Yellowstone National Park

A wolf in the Lamar Valley of Yellowstone National Park
A wolf in the Lamar Valley of Yellowstone National Park (Drew Rush/National Geographic/Getty)

Return of the Wolf to Yellowstone

Yellowstone National Park is a panorama alive with one of the greatest concentrations of large mammals in the lower 48 states—more than 30,000 elk, 3,000 bison, 2,000 mule deer, and hundreds of grizzlies, moose, bighorn sheep, and pronghorn antelope. But for decades this spectacle was missing a key participant: the wolf. This absence had both aesthetic and ecological significance. It was like a symphony without a string section.

In March 1995, when 14 wolves from Canada were released in Yellowstone, they became the first wolf packs here since extermination more than 60 years ago. At that time, the wolf was regarded as an extraneous villain in the Yellowstone drama; now the same animal is seen as an essential player in the cast of a complete ecosystem. This change in perspective has not come easily. The restoration program was implemented only after many years of public debate and careful planning, and it remains controversial.

Why Wolves Were Restored: The Ecology of an Endangered Species

For many years the only wolves in Yellowstone were two mounted in a display case at the Albright Visitor Center. These wolves were killed by a park ranger in 1922, near the end of an era when wolves, coyotes, and mountain lions were considered a menace to Yellowstone's other wildlife.

Although reports of wolves continued sporadically, most sightings were of lone wolves or large coyotes. The last solid evidence of wolf pack activity in Yellowstone dates back to the 1930s. That's a long time for a large wilderness area to be without one of its major predators.

Federal agencies like the National Park Service are mandated by the Endangered Species Act to protect species listed as endangered or threatened with becoming endangered in the foreseeable future. As stewards of Yellowstone, the Park Service must safeguard both animals and habitats and, where possible, restore viable populations of listed species like the gray wolf.

The recovery of the gray wolf in Yellowstone promotes ecosystem integrity and enhances the value of the park as one of America's premier natural areas. With resident wolves, Yellowstone is one of the largest and most intact ecosystems remaining in the earth's temperate zones.

The conservation of wolves and other large carnivores is truly a global concern. These species do not survive easily in industrial societies: people have to want them to survive. Long-term conservation of the wolf is as much a social issue as it is a species or habitat issue.

There are many reasons for restoring gray wolves to Yellowstone National Park. But, ultimately, wolf restoration shows that we respect the existence of other life forms, even when that may not be easy.

Wolves in the Wild

The wolves brought to Yellowstone from Canada are the same species that roamed what is now the United States hundreds of years ago. Given enough time and protection as an endangered species they would eventually arrive in Yellowstone on their own. Their history is both fascinating and complex.

Pack Hierarchy: Wolves are social, hierarchical, competitive, territorial, and predatory. They evolved as effective predators in part through pack formation. Packs average eight members or fewer, and consist of the "alpha" or dominant pair, their most recent litter of pups, the pups' older siblings, and occasionally other unrelated wolves. Usually only the alpha pair mate, beginning at about two years of age.

Raising Pups: Wolf litters, averaging six pups, are born in the spring. Pack ranking begins at birth, when the strongest pups push for position at their mother's teats. Since only about half may make it through the first year, the pups' survival is a top priority for each pack member. Adults feed young pups with meat regurgitated from kills.

Depending on how much territory is needed to find prey, a pack may range over an area 40 to 1,500 square miles in size (average size in the Rockies is 30 to 300 square miles), defending its territory from "strange canids," including coyotes and dogs. During territorial disputes, wolves may fight or even kill each other. In most cases, they simply avoid one another.

A pack announces its presence by scent marking and howling. These behaviors are used to warn away strange wolves, to help pack members locate each other, and to express the relationships of dominance and dependence in the pack.

Wolves disperse from packs for many reasons. For example, young adults may leave to seek their own mates. These lone animals often seek out a living between pack territories. Wolves that leave the pack have been known to travel up to 550 miles looking for a mate and a territory, but more often they settle close to their original territory. A dispersing wolf that does not find a mate may remain alone for life.

To Hunt is to Survive: Unlike some species, which are endangered because they require specific habitat being eliminated by human activity, wolves can live anywhere they find adequate supplies of prey and human tolerance. Their principal foods include elk, deer, and moose. Small mammals, such as beaver and hares may be seasonally important when ungulates are not available, or for pups learning to hunt.

Wolves typically rest during midday and hunt early in the morning and in the evening when their keen eyesight gives them an advantage and prey animals are active. Wolves generally seek out the most vulnerable animals: the young, the old, the lame, or those caught in crusted snow, which a wolf can walk across.

Wolves risk getting injured or killed in the effort to bring down a strong animal, and may make many unsuccessful attempts before obtaining a meal. Only by skillfully working the herd can a wolf pack bring down an elk or bison. As with the human species, the wolf's predatory success depends as much on cunning and cooperation as on brawn.

Wolves rarely live more than ten years in the wild, being killed by other wolves, disease, starvation, or injuries sustained while attacking prey.

Will Wolves Change Yellowstone? The impact of wolves upon Yellowstone will be far more profound than the consumption of some wildlife each year. Predation shapes the wolf and its prey: Both species grow stronger as they are pitted against each other on psychological and physical levels. And species other than prey will surely be affected by the presence of wolves.

Coyote numbers are likely to decline. While those scavenging wolf-kill carcasses will enjoy the leftovers, some coyotes have been killed by wolves. On rare occasions, wolves may kill some bear, especially cubs. But their presence may also be advantageous to bears, which can often displace wolves from a carcass.

Prey animals brought down by wolves help fill many other stomachs. Ravens, magpies, and eagles have been seen on wolf kills in Yellowstone. Other scavengers including red foxes, wolverines, weasels, martens, hawks, western tanagers, bluebirds, and insects such as carrion beetles may also benefit. In this respect, wolf restoration will likely support park biodiversity well beyond the addition of a single species.

There is much to be learned about how wolves will change Yellowstone. Through long-term research, the effects of wolf restoration on the ecosystem will be evaluated. You are invited to share the excitement of learning about Yellowstone after the return of the wolf.

How are They Doing? A Status Report

An Experimental Population: Some wolves will travel across or inhabit private land. Their presence among humans is not necessarily a problem—wolves have coexisted peaceably with people in various parts of the world for centuries. But the introduction of wolf packs into Yellowstone does mean that some of the 412,000 livestock grazing in the greater Yellowstone area will become prey. Good animal husbandry can help minimize livestock predation, but wolf restoration inevitably entails controlling certain wolves when they interfere with human activities.

Because of controversy surrounding reintroduction, the gray wolf has been legally designated an "experimental" population in the three Rocky Mountain recovery areas. This designation allows for added flexibility in managing an endangered species, permitting government agencies more options in certain situations.

Testing the Plan: Sixteen months after the first wolves were released in Yellowstone, many are roaming occasionally or regularly outside the park as they begin to establish their territories. Few of these wolves have had close encounters with humans or domestic animals. In one case, a hunting dog on private land ran into a wolf pack and was killed immediately. As of July, 1996, only one wolf had been killed for preying on livestock; several others were relocated to avert conflicts on private land.

Although unfortunate, these livestock losses have so far been low in number and, however unacceptable to some, well within the limits considered manageable in the restoration plan.

Defenders of Wildlife, a private organization, has raised a $100,000 fund to compensate ranchers for any livestock killed by wolves. They will also pay $5,000 to any owner of land on which wolves raise pups.

A Preliminary Progress Report: As of July, 1996, six wolf packs were establishing territories in the Yellowstone ecosystem. So far as is known, no wolves have traveled outside the recovery area. Wolves are predominantly killing elk, about one every two to six days.

Births: More wolf pups than expected have been born. As of July, 1996, the wolf population included seven surviving pups born in 1995 and at least 13 born in 1996.

Deaths: As of July, 1996, nine wolves had died in the Yellowstone recovery area. Three of the deaths were from nonhuman causes: A pregnant wolf died of thermal burns near Old Faithful, and two male wolves were killed by other packs in territorial disputes.

In addition to the wolf killed by government agents after it preyed on livestock, two were fatally hit by vehicles, and three wolves were killed illegally outside the park. In one case, a ranch employee apparently killed a wolf inadvertently while shooting coyotes in a calving pasture. He reported the death, cooperated with the investigation, and was fined $500. In a second case where the wolf's death was deliberate and concealed, the perpetrator was sentenced to six months and ordered to pay $10,000. The third case is under investigation.

Keeping Track of Yellowstone's Wolves: Keeping up with wolves is not easy. They travel considerable distances in short periods of time, and it may take up to 20 years for Yellowstone's new packs to settle into stable territories.

Most wolves will probably live in the north central part of the park, because that is where prey animals are most abundant. Some parts of the park will have no wolves, or just nomads, because too few prey animals live there, or because deep snow limits winter habitat. Some wolf packs may establish territories that lie partly or completely outside the park.

There is thought to be sufficient prey to support about ten packs within the park's boundaries, and up to 15 packs in or near the park. But because population size and distribution depend on many factors, they are impossible to predict with precision. When the recovery goal of ten breeding pairs is reached, the surrounding states could permit hunting or other means to control wolves outside the park.

Within the park, behavior, weather, disease, social stresses, territory limitations, and the availability of prey will combine to control wolf numbers in complicated ways. How many wolves ultimately reside in the Yellowstone area will vary over time.

What Remains to be Done? Wolf restoration entails more than just transporting wolves from Canada and releasing them in the park. Much work remains to ensure that the wolves of Yellowstone become a fully restored and self-sustaining population.

The wolves must be closely monitored to learn about their effects on other ecosystem inhabitants, to respond to any problems that may arise, and to determine if and when the goal of a self-sustaining population of wolves has been attained. Monitoring and research will continue well into the future.



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