Frozen Sperm Is Saving These Ferrets

Paul Marinari, the senior curator of animal operations at the Smithsonian Conservation Biology Institute, holds newborn black-footed ferrets on July 24, 2014. Researchers have used frozen sperm to help this endangered species recover. Evelyn Hockstein/For The Washington Post via Getty Images

"Scarface" must be one potent dude. Twenty years after his death, he became a father. A black-footed ferret, Scarface doesn't have super-sperm, but super-science is certainly on his side.

This endangered species could easily have gone the way of the dodo if it weren't for the planning of scientists and conservationists, who had the forethought to store frozen ferret sperm samples. The black-footed ferret, which once numbered in the tens of thousands in North America, was brought dangerously close to extinction by 1986, when only 18 were left, thanks to battles with canine distemper and sylvatic plague, a bacterial disease.

It's been an uphill climb since then to restore the population, but as of 2013 the species had increased to 300 in captive breeding and 500 in the wild. So, why revert back to frozen sperm when there are a number of healthy, virile ferrets up to the amorous task? The answer lies in genetics.

Although a significant number of healthy kits were born to living ferrets, they all branched out genetically from the same small number of males. Genetic diversity is very important to the long-term health and success of the species recovery effort, because when everyone is descended from the same pool you start to see problems with pregnancy success, the formation of sperm and the ability to fight off diseases — the same basic issues that also discourage humans from mating with their close relatives.

To sidestep this serious issue, scientists at The Smithsonian Conservation Biology Institute (SCBI) defrosted frozen sperm from Scarface, as well as other deceased ferrets. (The results of their work were published in the Aug. 13, 2015, issue of the journal Animal Conservation).

“Early on in the ferret program one of the key components to the overall recovery of the species was to look into these reproductive techniques,” says Paul Marinari, senior curator at SCBI. “[Researchers] had the idea to start capturing as much biomaterial, like blood, hair, semen and ovaries, and put it in the genome research bank. Genetic diversity is the key to long-term survival in a changing world.”

Although the availability of genetically diverse frozen sperm certainly contributed to the comeback of the species, the program's success is due to a complex web of efforts, including the preservation and restoration of their habitat, as well as an increase in the prairie dog population, which makes up 90 percent of the black-footed ferret diet.

“It's great that we can get frozen semen to produce offspring," explains Marinari, "but the real benefit is when those offspring go on to reproduce naturally and pass the genetics on into the population.”

Clearly, the black-footed ferret is just one of many endangered species under guard. Will conservationists be able to use the information from this study to save others, as well?

Marinari says some of the challenge is to empower others to use genome/sperm collections methods, while also understanding why particular habitats and animals are in trouble in the first place. Ideally, researchers can take samples from a diverse selection of animals periodically before they even become endangered.

“Once that genetic diversity is lost it's really tough to recapture,” Marinari says. Tough, but not impossible, as this program shows.


Lady ferrets are “induced ovulators,” meaning that the ovary won't let go of an egg(s) unless mating is actually occurring. SCBI pioneered a minimally invasive (also known as laparoscopic) artificial insemination method, complete with a hormone treatment that incites ovulation.