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Record number of wolf pups fostered into wild dens in the Southwest

Technique used to increase genetic diversity
Genevieve Fuller, a Mexican wolf biologist with Arizona Game and Fish Department, holds a wolf pup to be cross-fostered into a wild wolf den.

FARMINGTON – A record number of endangered Mexican wolf pups has been fostered into wild wolf dens in western New Mexico and eastern Arizona, state agencies announced.

Twenty wolf pups were cross-fostered into wild wolf packs during six weeks in April and May – 12 pups into four packs in Arizona and eight pups into three packs in western New Mexico. It was the first time the New Mexico Department of Game and Fish participated in the cross-fostering program since it rejoined protection efforts with the Mexican Wolf Recovery Program last year.

Cross-fostering helps increase the genetic diversity by placing captive-bred pups less than 14 days old into wild dens with pups of a similar age to be raised as wild wolves, according to the Arizona Game and Fish Department. Ensuring a diverse gene pool and managing the genetics of the animals is considered one of the biggest challenges facing the Mexican wolf conservation efforts.

The Mexican Wolf Interagency Field Team – a coalition tasked with the animal’s recovery efforts – says the cross-fostered pups have about the same 50% survival rate as wild-born pups in their first year. Long-term survival rates using the fostering method are also generally higher than other wolf release methods.

“The cooperation between the two state wildlife agencies was key given the challenges faced with the current pandemic,” said Stewart Liley, chief of the wildlife division for the New Mexico Department of Game and Fish. “Working together allowed a very successful cross-fostering season and keeping pace with improved genetics in the wild.”

Although this is the first year the state of New Mexico has participated, the fostering project has been ongoing since the first two pups were fostered in 2014. The interagency field team estimates at least 10 survive each year, but because it doesn’t tag every pup, it’s likely there could be even more cross-fostered wolves in the wild. Last year, 12 wolf pups were transferred to wild dens.

This year’s wolf pups came from a Missouri wolf center, a county zoo in Kansas, a New Mexico wildlife refuge, a wolf center in California and an Arizona zoo.

“Managing genetics is one of the biggest challenges facing Mexican wolf conservation, even as constant progress is being made on numeric recovery,” Jim deVos, assistant director for wildlife management for Arizona Game and Fish, said in a statement.

The Mexican wolves in the wild descend primarily from seven wolves caught and placed in a captive breeding program from 1961 to 1980 to save the species on the brink of extinction.

But activists still worry the wolf population, even with cross-fostering, is becoming less genetically diverse and is susceptible to inbreeding.

The Center for Biological Diversity – an advocate for the Mexican wolf recovery – won a lawsuit against the U.S. Fish and Wildlife in 2018. The U.S. District Court of Tucson found the federal agency failed to use the best available science to manage the wolf population. The agency has until May 2021 to revise its wolf management rule.

Last year, the Center for Biological Diversity and other environmental groups also wrote a letter to the secretary of the Interior Department asking him to encourage the release of entire wolf families to increase the genetic diversity of the animal.

The 2019 census showed at least 163 wild Mexican wolves – 87 in New Mexico and 76 in Arizona – an increase from the estimated 131 wolves in 2018.


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