Twenty Years of Wolf Recovery

By Douglas A. Smith, wildlife biologist at Yellowstone National Park

From Yellowstone National Park’s start in 1872, policy reflected cultural norms and allowed for the killing of wolves, cougars, coyotes, and other predators. The last surviving wolf was killed in 1926 and cougars were eliminated too. The coyote population was greatly reduced. Not surprisingly, the elk population exploded.

Attitudes slowly changed and legislation followed requiring restoration of rare plants and animals. In the west, in the 1980s, wolves had dispersed from Canada to northwest Montana, setting the stage for that area. But what about areas not connected to big wolf populations, like Yellowstone? A debate ensued between those who supported natural recovery and those who thought Yellowstone was too disconnected from northwest Montana and required an assist—reintroduction. Bipartisan work in Congress led to approval for wolf reintroduction to Yellowstone and central Idaho.

After twenty years of planning and preparation, fourteen wolves were captured in Alberta, Canada, then released into Yellowstone January 12, 1995. The next year, seventeen British Columbia wolves were reintroduced. In 1997, ten more from northwest Montana were released for a total of forty-one wolves in three years.

Yellowstone’s new wolf era was underway.

Wolf numbers quickly increased—reproduction even occurred that first year as wolves bred in the pens and denned upon release. With reintroduced wolves and abundant elk, wolves thrived. Conditions were so good it quite possibly led to the largest wolf pack ever recorded. In 2000, three females in the Druid Peak pack produced twenty-one pups—twenty pups survived, so the next year this pack numbered thirty-seven wolves. The pack was so large it was socially unwieldy and the wolves were rarely all together. Biologists documented them together enough to be considered one pack. But the next year they split into four wolf packs.

Wolf density in northern Yellowstone reached some of the highest levels recorded. This density led to many wolves being killed by other wolves. Each year (excluding disease to pups) wolf-wolf killing was the leading cause of mortality. This is unlike wolves that live in human dominated landscapes, where people cause more than eighty percent of mortality.

It is likely that these high densities contributed to three outbreaks of canine distemper in 1999, 2005, and 2008, causing high pup mortality. In 1999 and 2005, the population rebounded the following year, suggesting there was still adequate food to fuel wolf population growth. But after the outbreak in 2008 the population did not bounce back possibly because food was less abundant. Or maybe because this was the new normal.

Indeed, since 2008, the wolf population in Yellowstone has been fairly stable which suggests equilibrium with the available prey. Will these numbers persist? Will wolf numbers decline again due to disease? Or will numbers increase due to some unforeseen factor? These are some of the pressing questions for the future.

How Wolves Have Changed Yellowstone

Another question has led to a fiery debate: how is the park different? Woody vegetation was suppressed for most of the twentieth century due to too many elk (created by predator removal). Most agree on this.

Then starting in the late 1990s, willow started to regrow. Some felt wolves were changing elk behavior. Researchers hypothesized elk were avoiding habitats populated by wolves. Others thought it was due to fewer elk. Some thought it was both. Another group blamed a warming climate and longer growing season.

This debate continues. But as is so characteristic of science, we gradually inch toward a better answer as we conduct more research. It has become clear that some of the different camps are arguing about how these processes occur, not if they do. I am referring to what is called “top-down control,” or trophic cascade, in which predators eat herbivores and herbivores eat plants, so indirectly predators influence plants.

Researchers acknowledge trophic cascade but debate the level of its influence. In Yellowstone some emphasized top-down influence at the exclusion of other factors (like site conditions and water availability which are bottom-up factors), and that all fingers were pointed at wolves when cougars and bears had increased as well.

In fact, there are probably more predators in Yellowstone now than when the park was established. Also, some feel it is a misrepresentation that twenty years into wolf recovery (predator recovery), Yellowstone is now “fixed.” This discussion is ongoing and is the beauty of seeking the truth—it takes a while. Nature does not give up her secrets without great effort, thought, and debate.

But that is only part of the ways wolves have changed Yellowstone. Visitor enjoyment is different. The wolves of Yellowstone have meant a lot to people and local economies. Yellowstone is arguably the best place in the world to view free ranging wolves. Increasingly, humans are separated from nature. Seeing wild wolves in Yellowstone is an antidote to that problem. It’s about life and death and it’s real, which is something many of us lack in our daily lives.

I keep waiting for wolf enthusiasm to abate, but it does not. More people visit Yellowstone every year. Challenges for wolves remain, but wolf populations have increased worldwide. Yellowstone’s wolves are secure and protected. Telling their story will be a big part of future scientific endeavors. If the past is a guide, people will watch too, and tell their own stories about the Yellowstone wolves.

Doug Smith is the senior wildlife biologist for Yellowstone National Park. He will be speaking on campus Thursday, October 15 at Good Shepherd Lutheran Church at 7:30 p.m.