September 18, 2007
An analysis of 774 wolf-elk kill sites in Yellowstone National Park found that spatial patterns of predation between wolves and elk are more strongly influenced by landscape features than by wolf distribution.
“We found that even though wolf and elk populations overlapped in many areas of our study, the kill sites did not correlate with the areas of overlap as much as they were consistent with certain landscape features, such as proximity to roads,” said Mark Boyce, a biological scientist at the University of Alberta.
Boyce and colleagues studied the wolf-elk interactions over a period of 10 consecutive winters in a northern range of Yellowstone National Park.
In 1995, 14 wolves from the Canadian Rockies were introduced to Yellowstone. Wolves were extirpated from Yellowstone in the 1930s. While it was feared the elk population would be at risk upon reintroduction, wolf numbers on Yellowstone’s northern range has grown to 84 and elk numbers have not declined appreciably.
“We’ve found that the availability of refuge areas for elk, and their ease of accessing them, should buffer the elk population in the park from extreme levels of predation,” said Boyce.
Additionally, wolves are inefficient predators, with hunting success rates of around 20 percent, said Boyce.
Another factor is the large size and defensive capabilities of elk. Adult elk are largely invulnerable to predation from wolves, which are highly selective and target the young, old or weak.
“Our findings suggest that landscape features may often ‘tip the balance’ in predator-prey outcomes, thus influencing post-encounter outcomes,” Boyce said.
Elk “browse communities” — foraging areas in open, flat landscape near roads or rivers (which can cut off escape routes) — offer the greatest risk of wolf predation for elk, Boyce and fellow researchers found. Also dangerous for elk are deep, snowy areas, which are harder for the heavy, hoof-legged elk to move through than the lighter, wide-pawed wolves.
The challenge for the elk, however, is that the risky foraging areas provide sustenance during the critical winter months, when elk experience shrinking fat reserves.
“Our study makes clear that elk in winter face a clear trade-off between forage quality and predation risk,” said Boyce. “How elk perceive and manage the trade-off between food and safety will ultimately determine if they will survive.”
The research results were published in the journal Ecology Letters.
Source: University of Alberta.
Leave a Reply