The black-footed ferret, a critically endangered species native to North America, is the latest animal to benefit. The critters used to be quite numerous, but their population plummeted due to habitat destruction and food scarcity. In a study published Thursday in the journal Animal Conservation, researchers working as part of a U.S. Fish and Wildlife Service recovery program report successfully using sperm frozen as much as 20 years before to increase the genetic diversity of the small population.
It's not an easy process: Even inseminating a female black-footed ferret with fresh samples is an uphill battle. Because the species only ovulates when the physical act of mating triggers the process, scientists had to develop a hormonal treatment that would jumpstart the release of an egg. Once that was perfected (and resulted in over 100 live births, using recently harvested sperm) they moved on to using samples frozen 10 and 20 years prior.