BIOL 2300 Lecture Notes - Lecture 7: High Availability, Functional Response, Net Energy Gain
22 Jun 2018
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LECTURE 7 ORGANISMS AND PREDATION
Behavioural Ecology
• Behavioural ecology increases our understanding of how biotic factors
influence distribution/abundance of organisms
• Today – examine the behavioural ecology of consumer-resource (predator-
prey) interactions
Consumer-Resource Interactions
• Fitness depends on an individual’s ability to grow, survive, & reproduce.
• Require:
o Suitable environmental conditions (abiotic factors)
o Sufficient resources
▪ Acquire appropriate quantities of energy
▪ Acquire energy efficiently (gain > loss)
• Utilize ATP
• Can store for later use – glycogen in the liver, fats
• Use it structurally – cell wall
• Behavioural strategies of foraging have evolved under these pressures to
maximize fitness.
Predation
• Consumption of prey by a predator, where the prey is alive when attacked
A number of important questions
• Where to feed?
o How much time/energy to spend searching?
• What to feed on?
o Diet?
2
• How are predators affected by the density of their prey?
o Energy loss/gain during prey capture?
o High prey population size = high competition level
• Help us understand:
o How has natural selection favoured particular behavioural patterns?
o How does predator behaviour influence the size of predator and prey
populations? (abundance and distribution)
Effects of Prey Density on Predator Behaviour
• Functional Response: the relationship
between prey density and predator
consumption rate
• Consumption rate depends on:
1. prey abundance per unit area
(prey density) – all prey species
2. search efficiency for prey
(search time, s)
3. time to pursue, subdue & ingest and digest prey
(handling time, h)
3 Types of Functional Responses (Holling 1959)
**for the exam, draw and explain
Type I
• As prey density , encounter rates , search time
• Rarely observed
• S > H
o Search time varies with prey density
o Handing time is constant but near zero
