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U.S. Fish And Wildlife Swaps Mexican Grey Wolf Pups In Recovery Effort

The U.S. Fish and Wildlife Service is moving forward with efforts to recover the Mexican Grey wolf. While it's not clear yet if and when captive bred adult wolves will be released into the wild, two captive born pups were successfully exchanged with two pups from a wild den to foster genetic diversity for the species.

Sherry Barrett is the U.S. Fish and Wildlife Service’s Mexican Wolf Coordinator. KUNM’s Anna Lande asked her why a wild wolf doesn’t reject captive born pups. 

Credit Mexican Wolf Interagency Field Team

KUNM: Recently, two captive-born Mexican Grey wolf pups were cross-fostered into wild den in New Mexico to promote genetic diversity in wild wolf packs. How come their new mother doesn’t reject them?

Barrett: First we take the pups out of the den, and we mix them up with the new pups basically. We have them urinate on each other. We pull some litter and debris out of the den itself, and then rub that on all the pups. If the pups we are bringing in had some type of formula, we also put some of that formula on the mouths of the receiving litter as well.

Credit Mexican Wolf Interagency Field Team

We want to make sure they all smell the same. The wolves can’t count so they don’t really know there’s a new pup in there.

KUNM: Tell us more about these little pups, what do lobo pups look like, how old are they?

Barrett: When we cross-foster pups they are less than 14 days old. And we try to get the litters to be almost exact. So, they are about a pound, about the size of your hand. They’re deaf and they’re blind, so they are just really dependent on their mothers at that point of time.

KUNM: So, the permit requires a one-pup in, one-pup out policy. What happens to the wild pups that are now in captivity?

Barrett: So they are now with that original mother from the captive program. She’s accepted those pups, as well, into her pack. The captive population and wild population have been divergent for a while. So there is some value to some of these pups going back into the captive population. As well, we are trying to increase the younger animals that are in the captive population. So, demographically this has also been beneficial.

KUNM: What kinds of problems come from lack of genetic diversity?

Barrett: So, usually translates to a reduction in litter size or reproduction. We’re actually not seeing that in the wild right now. Although we are seeing some level of breeding depression in the captive population, with regard to mobility of sperm and the size of the litters.

So, we only started with seven animals, because of that small number of animals we have the potential to have inbreeding depression. In the captive population, we are able to determine which animals breed. We have a computer program that helps us determine which are the best ones for different pairings. But, in the wild population we don’t control that breeding to that extent. What we need to do is to reduce any relatedness in the population as much as we can by releasing those wolves from captivity. 

Credit Mexican Wolf Interagency Field Team

Back in 1982, when we wrote the first Mexican wolf recovery plan, there weren’t any Mexican wolves left in the wild in the United States and Mexico. That recovery team did not provide any criteria that are necessary for delisting the Mexican wolf, because they weren’t sure it was even going to work. What they said is to maintain a population in captivity of at least 250 animals. And try to get at least 100 wolves back out to the wild.

That whole recovery plan back in 1982 was really a hedge against extinction. Now, we are in the process of revising the recovery plan. We’ll have a draft this summer for public review, comment and peer review. Then a final in November of this year, as well.

KUNM: Do you know what’s the number of wolves that are needed to reach a sustainable population in which the US Fish and Wildlife does not have to intervene to keep the population genetically diverse or otherwise healthy?

Barrett: That is the number that we will be providing in that draft recovery plan this summer, and any other criteria that is necessary for us to take it off the endangered species list.

Credit Mexican Wolf Interagency Field Team
Mexican Wolf Interagency Field Team

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