PARENT SESSION
Oral Session #55: Predator - Prey Interactions.
Presiding: R. Dueser
Wednesday, August 7. 8:00 AM to 11:30 AM. Cochise Meeting Room, TCC.

Testing the ecology of fear: do prey operate with imperfect information on the whereabouts of their predators?

Laundré, John^*,1, Hernández, Lucina¹, Fowles, Gretchen², ¹ Instituto de Ecología, A.C., Aldama, Chihuahua, Mexico² Idaho State University, Pocatello, ID

ABSTRACT- Some have proposed that incorporating fear from predation risk into classic mass action predator prey models would stabilize these models. Imbedded in this ecology of fear model are assumptions of behavioral responses by prey and predator. For prey, the pivotal assumption is they operate with imperfect information on the whereabouts and lethality of a predator when it enters a habitat patch. In response, their level of apprehension at time t after a predator arrives should approximate a learning curve: m(t) = m' + (M + m')(1-exp(-t)). Here m' is background apprehension, M is the maximum apprehension, and is the rate of perception of the predator. We tested this assumption by fitting this curve with nonlinear regression to data from two ungulate species, elk (Cervus elaphus) and Rocky Mountain bighorn sheep (Ovis canadensis). For elk, we used vigilance data gathered over 5 years after wolves (Canis lupus) were reintroduced into Yellowstone National Park. For sheep, as a surrogate for apprehension, we used cumulative mortality by pumas (Puma concolor) over the first year after sheep were reintroduced into historic range in southern Idaho. In both cases, the learning curve fit the data well (P <0.001), supporting the hypothesis that prey respond with imperfect information when a predator enters a patch. These results provide support for the overall ecology of fear model.

KEY WORDS: Ecology of fear, Predation risk, Leaning curve, Ungulates