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Gray wolves create balance between predator and prey in Yellowstone

Contrary to what some wolf opponents claim, ecology expert says gray wolves in Yellowstone will not wipe out prey, such as elk and deer

Scott Creel, an ecology professor at Montana State University, does not think that Yellowstone wolves will wipe out their prey, as some critics of wolf reintroduction fear. Some critics have claimed that wolves will kill all the deer and elk, sterilizing the landscape. That doesn’t make sense to Creel or wildlife biologist Doug Smith.

“I studied predators for 10 years in Africa, where there is no control on predators, yet there is an abundant prey base on the Serengeti plains,” Creel said. Predators and prey balance out, he said, and Smith agreed.

“What I see is an evolutionary arms race between elk and wolf,” Smith said. Wolves are not super-predators and healthy elk are tough to kill, he said. Neither side is so formidable as to wipe out the balance between the two species, he said.

“They’re pretty evenly matched,” Smith said. Wolves can and do get injured or even killed when fang is countered by muscle, mass, horn and hoof.

“Wolves are having a harder time,” Smith said, because there are both fewer elk in the Yellowstone National Park and the herd has fewer individuals with problems – the old, sick or injured. A decade ago, elk population density was as high as 13-15 per square kilometer, Smith said. Today, it is down to 6-7 per square kilometer.

“Wolves are capable predators, but they’re not super-predators,” Smith said.

Population plateaus

Creel and Smith agree that as the prey base gets smaller, so do predator numbers.

Indeed, in 2011, for the first time since wolves were reintroduced to the park, wolf numbers appear to have hit a population plateau.

Smith estimates about 169 wolves in 15 packs in the park in 2011, down from 174 the year before, indicating wolves could be approaching the carrying capacity of the park. In 2014 the wolf count was 104.

Competition between packs has intensified, Smith said, while packs are beginning to run up against food limits. That means that wolves will kill members of rival packs. Even when a pack has a larger than expected number of pups, their survival rate is not as great as it was even a few years ago, Smith said, because there is less food.

Surprises About Wolf Packs

Smith and other biologists characterize the past decade as a series of surprising discoveries about wolves and wolf behavior. The classic pattern of a pack limiting breeding to an alpha male and an alpha female didn’t always hold true.

“We had one pack the winter of 2010-2011 that had four breeding pairs,” Smith said. “That’s pretty rare, because most packs hold to the classic norm of a single breeding pair.”

Some packs had multiple breeding pairs and large numbers of pups, leading some wolf critics to predict that wolves would breed and eat until there was no prey base left. That’s the most persistent wolf myth Smith encounters as he speaks to groups.

The myth hasn’t happened, as a predator-prey balance continually reasserts itself, said Smith. In the past few years, packs that have had large numbers of pups have also had pup survival rates more in line with average packs, he said.

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