As Mexican wolf populations rise in Arizona, genetic diversity continues to be great challenge

Mar 12, 2024, 4:05 AM | Updated: 9:10 am

Mexican gray wolf...

Mexican gray wolf populations have grown in Arizona, but it's not all good news. (Facebook Photo/Brookfield Zoo Chicago)

(Facebook Photo/Brookfield Zoo Chicago)

PHOENIX — The latest population census for the endangered Mexican gray wolf native to Arizona released last week, and the results indicate an increase in wild individuals for the eighth straight year.

However, conservation and advocacy groups didn’t share an overwhelming optimism for the update, warning a lack of genetic diversity shows there is a long way to go before the species stabilizes in its ancestral habitat.

Jim deVos, the Mexican wolf coordinator for the Arizona Game and Fish Department, told KTAR News 92.3 FM that genetic diversity is the greatest challenge wolf managers are experiencing now.

“In the aggregate, the 2023 data points out that Mexican wolf recovery has come a long way since the first release,” deVos said in a statement. “Each year, the free-roaming Mexican wolf population numbers increase and the areas they occupy expands. Genetic management using pups from captivity is also showing results.”

“I no longer worry that all the wolves could suddenly disappear,” Michael Robinson, a senior conservation advocate at the Center for Biological Diversity, said in a statement. “While that’s clearly a good thing, the government’s genetic mismanagement still threatens to doom this unique, arid-lands subspecies of the gray wolf.”

The Fish and Wildlife Service announced a minimum of 257 wild Mexican wolves across Arizona and New Mexico in 2023, up 6% from 242 the previous year. Arizona homes at least 113 individuals and 23 of the 60 wild packs, according to the survey.

The population recently jumped significantly from 196 in 2021 to 242 in 2022. A USFWS spokesperson told KTAR News years with low mortality and high pup recruitment like 2022 show expanded growth, but the Service is less concerned with annual variation than long-term trends. Climate also plays a role, deVos said, as drier years with less activity from wolf prey impacts the numbers. The logistics of hand counting wolves naturally brings variance, as well.

Mexican wolves are the smallest, most genetically distinct and rarest subspecies of gray wolves, one that has adapted to the arid climate. But their howls disappeared from the wild in the American Southwest due to conflicts with farmers and ranchers.

The species was listed under the Endangered Species Act in 1976, after which a captive breeding program led to the first reintroduction in the United States in 1998. America’s Mexican wolves are descendants of a group of seven.

Breeding captive pups and inserting them into wild packs, a strategy called cross-fostering, has been an integral element of the process.

“It’s encouraging to see success across the board with our recovery efforts,” Brady McGee, the Mexican wolf recovery coordinator for the USFWS, said in a statement. “Having fostered Mexican wolves survive, disperse, pair up, breed, and start packs of their own tells us that fostering is working.”

Adults were released early in the program with much thinner populations, but now carefully-planned pups are relied on for genetic impacts.

Ninety-nine pups have been placed in 40 wild dens since 2016, and FWS said 15 fostered pups survived to breeding age and at least 10 successfully produced litters in the wild. FWS said managers are ahead of schedule as the goal was to have 11 fostered wolves reach breeding age at this point, and deVos said more will get there this spring.

Breeding age is two years old, and most wolves are born in April.

Most population increase comes from the wild populations of wolves that stem from the original seven, although the Center for Biological Diversity says genetic diversity in today’s reintroduced population has dropped to only 2.09 of those seven due to killings, live removals and reintroduction.

Environmental groups continue to promote greater release of captive wolf families, along with expanding habitat and connectivity.

Claire Musser, executive director of the Grand Canyon Wolf Recovery Project, said in a statement there is suitable habitat north of the Interstate 40 in Arizona. Meanwhile, the border wall between the United States and Mexico impacts the ability for wolves to find their southern counterparts, another obstacle in genetic diversity.

“The survival of some cross-fostered pups, including one born at the Wolf Conservation Center in 2023, is a testament to the love and support shown by wolf parents to their families, but cross-foster survival alone won’t fix the genetic crisis,” Regan Downey, director of education at the Wolf Conservation Center said in a statement.

“There are hundreds of lobos in captivity, each waiting for the opportunity to reclaim their ancestral homes. We should aim to solve two problems at once and resume adult and family group releases to improve wild genetic diversity and create space in captive facilities.”

The last adult wolf released was a pregnant female in 2014 that gave birth in the wild.

There remain 350 Mexican wolves in more than 60 facilities in the U.S. and Mexico under the Mexican Wolf Saving Animals From Extinction program, FWS said.

Each summer, conservation plans are discussed at SAFE meetings, finding the best pairs for the following April using the genetic data they’ve attained over the years. Last summer, they came up with eight pairs to naturally breed and four for artificial insemination.

Managers are also looking into options using the “frozen zoo,” frozen gametes and embryos to produce potential offspring.

“There is no silver bullet,” deVos said, noting gene pool improvements have not come in leaps and bounds.

FWS gathers the population data November through February through its Interagency Field Team, which conducts ground and aerial surveys via remote cameras, scat collection and visual observation.

The U.S. Department of Agriculture’s Wildlife Services released a new set of standards to confirm livestock killings by Mexican wolves in Arizona and New Mexico last year after a male named Rusty was killed in New Mexico by authorities for alleged depredation of livestock.

At least 31 wolves died in 2023, according to the Center for Biological Diversity, 11 killed illegally.

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As Mexican wolf populations rise in Arizona, genetic diversity continues to be great challenge