A black-footed ferret dubbed Scarface lives on, siring two kits 20 years after his death.
Researchers of both the human and ferret variety at the Lincoln Park Zoo have been working together for a long time, coming up with clever ways to overcome captive breeding obstacles like inbreeding and reduced fertility. In August the team from the privately owned facility in Chicago made headlines when their captive Black-footed ferret females successfully whelped eight kits, using sperm samples stored at -196ºC for the last 10-20 years.
While many super-cold sperm banks are being built to help secure the genetic future of threatened species, few have actually used the frozen specimens in formal recovery programs. That’s why the news out of Chicago is so exciting. Not only were the sperm samples used seriously old, some also had fairly low counts of spermatozoa swimmers. But despite these facts, the new kits and their offspring are projected to increase gene diversity in the ferret population by 0.2 percent and lower inbreeding-measures by 5.8 percent.
‘Scarface lives on metaphorically through his kits, Dillinger and Capone,’ says Rachel Santymire, the Black-footed ferret reproduction advisor at the Lincoln Park Zoo, ‘but it’s not just ferrets who stand to benefit from this success. Our work can be a model for other species all over the world.’
The Black-footed ferret is one of North America’s most threatened carnivores, reduced to around 500 or so individuals in the wild and roughly 300 in captivity, though once prolific in patches throughout the Canadian, American and Mexican west. Humans dealt the ferrets a pretty rough hand, but not because of a direct dislike for the sleek mammals, but rather a historic hate-on for Prairie dogs—the bulk of the ferret’s diet. Ferrets also rely on the industrious dogs for homes and nesting sites, stealing their burrows.
‘Settlers despised the digging dogs as land users and the US government sponsored an eradication program. By the 1980s about 98 percent of both animals’ habitat was lost,’ says Santymire. ‘Things got even worse in the mid-1980s when a cargo ship carrying rodents with plague-fleas unleashed the bacterial infection into ground squirrels, soon decimating susceptible dogs and ferrets alike.’
Santymire says this final blow triggered a last ditch effort to save the small carnivores by the US Fish and Wildlife Service and others. All remaining ferrets were removed from the wild, but canine distemper and captive life stressors killed all but 18. Out of these founders, only seven proved capable of reproduction. That’s where Scarface, aka stud number 18, comes into play.
Scarface was a tough-guy, a notable scar running along his face likely obtained from a defensive Prairie dog or territorial rifts. He was also a pro at eluding capture efforts—being the last of the population to be caught—and sired plenty of offspring while alive.
‘Early on we realised to keep this species going, we’d need to ensure the persistence of each animal’s individual genes far into the future, ’ says Santymire. ‘Many species will come to rely on humans in the future, but our ferrets show there’s room for genetically healthy and diverse populations even in these circumstances. In other words, there’s still hope for their survival.’