The history of wolves in Yellowstone includes the removal, disappearance, and return of gray wolves (Canis lupus) to Yellowstone National Park and the Greater Yellowstone Ecosystem. When Yellowstone National Park was created in 1872, wolf numbers were already decreasing in Montana, Wyoming, and Idaho. The park’s creation did not protect wolves or other predators, and government programs to control predators in the early 1900s helped remove gray wolves from Yellowstone. The last wolves in Yellowstone were killed in 1926. After that, occasional sightings of wolves were reported, but scientists confirmed in the mid-1900s that gray wolves had been completely removed and were not present in Yellowstone or any of the 48 states.
In the 1950s, park managers, scientists, conservationists, and environmentalists began efforts to bring gray wolves back to Yellowstone National Park. When the Endangered Species Act was passed in 1973, it made legal reintroduction possible. In 1995, gray wolves were reintroduced to Yellowstone in the Lamar Valley. The return of wolves to Yellowstone has been a topic of debate, as have wolf reintroductions in other areas around the world.
Extirpation (1872–1926)
In 1872, when Yellowstone National Park was established, there were no laws to protect wildlife within the park. During the park’s early years, park officials, hunters, and visitors were allowed to kill any animals they encountered. The gray wolf was especially at risk because people viewed it as a harmful predator. Wolves were also being deliberately killed across North America to protect livestock. In January 1883, the U.S. Secretary of the Interior, Henry M. Teller, issued rules that banned hunting most animals in the park. However, these rules did not apply to wolves, coyotes, bears, mountain lions, and other small predators.
In 1890, the U.S. Army took over managing the park. Captain Moose Harris, the first military leader of the park, allowed people to hunt any wildlife and let the park’s administration handle predator control. Official records show that the Army did not begin killing wolves until 1914.
In 1885, Congress created the Division of Economic Ornithology and Mammalogy to conduct scientific research aimed at protecting wildlife. This group later became the U.S. Biological Survey, which eventually evolved into the U.S. Fish and Wildlife Service. In 1907, under pressure from western cattle and livestock industries, this agency started a program to control predators. This program led to the deaths of about 1,800 wolves and 23,000 coyotes in 39 U.S. National Forests in 1907 alone. In 1916, when the National Park Service was created, its founding law allowed the Secretary of the Interior to decide whether to destroy animals or plants that were harmful to the parks.
It is widely believed that gray wolves no longer lived in Yellowstone by 1926. However, the National Park Service continued its predator control policies in the park until 1933. A study from 1975 to 1977 found that between 1927 and 1977, there were many possible sightings of wolves in the park. From 1977 to the reintroduction of wolves in 1995, there were additional sightings of wolves, most believed to be single animals or pairs passing through the area.
Before the National Park Service took over in 1916, the U.S. Army killed 14 wolves during their time managing the park (1886–1916), mostly between 1914 and 1915. In 1940, Adolph Murie, a wildlife biologist, published a report titled Fauna of the National Parks of the United States—Ecology of the Coyote in the Yellowstone National Park. In this report, Murie listed the number of wolves killed each year from 1915 to 1935 as reported by park officials.
Research in the 1980s confirmed that the last official killing of wolves in the park happened in 1926, when two wolf pups near Soda Butte Creek were killed by park rangers. The last reported wolf killed in the Greater Yellowstone Ecosystem (before legal hunting or control measures were reintroduced) occurred in May 1943, when Leo Cottenoir, a Native American sheepherder on the Wind River Reservation, shot a wolf near the southern border of the park.
Absence (1926–1995)
After the wolves were removed from Yellowstone National Park, the number of elk increased. Over the next few years, the park's environment worsened significantly. Scientists who visited Yellowstone in 1929 and 1933 said, "The land was in very poor condition when we first saw it, and it has continued to get worse since then." By this time, many scientists were concerned about soil erosion and plants dying. The growing elk population caused damage to trees like aspen and cottonwood. To address this, the park service began trapping and moving elk. When this did not work, they started killing some elk. These efforts to control elk numbers lasted more than 30 years. While these actions stopped the land from getting worse, they did not improve its condition. Some people suggested bringing wolves back to control the elk population, but Yellowstone's managers were not interested in this idea, especially since they had already removed wolves from the park. Elk control continued until the 1960s. In the late 1960s, local hunters complained to their congressmen about having too few elk. The congressmen threatened to stop funding Yellowstone, so killing elk was stopped. This allowed elk numbers to rise again. As elk numbers increased, the quality of the land continued to decline, harming many other animals. Without wolves, coyote numbers grew rapidly, which hurt the pronghorn antelope population. However, the large elk population had the biggest impact on Yellowstone's ecosystem without wolves.
Efforts to bring back gray wolves to Yellowstone began with scientific studies about how predators and prey interact in the park. In 1940, Adolph Murie published Ecology of the Coyote in Yellowstone National Park. His work, along with The Wolves of Mount McKinley (1940–41), helped scientists understand the importance of wolves for conservation. In 1944, Aldo Leopold, a well-known wildlife biologist, wrote about the value of wolves in his review of The Wolves of North America.
By the 1960s, people's understanding of ecosystems changed, leading to more support for protecting wolves and other large predators. This included the idea of a "keystone species," introduced by Robert Paine in the early 1960s. In the 1960s, Douglas Pimlott, a Canadian biologist, called for restoring wolves in the northern Rocky Mountains.
In 1970, David Mech, an American wolf expert, published The Wolf: The Ecology and Behavior of an Endangered Species, which explained how wolves affect their environment. In 1978, John Weaver, a wildlife biologist, wrote Wolves of Yellowstone and recommended reintroducing wolves to the park.
The gray wolf was listed as endangered in 1967 under the Endangered Species Preservation Act of 1966. However, until the Endangered Species Act of 1973 passed, there was no legal way to reintroduce wolves to Yellowstone. This law required the U.S. Fish and Wildlife Service to create recovery plans for endangered species. The first plan was completed in 1980 but had little support. In 1987, a revised Northern Rocky Mountain Wolf Recovery Plan was published, which helped plan the reintroduction of wolves. This plan involved cooperation between the National Park Service, Fish and Wildlife Service, universities, state wildlife agencies, and environmental groups. The plan's summary stated:
— Northern Rocky Mountain Wolf Recovery Plan, USFWS, August 1987
In 1991, Congress asked the U.S. Fish and Wildlife Service to create an Environmental Impact Statement (EIS) to reintroduce wolves into Yellowstone and parts of Central Idaho. The final EIS, published in 1994, examined five options for reintroducing wolves. The chosen plan was:
— EIS-The Reintroduction of Wolves to Yellowstone National Park and Central Idaho, 1994
The EIS allowed the reintroduction to move forward, but not without challenges. The Sierra Club and National Audubon Society worried that "experimental" wolf populations would not be protected outside the park. The Farm Bureau of Idaho, Wyoming, and Montana argued the wrong type of wolf was chosen for reintroduction. These concerns were addressed, and in January 1995, wolves were reintroduced to Yellowstone.
Reintroduction (1995–present)
In January 1995, U.S. and Canadian wildlife officials captured 14 wolves from several groups of wolves east of Jasper National Park, near Hinton, Alberta, Canada. These wolves were sent to Yellowstone in two groups—January 12, 1995 (8 wolves) and January 20, 1995 (6 wolves). They were placed in three temporary enclosures—Crystal Creek, Rose Creek, and Soda Butte Creek in the Lamar Valley in the Northeast area of Yellowstone National Park. In March 1995, the enclosures were opened, and between March 21 and March 31, 1995, all 14 wolves were released into the wild in Yellowstone.
Seventeen more wolves captured in Canada arrived in Yellowstone in January 1996. These wolves were released into the park in April 1996 from the Chief Joseph, Lone Star, Druid Peak, and Nez Perce enclosures. Officials planned the reintroduction to take 3–5 years, but these were the final wolves released because they believed the wolves were reproducing and surviving well on their own.
Wolf population declines can happen due to conflicts within the same species, lack of food, mange, canine distemper, legal hunting of wolves outside the park (for sport or to protect livestock), and in one case in 2009, park officials removed a wolf that had become used to humans.
Data from 1995 to 1999 shows the status of wolves in the Greater Yellowstone Ecosystem. Since 2000, monitoring has focused on wolf packs within the park. Wolves have spread to areas outside the park, and the last official report counted 272 wolves in the Greater Yellowstone Area in 2002.
Scientists have studied the effects of wolves on the Yellowstone ecosystem since their reintroduction in 1995.
As the wolf population in the park has grown, the elk population, which wolves hunt, has decreased. Before wolves were reintroduced, scientists predicted wolves would kill about 12 elk per wolf each year. This estimate was too low because wolves now kill about 22 elk per wolf each year. The drop in elk numbers has changed plant life, especially willows, cottonwoods, and aspens near heavily wooded areas. While wolf hunting directly causes fewer elk, some research shows that elk behavior has changed because of wolves. Wolves have pushed elk into less ideal habitats, increased their stress, reduced their nutrition, and lowered their birth rates.
Wolves became a major predator of coyotes after their reintroduction. In 1995 and 1996, the coyote population in Yellowstone changed dramatically. Before wolves returned, Yellowstone had one of the densest and most stable coyote populations in the United States because of limited human impact. Two years after wolves were reintroduced, the coyote population dropped to about half its original size due to competition and wolves killing coyotes. Coyote numbers were 39% lower in areas where wolves were reintroduced. In one study, about 16% of radio-collared coyotes were killed by wolves. Coyotes now move to steeper terrain instead of open areas. Open areas no longer attract coyotes because wolves can chase them on flat ground and often kill them. Coyotes feel safer on steep terrain, where they can lead wolves downhill. When wolves chase them uphill, coyotes turn around and run uphill. Wolves, being heavier, cannot stop, and coyotes gain an advantage. While wolves usually dominate in fights, coyotes sometimes attack wolves if they outnumber them. Both species will kill each other’s young if given the chance.
Coyotes naturally control fox populations, so the drop in coyotes has led to more foxes. This change affects the survival of animals that coyotes usually hunt, such as hares, young deer, small rodents, and ground-nesting birds. These changes affect how often certain plants are eaten, which changes the balance of local plant life and continues down the food chain to fungi and microbes.
The return of wolves has also led to a large increase in the beaver population in Yellowstone. In 2001, there was only one beaver colony in the park, but by 2011, there were nine. Wolves have encouraged elk to eat more widely, reducing pressure on willows, which beavers need to survive the winter. Beaver dams help the local water system by storing water, reducing erosion, and creating new habitats for animals like moose, otters, mink, wading birds, waterfowl, fish, and amphibians.
Wolves also helped Yellowstone’s grizzly bear population because their hunting of elk increased the growth of berries, an important food source for grizzly bears.
Wolf kills provide food for many animals, including ravens, wolverines, bald eagles, golden eagles, grizzly bears, black bears, jays, magpies, martens, and coyotes.
Wolf packs sometimes take kills made by cougars, which has forced cougars to move back to their traditional mountain habitats instead of hunting in valleys.
The reintroduction of wolves, a top predator, has caused changes in plants and animals throughout the ecosystem. This is an example of a trophic cascade, which is a chain of changes in an ecosystem caused by the presence of a top predator like the wolf.
Because gray wolf populations in Montana, Wyoming, and Idaho had recovered enough to meet the goals of the Wolf Recovery Plan, the U.S. Fish and Wildlife Service changed the status of the gray wolf population known as the Northern Rocky Mountain Distinct Population Segment from Endangered to Experimental Population-Non Essential on May 4, 2008.
Wolves in Yellowstone and the Greater Yellowstone Ecosystem are part of this population. In response, state wildlife officials in Idaho and Montana created hunting seasons for wolves as part of their approved Wolf Management Plans. Environmental groups opposed the delisting and hunting seasons, but legal challenges to stop the hunts were unsuccessful. Wolf hunts in Montana began in September 2009.
Although wolves inside Yellowstone were still fully protected, wolves that left the park and entered Idaho or Montana could be legally hunted. During these hunts, Montana hunters legally killed several wolves in the Absaroka-Beartooth Wilderness, which is near the northeast corner of the park.
Reactions
From 2000–2004, the Montana Fish, Wildlife and Parks cut antlerless permits by 51%, reducing the number from 2,882 to 1,400. In 2006, they proposed only 100 permits, which was a 96% decrease compared to the 2,660 permits issued in 1995. At first, the impact of wolves hunting elk during the first five years of the recovery was not noticed, as elk numbers remained the same as in 1980–1994. However, from the winter of 1995 to the winter of 2004, elk numbers dropped significantly, decreasing from 16,791 to 8,335 as the wolf population on the northern range grew from 21 to 106. Other factors, such as predation by bears, increased human hunting, harsher winters, and droughts, also contributed to this decline. Since 2000, 45% of known deaths and 75% of deaths caused by predators among radio-collared cow-elk have been confirmed to be due to wolves. Human-caused deaths during the same period accounted for 8–30% of known deaths. Yellowstone elk make up to 92% of wolves’ winter diet. The estimated kill rate of Yellowstone wolves on elk during winter is 22 ungulates per wolf annually, which is higher than the 12 ungulates per wolf rate predicted in the ESA.
Historically, the wolves originally native to Yellowstone were classified as the subspecies C. l. irremotus. When the question of which subspecies to use for reintroduction was raised, U.S. Fish and Wildlife Service representatives stated that the taxonomy of gray wolves had changed many times and that C. l. irremotus was not a distinct subspecies but a geographical variant. Three publications discussed whether Canadian wolves should be used as the founding population: Brewster and Fritz supported this idea, while Nowak argued that the original Yellowstone wolves were more similar to C. l. nubilus, a subspecies already in Minnesota, and that the Canadian wolves proposed by Brewster and Fritz belonged to C. l. occidentalis, a much larger subspecies. Brewster and Fritz believed that wolves have little genetic diversity and that the original population was already extinct. Nowak disagreed, stating that Minnesota wolves were more similar in size and shape to the original Yellowstone wolves than the proposed Canadian wolves. He also noted that C. l. occidentalis may have been migrating southward before human intervention. Doug Smith stated that the size difference between the introduced wolves and the original wolves was only about 6–7%, and that Minnesota wolves had no experience with elk and bison and were not adapted to mountainous terrain. Smith and Yellowstone National Park deny the claim that the wrong type of wolf was introduced.
In popular culture
The podcast Criminal discussed the death of a male wolf named Wolf 10 in their episode titled "Wolf 10." Another podcast by the same group, This is Love, created an episode about bringing wolves back to Yellowstone National Park. This episode focused on the experiences of three wolves: a male named Wolf 8, a male named Wolf 21, and a female named Wolf 42.