Mexican Gray Wolf pups born at Brookfield Zoo

BROOKFIELD, Ill. (WLS) -- The call of the wild echoes at Brookfield Zoo, several times over.

A brand new litter of Mexican Gray Wolf pups have emerged from the den at the Regenstein Wolf Woods habitat.

PHOTOS: Mexican Gray Wolf Pups born at Brookfield Zoo

"It's very special. It's the first time we've ever had them here. They're endangered ... They're native to Mexico and Arizona and the state of New Mexico," Amy Roberts, Brookfield Zoo curator of mammals, said.

The keepers still aren't sure if there are four or five pups and they don't know the sexes of the pups yet. They do know Zana, 3, is good mom and Flint, 5, seems to be a good dad. But even though the pups are venturing out now, they still love their den.

"They're still only 30 days [old], so right now they're still spending the majority of the time in the den. So right now it's sort of hit or miss if you see them but every day they're spending more and more time outside," Roberts said.

For the past several years, the U.S. Fish and Wildlife Service has been introducing zoo-born Gray Mexican Wolves back into the wild. Puppies like these have to be raised with as little human contact as possible. Once they're bigger, they could stay at Brookfield Zoo or be introduced in the wild.

"We put a lot of effort into trying to keep these guys as wild as possible. We never go in and put their food in front of the, so they don't associate their keepers with their food," Roberts said.

The pups are fed only what they might hunt in the wild- rabbit, deer and elk.

Several litters of Gray Mexican Wolves have been born in their natural habitat through the program.