August 7, 2012
Elk in the greater Yellowstone ecosystem are not reacting to their wolf predators with a strong predator-avoidance behavior thought to apply to prey animals, according to U.S. Geological Survey research.
Elk express mild fear of wolf predators in Yellowstone
Researchers simultaneously tracked the movements of wolves and the foraging behavior, body-fat levels and pregnancy of elk to determine whether wolves slow elk reproduction through fear alone.
Although the presence of nearby wolves clearly affected elk behavior, these effects were not strong enough to make elk “skinnier,” said USGS. When wolves were within 1 kilometer (.62 miles) of elk, elk movement rates and vigilance increased slightly, but their habitat use did not change, researchers found.
In areas with particularly high wolf predation risk, individual elk experienced 1 km wolf encounters infrequently, limiting the potential cumulative effects of wolves on elk behavior.
Prey foraging, reproduction
USGS cited small-scale studies of invertebrates and amphibians that have often shown that the risk of being killed by a predator can impact the behavior of prey animals strongly enough to reduce their foraging rates, nutrition and reproductive success. The new study, said the agency, contradicts the idea that large mammalian predators help shape ecosystems through the predator-avoidance behavior of their prey.
The study was the subject of a recent presentation, Spatial and temporal context limit the effect of wolves on elk behavior.
