WHITNEY ROYSTER Star-Tribune environmental reporter | Posted: Friday, July 13, 2007 12:00 am
JACKSON - A University of Wyoming professor has concluded that wolves don't cause elk to vary their behavior enough to allow aspen stands to recover, contradicting in some ways earlier studies indicating an "ecology of fear" had taken root in the big game animals.
Matt Kauffman, a professor of zoology and physiology, undertook a three-year study that concluded this year. He, along with Yellowstone National Park biologist Doug Smith and researchers from the University of Montana and Alberta, analyzed 700 elk kill sites over 10 years in the northern range of Yellowstone.
His research showed that the predation risk is driven more strongly by habitat features than distribution of wolf packs. Elk are more likely to be killed in open meadows than in forested areas with slopes.
The research also concluded that elk do not adjust their willingness to forage based on areas that are riskier for predation. Instead, elk will forage where food is available, particularly in later months in the winter when there is less food.
That point contradicts an earlier study by a University of Oregon team, which concluded elk do change foraging patterns based on predation and called the phenomenon an "ecology of fear."
Kauffman said his team found elk do respond to wolf predation by moving into forested areas when wolves are present, but they will return to open areas when wolves are not present.
The Oregon team concluded the presence of wolves helped rejuvenate willow stands, as elk change foraging behavior to avoid risky areas by streamsides. Kauffman's study focused more on aspens and was broader in scope than Oregon's.
Aspens do not regenerate more quickly in areas considered "high risk" for elk, Kauffman said. Sixteen aspen sites selected at random, in both high- and low-risk areas for predation, showed similar growth rates during the study. Aspen stands do better in areas of high productivity for the trees - namely, wetter areas, he said.
The study team also tested elk foraging behavior by setting out food trays in 10 high-risk and 10 low-risk areas for elk.
"They forage in those patches as long as it's worth the risk," Kauffman said. "What we found is there is no difference in an elk's willingness to forage in a risky versus safe place."
Risky areas started out with fewer elk foraging early in winter, but as winter progressed, elk were more and more willing to forage in areas considered risky.
"My interpretation is elk are mostly choosing areas where they need to forage during the winter to reduce their risk of starvation," he said.
Kauffman's study did not examine the effect of wolves on elk reproduction. He said the fact that elk are willing to browse in risky areas shows the animal is more concerned with health than predation.
Portions of Kauffman's study have been published in the journal Ecology Letters, which is released in print next month. He presented his findings Thursday at the AMK Ranch in Grand Teton National Park.
Kauffman said there are other studies, including the University of Oregon study, looking into the results of wolf predation on elk. He said there is still debate whether willows growing back because elk are reducing their foraging there, but his study indicates this is not the case.
Instead, Kauffman suggests the decline in elk numbers on the northern range - from an estimated 17,000 in 1995 to 6,700 this year - is preventing the willows from being overbrowsed.
He said elk response to wolves doesn't appear to be helping the recovery of aspens.
Environmental reporter Whitney Royster can be reached at (307) 734-0260 or at royster@tribcsp.com.