Am. beech

1. Axis Tradeoff Am. beech Sugar maple Allocation of Energy: vertical or horizontal Sun to shade Cheetah Lion In capture techniques mass vs speed Prey size/speed BTGW Blackburnian Time allocation; adaptation to parts of the tree Micro-habitats in spruce trees G. pyramidum G. allenbyii Cream-skimmers must get to patches first, or monopolize access Patch quality

2. 77% turned in 2 HWs 45% 0 or 1 HW HW #3 (25 points): Mechanisms of Coexistence Due March 20th. See Website Next week: Mutualisms; Mark McGinley March 20-22: Communities and Food Webs; Travis Hinkelman Exam II: Post-LV competition up to spring break MARCH 29th

3. Effect * of species 1 on species 2 - + X - COMPETITION PREDATION Effect of species 2 on species 1 + PREDATION MUTUALISM * On per capita growth rate

4. Predation – species interaction where one party benefits • (predator) and one is hurt (prey) • - behaviorally: diet choice, patch use • community level: How does predation contribute to • species diversity ? • - population impacts: how predators control and/or • regulate prey numbers (or vice versa) • Lethal approach – predators kill their prey • Fear approach – predators scare their prey

5. Predators have two responses to their prey: • Numerical response -  predators with  prey • Functional response – predator consumption changes with prey • density type II - satiation type III # prey consumed type I - linear density of prey (N)

6. = conversion of consumed prey into new predators d = predator death rate (N) = predator functional response rate of prey consumption by an individual predator as a function of prey density. Predator-prey models 1N = r(K-N) - (N)P N t K 1P = (N)N - d P t mortality from predators logistic growth mortality birth via consumption of prey

7. What does it mean for the prey isocline to be humped? Pred (+) Pred (-) P Prey (+) Prey (-) K N What does it mean for the predator isocline to be a vertical line?

8. safety in #’s limits to growth What does it mean for the prey isocline to be humped? P N What does it mean for the predator isocline to be a vertical line?  no interactions among predators

9. Predator-prey Isoclines: per capita growth rates = 0 Apex of isocline: stable limit cycle (neither expands nor dampens) Region of pos. DD: expanding oscillations (unstable) Region of neg. DD: damped oscillations (stable) P N

13. Region of pos. DD: expanding oscillations (unstable) P N

14. Unstable dynamics leads to population eruptions, particularly among insects Eucalyptus psyllid Spruce budworm Pine beauty moth Viburnum whitefly

15. How do you stabilize unstable predator-prey interactions? (Huffaker’s 1958 experiments) prey predator Simple environments lead to simple outcomes -- EXTINCTION

16. So, create complex environments including barriers to predator dispersal and cycles emerge – illustrates the importance of REFUGES

17. Physical Refugia – Predators do not have access to prey

18. * * * * * * Behavioral Refugia – Predators and prey not together in time and space

19. Refugia work by reducing predator efficiency & go from unstable to stable P N Low N* = efficient predator High N* = inefficient predator

20. Feed deer (increases K to K’) (1) Productivity goes into building new predators NOT prey (2) Instability increases (3) Populations go extinct P* What NOT to do – the Paradox of Enrichment mountain lion stable EQ K K mule deer mule deer unstable EQ N* K K’

21. Summary: • Predator-prey interactions contain inherent time lags that result in • population cycles • (2) These cycles can be stable, unstable, or neutrally stable • (3) Relatively efficient predators lead to unstable cycles and extinction • (4) Complex environments and refuges can stabilize predator-prey • interactions • (5) Enriching the prey population is not a viable strategy, rather it • destabilizes interactions and leads to population extinction

22. The Ecology of FEAR

24. Fear in the South African Landscape – Augrabies NP Rock Hyrax

25. The view away from the Kopje -

27. Comparison of the lethal and fear approaches Lethal Fear • predators kill their prey • Population density driven systems • Brownian motion behavior of pred/prey • predators scare their prey • Fear driven systems: fierce predators and • fearful prey • Sophisticated game of stealth and fear L W W L W W L W

28. The Catch-22 of the lethal approach Inefficient predators lead to extinction of the predator in variable environments Efficient predators lead to highly unstable predator- prey interactions K K K

29. The Catch-22 of the lethal approach Inefficient predators lead to extinction of the predator in variable environments K K K

30. Incorporating the Ecology of Fear (Brown et al. 1999) Prey are apprehensive – i.e., they engage in vigilance behavior M Fear (i.e., predation risk) = ---------------- (prey have perfect info) (k + bu*) Fear: -  w/likelihood of encountering a predator, M -  w/predator’s lethality, 1/k -  w/effectiveness of vigilance, b -  w/level of vigilance, u* # pred, #prey, feeding opportunities

31. Tradeoff: Too much vigilance  miss out on valuable feeding opportunities Too little vigilance  likely killed by a predator • Bend down the predator’s • isocline. • Predator’s have reduced • efficiency because more • predators results in greater • vigilance in the prey making • them harder to catch • Interference or Behavioral Resource Depression Shift the hump in the prey’s isocline. Still safety in #s, but reduced vigilance @ high N reduces its effectiveness

32. Implications: • Greater stability in predator-prey interactions – no Catch-22, • and reduce the Paradox of Enrichment • (2) Territoriality in fierce predators may function to protect the • catchability of the prey – avoid the “wayward” Mnt. Lion • stumbling into your territory • (3) Behavior (e.g., vigilance) is a leading indicator of ecological • change

33. Wolves, elk, and bison in Yellowstone: reestablishing the “Landscape of Fear” (Laundre et al. 2001 – Can J. Zool. 79:1401) Wolves reintroduced into the Lamar Valley of Yellowstone in 1994-1995.

34. This now becomes a familiar scene – wohoo!!!

35. Vigilance in female elk w/calves increases… ...while time spent foraging declines

36. Similarly for bison, however, males and females w/o calves no show behavioral shift

37. 1996 2002

38. 1997 versus 2001

39. Three kinds of evidence: • The changes are much faster • than could occur from elk • mortality • Reduced herbivory is restricted • to risky habitats • Elk have exhibited behavioral • changes consistent with an • Ecology of Fear Hypothesis: • (1) favor areas with good visibility • & escape structures (scat) • (2) increased vigilance and • less feeding • These changes have left • physiological evidence

40. Cottonwood trees need wolves in order to establish their populations.... ...as does willow and aspen.

41. Experimental demonstrations of non-lethal effect of predators O. Schmitz et al. 1997 lethal spiders non-lethal spiders Control no spiders if spiders have (-) on grasshoppers GH Plants

42. 20% 29% Most of the decrease in grasshoppers is due to ‘non-lethal’ effects

43. How do grasshoppers die with non-lethal spiders? w/o w/spiders Shift in daily activity to safer (from predators) but high stress Exposure to Sun & Heat

44. Do we see an increase in plant biomass? Its less clear there is an effect on plants

45. Broad Conclusions: Predators have at least two general effects on prey: lethal and non-lethal Predators kill prey and are also involved in a sophisticated game of stealth and fear Incorporating behavior (Fear) has important consequences for pred-prey interactions ….”Ignore Behavior at your peril”

48. Raptors Voles Roots Raptors Lemmings Moss Are lemmings and voles predators orprey??