Critically endangered ferrets reproduced using 20-year-old sperm

A near-extinct species has been reinvigorated with fresh genetic material donated by a male that has been dead for 20 years.

Michelle Starr Science editor
Michelle Starr is CNET's science editor, and she hopes to get you as enthralled with the wonders of the universe as she is. When she's not daydreaming about flying through space, she's daydreaming about bats.
Michelle Starr
3 min read

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Black-footed ferrets at the National Black-footed Ferret Conservation Center in Colorado. USFWS

There may be a new hope for endangered species around the world. The critically endangered North American black-footed ferret population has been injected with fresh genetic material, thanks to a sperm donation made over 20 years ago.

A team of conservationists, including researchers from the Smithsonian Conservation Biology Institute, Lincoln Park Zoo, US Fish and Wildlife Service, Louisville Zoological Garden, Cheyenne Mountain Zoo, Phoenix Zoo and Toronto Zoo, used sperm donated in the 1980s by a male ferret nicknamed "Scarface," one of the last living members of his species.

Although Scarface died 20 years ago, his genetic material had been kept in frozen storage against future need. Now, eight baby ferrets have been born -- some of which are Scarface's offspring.

Their research was published last week in the journal Animal Conservation.

The black-footed ferret was discovered in 1851. during the 20th century, its numbers declined. Its primary food source, prairie dogs, was on the decline, and both prairie dog and black-footed ferret populations were hit by sylvatic plague, a flea-transmitted bacterial disease. In 1979, the ferret was declared extinct. In 1984, a small population was found surviving near Meeteetse, Wyoming.

Since that time, a team has been working to revive a population that stems from just 18 founders. This latest effort, however, marks the first time that sperm more than 20 years old has been used to successfully impregnate animals.

"Our study is the first to provide empirical evidence that artificial insemination with long-stored spermatozoa is not only possible but also beneficial to the genetic diversity of an endangered species," said David Wildt, lead author, senior scientist and head of the Center for Species Survival at the Smithsonian. "What we've done here with the black-footed ferret is an excellent example of how sperm preservation can benefit species recovery programs."

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Juvenile black-footed ferrets. USFWS

Over the past several years, the Association of Zoos and Aquariums' Species Survival Plan has been overseeing a black-footed ferret breeding program. At first, only fresh semen was used to artificially inseminate female ferrets that failed to mate naturally. These initial efforts resulted in 135 ferret kits, but greater genetic diversity was needed if the species was to survive.

One of the effects of limited genetic material is sperm deformation and increased difficulty breeding.

Artificially inseminating ferrets isn't easy, though. Black-footed ferret females only ovulate during mating, which means that the team had to develop a hormone treatment that induced ovulation. In 2008, samples that had been frozen for 10 years had been used to introduce fresh genetic material into the breeding population, with pairings for ideal genetic variation selected via genetic analysis.

The successful use of 20-year-old material indicates that such programs could provide hope for the futures of other endangered species. "Our findings show how important it is to bank sperm and other biomaterials from rare and endangered animal species over time," said Paul Marinari, senior curator at the SCBI.

"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."

The breeding population of black-footed ferrets currently consists of around 300 animals.