Print PageThe risk of predation is known to influence prey foraging behavior, prey reproduction, and primary production in many food webs, but few studies have evaluated whether these effects generalize to the vast landscapes occupied by large-bodied vertebrate predators and their prey. In the Greater Yellowstone Ecosystem (GYE), re-introduced wolves (Canis lupus) alter the behavior of their primary prey, elk (Cervus elaphus); however, it remains unclear whether the effects of wolves extend to elk nutrition and reproduction. We simultaneously monitored wolf movements (n = 15) and the behavior, nutritional condition, and reproduction of elk (n = 92) in a partially-migratory population of the GYE. We first evaluated the strength and consistency of elk antipredator behaviors, then sought associations between antipredator behavior, body-fat levels, and pregnancy probability.
Results/Conclusions
Elk behavioral responses to wolves were relatively weak and inconsistent. When wolves approached elk within 1 km, we detected modest increases in vigilance, movement rates, and 24-hour displacement, but no changes in elk habitat use. Wolf predation risk did not appear to influence elk body-fat levels or the probability of pregnancy. Even in high-risk areas, individual elk infrequently encountered wolves within 1 km, limiting the cumulative individual- and population-level effects of wolves. Our findings echo an emerging recognition that active-hunting predators like wolves may not produce the spatially and temporally consistent risk cues expected to drive population- and community-level processes. Resolving the generality of predation risk effects will be an important step in understanding the total effect of predators on prey populations - particularly where the interactions of large carnivores and their ungulate prey are of management and policy concern.
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