Understanding Predator-Prey Interactions: Strategies and Impacts

1. Predation Great White Shark and Fur Seal

3. Lions hunting – True Predator

4. Red squirrel – true predator

5. Moose Browsing – Partial Predator

6. Cookie-cutter shark – Partial Predator

7. Parasitoid Wasp

8. Specialists and Generalist Predators Advantages to being a specialist 1. Avoid interspecific competition 2. Allows evolution to overcome chemical defense 3. Allows evolution of cryptic coloration that matches prey - mostly for insects on plants 4. Increases chance of mate encounter Advantages of being a generalist 1. Flexibility in face of environmental uncertainty 2. Broad diet needed to get all necessary nutrients and vitamins 3. Avoid overdosing on any one toxin - mostly for animals grazing on chemically defended plants

9. Factors affecting predator behavior 1. Search time - the amount of time spent looking for food items 2. Handling time - the amount of time spent capturing prey once it is found, also includes time for consuming prey and time to digest before a predator can search for food again

10. Birds gleaning for insects - generalist

11. Lions – specialize a bit

12. Black-footed ferret – specialist – 90% of diet is prairie dogs

13. Predator-Prey Interactions

15. Food Preferences • A preference exists if the proportion of a type of food is higher in the animal’s diet than it is in its proportion in the environment • Ranked preference – predator preferentially eats prey which is most valuable (usually in terms of calories) • Balanced preference – predator eats prey items that provide integral parts of a balanced and mixed diet (usually in terms of nutrients and vitamins)

16. Pied Wagtail

18. Caribou feeding in winter

19. Preferences • Fixed preference – predator eats certain items regardless of what else is available – can be fixed in terms of species consumed or energy consumed

20. Edible mussel – Mytilus edulis

21. Shore crab and edible mussels

24. Backswimmers

25. Asellus aquaticus – prey for backswimmers

26. Guppy as predator

27. Guppy prey – tubificid worms and fly larvae

28. Eurasian oystercatcher

29. Search image – this image has dashes arranged as L, as T, and plus signs – can you find the Ts?

30. Bluegill sunfish

32. Effects on populations • Population regulation refers to the tendency of a population to decrease in size when above a particular level, and to increase in size when below that level. Population regulation can only occur as a result of one or more density dependent processes acting on birth or death rates.  • Population abundance is determined by the combined effects of all factors and processes that influence population size, whether they are density dependent or density independent.

33. Predator effect on individual prey

34. Mink Muskrat

35. Arctic Ground Squirrel – Predator population is self-limited

36. Red Grouse in Heather –Predator population is self-limited

37. Predator Switching Regulates Prey Population Bank vole Tawny Owl

39. Cinnabar Moth and Caterpillar on Ragwort Tansy

40. Snowshoe hare and Lynx

43. Lynx Ruffed Grouse Snowshoe hare

44. Sea Otter

45. Sea Urchin

46. Kelp Forest

47. Sea Otter eating Sea Urchin in Kelp Forest

48. Comparison of kelp and urchin biomass with and without sea otters

49. Sea Urchin Barren

50. Kelp forest ecsystems with and without sea otters