Predator vs. Prey: Predation and Fear for your life!

1. Predator vs. Prey: Predation and Fear for your life!

2. Marine Predators Upper level mesopredators Top predators Lower Level Mesopredators

3. Predation in Marine Communities • Predation contributes to the structure of many marine communities through trophic cascades Indirect Effect Predator Direct Effect Prey Direct Effect Resource

4. Predation in Marine Communities • Otters, Urchins, and Kelp Forests Estes,1978

5. Predation in Marine Communities • Blue crabs, Periwinkle Snails, Cordgrass Silliman Salt Marshes Silliman and Bertness, 2002

6. Loss of Top Predators

8. Predator-Prey Arms Race • Natural selection will • Favor predators that are efficient • And select for improvement in prey defenses to overcome predators • A cycle and escalation of adaptations and counter-adaptations– an arms race!

9. Predator-Prey Arms Races • Red Queen Evolution • “it takes all the running you can do to keep in the same place” • Without constant evolution, you would be eaten!

10. Predator-Prey Arms Races • Why is it that the arms race is always slightly in favor of the prey? • Life dinner principle- the rabbit is running for his life while the fox is only running for his dinner’ • Dawkins 1979 • It’s a lots more important to avoid being eaten than it is to miss a meal!

11. Predator-Prey Arms Races Temporal trends in bite mark frequencies on Mesozoic motile and sessile crinoids (A).

12. Don’t eat me! • Prey have developed multiple adaptations to avoid being eaten • 1) Camouflage • Used by many marine organisms • The master of camouflage

13. Don’t eat me! • Prey have developed multiple adaptations to avoid being eaten • 1) Camouflage • Can be visual

14. Don’t eat me! • Prey have developed multiple adaptations to avoid being eaten • 1) Camouflage • Often visual

15. Camouflage • Polymorphic cryptic coloration • Different color morphs exist within a population • May prevent predators from developing a search image • Search Image

16. Camouflage • Palma and Steneck , 2001 • Polychromatic variations enhance survival in polychromatic habitats

17. Don’t eat me! • Prey have developed multiple adaptations to avoid being eaten • 1) Camouflage • Or chemical • Decorator crabs

18. Don’t eat me! • Prey have developed multiple adaptations to avoid being eaten • 1) Camouflage • 2) Warning Coloration-Aposematism • Bright colors become associated with defended animals • Has evolved independently multiple times

19. Aposematism • Common in marine nudibranchs

20. Aposematism • Conspicuous colors help predators to learn to avoid unpalatable prey and may help to reduce recognition errors

21. Aposematism • Fish learn to avoid distasteful chemicals! • In order to examine chemical defenses, and identify the compounds responsible, scientists often extract and separate chemical from the organism • Bioassay guided fractionation • Extracted chemicals are then applied to a food and compared to the same food sans chemical

22. Aposematism • Different strategies to avoid nasty chemicals • Blennies regurgitate treated food and then refuse to accept anything that looks like it • Killifish just learned to avoid the noxious chemical

23. Mimicry • Batesian mimicry- a relatively scarce, palatable, and unprotected species resembles an abundant, relatively unpalatable, or well-protected species, and so becomes disguised. Advantageous when mimics are scarce relative to model Disadvantageous when mimics are abundant Although there is still lots of debate about this in the literature Batfish

24. Mimicry • Mullerian mimicry- when two unpalatable species grow to resemble each other • Predators who learn to avoid one, learn to avoid the other The two invertebrates on the left are different species of sea slugs, while the one on the right is a marine flatworm. All three secrete noxious substances and are unpalatable.

25. Don’t eat me! • Prey have developed multiple adaptations to avoid being eaten • 1) Camouflage • 2) Warning Coloration • 3) Defense- toxins and other physical protection • Constitutive defenses • Induced defenses

26. Induced Defenses • Bryozoans, barnacles, and many gastropods produce spines, thickened shells, or growth asymmetries in response to waterborne predator chemical cues

27. Induced Defenses • Marine Bryozoans Harvell 1986

28. Induced Defenses • Chemical defenses can also be up-regulated (especially in algae)

29. Constitutive Defenses • Less common than induced defenses in marine communities • In marine environments, these are mostly chemical defense s • Species or genera can differ on const. vs induced

30. Constitutive Defenses • Why might induced defenses be more common than constitutive defenses? • Allocation costs- defenses require energy to produce • Opportunity costs- resources allocated to defenses cant be allocated elsewhere

31. Chemical Defenses • Do chemical defenses actually reduce fitness or do they just taste bad? • Didemnins in tunicates

32. Don’t eat me! • Prey have developed multiple adaptations to avoid being eaten • 1) Camouflage • 2) Warning Coloration • 3) Defense- toxins and other physical protection • 4) Autotomy

33. Autotomy • Common in crab species • Porcelain crabs in particular have a hair trigger on shedding limbs Mantis shrimp vs crab Doesnt always work....

34. Don’t eat me! • Prey have developed multiple adaptations to avoid being eaten • 1) Camouflage • 2) Warning Coloration • 3) Defense- toxins and other physical protection • 4) Autotomy • 5) Behavioral Escape- Antipredator behaviors • In space or in time!

35. Behavioral Escape • Plankton and Small Nekton Vertical migrations • Occur in pelagic environments with no structure • Forage at the surface at night and migrate to the depths during the day • More pronounced in pigmented species that are more conspicuous to visual predators (Hays et al. 1994) • Migrations strength is often seasonally coordinated with predatory fish abundance

36. Behavioral Escape • Demersal fish are thought to inhabit shallow water during the day to avoid larger fish predators and migrate to deeper depths to forage at night • But this theory has been called into question by a few studies

37. Behavioral Escape • Predators also induce prey to seek refuges and/or reduce their activity to reduce their chance of being eaten –anti-predator behavior

38. Anti-predator Behaviors • These antipredator behaviors also result in prey feeding reductions

39. Anti-predator Behaviors • These antipredator behaviors also result in prey feeding reductions • Consumptive effects • Or Density Mediated Interactions • Changes in prey and resource abundance due to lethal interactions with predators • Non-consumptive effects • Or Trait Mediated Interactions • Changes in prey habitat or resource use in response to predator risk Predator Prey Resource

40. Non-Consumptive effects • Toadfish, mud crabs, oysters Grabowski, 2004

41. Non-consumptive effects • Toadfish, mud crabs, oysters Grabowski, 2004

42. Non-Consumptive Effects • Spiders, grasshoppers, and grass • Consuming vs scaring

43. Non-consumptive Effects • Which drives the majority of indirect interactions? • On average, TMI’s are responsible for 85% indirect effects Preisser et al. 2005

44. Behavioral Escape and NCEs • Behavioral escapes are often initiated once a predator has been perceived • Usually by chemical detection (although other sensory modalities are possible-they are less studied)

45. Behavioral Escape • Experimenting with predator chemical cues

46. Determining prey response to cues • Prey use information about cues and their environment to determine if, when, and how much they will respond • Threat sensitive predator avoidance (Helfman, 1989)

47. What predator traits do you think affect the magnitude of anti-predator behaviors and non-consumptive effects?

48. Risk is context-dependent • Threat sensitive predator avoidance (Helfman, 1989) • Predator Identity (Turner, 1999)

49. Risk is context-dependent • Threat sensitive predator avoidance (Helfman, 1989) • Predator Identity (Turner, 1999)

50. Risk is context-dependent • Threat sensitive predator avoidance (Helfman, 1989) • Predator Identity (Turner, 1999) • Predator Diet (Schoeppner and Relyea, 2005)