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Contact: Holly Neate [email protected] or��Valerie Mucciarelli [email protected]

• Water quality monitoring • Olympia Oysters/Coho Salmon research • Seaquaria in Schools Program • Gorge Waterway Nature House

Volunteer With

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Field&Assistant&Needed:&&Predator&Fear&in&&Coastal&Food&Webs&

& Apex predators (e.g., cougars, wolves and bears) play a crucial role in structuring ecosystems by suppressing species at lower levels of the food chain, and the fear that these predators induce in their prey may be key to fulfilling this role. Our research group will be conducting field experiments in Clayoquot Sound, on the west coast of Vancouver Island, aimed at understanding how fear alone of apex predators affects coastal food webs by altering the foraging behaviour of smaller predators (raccoons), and the implications for large carnivore conservation. We are seeking a field assistant to help implement these experiments during Summer 2015. The successful applicant will assist in surveying for raccoon and intertidal prey species abundance, setting up and maintaining remote cameras and audio playback equipment, and conducting behavioural trials with free-living raccoons. This project combines elements of behavioural ecology, community ecology and conservation biology, and is ideal for a passionate individual interested wildlife conservation and field ecology. This is a paid position with UVic, providing a stipend of $1500 per month ($6000 total for the summer field season).

Qualifications: 1) Previous field research and data collection experience is an asset 2) Previous boating experience is an asset. The field assistant will be required to obtain a Pleasure

Craft Operators Card by the start of the field season 3) Previous outdoor (camping, hiking) experience and knowledge of wilderness first aid are desirable 4) Valid drivers license is required 5) Residence in or near Tofino BC, or willingness to find accommodations there for the field season, is

necessary 6) Work will at times be physically demanding, requiring at least average strength and endurance.

Applicant must be willing to work long hours in adverse weather, including at night. Start and End Dates: May 1st through late August 2015 To Apply: Email a cover letter and CV to Justin Suraci ([email protected]) Application Deadline: March 20th, 2015

fb: Jobs in Environmental Studies and Ecology @ UVic

Where We’ve Been:Week 1 – Ecological Aims and ApproachesWeek 2 – The Importance of Scale in EcologyWeek 3 – Biodiversity PatternsWeek 4 – Diversity StabilityWeek 5 – Biodiversity Ecosystem Function

Where We’re Heading: Week 6 – Species InteractionsWeek 7 – Trophic Interactions and Food Web EcologyWeek 8 – Food Webs and Ecological NetworksWeek 9 – Macroecology Week 10 – Resilience or Metabolic Theory/Body SizeWeek 11 – Ecological Implications of Climate ChangeWeek 12 – The Future of Ecology

Week 6: Species Interactions.��Predator-Prey Interactions

Recommended Reading for this Week: Mittelbach 2012 Community Ecology – Ch. 5 (pages 83-95; Ch. 6 pages 103-123

Predator-Prey Interactions

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Predator’s Functional Response

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Three basics Functional Responses (Holling 1959): Type I: predators feeding rate increases linearly with prey density (unrealistic for most predators)Type II: predators feeding rate increases with prey density, but at a steadily decreasing rate. Modeled as a curve that approaches an asymptoteType III: Sigmoidal relationship in which a predator’s feeding rate accelerates over an initial increase in prey

density, then decelerates at higher prey densities. Prey’s per capita death rat peaks at intermediate density. Generalist predators.

Type I

Type II

Type III

Feeding Rate = # of prey consumed per predator per unit time. FUNCTIONAL RESPONSE: the relationship between prey density and predator feeding rate

N = prey population density a = predator’s per capita attack rate (a constant) h= handling time c = h-1, the max. feeding rate

d = (ah)-1, the half saturation constant, the prey density at which feeding rate is ½ the max

IMPACT on the PREY’s PER CAPITA DEATH RATE:

Predator’s Functional Response

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Type I

Type II

Type III

Feeding Rate: # of prey consumed per predator per unit time. FUNCTIONAL RESPONSE: the relationship between prey density and predator feeding rate

N = prey population density a = predator’s per capita attack rate (a constant) h= handling time c = h-1, the max. feeding rate d = prey density at which feeding rate is ½ the max

Prey-Dependent: predators feeding rate determined only by prey density vs.Ratio-Dependent Predation: predators may interfere with one another’s ability to capture prey, or they may facilitate one another’s success by group foraging

IMPACT on the PREY’s PER CAPITA DEATH RATE:

Selective Predators and Responsive Prey‘Most carnivores do not confine themselves rigidly to one kind of prey; so that when their food of the moment becomes scarcer than a certain amount, the enemy no longer finds it worthwhile to pursue this particular one and it turns its attention to some other species instead.’ – Charles Elton, 1927

Reference for this section: Mittelbach 2012 Chapter 6 In: Community Ecology

PREDATORS: Are predators selective?Does their preference change with prey density or behavior? PREY: Consequences for mortality ratesImpacts: prey behaviors, adaptations, population dynamics, coexistence of prey species

Predator Preference

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= the difference between the proportion of that prey type in the predator’s diet and the proportion of that prey type in the environment. Influenced by:

(1) ENCOUNTER RATE

(2) ATTACK RATE

(3) CAPTURE RATE

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Optimal Foraging Theory= an approach to understanding predator diet choice by asking what set of foraging decisions will maximize a predator’s energy gain per unit time spent foraging:

E = ENERGY gained during feeding period of length T. En = net gainT includes Th = HANDLING TIME

Ts = SEARCHING TIME(where the predator expends the same amount of E during searching and handling)

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Optimal Diet Model

Eq. 6.2 = the standard Optimal Diet Model. It predicts a predator’s diet choices.Developed in 1970s (Emlen; Maynard Smith; Charnov)

Now let there be k prey types, each with the following characteristics:

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Optimal Diet ModelThe model makes two general predictions about optimal diet choice:

These general predictions are well supported by empirical evidence

1.  Foragers should prefer the most profitable prey (i.e., prey that yield the most energy per unit handling time)

2. As the overall density of profitable prey decreases, an efficient forager should broaden its diet to include more of the less profitable prey

General Predictions:

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Optimal Diet ModelGeneral Predictions:1.  Foragers should prefer the most

profitable prey (i.e., prey that yield the most energy per unit handling time)

2. As the overall density of profitable prey decreases, an efficient forager should broaden its diet to include more of the less profitable prey

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A Field Test of the Optimal Diet Model

Tests of the optimal diet model support its predictions, but in most cases predators included some prey types in their diets that are not in the predicted optimal set.

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Optimal Diet ModelOverall:

§  In review of optimal foraging theory, Sih and Christensen (2001) concluded that 87% of studies (n= 31 / 35) that included quantitative tests supported the predictions of the O.D.M.

§  But, in every study predators included some prey types in their diets that are not in the predicted optimal set.

§  Questionable assumptions: predators have perfect knowledge of prey quality and prey density

MacArthur and Pianka 1966: Envisioned Optimal Foraging Theory could provide a tool to predict consumer diets, thus providing a mechanism to better understand consumer-resource interactions and community dynamics.

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Consequences of Selective Predation for Species Coexistence

http://en.wikipedia.org/wiki/Jane_Lubchenco

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Consequences of Selective Predation for Species Coexistence

Nonconsumptive Effects of Predators��The ‘Ecology of Fear’

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Prey may respond to the threat of predation by changing their behaviors, morphologies, physiologies, or life histories.

These nonconsumptive (or nonlethal) effects of predators act in concert with the direct consumption of prey to influence prey abundance and predator-prey dynamics.


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Inducible (temporary) morphological defenses may evolve when predation risk varies temporally or spatially; when prey have the ability to detect predators via reliable cues; and/or when the defense carries a fitness cost.


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1.  Habitat Shifts

2.  Activity Level

3.  Morphological Changes

4.  Life History Evolution


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1.  Habitat Shifts: may be short term w. little effect on prey’s population dynamics, or may have far-reaching effects on prey dynamics and life histories:

§  predators restrict vulnerable size classes (e.g. young) to protective habitats

§  Trade-off between mortality risk and foraging gain -> ‘optimal’ habitat choice depends on costs and benefits (energy gain)

§  Eg. Diel vertical migrations by zooplankton – response to temporal variation in predation risk


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2. Activity Level Many prey species reduce their activity level (reduced movement and/or increased time in refuge) in the presence of predators, but these less-active prey may incur a reduction in growth (i.e., a growth rate-predation risk trade-off).

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3. Morphological Changes

§  Changes in toxicity, color, body shape, shell hardness, presence of spines – to reduce chance of being eaten

§  Phenotypically plastic responses

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3. Morphological Changes

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Relative Importance of Consumptive and Nonconsumptive Effects

The relative importance of the nonconsumptive and consumptive effects can be addressed by performing experiments in which the effect on prey density or fitness of a nonlethal (e.g., caged or disabled) predator or a predator cue is compared with that of a functional predator.

However, such experiments do not address the complicated interactions of these effects in nature.

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