SAVING MEXICAN GRAY WOLVES
The smallest gray wolf subspecies in North America, Mexican gray wolves are also one of the rarest and most imperiled mammals on the continent.
The U.S. Fish and Wildlife Service (and its predecessor agency) poisoned and trapped almost all Mexican wolves from the wild from 1915 until 1973. Three of the last five survivors, captured between 1977 and 1980, were bred in captivity, and their descendants — along with the descendants of four previously captured wolves — were reintroduced in 1998.
The wild Arizona and New Mexico population grew to 286 in 2024. An unknown but much smaller number survive in Sonora and/or Chihuahua, Mexico. Even though the U.S. wild population has lost considerable genetic diversity due to mismanagement, the Service has refused to take measures that could grow the gene pool.
BACKGROUND
Beginning in 1915 the federal government trapped and poisoned wolves — even destroying pups in their dens — on behalf of the livestock industry.
By the 1930s wolves were almost completely absent from the U.S. West, and wolves entering the United States from Mexico were quickly killed. In 1950 the Fish and Wildlife Service began sending poison to Mexico, along with staff to set up a wolf-poisoning program, as a form of foreign aid.
After the Endangered Species Act was passed in 1973 and Mexican wolves were added to the endangered list in 1976, just seven wolves — three captured from the wild and four already in captivity — proved the foundation for captive breeding. No wild wolves were confirmed in Mexico after the last of the seven was captured alive in 1980.
Reintroduction began in 1998 in Arizona and New Mexico (thanks to the Center’s work) and in 2011 in Sonora, Mexico.
OUR CAMPAIGN
The Center has worked continuously to recover Mexican wolves in the wild since we filed the 1990 lawsuit that led, eight years later, to reintroduction. We’ve sought to protect the wolves from persecution, bolster their declining genetic diversity, oppose wolf removals that all too often target genetically valuable wolves, and push for releases of captive-born, well-bonded, family packs — which typically thrive.
We also oppose the regulatory northern boundary on wolf movements at Interstate 40, which serves to prevent interaction between Mexican and northern wolves and blocks the ancient flow of genes in both directions — connectivity that Mexican wolves need now more than ever.
Check out our press releases to learn more about the Center's actions for Mexican gray wolves.
We’ve helped defeat livestock-industry lawsuits and legislation to remove wolves from the wild. We induced the U.S. government to rerelease trapped wolves into New Mexico beginning in 2000. Our legally binding 2009 agreement with the Fish and Wildlife Service threw out a policy that drove the trapping and shooting of wolves based on an arbitrary and inhumane formula that ignored their genetic value and family roles, such as caring for pups.
Our 2004 petition and subsequent lawsuits led to a 2015 management rule authorizing, for the first time, the releases of captive-born wolves in New Mexico — and vastly expanding where they can roam and live in both New Mexico and Arizona. We won a 2018 court victory that led the Fish and Wildlife Service to limit the killing of genetically valuable wolves (though not sufficiently). The Center’s petitions and litigation also led to Mexican wolves gaining their own place on the endangered list, separate from other gray wolves, in 2015, and the related development of a Mexican wolf recovery plan in 2017 and its revision in 2022.
Through our work we’ve educated thousands of people about the crucial ecological role of wolves and rallied the public to oppose the policies leading to ongoing government shooting and trapping of Mexican wolves, as well as to support wolf releases.
+ NATURAL HISTORY
MEXICAN GRAY WOLF (in Spanish, el lobo) } Canis lupus baileyi
FAMILY: Canidae
DESCRIPTION: Roughly 5 feet in length, Mexican gray wolves generally weigh between 50 and 80 pounds. Their coats are buff, gray, and rust colored, often with distinguishing facial patterns. They have large heads with thick muzzles, bushy tails, oversized paws, and long legs. Wolves are known for their keen sense of smell, excellent hearing, and binocular vision. Mexican gray wolves are the smallest of all the gray wolf subspecies in North America.
HABITAT: Mexican gray wolves were originally found in a variety of habitats, including mountain woodlands and the Chihuahuan and Sonoran deserts.
RANGE: Historically, Mexican gray wolves were found throughout southwestern Texas, southern New Mexico, southeastern Arizona, and as far south as central Mexico. Today, reintroduced wolves are limited to eastern Arizona and western New Mexico and a portion of the Sierra Madre in Mexico.
MIGRATION: Wolves don’t migrate seasonally, except in areas where prey animals migrate to lower elevations in winters with heavy snowfall (increasingly rare) and wolves follow (for instance, when elk on the Apache National Forest migrate to the San Carlos Apache Reservation). In most current Mexican wolf home territories, this isn’t the case. Regular travel through home ranges is a constant for wolves. Males and females disperse to set up new territories or reclaim lost habitat, and they can travel hundreds of miles; territory sizes are a function of prey density.
BREEDING: The Mexican gray wolf lives in packs of four to nine animals, consisting of two adults and their offspring. The alpha pair will mate for life, and they’re normally the only breeding animals in the pack. Mexican gray wolves breed in February and March, and following a gestation period of approximately 63 days, the mother gives birth to four to seven pups. A pack will establish its territory, ranging up to several hundred square miles.
LIFECYCLE: The lifespan of a Mexican gray wolf is 6 to 8 years, though the majority die at a much younger age from human persecution.
FEEDING: Mexican gray wolves are carnivores, preying on elk, mule and white-tailed deer, pronghorn, javelina, rabbits, and other small mammals.
THREATS: Mexican gray wolves were trapped, shot, and poisoned to near extinction. Today human activity still poses a grave threat — particularly U.S. government trapping and shooting on behalf of the livestock industry and government-facilitated poaching. Ongoing mismanagement has reduced the gene pool of the U.S. reintroduced population to a level that will likely eventually result in extinction if not significantly increased soon.
POPULATION TREND: By the early 1930s, Mexican gray wolves had been eliminated from the United States, and for several decades the government maintained a hunter on the border to kill wolves traveling north from Mexico. Beginning in 1950, the U.S. Fish and Wildlife Service extended its extermination program into Mexico with shipments of government-produced poison and deployment of personnel to instruct in poisoning. The Mexican gray wolf was listed as endangered in 1976. Reintroductions began in 1998. The counted number of adult gray wolves remaining in the wild in March 2025 was 286. Approximately 380 wolves survive in specialized facilities, zoos, and museums as part of a captive-breeding program.
