Scientists help Mexican wolf population rebound
Teams use artificial insemination to save endangered species.
The scene mirCHICAGO — rors one popular in most medical television dramas: A sedated patient lies on a table as practitioners, their hands gloved, bustle about handling tubes and tongs, vials and syringes. Computer monitors, flickering with realtime vital information, hum in the background of beeping machines, walkie-talkie static and urgent voices.
And though the procedure being done this day, artificial insemination, is fairly typical, the patient, Zana, a Mexican wolf living at the Brookfield Zoo, is anything but.
For the first time in the state, scientists from the Chicago Zoological Society and a team assembled by the Reproductive and Behavioral Sciences Department at the St. Louis Zoo used artificial insemination in an effort to improve the genetic diversity of the Mexican wolf population, which has been endangered since 1976. At that time, only seven of these wolves were left in the wild, experts said.
Decades later, and more than 1,000 miles away from the species’ original habitat in the Southwestern U.S. and Mexico, scientists at Brookfield are deploying new reproductive tools and technologies to advance the recovery of the Mexican wolf. Artificial insemination is among the latest of these. Scientists say it holds prom- ise for the Mexican wolf — which now has a population of over 280 in 55 zoos and other institutions and an esti- mated 150 living in the wild — as well as other species at the fringes of extinction.
The recent procedure, which used a frozen semen sample from Redford, a Mexican wolf living in Arizona, is “pretty revolutionary,” said Joan Daniels, curator of mammals at the zoological society, which manages Brookfield.
Frozen samples, col- lected in a medical setting, are easier to transport than actual animals, veterinary and repro ductive physiology experts point out. That was previously the practice for many breeding programs, in which ani- mals were paired with the hope they would produce offspring. That method, both time- and resource-inten- sive, was not always certain to work, either.
“Many (animals) are really fussy,” said Cheryl Asa, a reproductive physiologist and former director of research at the St. Louis Zoo. Some animals rebuff proposed partners, she said, even after a year or two of expert-engineered courtship.
“Using artificial insemina- tion completely gets around that,” Asa said. “It’s so much easier if you can ship a semen sample.”
The decision to use Redford’s sample, collected in 2014 when he lived at Brookfield, was deliberate. The pairing was orches- trated using complex computer software to ward off a “genetic bottleneck,” which happens when there are lim- ited animals for breeding. That situation decreases the genetic diversity of the overall wolf population and weak- ens the species, experts said.
Because many of Brook- field’s wolves are already related, Zana, the pack’s alpha female, and the other two female wolves are kept separately from the seven males during winter, when the females experience their once-yearly ovulation. (Female wolves, like their human counterparts, also have hormonal contracep- tive options that include a pill and an implant, though these can have worrisome side effects, Daniels said.)
The software, which Asa jokingly dubbed “computer dating for wolves,” was developed by a team that included a population geneticist from the Chicago Zoological Society and is used nationally in Mexican wolf recovery efforts in South Salem, N.Y.; St. Louis; Seattle; Minne- apolis; San Francisco; and San Diego.
The zoological society has been a partner in the Mexican Wolf Recovery Program of the U.S. Fish and Wildlife Service since 2003, and has contributed by collaborating on fostering wolf puppies as well as on the release of an adult female to the wild. She subsequently had a litter of pups.
Two fostered pups, who were born in the wild, were raised by Zana and Flint, the alpha male in the pack, with one of their litters. Both Zana and Flint, mates for life, accepted the pair, zoo staff said, treating them like their own offspring. They are great parents, staff members said.
For artificial insemination, scientists typically use fresh semen for the procedure but are moving toward using frozen samples because they are easier to store and transfer. The use of frozen samples in artificial insemination for the species is complicated and still being perfected, experts agree; its success rate will determine its use in future wolf breeding programs.
At Brookfield, Daniels and her team members hope Zana will become pregnant soon. Before long, they expect to see telltale signs indicating a wolf is expecting, including weight gain and a noticeable shedding of hair on the belly, signifying that she will develop mammary glands there. In just over 60 days, if she has conceived, she will give birth to a litter of pups, which are born with no eyesight or hearing.
A one-way mirror separates the Mexican wolf family at the Brookfield Zoo from the many human families visiting the site each day. But guests and their families and their canine counterparts are not that different from each other, zoo staff members said.
“The whole ‘big bad wolf ’ thing is really a fallacy,” said Daniels, fresh from feeding the male wolves some elk.
The blended family of wolves here, she said, are fiercely protective of one another, just like most human families. As a pack, they dine on deer carcasses, their favorite meal. Like children everywhere, the youngest often playfully tussle and tumble together in their more than 2-acre, snow-blanketed home at the zoo, designed to replicate their natural habitat. The male wolves fight sometimes but are not hostile to one another, Daniels said. Even the sibling rivalries, she said, remind her of a big brother picking on a little one.
“It’s got about as much drama as ‘This Is Us,’” said Daniels, referring to the popular television series.