PHOENIX — Scientists involved in Mexican wolf recovery say environmental groups distributing old and faulty data that calls for the release of captive adult wolves are not helping the recovery of the endangered subspecies. Biologists at the Arizona Game and Fish Department (AZGFD) say maintaining a savvy wild-born population and limiting introductions of naïve captive-raised adult animals have been the keys to the ongoing success of the recovery program.
“This period of strong population growth has happened with almost the entire population being wild- born wolves,” said Jim Heffelfinger, a University of Arizona research scientist, AZGFD wildlife science coordinator and co-author of multiple peer-reviewed scientific studies on wolf recovery. “We’ve also learned that releasing captive singles and pairs that have spent their lives in a zoo setting has been ineffective in enhancing genetic diversity. The sobering truth is that in the last decade, no captive-raised adult wolf released in the wild has subsequently raised pups in the wild to contribute to the gene pool.”
The Center for Biological Diversity (CBD) and other environmental fundraising organizations have been pushing a narrative that captive-raised adult wolves should be released into the wild. A July 12 news release from the groups called for the release of three packs of zoo-raised wolves. The piece also misstated the number of wolves already released and omitted an entire year of successful cross-fostering data from their analysis.
Contrary to the incorrect information issued by these organizations, AZGFD and its conservation partners have released 20 wolves from captivity since 2014 through “cross-fostering,” or selectively placing genetically valuable pups from captivity into wild packs to be raised by wild parents and with wild siblings. The latest wolf survey (2017) documented an all-time record number of 114 Mexican wolves in 22 packs, with 26 potential breeding pairs and 88 adult wolves in the wild population.
Of a potential eight cross-fostered wolves that are now of breeding age, three have bred and two have already produced offspring (four pups), meaning about 37.5 percent of cross-fostered pups are contributing valuable genetics to the wild population. Of the 12 pups cross-fostered between 2014 and 2017, five were found to have survived to the end of the year, a much higher survival rate than the groups assert. In contrast, only one of the last nine adult captive wolves released into the wild produced pups that survived more than one year, and only because the pups were cross-fostered into a wild pack.
Despite the CBD’s assertion that releasing packs of naïve captive-raised wolves is “badly needed to improve numbers and enhance genetic diversity,” an honest look at the data clearly shows that the recovering Mexican wolf population can grow in numbers without additional releases of adult wolves. Only five adult captive-raised wolves have been released since 2007, yet the wild Mexican wolf population has increased from 42 in 2009 to 114 in 2017 (171 percent).
According to Jim deVos, assistant director for AZGFD’s Wildlife Management Division, cross-fostering bolsters genetic diversity in the wild population while protecting genetically valuable adults in captivity.
“It’s important to review Mexican wolf recovery based on data and not misleading and disingenuous statements that hide the real success of this recovery program,” said deVos. “The population is growing very well without releasing more zoo animals into the woods to fend for themselves. It is counter- productive to use purposely misleading and erroneous statements to oppose these successes and the hard working people bringing the Mexican wolf back to the Southwestern landscape.”