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Mexican Wolves Outside Historical Range Threatens Recovery

International Study: Perils of Recovering Mexican Wolves Outside Their Historical Range

PHOENIX — The latest international research study on Mexican wolves says that encouraging recovery of the endangered subspecies north of its outlined historical range would be detrimental to preserving the wolf’s unique characteristics.

The leading wildlife science journal Biological Conservation recently highlighted the new research, further rebuking calls for Mexican wolves to be released far outside their historical range, defined as southeastern Arizona, southwestern New Mexico and the Sierra Madre Mountains in Mexico. Doing so would encourage genetic mixing with northwestern wolves originally from Canada, which threatens the genetic uniqueness of the Mexican wolf. Wolf Research

“The latest science clearly shows that Mexican wolf dispersal outside the species’ historical range before it’s recovered will lead to the large wolves of Canadian origin genetically swamping the Mexican wolf,” said AZGFD biologist Jim Heffelfinger, who co-authored the study. “Our obligation is to make recovery decisions based on the latest research, solid science and management experience to preserve this unique wolf subspecies under the Endangered Species Act.”

Gray Wolves southward movement

Sources prior to the mid-1990s defined the core historical range for Mexican wolves as southeastern Arizona, southwestern New Mexico and portions of Mexico. Because data shows that at some point Mexican wolves were on the Mogollon Rim, the recovery boundary now includes a 200-mile expansion from the core historical range to the north into central Arizona and New Mexico.

Historical data shows larger subspecies of wolves roamed northern New Mexico and Arizona along the Utah and Colorado state lines, but each differed from the smaller, distinctive Mexican wolf. Data also illustrates that Mexico is critical for wolf recovery, given that 90 percent of the animal’s historical range and more than 20,000 square miles of high-quality habitat is found south of the border.

Encouraging Mexican wolf recovery north of the current reintroduction area would place Mexican wolves north of where the species historically transitioned into the larger northern wolves.

“Mexican wolves are physically smaller, have smaller pack sizes, less stable packs and higher levels of inbreeding than wolves in the Rocky Mountains,” Heffelfinger said. “Directing wolf recovery north of historical range threatens the genetic integrity and recovery of the subspecies and is unnecessary because large tracts of high quality habitat exist within that range.”

“Hybridizing with wolves originally from Canada not only threatens the unique characteristics for which the Mexican wolf remains listed, but would undo decades of success returning iconic Mexican wolves to the Southwest,” Heffelfinger added.

The Arizona Game and Fish Commission and Department have been at the forefront of Mexican wolf recovery for more than 20 years. The latest wolf survey (2017) documented all-time record numbers of Mexican wolves at 114, packs at 22, potential breeding pairs at 26 and adult wolves in the wild at 88.

The study entitled “Perils of recovering the Mexican wolf outside of its historical range” was authored by experts in their respective fields and included biologists and scientists from AZGFD, Colorado Parks and Wildlife, New Mexico Department of Game and Fish, University of Montana, Universidad Nacional Autónoma de México, Universidad de Guadalajara, Universidad Nacional Autónoma de México and Centro del Cambio Global y la Sustentabilidad en el Sureste.

For more information about Mexican wolf recovery, visit

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