Why 'Success' Of 1 Female Mexican Gray Wolf Creates Problems For The Entire Species

By Carrie Jung
Published: Thursday, May 14, 2015 - 5:05am
Updated: Thursday, May 14, 2015 - 3:37pm
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(Photo by Jim Clark - U.S. Fish and Wildlife Service)
Mexican gray wolf.
(Photo by Carrie Jung - KJZZ)
Keeper Shawna Farrington joins other staff to clean the zoo's Mexican gray wolf habitat.
(Photo by Carrie Jung - KJZZ)
The Phoenix Zoo houses four of the more than 240 of the country's captive Mexican gray wolf population.

The Mexican gray wolf recovery program has been controversial since its inception. And it's not just political opposition causing issues.

A lack of genetic diversity and inbreeding also pose a major threat to the endangered species’ recovery. But a complex captive breeding system and careful genetic planning is showing some promising results.  

The Mexican gray wolf habitat at the Phoenix Zoo is a popular place, especially today because the pack is particularly active. For Logan Peterson, it’s his first time seeing the animal up close.

"I only seen one in movies but never in real life before," he said. 

But this isn’t your average zoo exhibit. These animals are being managed by the U.S. Fish and Wildlife Service for potential release into the wild.

Keeper Shawna Farrington said they can’t train the wolves or introduce any unnatural behaviors, meaning staff mix up their schedules so the animals don’t come to expect them. It makes tasks like exhibit cleaning a tricky prospect. 

"One person leads and one person collects fecal material," she said. "And then the back person follows. The people on the ends of the threesome they actually make sure that the wolves aren’t getting too close so that we're all safe."

The exhibit is a holding facility for four of about 240 Mexican gray wolves living in captivity around the country.

"The entire global population of Mexican gray wolves actually started with only seven wolves," said Maggie Dwire, a biologist with the U.S. Fish and Wildlife Service. "We completely eradicated the Mexican wolf from the wild in the United States. In the late 1970s we captured what may have been the last remaining wild wolves in Mexico."

She said when it comes to restoring a healthy population, working with just seven animals created a genetic bottleneck. But that wasn’t the species only problem.

"We’ve had one particular wolf achieve such success out there that nearly all of the wild population is somehow related to her," Dwire said.

In other words, one female wolf super mom is related to almost all of the roughly 110 animals living in the wild right now. And that’s a problem.

In response, Dwire said the agency launched an experimental and labor-intensive method of genetic rehabilitation.  It starts out with an annual two-day meeting where wildlife managers analyze the results of computer program mapping out the entire population’s pedigree. They’re looking to find a wolf in captivity that will thrive and, more importantly, breed in the wild.

"We’ll look at the current genetic makeup of the wild population and then look for a wolf in captivity that would, if released to the wild, increase gene diversity, reduce inbreeding, reduce the relatedness of the wild population," said Dwire.

Relatedness and inbreeding can lead to low birthweight and increased pup mortality rates — which is why captive wolves who are the least related to that one wolf super mom become candidates to reproduce and get transferred to what’s known as a pre-release facility in Sevietta, N.M. There they get conditioned to living in a wild environment and evaluated for potential release.

"One to two effective migrants per generation would help us keep this population on the right trajectory genetically," said Dwire. "So far we’ve had about a 30 percent success rate, and our most successful type of release has been an adult pair of wolves with offspring."

The U.S. Fish and Wildlife Service and Arizona Game and Fish Department have released about 95 animals to the wild since the program began in 1998. And population numbers are trending up, increasing by almost 30 animals since last year.

But Dwire said while the genetic issues are showing signs of improvement, the species is far from out of the woods in terms of survival, as coexistence with local livestock still remains a hotly debated issue.

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