Captivity chosen to save the ferret.

Captivity chosen to save the ferret

A few months ago it was the condor (SN:6/21/86, p.389). Now it's the black-footed ferret. Last week wildlife officials decided to bring the last surviving wild members of this severely endangered breed into a captive-breeding program. Biologists fear its numbers have dwindled so dramatically over the past two years that leaving this ferret in the wild would be tantamount to prescribing its extinction.

A new census indicates there may be only 21 of these ferrets left. This

includes six captured last year as the core of the Wyoming Game and Fish Department's new captive-breeding program. By the end of this week, the Wyoming agency hopes to have most if not all of the remaining wild black-footed ferrets in captivity and undergoing a quarantine, according to Harold Harju in Cheyenne, project leader of Wyoming Game and Fish's ferret program.

Just two years ago wildlife biologists were congratulating themselves on the apparent comeback of this species. Feared extinct for many years, the animal was sighted in 1981. By 1984, at least 128 of them had been spotted roaming freely in prairie dog towns outside Meeteetse, Wyo. But then nature dealt North America's only native ferret species a double whammy--back-to-back epidemics that killed off first the ferret's principal prey and then the ferret itself.

The ferret's most recent decline started when a bout of sylvatic plague, the disease that in humans causes bubonic plague, swept through Wyoming's prairie dog towns in September 1984. On the ferret's behalf, wildlife officials mounted one of the largest-ever U.S. plague eradication programs--a project involving 6,200 acres. "As it was the first such program to protect an endangered species, this was unquestionably a unique effort,' says Allan Barnes at the Centers for Disease Control's plague laboratory in Ft. Collins, Colo. Though the ferret is relatively immune to the direct ravages of plague, mortality among prairie dogs--its principal prey--depleted the wild ferret population by more than 50 percent. No sooner had the plague been controlled than an epidemic of canine distemper broke out, all but wiping out the remaining wild ferrets.

The census indicates that in addition to the six in captivity, only five adults survived last year's distemper, including two breeding females--each with a litter of five. The other three appear to be males. With only two breeding females in the wild, "we had such a genetic bottleneck' that inbreeding seriously threatened their ability "to maintain a viable population,' says Max Schroeder of the U.S. Fish and Wildlife Service (FWS) in Denver, federal coordinator of the black-footed ferret program. Moreover, notes Harju, with the census showing that the few remaining wild adults live miles from each other, there is some question whether reproductively mature animals would be able to find each other during their short mating season.

"Wonderful' is how James Carpenter responded upon learning of the decision to capture the wild ferrets. Carpenter, a veterinarian at the FWS's Patuxent Wildlife Research Center in Laurel, Md., was involved a decade ago in the last black-footed ferret captive-breeding program. With only one reproducing female--a very old animal and a poor mother--the program ended in failure. "In retrospect we did not have enough animals,' he says. "But with the 21 animals available to this [Wyoming] program, I'm very encouraged. In captivity they should breed relatively well.'

In case they don't, biologists are preparing an arsenal of technologies to help nature along. Explains David Wildt of the National Zoo in Washington, D.C., "We . . ., along with others from the universities of Wyoming, Colorado and Idaho, are all looking at developing procedures that might be applied to the artificial breeding of this ferret--in the event natural breeding is unsuccessful.' Experimenting with other types of ferrets, they aim to have nonstressful artificial insemination techniques available within five months, in time for the black-footed ferrets' short, annual mating season, which will begin next February.

Photo: Black-footed ferret in the wild and (inset) peering out of a hole at the Sybille Research Station near Laramie, Wyo.--home of the new captive-breeding program.