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, for the first time since wolves were reintroduced to the park a decade ago, wolf numbers appear to have hit a population plateau.
Smith estimates about 169 wolves in 15 packs in the park, down from 174 the year before, indicating wolves could be approaching the carrying capacity of the park.
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
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 this winter 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.
By the Numbers
According to the 2004 wolf report by the U.S. Fish & Wildlife Service, the 66 wolves reintroduced to Yellowstone National Park and neighboring Idaho (in the Frank Church-River of No Return Wilderness) in 1995 and 1996 have grown to 835 in the Northern Rocky Mountains: 452 in central Idaho, 324 in the Greater Yellowstone Recovery Area and 59 in the Northwest Montana Recovery Area. By state boundaries, that’s 422 wolves in Idaho, 260 in Wyoming and 153 in Montana.
Of approximately 110 packs (groups of two or more wolves), 66 packs met the definition of a “breeding pair,” defined as an adult male and female raising two or more pups. That makes 2004 the fifth year in which 30 or more breeding pairs were documented within the three-state region, and that means that recovery criteria have been met for removing the Northern Rocky Mountain wolves from the Endangered Species list.
