Wolves have been a vital part of North America's ecosystems for thousands of years, ranging from the Arctic tundra to forests, grasslands, and deserts. Once widespread across the continent, they played a key role as apex predators, maintaining the balance of prey populations and supporting biodiversity. However, due to habitat loss, hunting, and government eradication programs, wolves were nearly eliminated from most of their historical range by the mid-20th century. Conservation efforts, including reintroduction programs, have since helped restore wolf populations in select areas, highlighting their ecological and cultural significance.
Ranger Ted Ogsten & Chief Ranger Sam Woodring with coyote pelts, 1927
Early Wolf Management
In the 1800s, westward expansion brought settlers and livestock into direct conflict with native predators like wolves. As agriculture expanded, much of the wolves’ prey was wiped out, leading them to target livestock. In response, humans launched widespread eradication efforts, including poisoning, which eliminated wolves from most of their historical range. Even within Yellowstone, predator control measures in the late 1800s and early 1900s targeted wolves, bears, cougars, and coyotes to protect livestock and "desirable" wildlife like deer and elk.
When Yellowstone was established in 1872, gray wolves were present. However, early park managers, lacking an understanding of ecosystems, viewed wolves as destructive predators. Between 1914 and 1926, at least 136 wolves were killed in the park, and by the 1940s, wolf packs were nearly extinct in the area. By the mid-20th century, wolves were virtually eliminated from the lower 48 states.An intensive survey in the 1970s found no evidence of a wolf population in Yellowstone. Occasional sightings occurred, such as a wolf-like canid filmed in Hayden Valley in 1992, but no breeding pairs were confirmed. During the 1980s, wolves began to reestablish breeding packs in northwestern Montana, with 50–60 wolves reported by 1994.
In the 1960s, National Park Service (NPS) wildlife management policies shifted to let populations manage themselves, emphasizing the importance of predators like wolves. Growing national awareness of environmental issues led to laws like the 1973 Endangered Species Act (ESA), requiring the restoration of endangered species. By 1978, all wolf subspecies except those in Minnesota were federally listed as endangered, aligning with NPS policy to restore native species where feasible.
Restoration Efforts
In 1987, the USFWS Northern Rocky Mountain Wolf Recovery Plan proposed reintroducing an “experimental population” of wolves into Yellowstone. Under section 10(j) of the Endangered Species Act, experimental populations are nonessential, allowing greater management flexibility. Scientists predicted wolves would have minimal effects on mule deer, pronghorns, bighorn sheep, white-tailed deer, or bison, with minor impacts on grizzly bears and cougars. They expected wolves to reduce coyote numbers and increase red fox populations.
In 1991, Congress funded the USFWS to prepare an Environmental Impact Statement (EIS) on wolf restoration, in consultation with the NPS and US Forest Service. After extensive public input, the Secretary of the Interior signed the Record of Decision in June 1994, approving gray wolf reintroduction to Yellowstone and central Idaho.
Preparations involved Yellowstone staff, the USFWS, and state partners. The USFWS developed special regulations for managing the experimental population. Release sites, roughly one acre each, were enclosed with 9-gauge chain-link fences designed to prevent climbing or digging. Each pen included a small holding area for individual wolves needing medical attention and plywood shelters for isolation. Archeological and sensitive-plant surveys ensured minimal environmental impact at these sites.
Truck carrying wolves driving through the Roosevelt Arch with school children watching, January 12, 1995
NPS / Diane Papineau
Relocation and Release
In late 1994, early 1995, and again in 1996, USFWS and Canadian wildlife biologists captured wolves in Canada and relocated them to Yellowstone and central Idaho. In January 1995, 14 wolves were temporarily penned in Yellowstone: eight arrived on January 12 and six more on January 19. Each social group was kept together in acclimation pens. A second group of 17 wolves arrived in January 1996, with 11 brought on January 23 and six more on January 27. The wolves, ranging in age from nine months to five years and weighing 72–130 pounds, included individuals known to hunt bison and included breeding adults and younger pack members.
Each wolf was fitted with a radio collar before relocation. While penned, wolves were fed twice weekly with elk, deer, moose, or bison carcasses and had minimal contact with humans. Law enforcement rangers guarded the pens, and the surrounding areas were closed to visitors to prevent unauthorized access. Biologists monitored the wolves’ welfare twice weekly using telemetry or visual observation during feedings.
Although a five-year reintroduction plan was anticipated, no transplants were needed after 1996 due to the program’s early success. Some expressed concerns about wolves becoming habituated to humans while in pens, but confinement reinforced their natural avoidance of people, as it was a negative experience for them.
Restoration Results
Preliminary studies indicate that wolf recovery is likely to enhance biodiversity in the Greater Yellowstone Ecosystem (GYE). Wolves primarily prey on elk, with their kills benefiting a variety of scavengers. They are also increasingly preying on bison in late winter, though most bison biomass consumed comes from scavenging carcasses of bison that died naturally. Grizzly bears frequently usurp wolf kills, providing bears with a crucial food source in low-food years—contrary to expectations based on other regions. Additionally, wolf aggression toward coyotes has reduced their numbers in wolf territories, likely benefiting smaller predators, rodents, and birds of prey.
Wolves have contributed to decreased survival rates of elk calves and adults while also influencing elk habitat use. These effects, while partly predictable, are more complex in Yellowstone’s ecosystem, which features multiple large predators—grizzly bears, black bears, coyotes, and cougars—as well as human hunting outside the park. This complexity makes it challenging to project long-term elk population trends.
The impact of wolves on northern Yellowstone elk dynamics cannot be generalized across the GYE. Variations depend on factors like elk densities, predator abundance, alternative prey availability, winter severity, and human influences such as hunting and livestock interactions. A coalition of professionals and researchers is studying additional wolf-ungulate systems in the western GYE. Findings suggest that wolf predation’s effects on elk range from significant to minimal, depending on the specific context.
"No Wolves" bumper sticker
NPS / Jim Peaco
Legal Challenges
Several lawsuits were filed to halt wolf restoration, citing various concerns. The cases were consolidated, and in December 1997, a judge ruled that the reintroduction program in Yellowstone and central Idaho violated section 10(j) of the Endangered Species Act. The ruling found insufficient geographic separation between fully protected wolves in Montana and the reintroduction areas, where special management rules applied. The judge, expressing “utmost reluctance,” ordered the removal—but not the killing—of reintroduced wolves and their offspring. However, he stayed the order pending appeal.
The Justice Department appealed, and in January 2000, the decision was reversed, allowing the wolf reintroduction program to continue.
Legal Status
The biological requirements for delisting wolves from the Endangered Species Act (ESA) were met with at least 300 wolves and 30 breeding pairs sustained for three consecutive years across three recovery areas. In 2008, the USFWS delisted wolves in Idaho, Montana, and Yellowstone and Grand Teton national parks after approving management plans in Idaho and Montana. However, lawsuits from environmental groups successfully argued that Wyoming's wolf management plan was inadequate and that genetic connectivity between recovery areas was not established. As a result, wolves were relisted as endangered.
In 2009, wolves were delisted again in Montana and Idaho, though not in Wyoming. Legal challenges led to the Northern Rocky Mountain wolf population being relisted under the ESA. In 2011, Congress delisted wolves in Montana and Idaho, and in 2012 directed the USFWS to reissue its 2009 delisting rule, contingent on Wyoming developing an approved regulatory framework. On September 30, 2012, wolves in Wyoming were delisted and managed under the state’s plan, but litigation led to their relisting on September 23, 2014. Following an appeal, wolves in Wyoming were delisted again on April 25, 2017, and are now managed under regulated hunting seasons in Montana, Wyoming, and Idaho.
The USFWS continues to monitor wolf populations in Montana and Idaho for at least five years post-delisting, with the option to relist or emergency relist if necessary. Wolves are now managed by state, Tribal nations, and federal agencies, with management in national parks and wildlife refuges guided by existing legislation and regulations.
The Future of Wolf Management
The future of wolves in the GYE will depend largely on how livestock depredation and wolf hunting outside the park are managed. Wolf populations will also be influenced by the availability of prey species such as elk, deer, and bison, which fluctuate due to hunting quotas, winter severity, and disease. The extent to which wolves have contributed to the decline of the northern Yellowstone elk population since the mid-1990s—and the potentially related resurgence of willow and aspen in some areas—remains an active area of research.
