The conservation efforts to protect and reintroduce the Mexican grey wolf in its native habitat are paying off. As part of the Mexican Grey Wolf Recovery Programme an adult female wolf from Brookfield Zoo, which is managed by the Chicago Zoological Society was released to the wild in 2015 and gave birth to a litter of six puppies. Additionally, two wolf puppies born at Brookfield Zoo were placed in a wild pack, while now – in 2017 – a further cross-fostering endeavour among the wolf population appear to be successful.
Since 2003, the Chicago Zoological Society (CZS), which manages Brookfield Zoo, has been a partner in the U.S. Fish and Wildlife Service’s (USFWS) Mexican Wolf Recovery Programme. As part of this effort, adult wolves and their offspring at Brookfield Zoo are potential candidates for release to the wild. When the Zoo’s female wolf Zana gave birth to a litter of five pups on 22 April, USFWS officials recommended that two pups from Brookfield Zoo’s litter and two wild-born puppies be . In this particular case, the objective was to place two pups from Brookfield Zoo’s litter with a wild pack and place two wild-born puppies in the zoo’s pack.
Approximately 4,000 Mexican wolves (Canis lupus baileyi) once roamed throughout vast portions of their historic range in Arizona, New Mexico, Texas, and Mexico. But, as human settlement intensified across the Southwest in the early 1900s, wolves increasingly came into conflict with livestock operations and other human activities. Private, state, and federal extermination campaigns were waged against the wolf until, by the 1970's, the Mexican wolf had been all but eliminated from the United States and Mexico.
Sherry Barrett, USFWS’s Mexican wolf recovery coordinator
On 3 May, following a neonatal examination at the zoo, CZS animal care staff travelled with a male and a female pup from Brookfield Zoo to New Mexico, where they met a team of biologists from the Mexican Wolf Interagency Field Team. The pups were successfully placed in the den of the San Mateo wild wolf pack, where the alpha female had recently given birth to her own litter of six males and two females – one of the largest documented litters in the wild. At the same time, the CZS team received a male and a female puppy from the San Mateo pack for care and transfer to the zoo. CZS staff returned to Illinois and successfully placed the wild-born puppies in the den at Brookfield Zoo where Zana has been observed caring for the litter.
Wolf pack social structure
Since the five pups, including the two born to the San Mateo wild wolf pack in New Mexico, emerged from the den in the Zoo’s enclosure on 16 May, visitors have an incredible opportunity to witness the complex social structure of the wolf pack. A wolf pack usually consists of an alpha male and female (the breeding pair), yearlings from the previous year’s litter, and new pups. This is precisely the structure of the 10-member pack at Brookfield Zoo: 5-year-old Zana and her 7-year-old mate Flint, three of their offspring born in 2016, and the puppies. The species has bonding and caregiving behaviours in a social structure that is second only to those of humans and primates in complexity. Pack members use an array of vocalizations to communicate, including howls, yips, squeals, growls, and barks. Guests visiting the zoo may witness pack members displaying a variety of facial expressions and body postures that also play an important role in communication. These displays may signify dominance or submission, play, and greeting ceremonies with lots of licking. Additionally, once the pups are weaned between six and eight weeks, they will whine, nudge, nibble, or lick the face and corners of an adult’s mouth to encourage it to regurgitate food for them. Remarkably, the pups born last year will assist their parents in rearing the new pups by regurgitating food for them and engaging them in play, among other behaviours. In addition, the yearlings will learn important parental skills from Zana and Flint for when they have their own litters.
Bill Zeigler, senior vice president of animal programmes for the Chicago Zoological Society
This cross-fostering endeavour is not the first time CZS has contributed to the programme. In 2016, two wolf puppies born at the zoo were placed in a wild pack. Additionally, in 2015, an adult female from Brookfield Zoo was released to the wild and gave birth to a litter of six puppies. Sadly, she was found deceased in January 2015, but her legacy lives on with her pups. Wildlife biologists havein Arizona (another release site) of wolves originating or associated with Brookfield Zoo.
The recent cross-fostering is considered a success. Zana, the alpha female at Brookfield Zoo, has been seen caring for the litter, and although USFWS biologists do not have full visual access to the San Mateo litter, they report the adult pair has continued to stay in the area of the wild den site likely caring for the puppies.
Fortunately, not only cross-fostering successes from the Brookfield Zoo pack are reported. In May, two Mexican wolf pups born at the Endangered Wolf Center in Missouri (EWC) were placed in the den of the Panther Creek Pack in Arizona, which was documented with five pups. The two additional pups from the EWC increased the total litter size to seven. The Panther Creek Pack was recently confirmed as having a minimum of 6 pups.
In addition to cross-fostering more success of the Mexican wolf recovery efforts has recently been reported with the world’s first Mexican wolf pup born from artificially inseminated frozen/thawed semen at the EWC. The sperm used was collected in January 2015 from a male Mexican wolf at the EWC and stored at the Saint Louis Zoo’s cryopreservation gene bank – one of the world’s largest gene banks established specifically for the long-term conservation of an endangered species.
(Source: Chicago Zoological Society press release, 09.05.2017; Chicago Zoological Society press release, 16.05.2017; CZS - Center for the Science of Animal Care and Welfare – blog, May 2017; U.S. Fish and Wildlife Service press release, 24.10.2016; Endangered Wolf Center news blog, April 2017)