Study: Wolves Sustain Wildlife by Sharing Prey

That's a huge amount of food, but it's concentrated in a relatively small area, and it's available for only a few weeks. Wilmers calls that a "pulse" resource because it is limited in both time and space.

"There's so much food that it's just saturating the local scavenger community and so the animals that are best able to utilize it are the ones that can get there from farther and farther away, like ravens and bald eagles," he says.

So it's an important, though temporal, resource for some speedy scavengers. Wolf kills, by contrast, occur throughout the region and during the entire year.

Whether the hunters or the wolves are more important to the survival of other species depends on your point of view, he adds.

"If the elk are killed by wolves, then that food is going to be more evenly distributed among the scavengers," Wilmers says. "If they are getting killed by hunters, then that food will go almost exclusively to bald eagles and ravens.

"So it just depends on what your value judgments are. If you want to feed more species, then you go with wolves. If you want to feed bald eagles and ravens then you go with hunters."

Unexpected Bonus

It's a curious footnote to the troubled history of Yellowstone wolves. They were all over the place when Yellowstone was established in 1872, but under the banner of predator control the wolves were gradually killed off, including at least 136 killed by park employees.

By 1970, they were gone entirely from Yellowstone, and survived only in two areas of the lower 48 states, upper Minnesota and on the Isle Royale in Michigan.

In 1987, the U.S. Fish and Wildlife Service proposed reintroducing wolves on an experimental basis to Yellowstone, although that clearly posed a danger to other animals in the park. The University of Wyoming predicted that wolves would reduce the elk population by 15 to 25 percent, for example. Moose and deer were expected to suffer similar declines. Whether they have had this effect remains to be determined.

But no one knew in those days that other animals would benefit from the reintroduction of the wolf. There are many days and nights when the snow covers the region so completely that it's hard for any animal to find a decent meal.

Except, it turns out, for the wolves. And those that dine on whatever the wolves leave behind.

The elk, of course, probably aren't a bit fond of this turn of events.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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