Oblivious to danger at dinner time, bull elk in the Gallatin Canyon are about six times more likely than females to be killed by wolves, said Scott Creel, an ecologist studying wolf-elk interactions in the Porcupine, Taylor and Tepee/Daly drainages between Bozeman and West Yellowstone. Cow elk, on the other hand, figuratively put down their forks and become vigilant when they sense wolves.
"For elk in winter, there's a trade-off between doing the things that will keep them well fed and doing the things that minimize the risk of falling prey to wolves," Creel said. "Because cows have more stored fat, they are in a better position than bulls to stop foraging, become vigilant and seek cover when wolves are present."
John Winnie Jr., a doctoral student working with Creel, said the researchers originally thought the bulls ignored wolves because the bulls were "the big, bad dudes in town. Wolves aren't going to mess with them."
But the scientists learned differently.
The bull elk are famished, Winnie said. Entering winter in much worse condition than the cows, they're desperately trying to cope with the weight they lost during mating season. They're also trying to chow down when food is hard to find. A bull elk can lose more than 100 pounds from early September until early November. He's already lost 20 percent of his weight when December and January bring some of the winter's worst weather.
"They probably can't afford to be as vigilant as cows," Winnie said. "They simply cannot stop grazing since they are already in such crummy shape."
Creel joked that, "The bulls will pretty much keep eating ‛til you pry the grass from their cold, dead lips."
Creel, Winnie, MSU graduate student Dave Christianson and Ken Hamlin, research biologist with Montana Fish, Wildlife and Parks, have conducted their research during the past four winters. They expect to continue at least three more years and expand their project to see how elk responses to predators affect calves. Their first scholarly paper on the study has been accepted for publication in the journal "Animal Behavior." It reports that elk, contrary to expectation, form smaller herds when wolves are in the area.
"Prior research with other species has mostly found that prey can reduce the risk of predation by forming larger groups, because big groups have more eyes to detect predators and can defend themselves cooperatively," Creel said. "We were a bit surprised to find that elk break into smaller herds when wolves are present. We think this serves to reduce the odds of being detected."
The study area covers about 125 square kilometers and contains approximately 1,700 elk and five to 15 wolves. The researchers observe the animals with binoculars, radio collars, global positioning systems, scat, tracks and howls.
The study originally focused on direct relationships between elk and wolves, Winnie said. How many elk did the wolves kill? But the researchers eventually noticed indirect effects, too.
"It's pretty clear there are lots of strong responses by elk to wolves," Creel said. "They are not going about things the same way. They are changing pretty much everything we looked at, and it's likely that these changes carry some costs for the elk."
The elk, for example, head into conifer forests to avoid wolves. That means they're eating less grass -- the most calorie-laden food and easiest for them to digest -- and more shrubs, leaves, sticks and small branches.
"Gallatin elk move into the timber when wolves are present, as well as splitting into smaller groups and spending less time eating and more time on guard," Creel said. "Now we're getting information on how these changes might alter their nutrition, birth rates and calf survival."
Funding for Creel's study comes from several sources, including the National Science Foundation. Winnie received fellowships from the NSF's EPSCoR program, MSU's Big Sky Institute, and Transboundary Research.
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Evelyn Boswell, (406) 994-5135 or email@example.com