The El Paso Zoo has welcomed five new Mexican gray wolves transported from the Phoenix Zoo as part of continued conservation efforts. The new pack’s arrival is part of a cooperative breeding program between the Association of Zoos and Aquariums Mexican Gray Wolf Species Survival Plan and the U.S. Fish and Wildlife Service’s Wolf Recovery Plan, which aims to restore the species to their native territory. Take Action now – Join the Texas Wolf Pack!
The U.S. population of endangered Mexican gray wolves grew by 23 animals, from 163 in in 2019 to 186 in 2020, according to a legal filing by the U.S. Fish and Wildlife Service. “It’s gratifying that more Mexican wolves are roaming this little corner of the Southwest,” said Michael Robinson of the Center for Biological Diversity. “But even as wolf howls echo in a few more canyons than before, this population is still vulnerable and needs more stringent protections and more effective releases from captivity to the wild.”
The increase of 23 wolves reflects scant population growth. Last spring 20 captive-born wolf pups were released into the wild to be raised by unrelated wolves to introduce genes from the more diverse captive population into the wild population. Six of those pups were known to still be alive through the end of the year.
Thirty-four wolves are known to have died in the wild in 2020, and five of those were shot dead by federal snipers in response to predation on cattle. Ten wolves were removed alive from the wild by federal trappers, though two ended up dying. In addition to the losses of those 44 wolves, several other radio-collared wolves disappeared during the year.
The Service is requesting a 14-month extension of its May 17, 2021 deadline to revise its 2015 wolf management rule, which was found to be illegal because the agency ignored scientists’ warnings that losses to the population would result in irreparable harm to the reintroduced wolf population’s genetic health.
The Service acknowledges that wolf releases from captivity and limiting mortality are necessary to increase the Mexican wolf’s genetic diversity. The 27% rate of wolf losses in 2020 exceeds the Service’s intended cap of 25% losses.
Releases from captivity consist solely of transferring newborn pups into the dens of wolves already in the wild. Since this practice began in 2016, 50 captive-born pups have been released and just 11 are known to be alive. Three released pups have matured, bred and raised pups of their own.
Conservationists have called upon the Service to release well-bonded wolf pairs with their dependent pups — family packs — from captivity into the wild. Wolves previously released in this manner survived at higher rates than pups separated from their mothers for release.
Mexican wolves are the southernmost, smallest and most genetically distinct subspecies of gray wolf in North America. A federal wolf trapping and poisoning program on behalf of the livestock industry eliminated Mexican wolves from the U.S. Southwest by the 1930s, and actively prevented natural wolf recovery from Mexico. In 1950, the U.S. Fish and Wildlife Service extended that extermination program to Mexico, in the form of wolf poisons and instruction in their use, exported as foreign aid.
After the 1973 passage of the U.S. Endangered Species Act and the 1976 placement of the Mexican wolf on the endangered species list, five wolves were caught alive in Mexico for emergency captive breeding, and three of them were successfully bred. No other wolves were confirmed alive in the wild after the last was caught in 1980. Descendants of those three were later bred with descendants of three other wolves caught in previous decades in Mexico and one caught in 1959 in Arizona, for a total of seven wolves who contributed to their subspecies survival.
All 186 Mexican wolves in the U.S. Southwest today stem from the genetic equivalents of just two of those seven originators of the captive population. The Mexican wolves in captivity retain the genetic equivalents of three of those seven founding wolves.
Top: Rick LoBello
Bottom and Cover: Gila Wilderness Expedition, Wikimedia Creative Commons