Species 1 (victim V)

1. + Species 2 (predator P) Species 1 (victim V) - EXPLOITATION

2. Getting into the mind of the predator: What constrains consumption?

3. Inside the predator’s daily planner: 6:00 am Get up and clean. Re-assert dominance in family group. 8:00 am Begin searching for victims. 12:00 pm First victim spotted. Pursuit begins. 1:00 pm Abandon pursuit. Victim got away. 3:00 pm Second victim spotted. 3:20 pm Victim subdued and killed. Begin eating. 6:00 pm Victim eaten and sufficiently digested. Return home. 7:00 pm Arrive home. Try to mate. 7:10 pm Rest.

4. The point is: • Time is limited. • There are other things to do besides activities related to eating (e.g. social interactions, mating rituals, grooming, sleeping). • Eating-related activities consist of: • searching for prey • pursuing prey • subduing the prey • eating the prey • digesting (may not always exclude other activities)

5. The time constraints of foraging Foraging time other essential activities foraging

6. The time constraints of foraging Foraging time other essential activities Handling time Search time search handling

7. The time constraints of foraging Foraging time other essential activities Handling time Search time eating search pursuing & subduing eating time pursuit & subdue time

8. Filter feeder: Sit & wait predator (spider) eating waiting eating subduing Different species will allocate foraging time differently:

9. Well-fed mammalian predator: Starving mammalian Predator (victims at low dnsity): eating eating searching pursuing & subduing pursuing & subduing searching Time allocation also depends on victim density and predator status:

10. Total search time per day Total handing time per day Total foraging time is fixed (or cannot exceed a certain limit). C.S. (Buzz) Holling Building a theory of predation: (After C.S. Holling)

11. 1) Define the per-predator capture rate as the number of victims captured (n) per time spent searching (ts): 2) Capture rate is a function of victim density (V). Define a as capture efficiency. 3) Every captured victim requires a certain time for “processing”.

13. Capture rate limited by predator’s handling time. Capture rate Capture rate limited by prey density and capture efficiency Prey density (V)

14. nymph Damselfly (Thompson 1975)

15. Asymptote: 1/h Decreasing prey size The larger the prey, the greater the handling time. (Thompson 1975)

16. Three Functional Responses (of predators with respect to prey abundance): Holling Type I: Consumption per predator depends only on capture efficiency: no handling time constraint. Holling Type II: Predator is constrained by handling time. Holling Type III: Predator is constrained by handling time but also changes foraging behavior when victim density is low.

17. Type I: Type II Type III Type I (filter feeders) Type II (predator with significant handling time limitations) Per predator consumption rate Type III (predator who pays less attention to victims at low density) victim density

18. Thin algae suspension culture Daphnia path Thick algae suspension culture Holling Type I functional response: Type I functional response Daphnia (Filter feeder on microscopic freshwater organism)

19. Holling Type II functional response: Slug eating grass Cattle grazing in sagebrush grassland

20. Holling Type III functional response: Paper wasp, a generalist predator, eating shield beetle larvae: The wasp learns to hunt for other prey, when the beetle larvae becomes scarce.

21. We have seen that there are four possible outcomes for two-species competition. • What are the possible outcomes for a predator-prey system?

22. Gause’s Predation Experiments: Didinium nasutumeatsParamecium caudatum:

23. Paramecium in oat medium: • logistic growth. 2) Paramecium with Didinium in oat medium: extinction of both. 3) Paramecium with Didinium in oat medium with sediment: extinction of Didinium. Gause’s Predation Experiments: