A Mexican wolf pup born this spring at Brookfield Zoo and released into the wild as part of a species recovery program was tracked down in New Mexico and is healthy, the zoo announced this week.
In April, a wolf named Zana gave birth to a litter of five pups at the zoo. Days later, two of the pups – Connie and Dennis – were transferred to the den of the San Mateo wolf pack in New Mexico.
Their move was proposed by the U.S. Fish & Wildlife Service as part of a cross-fostering initiative, where young pups are transferred from their litter in captivity to another litter of similar age in the wild. The program aims to diversify the genetics of the species, which is the most endangered subspecies of wolf in the world.
Shortly after the cross-fostering effort began in 2015, a Mexican wolf born at Brookfield Zoo and released into the wild was found dead in western New Mexico. USFWS conducted an investigation but was unable to determine the exact cause of death, spokesperson John Bradley said.
The cross-fostering program has, however, had more positive outcomes.
“We’ve had a couple definite successes where we’ve had a pup be found and then actually meet up with a female and start breeding,” Bradley said. “That is the real key to success, that they grow up to an age where they can breed and they breed with someone not in their immediately family.”
Last month, USFWS biologists located Connie in New Mexico and fitted her with a GPS radio collar before releasing her back into the wild to join her pack. Like all newborn wolf pups, Connie was too small to be equipped with the collar when she was released from the zoo shortly after birth.
Dennis, Connie’s brother, has not yet been located, but the biologists are hopeful that they will be able to locate and collar him during an upcoming annual census.
“The genetics of this particular animal – the Mexican gray wolf – is very narrow,” said Joan Daniels, curator of mammals at Brookfield Zoo, which participates in the recovery program. “So there’s not a lot of genetic diversity in the population. [Cross-fostering] is used to increase the number of pups in a litter or change out the genetics between two different litters.”
Mexican wolves were once common in the Southwest but were wiped out in the mid-1970s, with only a few of the animals remaining in Mexico. Starting in 1998, 11 Mexican wolves were reintroduced to the wild in Arizona after being bred in captivity.
Although their numbers have grown, there are still only about 300 Mexican wolves in captivity, and another 97 in the wild, according to the nonprofit Defenders of Wildlife.
In return for releasing Connie and Dennis, Brookfield Zoo received sibling pups Mateo and Springer from the wild. The zoo says they are thriving in their pack.
“I find them absolutely fascinating,” Daniels said of the wolves. “They are incredible parents, and the ability to see them here at the zoo has been wonderful because we get to experience them rearing their babies and watching them very tenderly take care of the puppies. They’re very protective of them.”
For several days after birth, Mexican wolf pups cannot hear, and their eyes remain closed, Daniels said. In the cross-fostering program, the wolf pups must be transferred to their new pack relatively soon after birth – before they have become too attached to their mothers.
“We let the mom bond and nurse with the puppies for a few days, and then we coordinate the cross-fostering within 10 days of birth,” Daniels said. “If you wait too long, their eyes open and it’s not as successful.”