Ecology Lecture 16 - Predation PDF

Ecology Week 10 Lecture 16 – Predation 16c: Functional & Numerical Responses Lotka-Volterra Predation Model Provides an explanation for predator- prey population cycles But, has many assumptions and is very simplistic – For e.g., the more prey available the...

Ecology Week 10 Lecture 16 – Predation 16c: Functional & Numerical Responses Lotka-Volterra Predation Model Provides an explanation for predator- prey population cycles But, has many assumptions and is very simplistic – For e.g., the more prey available the more an individual predator eats 2 (per predator) (even if only one predator) Why is Type I unrealistic? 3 (per predator) (even if only one predator) 4  The functional response A more realistic description of predator behavior incorporates alternative functional responses, proposed by C.S. Holling: type I response: rate of consumption per predator is proportional to prey density (no satiation) type II response: number of prey consumed per predator increases rapidly, then reaches a plateau with increasing prey density type III response: like type II, except predator response to prey is depressed at low prey density 5 6  The Holling Type III response What would cause the type III functional response? 7  The Holling Type III response What would cause the type III functional response? Heterogeneous habitat, which provides a limited number of safe hiding places for prey Lack of reinforcement of learned searching behavior due to a low rate of prey encounter (no search image) Switching by predator to alternative food sources when prey density is low 8 Switching food sources 9  The numerical response If individual predators exhibit satiation (type II or III functional responses), continued predator response to prey must come from: – A numerical response: Increase in predator population (population growth or immigration) 10 11