Mexican wolves (Canis lupus baileyi) have persevered against what many might consider overwhelming odds. The 1982 recovery team saw no possibility of complete delisting of the Mexican wolf and instead established a prime objective “to conserve and ensure the survival of Canis lupus baileyi by maintaining a captive breeding population and re-establishing a viable, self-sustaining population of at least 100 Mexican wolves in the middle to high elevations of a 5,000-square-mile area within the Mexican wolf’s historic range.”
Given the small number of wolves and limited genetic diversity, fully recovering the subspecies seemed insurmountable in 1982. The captive breeding stock at the time consisted of ten animals and three founders—called the “certified lineage” captured in Mexico in the late 70s and early 80s. With few options to capture more wolves in Mexico, the prime objective of the 1982 Mexican Wolf Recovery Plan was an ambitious goal. However, genetic results confirmed that two additional lineages—stemming from four additional founders—living in captive facilities were pure Mexican wolves. All three lineages were combined to improve the genetic variability of the subspecies. No additional Mexican wolves were ever captured, and surveys in the mid-90s suggested that Mexican wolves were extinct in the wild in Mexico and the United States.
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Mexican wolves are the southernmost subspecies of gray wolves (historically occupying mountainous areas of central to southern Arizona and New Mexico, western Texas, and Mexico) and their story of persecution mirrors that of many other predators in the United States. Ill-treatment and removal of wolves was a direct reflection of the societal values of the time and the US government led those efforts. The US government exported their control methodology to Mexico. But societal attitudes began to change and with it came the passage of the Endangered Species Act that required restoration of wolves and the end of their persecution in the United States. However, with the exception of the few Mexican wolves in captivity, the stage for extinction seemed already set for the Mexican wolf, as persecution continued in Mexico.
But grim starts met with perseverance can yield extraordinary success. The biggest concern in the 1982 Mexican Wolf Recovery Plan was how to recover a species with only a few remnant wolves in captivity. Mexican wolf recovery could not depend on natural recovery like the Great Lakes population, or reintroduction of wild wolves from other wild populations like Yellowstone and central Idaho. But the challenge was met, and the establishment of a healthy captive population of Mexican wolves was the first success of Mexican wolf recovery. The subspecies persisted due to the Association of Zoos and Aquariums Society’s Species Survival Plan (SSP) for the Mexican wolf. Without the hard work of the SSP, Mexican wolves would have become extinct. The SSP’s success eventually resulted in ample Mexican wolves for the US Fish and Wildlife Service (Service) to consider reintroduction.
After decades of planning and effort, and buoyed by the success of the reintroduction programs in Yellowstone and central Idaho, the Service made plans to reintroduce Mexican wolves into the mountains of central Arizona and New Mexico. Yet, the reintroduction project had numerous obstacles relative to the more celebrated reintroductions of gray wolves in Yellowstone and central Idaho. First and foremost, the wolves had to be released from captivity rather than transplanted from the wild. Captive wolves were conditioned in remote, pre-release facilities and their behavior was evaluated to determine suitable candidates for release. But even the most suitable candidates would prove establishing a wild population from captive stock is not without challenges. Wolves frequently exhibited nuisance behavior for several months following release. Many released wolves died or were removed for behavioral reasons; in fact, only about thirty percent of Mexican wolves from captivity have successfully produced pups in the wild.
Also, the Mexican wolf reintroduction area was not in a large national park or wilderness system, but rather on a multiple-use landscape where wolves would more consistently come in contact with livestock and be exposed to people intent on doing harm to the wolves. Additionally, cattle grazed year-round on federal grazing allotments in the reintroduction area and produced young, vulnerable calves throughout the year, whereas cattle in the northern Rocky Mountains of the United States graze on federal grazing allotments primarily during the summer months and have synchronized calving in the winter on smaller private pastures.
Mexican wolves were required to remain within the 7,000 square mile recovery area and were not allowed to persist in other areas—even if they were not causing management concerns (e.g., depredations), unlike reintroductions in Yellowstone and central Idaho where wolves were allowed to roam over a large tristate area provided they were not causing depredations. Finally, many biologists suggested that Mexican wolves were primarily predators of the diminutive Coues white-tailed deer and because of Mexican wolves relatively small size (fifty-to-eighty pound adults), they were unable to prey upon the primary wild ungulate (elk) that existed in the area. Thus, on March 29, 1998, when Mexican wolves were first released in the wild, the odds were still stacked against them and many predicted reintroduction failure.
The first groups of Mexican wolves released in 1998 were not successful and by the end of the year, only four (from releases in December) remained in the wild. Thus, predictions of failure continued to haunt reintroduction efforts. Release efforts in 1999 were more successful, but the population at the end of the year was still only fifteen animals despite the release of thirty-three Mexican wolves from captivity in 1998 and 1999. By the end of 1999, biologists determined that releases conducted in areas where deer were the primary prey, and year-round cattle grazing occurred were not successful. Thus, releases from 2000 forward occurred in areas where elk were the primary prey available and cattle grazing was absent or seasonal in the summer months. This shift in release areas helped to establish a growing population and a minimum of fifty-five Mexican wolves were documented in the wild at the end of 2003. However, difficulties with human-caused mortality, depredations, and maintaining a population within a relatively small area persisted.
From 2003 to 2009, the reintroduction project conducted fewer releases and adopted a more aggressive management response to depredations (e.g., more removals of wolves). As a result, the population did not grow and the project needed to adjust again. The project shifted management focus towards removing fewer wolves, while applying new management techniques to reduce conflict with livestock. The project focused on diversionary food caches near den and rendezvous sites to prevent depredations during April through September. In addition, the Defenders of Wildlife and the Mexican Wolf Fund increased their funding for range riders and the project focused on other non-lethal techniques (e.g. hazing wolves). Combined, these efforts appeared to keep depredation rates at the same level as the time period when the project was conducting aggressive removal and the population increased from forty-two wolves at the end of 2009 to around 110 wolves at the end of 2014.
Unfortunately, due to ending releases from captivity and the disproportionate reproductive success of some wolves, the wild population did not represent the available genetic diversity from captivity. However, releases from captivity were inordinately controversial and again the project adjusted to potentially accomplish genetic goals with less impact to stakeholders. Cross-fostering (placing young pups less than fourteen days old) produced in captivity into wild dens of similarly aged pups) has been utilized since 2014, with some promising initial results. These pups are raised in the wild by experienced packs and have not displayed the nuisance behavior or vulnerability to human-caused mortality that plagued earlier releases of captive adults.
In addition, three of the eight cross-fostered pups released in 2014 and 2016 have bred and produced pups in the wild. An additional twelve cross-fostered pups were released in 2017 and 2018, yet they are too young to have produced pups at this time. Regardless, the project has resumed releasing animals from captivity because cross-fostering is more socially acceptable. The SSP continues to be an important partner to assist in cross-fostering efforts.
With wolves successfully established on the ground, it was clear that the Service needed policy adjustments. After all, the Mexican wolf population in the United States had reached the extent of the 1982 recovery team’s imagination. A new non-essential experimental rule in 2015 allowed Mexican wolves to occupy areas south of Interstate 40 in New Mexico and Arizona, and an updated 2017 recovery plan established delisting goals for a population in the United States and Mexico. In addition, our colleagues in Mexico have started to establish a population of Mexican wolves. Mexico will face similar and in some cases, more severe challenges during their reintroduction project and doubts will be voiced, but the story of the Mexican wolf is one of overcoming tremendous odds and the ability of biologists and wolves to adapt to challenges.
The dedicated and adaptable staff of Arizona Game and Fish Department, New Mexico Department of Game and Fish, US Department of Agriculture-Animal and Plant Health Inspection Service-Wildlife Services, US Forest Service, US Fish and Wildlife Service, and White Mountain Apache Tribe have been critical to the successful establishment of a population of Mexican wolves in the United States.
John Oakleaf is the featured Timber Wolf Alliance speaker for Wolf Awareness Week at Northland College. He will be part of a panel discussion Thursday, October 24 and will give a keynote address Friday, October 25.