JACKSON HOLE, WYO – A new study released in Ecology Letters this month highlights how elk navigate areas where more than one predator is present. Specifically, the results suggest elk are more afraid of mountain lions than wolves because cougars are better at killing than canines.
The study begins with the accepted notion that many ecosystems, including the GYE, contain sympatric predator species that hunt in different places and times. The question researchers wanted answered was whether there exist places and times when prey can feel relatively safe, and whether they adjust their behavior accordingly.
What the authors of the study found is that prey, in this case, elk, do indeed minimize threats from multiple predators simultaneously by adjusting their movements to certain types of terrain at certain hours of the day or night. For the most part, elk are able to avoid one predator without necessarily increasing its exposure to the other.
“We tested the extent that elk selected for vacant hunting domains to avoid predation from wolves and cougars in northern Yellowstone National Park,” stated lead author Michel T. Kohl. “Wolves are cursorial predators that kill mainly in flat, open areas at morning and dusk, whereas cougars are spot-and-stalk/ambush predators that kill mainly in topographically rugged, forested areas at night. We predicted that elk selected for flat, open areas at night (night-flat and night-open domains), and for rugged, forest areas during daylight (day-rugged and day-forest domains). We studied elk habitat selection in winter when wolves and cougars were the only major elk predators inside [the park] and during a period (2001–2004) when densities of both predators were highest.”
Authors of the study said one main takeaway from their research is exposing the false notion that wolves are solely responsible for elk predation or any population reduction.
“We demonstrate how it is perilous to assume that prey habitat selection in a multi-predator environment is sensitive to just one predator species. When wolves were reintroduced to Yellowstone National Park in 1995–1997, they joined a system that was already populated by other predators of elk, including growing numbers of grizzly bears and cougars,” Kohl wrote. “Despite this predator diversity, subsequent research and commentary about elk space use in and around Yellowstone have assumed, implicitly or explicitly, that wolves are the only (or primary) predator that elk respond to. Our study is the first to test this long-held assumption, and our results suggest it is false.”
The study found strong evidence that elk habitat selection is shaped by the risk of predation from both wolves and cougars. Further, wolf-only models of elk habitat selection performed poorly compared to other models that included male cougars.
“We also found that male cougars, not wolves, exerted the most pressure on elk habitat selection,” Kohl added.
Researchers were not sure why male mountain lion activity and not females had the most effect on elk but could not rule out the role females play in elk predation.
Bottom line, researchers say, is their results shed new light on how multiple predators can drive prey habitat selection in a predator-rich environment, and how prey are able to minimize these multiple threats simultaneously.
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