The Black-footed Ferret: Species Resurrected
Posted: Tuesday, September 27, 2011
by Jack H. Schick
When I moved to Wyoming, back in the early 1970’s, the black-footed ferret (Mustela nigripes) was an extinct species. There were no American polecats or prairie dog hunters, as they had also been known, living anywhere on the planet. They had gone the way of the passenger pigeon and the dodo bird and could be seen only in photographs or as stuffed exhibits. Consequently, there was a celebratory banner headline in the Casper Star Tribune, and announcements in newspapers and scientific journals around the world when, in 1981, a colony of the weasel-like animals were found, living in a prairie dog village near the town of Meeteetse, in the Big Horn Basin of Wyoming.
The black-footed ferret is almost exclusively a prairie dog hunter. The familiar western rodent provides well over 90% of its diet. Since the animal was first described by Audubon, in 1851, black-footed ferrets have always been found near prairie dog villages. They make their homes in abandoned prairie dog borrows. The oldest fossils of the diminutive predator have always been found in association with prairie dog bones, confirming that the relationship between the two species is an ancient one.
The prairie dog hunter has a very long body and a blunt head. The forehead is arched and broad and the muzzle short. It has few whiskers and its ears are triangular, short, erect and broad at the base. Its neck is long and its legs short and stout. Its feet are armed with sharp, slightly arched claws. Its entire foot is covered in hair, including the soles. The American polecat is about the size of a mink. Males of the species have an average body length of 21 inches with a tail about five inches long. Adults weigh from one to three pounds. Females are about 10% smaller than males.
The black-footed ferret is basically buff colored or pale yellowish. The top of the head and neck have dark tipped hairs that give it a cloudy look. The face is crossed by a broad band of sooty black which covers the eyes like a mask. The feet, lower parts of the legs and the tip of the tail are black. There is a patch of dark brown half way between the front and back legs. There are light colored ‘dots’ above their eyes in their masks. The sides of their heads and ears are dirty white.
The American polecat is a solitary creature, except when breeding or raising litters. It is nocturnal and primarily hunts sleeping prairie dogs in their burrows. Prairie dog hunters spend most of their time underground. They may remain inactive there for up to six days at a stretch in the winter. Above ground activities are most common in the summer and early autumn, but are usually limited to between dusk and midnight, and again between about 4:00am and mid-morning. These “timetables” seem to be unaffected by local climate.
Black-footed ferrets mate in February or March. While most mustelids species (weasel family members), inhabit a variety of environments, the Black-footed ferret is a “habitat specialist” being always near a prairie dog town. Perhaps consequently, they have a low reproductive rate. There has been limited study of behaviors in the wild due to the scarcity of the animals, but in captivity, gestation has been observed to be 42 to 45 days. Litters range from one to five “kits.”
Black-footed ferret kits are altricial (need to be fed and taken care of for a relatively long time). They are raised underground by their mothers for several months after birth. They emerge from their burrows in July when they are about six weeks old. They are separated into individual neighboring burrows by their mother. Kits reach adult weight and become independent from late August to October. They become sexually mature at about one year of age.
The juvenile ferrets dispers throughout the colony from early September to early November. Observations of this dispersal made near the original Meeteetse colony revealed that nine male and three female juveniles relocated to burrows one to four miles away after the break up of the litters. Four females traveled less than 0.2 miles from ‘home.’ Males usually disperse the furthest distances.
The average lifespan of a black-footed ferret in the wild is only about one year, though they may live up to five years. Males have a higher mortality rate than females because they travel longer distances and are more vulnerable to predators. The prime causes of death include habitat loss—they must have prairie dogs—human introduced diseses and indirect poisoning from prairie dog control efforts. A four year study at the Meeteetse colony showed a mortality rate among juveniles and adults of 59% to 83%.
Black-footed ferrets are susceptable to numerous diseases. Canine distemper is extremely dangerous to a colony. A few years after the only remaining population was discovered at Meeteetse, despite supreme efforts to isolate and protect the colony, an epidemic of distemper nearly wiped them out. As many animals as possible were captured and taken into protective custody. They were given a short-term vaccination that offered temporary protection. For a period of time there were no longer any black-footed ferrets exiting in the wild. The animals are also susceptable to rabies, tularemia and human influenza. Sylvatic plague does not directly affect the ferrets, but can wipe out a prairie dog village leaving the ferrets to starve.
Efforts in Wyoming and at other facilities saved the American polecat from extinction. 122 of the first 128 animals reintroduced to the Meeteetse colony died soon after being released into the wild. But persistance paid off and the population is now viable. Since 1991, US federal and state agencies in cooperation with private landowners, conservation groups Native Americans and North American zoos have been reintroducing the critically endangered animals into other native habitats. Beginning with Wyoming the efforts have expanded to Montana, South Dakota, Arizona, Utah, Colorado and Chihuahua, Mexico. As of 2007, the total wild population of black-footed ferrets in the United States was well over 650 individuals with another 250 living in captivity. All of the animals are descendants of the original distemper epidemic survivors that were rescued at Meeteetse.
This month (September, 2011), near the town of Interior in the Badlands of South Dakota, black-footed ferret #7505 was released. He hesitated when his cage door was opened, poked his head out, spotted the prairie dog burrow a few feet in front of him and darted in, disappearing below the ground. The release was an invitation-only event. It kicked off a weekend of nationwide festivities celebrating the 30thanniversary of the discovery of the Meeteetse colony, and the beginning of the supreme efforts that have been successful, so far, at resurrecting this marvelous animal and removing it from the saddly lengthening list of extinct species.
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