4 Yellowstone Wolf Experts Share Observations on Adaptation

A flood of science has emerged from research focused on the impact that wolves have on a host of other species after wolves were reintroduced to Yellowstone in 1995.

Mike Jimenez, the Wyoming Wolf Recovery Project Leader, has been studying predator/prey relations south of Yellowstone for several years, with ongoing research on wolves’ impact on elk feeding grounds. During the winter of 2006, the National Elk Refuge had a highly concentrated mix of wolves and elk, he said. “We didn’t see any surplus killing,” said Jimenez, only predation rates along the lines that biologists have come to expect.

“Wolves go for what’s available,” he said, focusing on the vulnerable, the old and the young.

Elk Behavior Changes Because of Wolves

Ed Bangs, the Wolf Recovery Coordinator U.S. Fish and Wildlife Service, said researchers – like those at Montana State University – are finding abundant evidence that elk are becoming wilder and more difficult to find as they strive to avoid wolves.

“We’re finding that in response to the reintroduction of a key predator, all kinds of species are showing huge adaptability,” said Bangs. For example, ravens have figured out that hunting wolves generate food when they catch and kill prey, so ravens are following wolves, he said.

Todd Atwood, a doctoral candidate in the Utah State University wildlife ecology program, has found some adaptability among elk and coyotes, as they react to the presence of wolves.

“We were lucky in that our study began with wolf recolonization in our study area,” he said, referring to a ranch north of Yellowstone. “As elk figured out that wolves were not good for them, they moved into more complex, rugged habitat – which happens to be the primary hunting area for mountain lions,” said Atwood.

During the course of three years of research, said Atwood, the elk moved up into more rugged country, pursued by the wolves, only to be killed in increasing numbers by mountain lions. Cougars benefited from a new prey animal, said Atwood, taking fewer mule deer than before.

Coyotes Practice Risk Management Because of the Presence of Wolves

Atwood also found that coyotes are adapting to wolves, after an initial pounding where wolves attacked coyote packs. “Basically, it becomes an issue of risk management,” said Atwood. Coyotes benefit from the carrion produced by wolf kills, but are at risk of attack when they approach wolf kills while wolves are still around.

Alpha male and female coyotes are taking greater chances, moving in before carrion is abandoned by wolves, said Atwood, because that act is balanced by access to better quality foods, the internal organs and muscles. “We started seeing greater pup litter size as alpha pairs had access to more and better food,” said Atwood.

He believes results would be different in Yellowstone. “In our site, wolf population was pretty low,” he said, noting that when coyotes outnumbered wolves, the coyotes would approach within 15 yards of a wolf kill – all the better to zip in and out when the chance arose.

Genetic Research of Wolves

Doug Smith, the wildlife biologist in charge of the Yellowstone Wolf Project, said the hottest research topic right now is wolf genetics, in a study conducted by UCLA researchers.

“It’ll give us a pedigree of all Yellowstone wolves, we’ll know the breeding history,” said Smith. The genetic analysis looked to see how much gene exchange is going on between the three main recovery populations. “It doesn’t appear to be a lot of (gene) exchange,” said Smith. Yellowstone is relatively isolated from other populations, but in the short-term, that’s not a great concern, he added. “We still have high diversity in wolf genes.”

Further Impact of Wolf Reintroduction

Trophic cascade – the domino effect on a range of species because of a key change – is a huge, ongoing debate, said Smith. For example, the presence of wolves prevents elk herds from eating willow stands and young aspens down to the nub. As a result, willow and aspen communities are bouncing back, to the benefit of other species, like beaver and song birds.

“Scientists love to argue,” said Smith, “and there’s lots of fodder on this.” Smith doesn’t believe the many observed changes are due exclusively to wolves, but that the cascade effect was multi-causal, of which wolves were a necessary part.

Like a catalyst in a chemistry experiment, said Smith, wolves have helped trigger lots of changes in the Yellowstone. “They’re necessary, but not sufficient (by themselves) for trophic cascade to occur.”