Black-footed ferret numbers being revived in Canada thanks to sperm freezing program

Dene Moore
National Affairs Contributor
Daily Brew
Black-footed ferret (Ken Ardill/Toronto Zoo)

It has been generations since the black-footed ferret has been seen in Canada.

Cute enough to give pandas a run for their money – only about 50 centimetres long with black bandit masks, round pinkish ears and black boots – they disappeared from Alberta and Saskatchewan in the early 20th century.

Now several breakthroughs are giving biologists hope that the only ferret native to North America could yet make a comeback.

Scientists have successfully used frozen semen from a ferret dead 20 years to artificially inseminate captive ferrets in a North American breeding program.

Eight kits were born, vastly increasing the genetic gene pool of one of the most endangered animals on the continent.

“The wild population was down to 18 individuals. Out of them, only seven individuals actually bred so the whole black-footed ferret population is from seven founders,” says Maria Franke, curator of mammals at the Toronto Zoo, the only Canadian facility that is part of the captive breeding program trying to bring black-footed ferrets back from the brink.

“The fact that we can go back, the Smithsonian can go back, and thaw frozen semen from animals that were collected originally back in the 80s, those kits become really genetically valuable founders in today’s population.”

Black-footed ferrets, whose original range stretched from Mexico to the Canadian Prairies, were actually believed completely extirpated from the continent until a small pack was discovered in Wyoming in the 1980s, according to Parks Canada.

Eighteen ferrets from that wild population were brought into a captive breeding program run by the U.S. Fish and Wildlife Service.

There are six facilities involved with the wildlife service: the Toronto Zoo, Lincoln Park Zoo, the Smithsonian Conservation Biology Institute, Louisville Zoological Garden, Cheyenne Mountain Zoo and Phoenix Zoo.

Because of the small number of ferrets, the program scientists have long known that genetic diversity posed a problem. Over time, a shallow gene pool can lead to increased sperm malformation and lower success of pregnancy.

While captive breeding initially concentrated on live males and females, Franke says captive breeding programs like Toronto Zoo’s anticipated that would have to change.

“We do attempt to collect semen from out males every year which then can be banked and preserved,” she says.

While Toronto does natural breeding, other facilities have been working on assisted reproductive technology for the ferrets.

The latest breakthrough was published last month in the scientific journal Animal Conservation.

“Our findings show how important it is to bank sperm and other biomaterials from rare and endangered animal species over time,“ Paul Marinari, senior curator at the Smithsonian Conservation Biology Institute, says in a news release from Lincoln Park Zoo. "These ‘snapshots’ of biodiversity could be invaluable to future animal conservation efforts, which is why we must make every effort to collect, store and study these materials now.”

There are approximately 300 animals in the captive breeding program. Toronto Zoo has 16-17 animals per breeding season at its quarantined facility, which is not viewable to the public.

Since it began in the mid-1980s, more than 7,000 kits have been born under the species survival plan and most of them released into the wild at 17 sites throughout North America. The Toronto Zoo has produced more than 500 kits.

In 2009, several dozen ferrets were released into Grasslands National Park in southern Saskatchewan.

For a few years, they did well. Monitoring by Parks Canada and the Toronto Zoo found them reproducing.

“That was very exciting, the first Canadian-born ferrets in 70 years on Canadian soil,” says Franke.

But the challenges are great.

Black-footed ferrets and their primary food source – prairie dogs – are susceptible to sylvatic plague, a bacterial disease that can wipe out an entire colony of prairie dogs. While the ferrets are immunized before their release into the wild, too often their food source disappears with an outbreak of the disease in their local prairie dog towns.

“Unfortunately it raised its ugly head in Grassland the second year after the release,” says Franke. “That’s had a huge impact on our recovery goals in Canada.”

The release program was suspended in Canada. Monitoring in Grasslands National Park last month by Parks Canada and the Toronto Zoo found no ferrets, though they did find a lot of pregnant prairie dogs, Franke says.

Conservationists are in the midst of an oral bait vaccine program for wild prairie dogs in the U.S. If it proves successful, it will be tried in Canada and, if successful here, ferret releases may resume north of the border.

Though small, black-footed ferrets are a key predator in the grassland ecosystem.

“They’re definitely required for the whole web,” Franke says. “And they’re ridiculously cute. That doesn’t hurt.”