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AZ: 20 Mexican gray wolf pups are released into the wild, aiding the species’ recovery effort

Erin Stone, Arizona Republic

The Mexican gray wolf recovery effort got a new genetic boost with the release of 20 wolf pups into litters of wild wolf packs.

Over a six-week period in April and May, 12 tiny pups from captive facilities across the U.S. were fostered into four different dens in eastern Arizona and eight were fostered into three dens in western New Mexico.

With only 163 Mexican gray wolves in the wild, that’s potentially good news for the endangered predator. Lack of genetic diversity leads to deformities, worsens reproductive success and generally hurts survival.

“The real key to recovery is managing genetics,” said Jim deVos, assistant director for wildlife management at the Arizona Game and Fish Department. “Numerically, there’s a lot of excitement. We added 20 hand-selected pups into this population. That’s a huge infusion of genetic material. And it’s more important when the population is smaller than it ultimately will be.”

Since the cross-fostering program was established in 2014, the state agency and the U.S. Fish and Wildlife Service, which are responsible for the recovery of the wolf in Arizona and New Mexico, had released at most 12 pups at a time. The release of 20 is the most yet.

The recovery effort involves a collaboration between Mexico and the states of Arizona and New Mexico and the White Mountain Apache Tribe. With the release happening at the height of the COVID-19 shutdown, officials said bringing 20 pups to their new homes in the wild was even more of an accomplishment.

The captive-born pups are flown in from all over the country: Missouri, Kansas, California, New York, with some bred in Arizona and New Mexico. The agencies raced to adjust their protocol to adhere to safety standards and the New Mexico governor’s directive that anyone flying into the state must quarantine for 14 days.

To stay safe, the pilots never left the planes, and biologists handed pups over one at a time, decked out in appropriate personal protective gear.

“We got it done in a really tough time,” deVos said. “We only have a very small window to get all of this done.”

Wolves start giving birth to pups in late April and early May. Wolf pups grow quickly once they hit two weeks, which gives wildlife biologists a narrow window to introduce the pups to wild mothers.

When biologists bring the pups to the wild den, they rub them in the feces and urine of their new adopted brothers and sisters, so they all smell the same. Mother wolves don’t notice if the litter has expanded from five to eight as long as they all smell like her offspring.Newborn Mexican gray wolf pups await release into a "foster den" of a wild wolf mother in wolf recovery habitat.

Newborn Mexican gray wolf pups await release into a “foster den” of a wild wolf mother in wolf recovery habitat. (Photo: Courtesy of Interagency Field Team)

Still, the pups have to be almost the same age, a logistical challenge for researchers as they identify wild packs that are both a fit for the captive pups’ genetics and are the same age.

“While mom can’t count, she can tell a giant one from a little one,” deVos said. “The rule of thumb is that the pups can be no more than 14 days old, so both the wild and captive litters have to be born very close in time to each other so we don’t see this giant size differential. Things change pretty quickly at about 14 days.”

This strategy has been successful so far, with survival rates as high or higher than for the wild pups that are naturally born, deVos said. Of the 90 pups born and released in 2019, at least 52 survived their first year — a 58% survival rate, higher than the average pup survival rate of 50%.

A wild mother has never rejected a captive-bred pup since the program in 2014.Get the Law & Order newsletter in your inbox.

Still an uphill battle

Thousands of Mexican gray wolves once roamed the Southwest. When European settlers arrived and increasingly hunted the wolves’ native prey, deer and elk, wolves turned to livestock for sustenance, putting them in the way of settlers’ bullets too.

Between 1915 and 1925, under pressure from the livestock industry, the U.S. Biological Survey, which would later become the U.S. Fish and Wildlife Service, exterminated hundreds of wolves in Arizona and New Mexico. By 1970, Mexican gray wolves faced extinction due to hunting and habitat loss.

But in 1973, Congress passed the Endangered Species Act, which was signed into law by President Richard Nixon. In 1976, the Mexican wolf was listed as endangered and the the U.S. Fish and Wildlife Service was tasked with returning the predator to its historic range in the Southwest.

From just seven survivors, Mexican wolves have clawed their way back to a population of 163 in the wild today. 

Though the population has increased an average of about 15% for the past 10 years, the Mexican gray wolf remains the most endangered subspecies of gray wolf in the world.

The U.S. Fish and Wildlife Service’s 2017 recovery plan aims to take the wolf off the endangered species list by getting the population to an average of 320 wolves over an 8-year period.

Their return will drastically help the ecosystem as a whole, scientists say.

“They’re a top predator so there’s going to be a chain reaction in the ecosystem where they’re going to control, for instance, the elk population from exploding, they’re going to control the coyote population from exploding,” said Heather Vetter, carnivore senior keeper at the Phoenix Zoo, which houses a pack of ten Mexican gray wolves, including a new litter of pups.0:000:44AD

Mexican gray wolves housed at the Phoenix Zoo on May 10, 2020. Arizona Republic

“And that’s just going to trickle down and benefit the whole ecosystem to the point that even things like your Aspen trees and your willow trees are going to be more lush and abundant because they’re not being overgrazed by the elk, which are overpopulated.”

On a recent morning, the Phoenix Zoo pack played together, a way for yearlings to practice hunting. The alpha female stayed close to her den, which has two pups that were born at the beginning of May. Two of their siblings were relocated this year by state and federal wildlife agencies and their partners to a den in New Mexico.

While the Fish and Wildlife Service could decide to release the wolves at the zoo at any time, it likely won’t happen because of pushback from ranchers and rural communities within the bounds of wolf territory.

For Vetter, the exhibit is a way for people to appreciate the predators, which still have stigma in the American imagination.

“I think it’s absolutely amazing that I can come up here every day and actually view a pack of wolves,” Vetter said. “In the wild, you are lucky to see a wolf. They’re going to stay away from you. You’re lucky if you hear a wolf howl, much less see one.”

Efforts help, but challenges remain

If all 20 of the recently-released pups survive, the population will be at more than 50% of the target goal in the U.S.

Still, there are challenges. Some environmentalists say the agencies are not doing enough to aid wolf recovery.

Furthermore, as more wolves have been released into the wild, there has been an increase in livestock deaths, deVos said. Though the people who live in the same areas as wolves are generally accepting of wolf pups being released, it’s been more difficult to get the public on board with releasing adults.

“Trying to develop management concepts for livestock that reduce depredation — that’s our biggest challenge that we have now with wolf recovery in the United States,” deVos said.

The pups are usually more successful than adults released into the wild, because most adult captive-bred wolves become somewhat habituated to humans no matter the steps taken by the facilities to avoid that.A biologist with Arizona Game and Fish Department holds a Mexican gray wolf pup before placing it in its new den in the wild.

A biologist with Arizona Game and Fish Department holds a Mexican gray wolf pup before placing it in its new den in the wild. (Photo: Courtesy of Arizona Game and Fish Department)

For those who support wolf recovery, now is a moment to take pause and celebrate, deVos said.

“There are a lot of divergent views about the wolf program,” deVos said. “The re-introduction of a top predator is a hard job. There are so many different opinions. But we seldom, as a conservation community, really sit back and say, wow, 163 wolves. In 1997, there was not a single one in the wild. The job’s not done. But we’ve made a lot of progress.” 

Erin Stone covers the environment for The Arizona Republic and Send her story tips and ideas at and follow her on Twitter @Erstone7.

Environmental coverage on and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at and @azcenvironment on Facebook, Twitter and Instagram.