Save the Black-footed ferrets

A series of natural and man-made disaster nearly elimiated the black-footed ferret. In 1986 all the ferrets in the wild were trapped and brought into a captive breeding program.

The ferret's crucial prey

The black-footed ferret preys exclusively on prairie dogs- ground squirrels that inhabit the North American prairie from Canada to Mexico. Prai-rie dogs dig burrows in which they live as part of a group called a coterie. The burrows of a number of coteries inter-connect to form a prairie dog town, which can extend sev-eral square miles.

The black-footed ferret takes over an uninhabited section of the underground town and preys on the prairie dog popu-lation. It hunts at night, killing each victim with a bite on the neck. A solitary female makes a kill every three days or so, but when she has a litter of hungry kits to feed, she must provide fresh food almost every day.

Because the black-footed ferret’s diet is limited to prai-rie dogs, its survival depends on the success or failure of prairie dogs.

Why the decline?

Black-footed ferrets were never were too numerous but they survived successfully until humans inter-fered. Ranchers wanted to get rid of prairie dogs, which com-peted with ranch animals for vegetation.

A massive poison-ing campaign killed off 95 per-cent of the prairie dogs. Many ferrets died from eating the poisoned prairie dogs, and others died from starvation and dis-ease. Although the prairie dog population recovered, there were too few ferrets left to take advantage of the increase.

Initial attempts at conservation

In the late 1960s a group of scientists captured nine ferrets with the hope of breeding the animals in captivity. Because canine distemper is often a fa-tal disease for the black-footed ferret, the scientists injected the ferrets with a weak distem-per virus solution. But the vac-cine infected them, and four died. The others died of old age without raising any litters. By this time, the colony in the wild seemed to have died out.

Hopes were rekindled about 10 years ago, when a rancher’s dog killed a black-footed ferret in Wyoming. Scientists then lo-cated a colony living in the wild elsewhere in Wyoming, and they learned a lot from this colony about the ferret’s lifestyle. At the time the popu-lation seemed to be increasing.

Then, in 1985, prairie dogs were hit by bubonic plague. Although the black-footed ferret was not susceptible to this disease, a decline in its prey spelled disaster. Soon another disaster hit an outbreak of canine distemper, which killed nearly all of the remaining ferrets. Scientists, however, managed to trap 18 ferrets, and they began a suc-cessful captive-breeding pro-gram.

Captive breeding

In 1986 the black-footed ferret faced extinction from canine distemper. Scientists caught all the ferrets that they could find and vaccinated them against distemper. To make sure the vaccine was safe, they tested it first on the Siberian ferret, a close relative.

The scientists set up a captive breeding program, but little was known about the black-footed ferret’s reproductive life, so it took some time before two were successfully mated. A female Siberian ferret was mated at the same time, so she could stand in as a moth-er in case the black-footed fe-male died.

In 1987 the first young were born: two litters of seven kits. Each year more kits were born, and by the middle of 1991 there were 325 black-footed ferrets in captivity.

In fall 1991 researchers began to release a few black-footed ferrets into the grasslands of southeastern Wyoming, where there are still some prairie dog towns. These ferrets have been trained to recognize and react to their main natural predators- the great horned owl and the badger-by being confronted with stuffed versions of their enemies. Some black-footed fer-rets are also being kept in cap-tivity as a safeguard against future disasters.