The species was thought to be extinct in the wild until 1981, when a ranch dog named Shep dropped a dead black-footed ferret on a porch near Meeteetse, Wyo. The rancher’s wife took the dead ferret to a local taxidermist, who realized he was holding a freshly killed extinct species, and alerted the Wyoming Game and Fish Department.
The newly discovered population flourished for a few years but was nearly extinguished by canine distemper and sylvatic plague, a disease from the same bacterium that causes bubonic plague in humans. The Fish and Wildlife Service captured the remaining 18 ferrets, but only seven passed on their genes, leaving behind a population with limited genetic diversity that is vulnerable to pathogens or health disorders caused by inbreeding. All black-footed ferrets alive today are essentially half-siblings — except for Elizabeth Ann.
The path toward cloning a black-footed ferret began in the 1980s, at a conservation biology conference. Dr. Ryder, the geneticist at the San Diego Zoo, happened to sit at a banquet table with Tom Thorne, who worked at the Wyoming Game and Fish Department. Seizing the moment, Dr. Ryder asked Dr. Thorne if he would consider sending skin biopsies from black-footed ferrets to the Frozen Zoo, a growing collection of cryopreserved samples of animal tissue. “I told him we didn’t know what they might be able to be used for,” Dr. Ryder said. “I don’t recall a resounding yes.”
On October 23, 1985, Dr. Ryder unexpectedly received a box from Wyoming. “Well, hot dog, we have black-footed ferret individuals,” he recalled saying.
Dr. Ryder’s lab received more samples in 1988, one belonging to a ferret named Willa who was caught in the wild. Willa had offspring but they had died; by black-footed ferret standards, she was brimming with potential genetic diversity. The Frozen Zoo established a cell culture from Willa and stored it in their enormous freezer, which cradles the cells of 1,100 different species of animals including an extinct Hawaiian honeycreeper and the highly endangered vaquita, a porpoise species, at minus 320 degrees Fahrenheit.