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But the consequences of such carnage were soon felt. An ecosystem stripped of the wolf doesn't simply become more peaceable; rather, it becomes flabby and unbalanced. With the dominant predator gone, the next biggest hunter--typically the coyote--assumes the top spot. As the coyote population explodes, the populations of foxes, badgers and martens, which compete with coyotes for rodents and other small game, dwindle. At the same time, large prey like elk, which were once brought down by wolves, begin to multiply excessively, stripping vegetation from highlands. And with no elk carcasses lying around, scavengers like magpies, ravens and grizzly bears, accustomed to dining on scraps from wolf kills, have to scrounge elsewhere for protein. "The wolf is a keystone species," says Yellowstone biologist Douglas Smith. "You remove it and the effects cascade down to the grasses."
In Yellowstone that cascade has long been felt, and since the 1930s, wildlife managers have watched in dismay as the park's ecosystem--once well balanced between predator and prey--grew more and more bottom-heavy. Finally, in the 1970s, they decided to do something about it. Working through the then new Endangered Species Act, they proposed a plan under which wolves would be imported from Canada to reclaim their place in the ecosystem. Twenty years later, the plan was approved, and wolves were trucked from across the border--31 to Yellowstone and 35 to Idaho.
The impact is now apparent. Around Yellowstone, elk kills are more common, a welcome development for park managers hoping to bring that animal's population back to manageable levels. The wolves often eat only 200 lbs. of the meat on a 500-lb. animal they fell, leaving plenty for other animals to scavenge. Wolf packs also appear to have killed as many as half the coyotes in at least two areas of the park, opening up ecological breathing room for foxes and other species. Even highland vegetation, no longer chewed up by hungry elk, is expected to start making a comeback. "We're seeing beneficial effects from the top down," says Robert Crabtree, a wildlife ecologist. "Who knows how far it will go?"
Some people are worried that it has already gone too far. Conservationists knew that a few wolves would inevitably wander off the grounds of the park, find their way to farms and attack livestock; since 1995, seven head of cattle and 84 sheep have been killed this way. The Defenders of Wildlife set up a fund to compensate owners for their losses, and to date the group has paid out more than $21,000. But money isn't the only issue. "There's also the stress of not knowing if wolves are in the area and when they'll strike," says Vern Keller, 71, a rancher who has been in the business for 48 years. "It keeps us on edge all the time."