PARENT SESSION
Thursday, August 10, 1:30-5:00 pm
COS 99 - Predation risk
L-11, Lobby Level, Cook Convention Center
Presiders: E Preisser and S Hall
Foraging and its influence on plant populations are not controlled by predation risk gradients in a large mammal predator-prey system.
Kauffman, Matthew *,1, Brodie, Jedediah1, Jules, Erik2, 1 University of Montana, Missoula, MT2 Humboldt State University, Arcata, CA
ABSTRACT- Ecologists have argued that carnivores can have strong indirect effects on plant populations by changing the behavior of herbivorous prey, and that such trait-mediated effects are ubiquitous in nature. However, empirical evidence for these effects in large mammalian systems is scant. Here we provide an evaluation of the potential indirect effects of wolves (Canis lupus) on aspen (Populous tremuloides) demography brought about by antipredator behavior in elk (Cervus elaphus) on the northern range (NR) of Yellowstone National Park. We first show that aspen recruitment is completely suppressed, with no stands we studied having any individual suckers >2 m in height. Sampling within long-term exclosures indicates that this suppression is mainly due to elk herbivory. Next, we present a spatially explicit map of predation risk across the NR built from the distribution of wolf-killed elk over ten years (1995-2005). We evaluate whether this strong risk gradient forces elk to change their foraging behavior by conducting Giving-Up Density (GUD) experiments. Results suggest that elk willingness to forage in safe versus risky habitats is similar, but that that they alter their foraging in response to the daily distribution of wolf packs. This is consistent with the lack of any discernable relationship between habitat-based predation risk and the survivorship of young browsable aspen. Our work shows that wolves do not appear to have strong, behaviorally mediated, indirect effects in this system, a pattern that we argue is consistent with the natural history of predation in large mammalian systems.
Key words: predation risk, large mammals, food webs