A federal wildlife official said on Friday that, for the first time in decades, a radio-collared endangered Mexican wolf crossed from the United States into Mexico last week. The male wolf moved from a remote portion of the New Mexico Bootheel into Chihuahua, according to Aislinn Maestas, a spokesperson for the U.S. Fish and Wildlife Service, which monitors members of the smallest and rarest subspecies of North American gray wolf, also referred to by its Spanish name, lobo.
Once common across the Southwestern United States and Mexico, the Mexican wolf population was pushed to the brink of extinction in the 1970s after government agencies and ranchers targeted the animals as a means of protecting livestock. Conservationists say the wolves have historically traversed the Bootheel’s grasslands, desert and wooded mountains for millennia, following migration corridors that cross what are now international borders in search of prey and mates.
Construction of a steel border barrier, installed by successive U.S. administrations, has extended westward across New Mexico. The Trump administration and the Biden administration both advanced construction projects intended to curb migrant and drug trafficking, and current work in the Bootheel region includes sections of barrier standing between 18 and 30 feet high, according to conservation advocates and officials cited by federal wildlife staff.
Michael Robinson, a senior conservation advocate at the Center for Biological Diversity, said on Friday that last week’s crossing might be the final time this subspecies moves freely across that stretch of the border if construction continues. Robinson cautioned that sealing off the Bootheel would isolate Mexican wolves and other rare mammals, including jaguars, and would ultimately make their survival less likely.
Conservation groups and some U.S. wildlife officials have argued that expansion of the border barrier will fragment habitats and disrupt animal migration routes in several regions, including the Big Bend area of Texas, the San Rafael Valley of Arizona and the Otay Wilderness in California. Those groups point to legal steps taken by the Department of Homeland Security as facilitating construction; DHS has at times used legal authority to override environmental protections, a practice that has prompted lawsuits related to barrier projects.
Officials from the Department of Homeland Security and U.S. Customs and Border Protection, agencies responsible for planning and erecting the barrier, did not immediately respond to a request for comment.
U.S. administrations have acknowledged environmental risks tied to the barrier while maintaining that the structures are necessary for national security. In response to ecological concerns, officials have added mitigation measures in some locations, such as ground-level openings intended to allow small animals, including reptiles and rodents, to pass beneath certain sections of the wall.
For the Mexican wolf specifically, crossing the international border matters for genetic diversity. Cyndi Tuell, Arizona and New Mexico director at Western Watersheds Project, said that mating between animals from the United States and Mexico could bolster critically low genetic diversity in the wild population.
All living Mexican wolves today descend from a very small founder group. Conservation advocates note that modern Mexican wolves trace their lineage to just seven wolves that were successfully bred after being captured as part of a binational breeding program initiated in the late 1970s.
Population figures cited by the U.S. Fish and Wildlife Service and conservation organizations indicate there are at least 319 wild Mexican wolves in the United States, roughly 36 in Mexico, and about 380 animals in captive breeding programs as of this year. Conservationists warn that blocking cross-border movement would exacerbate chronic inbreeding, a problem already linked to reduced pup survival rates as well as occurrences of cancers and birth defects.
Key points
- A radio-collared male Mexican wolf crossed from New Mexico into Chihuahua last week, confirmed by U.S. Fish and Wildlife Service spokesperson Aislinn Maestas.
- Ongoing construction of an 18- to 30-foot-high steel border barrier across the New Mexico Bootheel may prevent future cross-border movements, heightening inbreeding risks and lowering survival odds for the species.
- Policy and construction decisions affect multiple sectors, including federal security agencies overseeing the barrier, construction contractors, and environmental and wildlife management organizations.
Risks and uncertainties
- Genetic risk to the Mexican wolf population - Continued habitat fragmentation could further isolate wolves and reduce genetic diversity, with implications for survival rates and health of the subspecies. This principally affects wildlife conservation and biodiversity sectors.
- Legal and regulatory uncertainty - The Department of Homeland Security’s use of authority to override environmental laws has prompted lawsuits, creating uncertainty for agencies, construction firms, and conservation groups involved in border projects.
- Mitigation effectiveness - While officials have added ground-level openings for small animals, it is unclear whether such measures will meaningfully address movement needs of larger species like wolves and jaguars, leaving ecological outcomes uncertain.