Reports of its extinction have been greatly exaggerated—twice. After close to fifteen years of careful captive breeding and boot camp, the black-footed ferret may be making a comeback. The recent birth of the 100th ferret via a new artificial insemination technique was a small but significant conservation milestone along the road to recovery.
Black-footed ferrets, which were listed as endangered in 1967 and were one of the first mammals listed under the Endangered Species Act of 1973, were already considered extinct by 1979. But in 1981 a ranch dog in northwestern Wyoming killed one that had tried to eat from its bowl. In 1984 a small population was discovered in Meeteetsee, Wyoming, but within a year canine distemper had infected the colony and threatened to wipe out every last ferret. Biologists mounted an emergency effort to rescue the species and snatched 18 of the animals from the jaws of extinction, including the very last known member of the species. All black-footed ferrets bred in captivity in North America are descendents of these 18 animals.
Snatched From the Jaws of Extinction
In 1986 the American Zoo and Aquarium Association established a Species Survival Plan for the ferret that involved captive breeding under strict genetic guidelines. Rules were created to prevent as much inbreeding as possible.
"Tremendous attention was paid to ensure that we were never breeding cousins or brothers and sisters," said Samantha Wisely, a new postdoctoral fellow at the National Zoo in Washington, D.C., who studied the genetics of this captive-bred population. Her study of genetic markers reveals that over the last 15 years "they have done a tremendous job of conserving the genetic diversity of these 18 animals."
"The main reason to use artificial insemination [AI] is to keep genes in the population," said Jo Gayle Howard, an animal reproduction specialist at the Smithsonian National Zoological Park and its Conservation and Research Center (CRC) in Front Royal, Virginia, who pioneered the new technique. From early breeding efforts Howard noticed that more than 50 percent of the males didn't sire offspring. Some males were behaviorally incompatible, some tried to fight and kill the females, and some just didn't know how to breed, said Howard.
"If we let those males who don't breed die without any representation in the population, we're going to lose their genes," said Howard.
Males from breeding programs around the country that are deemed the "most genetically valuable"—those which have not bred and not contributed to the gene pool—are sent to Virginia for AI.
"This is the only endangered species for which assisted breeding has become routine," said Howard. Artificial insemination has been tried in many endangered cats, for instance, but none with the same degree of success. Using AI, Howard gets a 70 percent pregnancy rate—about the same as from natural breeding. "So we couldn't ask for better than that."
Howard's AI technique differs because it employs a surgical approach. She uses a laproscope to guide a needle directly to the duct leading from the ovary to the uterus where the sperm await ovulation.
Ferret Boot Camp
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