Gray Wolf (Canis lupus)

Gray Wolf Yellowstone National Park

Image above: Gray Wolf, Yellowstone National Park. Photo by NPS.

The information below is a shortened version of an article on the gray wolf in the June, 2019 Sierra Voice newsletter. Here we have focused on the population segment of wolves descended from the Rocky Mountain region and western North America, and which are the source of the wolves that are now beginning to expand into California and into the Sierra Nevada.


Prior to 1870, the gray wolf was once common in the northern Rocky Mountain states. After bison, deer, elk, and other ungulates were decimated by unregulated hunting and human settlement, people tried to exterminate all remaining large predators, primarily because of conflicts with livestock. Wolf
populations had completely disappeared from the western United States by 1930. In 1973, the Endangered Species Act (ESA) listed wolves as endangered.

In 1995 and 1996, more than twenty years after lisiting under the ESA, the US Fish and Wildlife Service (FWS) captured a total of 66 wolves from southwestern Canada and released them in remote public lands in wilderness areas in central Idaho and Yellowstone National Park. Wolves have since become established throughout central Idaho and the Greater Yellowstone Area, demonstrating the wolf’s adaptability and resilience when they are protected from extermination campaigns.

The single significant threat to the gray wolf's continued survival in North America is the ongoing slaughter of wolves by hunters and ranchers. Hunters believe that wolves compete with them for deer and elk, thus reducing their own chances of a successful kill; and owners of livestock are concerned that wolves threaten the survival of their cattle and other livestock. Both of these groups are right: wolves do reduce populations of ungulate game species, and they sometimes hunt and kill vulnearable livestock. Wolves are more likely to hunt livestock when they are forced into unsuitable habitat due to a lack of wilderness areas and insufficient prey species. Nevertheless, the experience gained since the reintroduction of wolves to the Greater Yellowstone Area in 1995 has shown that it is possible to manage wolves, hunting, and livestock so that wolves can coexist with these human enterprises.

To offset  livestock losses, for example, in 1987 Defenders of Wildlife started a compensation fund for ranchers with verifiable livestock kills from wolves. The program paid out $1.3 million to livestock producers in Montana, Idaho, and Wyoming from 1987-2009. Defenders of Wildlife continues to provide grants, in-kind donations, education in non-lethal methods for discouraging wolves, and other types of support to promote coexistence with wolves. Compensation programs for livestock losses are today funded by the states, with federal grant funds providing support for non-lethal wolf control methods and livestock management techniques that minimize wolf proximity to livestock during vulnerable times, such as calving. Additional funds have been raised by non-profit groups to buy out available federal grazing leases in the proximity of Yellowstone National Park.  

Biology and Ecology

Adult gray wolves range in size from 18 to 80 kg (40 to 175 lbs), depending on sex, environment, and genetic differences. Their coloration is usually a grizzled gray, a mix of gray, black, rust, and cream, but individuals may be all black or all white. In North America, wolves are primarily predators of medium and large mammals, such as moose, elk, white-tailed deer, mule deer, caribou, muskox, bison, and beaver, but they also prey upon domestic livestock, pets, and smaller mammals when the opportunity arises.

Gray wolves are highly territorial, social animals and group hunters, normally living in packs of seven or fewer family members consisting of a breeding pair, their pups from the current year, offspring from previous years that have not yet dispersed, and occasionally another non-relative. However, packs with as many as 37 members have been documented in Yellowstone National Park since reintroduction, and packs as large as 27 have been reported elsewhere historically. Litters are generally 5 to 6 pups born from early April into May. Offspring usually remain with their parents for 10–54 months before dispersing. In general, by the age of 3 years, most wolves will have dispersed from their natal pack to locate social openings in existing packs or find a mate and form a new pack.

Packs live within territories that they defend from other wolves. Wolves can and do kill rival pack members, including their pups, although they never eat their own kind. Wolves howl to communicate with each other and to signal rival packs. Territory sizes range from approximately 20 to 215 square miles, depending on available prey and seasonal prey movements, but in the Northern Rockies territories are much larger, typically varying from 200-400 square miles. Single wolves that have been collared with GPS satellite tracking devices have been known to cover 6,000 miles or more.  

Wolves are a top predator species, and have shaped the coevolution of species that share their habitats. They are thus thought to be essential to keeping ecosystems in balance. Wolves are thought to be very resilient and adaptable in response to environmental changes and stress, and if humans can learn to accept the presence of wolves, there is a good chance that they will once again become widespread. Wolf habitat is non-specific, as wolves are able to occupy virtually any habitat where there is sufficient prey and protection from human persecution. Wolves are thought to have once been the most widespread predatory mammal on the planet.  


The criteria for recovery, or delisting criteria for the gray wolf determined by FWS, were not particularly scientifically rigorous. The wolf’s successful and rapid population increases and establishment in new areas is nevertheless a real success story—despite ongoing harrassment from humans—and the wolves appeared to have exceeded the minimum requirements for recovery in the Northern Rocky Mountains and the Western Great Lakes regions. In 2000, FWS began the process of delisting, downlisting, and reclassifying wolf distinct population segments (DPS) across the US.

Pointing to the lack of scientific rigor, environmental groups have responded with court challenges.

In November 2018, the U.S. House of Representatives passed a bill (HR 6784), that would mandate delisting the wolf throughout the continent (excepting the Mexican gray wolf, which remains highly endangered in an environment abounding with threats). The bill has not been passed by the Senate.

Map of current ESA status for gray wolf Mar 2019

Figure above: Current legal status of C. lupus under the ESA. From Federal Register, March 15, 2019, p. 5696. The FWS is currently proposing to remove these designations, except for the Mexican wolf.

For now, wolves outside of the delisted Northern Rocky Mountain distinct population segment remain fully protected under the ESA as endangered species. In Washington and California, the wolf is listed under the states' ESAs as well. It is explicitly unlawful to kill or intentionally harm gray wolves under these statutes, regardless of the federal status.  

The story of wolf conservation in the years since the enactment of the Endangered Species Act is one for the historians. Several books have been written about the reintroduction and the conflicts that ensued between wolf proponents and opponents.

Wolves continue to be shot and killed with impunity. The motto “shoot, shovel, and shut up” in cattle country is too often embraced where wolf reestablishment is vigorously opposed. The single greatest cause of wolf mortality today is the same as it was a century ago: humans killing wolves. You can read a summary timeline of the history thanks to EarthJustice, here, and a summary from the Center for Biological Diversity, here. Despite the demoralizing cruelty displayed by our own species, the wolf is recovering, and it is thought that approximately 5,000 to 6,000 wolves are alive in the lower contiguous states, and they continue to establish in new areas. There are also an estimated 65,000 wolves across all of Canada and Alaska. We now must turn to the latest development, wolves in California, and the proposal by the Trump administration’s FWS to delist the gray wolf across the entire United States (excepting the Mexican wolf).

The Gray Wolf in California

The gray wolf is returning to California after its disappearance in the 1920s. California is well within documented dispersal distances from extant wolves that have established packs in Oregon, Washington, and Idaho. On December 28, 2011, a male collared wolf born into the Imnaha Pack in northeast Oregon in 2009, OR-7, crossed over the California border just north of Dorris in Siskiyou County. OR-7 spent most of a year in California, in mountain habitats west of Lake Almanor and throughout northeastern California, including the Sacramento Valley near Redding and Red Bluff. He eventually went back to Oregon, where he found a mate and founded the Rogue Pack.

Since then, two wolf packs have been documented in California, the Shasta and the Lassen packs, and four individual collared wolves have been detected with GPS. In 2015 the first pair of breeding wolves were discovered in eastern Siskiyou County. Named the Shasta Pack, the pair had a litter of five pups in August, 2015. Genetic testing revealed that the breeding pair were both descended from the same Oregon pack that produced OR-7. There have been no verified detections of the pack since late 2015, but one of the male offspring was detected in northwestern Nevada a year later in November 2016. The pack appears to be no longer in existence.

The Lassen Pack is the only currently known wolf pack in California. The female was first seen in 2015. By 2016, it appeared that she had found a mate. The male is descended from the Rogue Pack, as determined genetically from scat, and the female is thought to be dispersed from the Rocky Mountain wolf population. In June 2017, CDFW biologists were able to locate the female and outfit her with a GPS collar, and are now regularly monitoring her whereabouts. The pair had at least four pups in 2017 and five pups in 2018. The pack may have at least five members today, although an uncollared female yearling was found dead in Lassen County in September 2018.

In February, 2020, OR-54, a female gray wolf descended from OR-7 and the Rogue Pack, was found dead in Shasta County. She was outfitted with a radio tracking collar, so her travels were well documented--nearly 9,000 miles since her collaring. OR-54 had also traveled further south than any other wolf since their return to California in 2011, having once traveled south of I-80 and into Nevada, until returning to California and Shasta County.

Approx. area of gray wolf Apr 2019Image left: Approximate location of Lassen Pack wolf activity as of April, 2019 (yellow). California Department of Fish and Wildlife.

Gray wolves prefer to hunt ungulate species, primarily elk. There are three species of elk in California. While two of the three subspecies—Tule elk and Roosevelt elk—appear to be making a  comeback after decades of stewardship by state wildlife biologists, the Rocky Mountain elk that occur in the northeast part of the state are not increasing in numbers. Mule and black-tailed deer, the secondary prey species, have been in a long period of decline in the state, due to loss of habitat from agriculture and other types of human development, forestry practices that favor conifers over early successional habitats needed by deer, fire suppression, and plantation forestry. Thus it is unlikely that wolves will establish in densities or as successfully here as they have in the Greater Yellowstone Region, the Great Lakes region, or further north.

California Department of Fish and Wildlife finalized the state’s management plan for the Gray Wolf in 2016. You can download the two volumes of this document here.

Gray wolf delisting proposal 2019

On March 15, 2019, the FWS again proposed delisting the gray wolf in the entire 48 contiguous states, excepting the Mexican wolf that will remain endangered. The agency based its proposal on the modest recovery criteria that originated as a compromise to anti-wolf interests. The comment deadline on the proposal has been extended to July 15, 2019. All the associated documents can be accessed here.



Scientific Research

Gray Wolf Biological Report (FWS 2018)

Status Review of the Gray Wolf in California (CDFG 2014)

US Fish and Wildlife Service. 2012. Lower 48-State and Mexico Gray wolf (Canis lupus) listing, as revised 5-Year Review: Summary and Evaluation

The Wildlife Society. 1991. Restoration of Wolves in North America. Technical Report of the Technical Advisory Committee on Wolf Reintroduction (ad hoc).


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