If They Would Only Eat Bison

By Bill Schneider, 11-28-05

As elk hunting concludes for the year, controversy lives on. Hunters and outfitters in south central Montana continue to bemoan the dramatic—possibly as much as 50 percent—decline of the famous northern Yellowstone elk herd. They blame the wolf, which has greatly expanded its numbers since its historic re-introduction back in 1995. From the original dozen wolves introduced, the population has grown to 171 in the park, 106 of which live on the northern range.

In a November 21 article in USA Today Dan Vergano quotes several biologists debating the cause of the reduction. These scientific opinions weren’t music to the hunters’ ears because they concluded that hunting is partly responsible for the decrease.

In the article, biologist John Vucetich said a reduction was no surprise because wolves were expected to take a bite out of the northern elk herd, but he admits the decline has been greater than expected. Estimated at about 17,000 animals in 1995, the herd has now slipped to about 8,000.

In his research, Vucetich discovered that although wolves were partially responsible, weather and hunting were the main contributors to the decline. The park has had a seven-year drought, and the number of elk permits has been increased—both occurring at the same time the wolf population was rapidly building.

I called Doug Smith who supervises wolf research in the park for the National Park Service to ask about this, and he agreed that the decline was “multi-causal�—a combination of wolves, hunting and drought, with one additional culprit, the grizzly bear, which has also nearly tripled its numbers in the past twenty-five years, going from a low of about 150 animals to 600 or more.

In the Yellowstone Science magazine, renown wolf biologist Dave Mech and several co-researchers side with Smith, concluding that bears (both grizzly and black) have a big impact on elk numbers, probably greater than wolves. In fact, they discovered that bears kill roughly six times more elk calves than wolves do.

Elk calves are actually quite vulnerable because they stay in place near danger instead of running. In May and June, bears sigzag through elk calving areas finding many easy meals.

Like wolves, grizzly bears are Yellowstone success story, bouncing back from the brink of extinction to a point where the federal government now wants to remove the protections provided by the Endangered Species Act in place since 1975, and Wyoming plans to have an open season on the big bear. Stacked in queue behind the grizzly “delisting� proposal is a similar, but currently stalled, proposal to delist the wolf. The success of the wolf and grizzly bear might have, according to Mech, come partially at the expense of elk.

All researchers agree that all four factors—weather, bears, wolves, and hunters—have combined to create a perfect storm for the elk herd, which may have been due for decline anyway. At least some biologists feel the herd had far outgrown its habitat’s ability to support such high numbers.

Here’s the rub. Sometimes things don’t happen as planned. While elk numbers decrease and hunters’ blood pressures increase, bison numbers keep going up, prompting Montana to have its first hunt in fifteen years—and suffer some severe political pain in the process. Ten years ago, biologists wanted the return of the wolf, in part, to help control bison, but alas, wolves prefer elk.

Imagine our situation if wolves preferred bison to elk. And why not? On the surface, you’d think elk would be much harder to catch than a bison, which most of time seems as mobile as a rock. But that’s an illusion, according to Smith. “Bison are cantankerous and harder to kill than elk,� Smith explains. “Wolves are basically cowardly hunters, so when the prey stands its ground, they don’t like it. Bison do that more than any other prey. This is intimidating to a wolf. They have to be careful because they can’t risk an injury.�

Wildlife researchers have observed many times that an injured predator rarely survives. Bison might not look dangerous to tourists as they whiz by at 50 mph on Yellowstone highways, but they are quick and can easily injury a predator.

But as always, there’s hope for the future. Smith and his researchers have found two wolf packs in the interior of the park that eat primarily bison, especially in winter, because there aren’t many elk in that part of the park.

Even on the northern range, wolves are killing more bison. “The wolf take of bison is slowly increasing,� Smith reports. “Each year, the percent of bison (in the wolf’s diet) increases, but it’s still dominated by elk. As long as we have elk, there probably is not going to be much bison predation on the northern range.� [End of article]