. For example, the Adelaide Zoo in Australia is building overhead lines and towers to

allow orangutans to pass over and rest above the adjacent tiger display (Coe and Dykstra, 2010).

Other animal exhibits in the surrounding of orangutan exhibits may hence serve as a form of

enrichment. However, response to environmental stimuli ultimately depends on individual

temperament and captive rearing history (Hosey et al., 2009).

orangutans first have to be considered before deciding if environmental stimuli will be enriching

or not.


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Recommendations on husbandry routine

F eeding routine and regurgitation

Husbandry routines are generally known to have strong influence on captive animal behaviour

(Shepherdson et al., 1998). By varying the frequency and types of food provided, primate

caretakers can encourage species-specific behaviours and reduce inactive or stereotypic

behaviours (Kerridge, 2005). Most of the individuals in this study were noted to immediately feed

once browse (fresh leaves) or other foods were provided. Because wild orangutans spend more

than 50% of their time feeding (Morrogh-Bernard et al., 2009), reduced feeding opportunities in

captivity may lead to behaviours such as regurgitation, which is thought to be a way of increasing

feeding time (Akers and Schildkraut, 1985; Gould and Bres, 1986). Interestingly, regurgitation

was present in this group of orangutans, even though they were housed in a large, naturalistic

exhibit. Of the orangutans observed, only a few individuals performed regurgitation and

reingestion regularly. Two young orangutans in particular, Budi and Merlin (aged seven and five

respectively), regularly regurgitated after being fed. They spent on average, 15% of their activity

budget on this behaviour (see Appendix). Adhoc observations also showed that another young

orangutan, Bento (aged three), seemed to be learning from the other orangutans, and showed

increasing levels of regurgitation over the course of this study. Conversely, an older individual,

Chomel (aged 13), seemed to be making attempts to mimic this behaviour, but usually only

managed to regurgitate a bit of food, before moving on to another behaviour. Because

regurgitation can be caused by a multitude of psychological, housing or nutritional factors, and

also acquired via social learning (Lukas, 1999) especially when the animal is young, any

measures to address this behaviour need to be multi-pronged (Hill, 2009, Lukas, 1999). One

recommendation is to investigate the possible causes of regurgitation in this group of orangutans,

especially in Budi and Merlin, because the presence of this behaviour may indicate underlying

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welfare issues. In particular, it may be interesting to look at captive rearing history for this group

of orangutans, for example, the age at which the orangutan was separated from its mother, and the

conditions under which it was reared when young. Also, the daily feedings of milk and Milo may

be interesting to consider, as regurgitation in captive gorillas was reduced by 28% when milk was

removed from their diet (Lukas et al., 1999).

An alternative way of varying the feeding routine would be to provide food at different areas in

the exhibit. Fresh leaves and snacks were usually provided at fixed areas in the exhibit; as a

result, feeding behaviour usually occurred at the same locations. By varying where food is

provided, greater enclosure use can be encouraged; this can also serve as a source of physical

exercise as animals have to move towards the keeper. In addition, besides providing leaves, foods

which require greater processing time may also be enriching. In the wild, orangutans are known

to feed on foods which have tough skins or require longer processing times (Mackinnon, 1974).

Food items of such nature (e.g. novel fruits, insects) should be incorporated into captive animal

feeding routines as much as possible.

Animal handling

The presence of visitor photography sessions and animal shows involving orangutans gives rise to

unusual husbandry routines in Singapore Zoo. Unlike many European and American zoos, hands-

on contact with orangutans is much more common in Singapore Zoo (Raj, 2010, pers. comm.14).

During visitor photography sessions which occur several times a day, orangutans and visitors sit

at close proximity from one another. For this to be possible, good keeper-animal relationships are

first necessary. A model of human-animal relationships by Hosey (2008) suggests that animals


106

keepers, a strong bond of trust is present between the orangutans and their caretakers (pers. obs.;

orangutan keepers, pers. comm.). Anecdotal observations (in Singapore Zoo), such as orangutan

mothers which voluntarily hand their infants to the keepers provide evidence of the trust that

these orangutans have in their caretakers. This excellent keeper-animal relationship possibly

reduces fear of unfamiliar humans in the orangutans, hence visitor photography sessions, whereby

strange humans sit in close proximity to the orangutans, are possible. Similarly, any stressful

effects from visitors viewing the exhibits may be reduced. This particularly hands-on routine may

therefore improve welfare in this group of captive orangutans.

Other considerations and recommendations

Social housing for semi-solitary apes

Even though orangutans in the wild are semi-solitary, it is hypothesized that such social structures

are influenced by food availability. Orangutan food sources are located patchily throughout the

forest, and association in groups may increase costs of foraging (Setia et al., 2009). In captivity,

however, food availability is no longer a concern, and captive orangutans are known to be more

social (Zucker et al., 1986). Social stimulation may substitute for a lack of variability in captive

environments. This appears to be why orangutans in this study, despite having less feeding

activity than wild orangutans (in irregularly fruiting forests), were not more inactive than the

latter. The time not spent on feeding by captive animals was instead spent on social and play

behaviour. Because orangutans are intelligent animals (Tomasello and Call, 1997), housing

captive apes in social settings may be a good alternative which provides physical and mental

stimulation.

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Visibility of orangutans in the Island exhibit

I observed that in the Island exhibit, more than half of the visitors passed under the trees without

noticing the orangutans. Considering the effort and costs spent on maintaining naturalistic

exhibits, it is suggested that more signage be put up to draw visitor attention to the arboreal apes.

Even though the orangutans are sometimes difficult to spot in the tree canopy, it has been found

that visitors enjoy searching for free-ranging animals, even when they do not find them (Price et

al., 1994). Hence, opportunities to experience the orangutans as arboreal animals may further

enhance visitor appreciation of this endangered ape (Coe, 1989; Finlay et al., 1988).

F easibility of replicating Singapore Zoo orangutan exhibit design

The orangutan enclosures in this study are complex and provide exposure to environmental

stimuli. They appear to reduce visitor stress in the animals, and allow for species-specific

behaviours. The orangutan keepers have also noted that the fur coats of the orangutans have

become glossier, and their muscles more well-defined, after the introduction of the exhibits. In

addition, because the exhibits were built upon existing trees, they do not take up additional space.

In view of these benefits, the replication of such an exhibit design in other zoos may be worthy of

consideration. However, some features of these enclosures must first be addressed.

One aspect of these orangutan exhibits which was not discussed earlier is how orangutans are

introduced into the enclosures. Unlike traditional enclosures where a sliding door or partition is

opened to let animals enter an exhibit, keeper-animal contact is required to introduce orangutans

into the free-ranging exhibits. Keepers hand-hold the orangutans and walk them out from their

night dens to specific areas in each exhibit. At a special point near each exhibit, a log can be

lowered to form a bridge onto the exhibit (see Fig. 5.1). When orangutans are to be introduced

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into the enclosure, the log, operated by hydraulic mechanism, is lowered to join the ground and a

branch in one of the exhibit trees. At all other times, the log stands vertical, away from the exhibit

trees. Orangutans are prevented from leaving the exhibit by low-current electrical wires midway

up each tree. Such an exhibit design requires keepers to handle the animals on a daily basis. The

orangutan husbandry routine in Singapore Zoo is such that female orangutans are handled up to

more than 40 years of age by the keepers, and male orangutans have been safely handled up to 17

years of age. Because mature males may not be handled due to safety considerations, only

females and younger males, of below certain weights to prevent branch breakage, may be

displayed in the treetop exhibits. For purposes of replication elsewhere, this exhibit design could

be modified so that keeper-animal contact is not required for animal release. However,

orangutans have been seen on occasion to jump down from the tree canopy. These events are

sporadic, and are due to aggressive interactions between conspecifics. Occasionally, orangutans

also manage to exit the enclosure and escape onto surrounding trees. In view of this, there is

always at least one keeper watching the animals. In the event of enclosure escape, the keeper is

required to retrieve the animal and if necessary, return it to the night dens. This suggests that for

-

animals. This is so that the orangutans, which can jump down from the enclosures if they choose

to, are less likely to travel far, before being called back by their keepers.

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F ig 5.1. Log that facilitates entry into Island orangutan exhibit. Left: Log not lowered, standing vertically away from exhibit (denoted by white arrow). Right: Log is lowered and bridges ground and exhibit.

Study limitations and future directions

In this study, results were pooled for animals in the same age group. When individual data were

examined (see Appendix), some orangutans in the same age group showed very different levels of

the same behaviour. Animal welfare has been defined as being specific for each individual, hence

consideration of individual (Hosey et al., 2009). Such unique

characteristics occur within a species and are something that animal caretakers are generally

aware of. It was discussed in the visitor effects chapter how individual orangutans differed in

their responses to visitors. Studies on rats also show that differing degrees of neophobia (fear of

novelty) in rats were linked to different probabilities of illness and death. Animals which were

more active in exploring their surroundings were more likely to live longer than their neophobic

siblings. (Cavigelli et al., 2006; Hosey et al., 2009). Considering such personality effects, zoo

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management could try to take into account individual orangutan preferences when designing their

husbandry routine and enrichment programmes. Future studies that match great ape personalities

via keeper surveys to empirical behavioural observations (Uher and Asendorpf, 2008; Uher et al.,

2008), may also be useful in improving captive orangutan welfare.

C O N C L USI O NS

The study of activity budgets, enclosure use, and visitor effects in a group of captive orangutans

has provided considerable information on behaviour in two naturalistic, novel enclosures. This

knowledge will be useful for zoo management and can provide guidelines for future study on

captive orangutan behaviour.

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APPE NDI X

1. Activity budgets for individual orangutans

0

10

20

30

40

50

60

Perc

enta

ge o

f Act

ivity

bud

get (

%)

(1) Bento(1) Merlin(2) Budi(2) Gunta(3) Vira(3) Labu(3) Chomel(4) Binti(4) Anita

0

10

20

30

40

50

60

Per

cent

age o

f A

ctiv

ity B

udge

t (%

)

(1) Bento(1) Merlin(2) Budi(2) Gunta(3) Vira(3) Labu(3) Chomel(4) Binti(4) Anita

F ig. 1. Activity budgets for individual orangutans in Boardwalk (top) and Island (bottom) exhibits (number in bracket indicates age group).

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Although there were trends in behaviour across age groups, it is interesting to note that

orangutans of similar age can differ greatly in their behaviour. The following are some examples.

Although Budi and Gunta were both 7 years of age, Gunta was much more attentive to his

idled less as well. Similarly, comparing Anita and Binti, who were around the same age (25 and

24 respectively), Anita spent about 50% of her activity budget idling (which was double of almost

ovement was

rearing history, in which she was the only orangutan amongst the nine studied to be human-

reared, rather than mother-reared. Unlike the other animals, especially Binti, who all appear to be

on the slim slide, it is interesting that Anita is the only orangutan that looks slightly obese. Hence,

rearing history may play an important role in individual behaviour.

Alertness to surrounding, i.e. looking was distinctly higher at 30-40% in three individuals, Gunta,

Labu (aged 11) and Binti. They looked almost 150% of that in other orangutans. Similarly, Budi

and Merlin showed the highest amounts of regurgitation, between 15-20%, which was triple or

quadruple that of other orangutans. And human interaction (i.e. begging for food from visitors)

was mostly performed by Chomel, Labu and Budi.

The amount of play by Bento (age 2) was double that of Merlin (age 4). Although this difference

in play could be due to age differences, it was also possible that the presence of younger

immature animals play more than adults, it is known that the proportion of immature individuals

in the group is critical factor. (Zucker and Clarke, 1992). Additional evidence comes when we

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in the other group. Hence social grouping seems to have an effect on orangutan behaviour.

Table 1. Raw percentages used to plot activity budget graphs for Boardwalk exhibit in Fig. 1. (Age gp) Orangutan Idle Look Move Feed Play/social

Human interaction Regurgitate

(1) Bento 26.0 12.7 16.2 18.1 21.9 1.6 3.5 (1) Merlin 26.8 11.0 14.0 18.8 11.3 1.8 16.4 (2) Budi 27.0 13.7 9.5 17.1 10.5 4.4 17.8 (2) Gunta 16.5 37.1 13.0 24.4 3.8 2.5 2.5 (3) Vira 23.4 26.7 10.1 27.0 3.6 0.9 8.3 (3) Labu 27.6 35.9 11.3 16.6 3.0 2.7 3.0 (3) Chomel 36.5 23.2 5.7 10.2 13.0 6.7 4.8 (4) Binti 23.4 38.0 11.6 19.3 2.4 2.1 3.3 (4) Anita 43.7 23.7 4.1 15.2 7.3 5.1 0.9 Average 27.9 24.7 10.6 18.5 8.5 3.1 6.7

Table 2. Raw percentages used to plot activity budget graphs for Island exhibit in Fig. 1. (Age gp) Orangutan Idle Look Move Feed Play/social

Human Interaction Regurgitate

(1) Bento 21.4 8.6 27.0 24.0 18.1 0.0 1.0 (1) Merlin 28.9 12.5 14.7 20.9 8.1 0.4 14.7 (2) Budi 28.3 11.8 13.2 27.0 5.9 0.7 13.2 (2) Gunta 21.7 22.4 13.5 34.5 5.9 0.3 1.6 (3) Vira 17.9 17.9 14.6 40.5 5.5 0.0 3.6 (3) Labu 26.3 25.9 19.0 25.9 2.2 0.4 0.4 (3) Chomel 42.8 17.8 8.2 15.1 11.5 2.0 2.6 (4) Binti 28.0 25.8 24.7 15.3 2.2 1.1 2.9 (4) Anita 56.9 13.5 3.9 19.1 4.6 1.3 0.7 Average 30.2 17.4 15.4 24.7 7.1 0.7 4.5

Choo Yuan Ting is now contactable at [email protected]

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