Earth & Sky

Our thanks to the following individuals and institutions who assisted in the preparation of this script:

Mike Lockhart
US Forest service

The following books, articles and web sites were used in preparing this script:

The Black-footed Ferret – Forest Service Website

Black-footed Ferret Recovery Program

USFWS Black-footed Ferret Factsheet

USFWS Press Release

Endangered and Threatened Wildlife and Plants; Establishment of a Nonessential Experimental Population of Black-Footed Ferrets in North- Central South Dakota.= (50 CFR Part 17 / RIN 1018 – AG26) – Federal Register/ Vol. 65, No. 199 Friday October 13, 2000/ Rules and Regulations (Federal Register Documents On-line)

The Ferret: an Owner’s Guide to a Happy Healthy Pet Mary R. Shefferman 1996 Howell Book House

Author’s Notes:

Do you want to hear ferret noises? Go here click on “Facts”

More on the Black-footed Ferret (Mustela nigripes) by Shireen Gonzaga

Many people confuse ferrets sold at pet stores with the Black-footed ferret. Although they look quite similar, both are actually different but related species belonging to the Mustelidae family that also includes mink, badgers, weasels, skunks, and otters. The domestic ferret is of European origin; it has been domesticated, as working animals and as pets, for more than 2,000 years. The Black-footed ferret, the only endemic ferret in North America, on the other hand, has never been domesticated by humans. Its closest relative is the Siberian polecat of Eastern Asia. It’s quite probable that Black-footed ferrets descended from the ancestors of Siberian polecats that came to North America during the Pleistocene (the time period spanning 1.8 million to 11,000 years ago) when East Asia and North America were connected by the Bering land bridge. The ferrets carved a niche for themselves in the New World, and have since evolved to become a separate species.

The Black-footed ferret also has the unfortunate distinction of being the most endangered mammal in North America. Their historic range coincided with that of their primary prey, three species of ground-dwelling rodents called prairie dogs. Black-footed ferrets and prairie dogs once occupied the shortgrass and mixed-grass prairies of the Great Plains from Canada to northern Texas. Being high on the food chain, the ferrets were never very abundant to begin with.

Beginning in the 1870s, much of the prairie began to be converted to farmland and pastures. Farmers began systematically poisoning prairie dogs, regarding them as competitors with their livestock for forage. An introduced disease, the sylvatic plague, also began to decimate large populations of prairie dogs and ferrets. This loss of habitat, the severe population decline of their primary prey, and disease started pushing the Black-footed ferret down the road to extinction.

Although diminutive in size, about 18 to 24 feet in length, and weighing between 1.5 and 2.5 lbs., these North American ferrets are powerful little creatures. They are able to take on prairie dogs that are usually as large, sometimes larger than themselves. Black-footed ferrets are primarily nocturnal, so their night hunting often takes a resting prairie dog by surprise The ferret lunges for its prey’s throat, gripping tightly to suffocate the prairie dog till it goes limp. The prey is then dragged back to the ferret’s burrow to be eaten in peace in a familiar environment. Prairie dogs are not just a source of food for the Black-footed ferret. Ferrets use prairie dog burrows as their homes, where they sleep, store food, and raise their young.

Male Black-footed ferrets tend to be larger than females, otherwise, both sexes appear similar. They are well camouflaged for a life on the prairie; their sides are generally a buffy pale yellow with lighter patches on the face, throat, chest, and abdomen. The top of the head and middle of the back are darker brown. Their feet, as their name implies, are black, as is the tip of the tail. And perhaps the most distinctive feature, that has made them so endearing to many people, is the black mask across the face. Ferret bodies are long, and they have short feet, ideal for wiggling through small tunnels.

Unlike their domestic ferret cousins that are quite sociable, the Black-footed ferret is a solitary animal. The only time they get together is during breeding, or when a female is raising her young. Ferret babies, known as kits, are usually born in March and April, in litter sizes averaging about three to four kits. They enter the world blind and helpless, but grow rapidly-by July, they are about three-quarters of their adult size. The youngsters begin hunting on their own around August, and a month later, are capable of living independently. A year after their birth, they reach sexual maturity and are ready to start their own families. Ferrets in the wild, subjected to the constant threat of predators and disease, can live as long as 3 to 4 years. Captive ferrets, however, have lived as long as 9 years.

Black-footed ferrets have huge appetites. Because of their high metabolic rate, they need a good supply of food to sustain them. While prairie dogs make up about 90% of their diet, ferrets also prey on mice, rabbits, birds, and the occasional lizard or insect. The ferrets themselves fall prey to other predators, like great horned owls, coyotes, and foxes. It’s for that reason that they spend just a few minutes each day above the ground, at night and for a few hours after sunrise, just long enough to hunt for a meal.

Large and healthy prairie dog colonies are essential to the Black-footed ferret’s survival. Today, prairie dogs occupy just 1% of their original range. Prairie dogs were once subjected to widespread extermination using poison on public and private land. Poisoning on public land is now prohibited, but still occurs on privately-owned land where livestock is raised. Most prairie dog habitat is also fragmented, surrounded by farmland and human developments. Such isolation retards the flow of animals across their wider range; this confinement has the potential to create problems such as inbreeding that brings out unhealthy traits, and the spread of disease that can wipe out an entire prairie dog colony. One particularly insidious disease that affects prairie dogs, ferrets, and other small mammals is the sylvatic plague. It was introduced from the old world more than one-hundred years ago, and is spread by fleas. This disease has decimated entire prairie dog colonies as well as the black-footed ferret populations associated with it.

In 1964, what was believed to be the last Black-footed ferret population was found in southwestern South Dakota. But that population began to decrease, and fearing that the animals would become extinct, the remaining ferrets were taken into captivity for breeding in the 1970s. But efforts to increase this fragile ferret population failed, partly due to problems brought about by in-breeding. In 1979, the then-last Black-footed ferret in captivity died, and many believed that this species had met its end.

In 1981, there was an unexpected resurrection of the Black-footed ferret, of sorts. A ranch dog in northwestern Wyoming killed an animal that was later identified as a Black-footed ferret. About 130 ferrets were found in that area in 1984. Unfortunately, not long afterwards, a plague outbreak killed many prairie dogs, followed by an outbreak of canine distemper that almost killed off the ferrets. Concern that this only known ferret population was also headed for extinction prompted wildlife officials to capture the remaining 18 animals between 1985 and 1987, for captive breeding.

These animals were sent to their new home, a facility run by the Wyoming Game and Fish Department in Sybille Canyon (now known as the National Black-footed Ferret Conservation Center, run by the U.S. Fish and Wildlife Service). This time, the first efforts at captive breeding were successful. In 1987, seven kits became the first ferret litter born in captivity to survive. So as to not put all their eggs in one basket, lest a local catastrophe or disease wiped out the entire population of ferrets, captive breeding is now done at six locations; since 1985, zoos in the United States and Canada have also joined in the effort to breed ferrets in captivity.

All Black-footed ferrets in the US and Canada today are descendants of 7 individuals from the captive Wyoming population. There was initially some concern about in-breeding problems with this group of ferrets. The ferrets are currently into the 13th and 14 generations since the seed population, and the good news is that there are no genetic-related problems, except for the occasional kinked tail. Currently, about 240 adult ferrets make up the core of the captive breeding population, and they represent the current genetic diversity of the species. Surplus animals are used in reintroductions to the wild.

The U.S. recovery plan for the Black-footed ferret calls for establishing 1500 animals in the wild, in 10 or more populations. The first step in that direction took place in September 1991, when a group of young ferrets were reintroduced to the wild in Shirley Canyon in Wyoming. Successful breeding in the wild led to more introduction between 1991 and 1994. But an outbreak of sylvatic plague in 1995 that decimated the prairie dog colonies brought that effort to an end.

Black-footed ferrets have also been introduced to other sites in Wyoming, South Dakota, Arizona, Montana, Colorado, and Utah. Since 1997, ferrets have been “preconditioned” before reintroduction, raised in pens mimicking their natural wild habitat, complete with natural burrow systems and live prairie dogs, This has resulted in a much higher survival rate in the wild, compared with ferrets raised in cages.

According to Mike Lockhart of the U.S. Fish and Wildlife Service, reintroduction results have been mixed. Scientists now have a good handle on raising Black-footed ferrets in captivity, and know how to properly introduce them to the wild. But the main challenge now is keeping the ferrets alive in the wild. In South Dakota, wild ferret populations have been doing well, thanks to a relatively large and continuous prairie dog habitat, and the absence of plague. But some other sites have not done as well, due to such factors as limited habitat and plague outbreaks. Some reintroduction areas are currently being studied to better understand what it takes to sustain ferrets in the wild.

Meanwhile, ferret reintroductions have continued, with the latest site at the Cheyenne River Sioux Reservation in Wyoming in October 2000, where a mix of captive and wild ferrets from other locations have been introduced. Encouraged by some of the successes, and despite some of the setbacks, Lockhart remains optimistic that a self-sustaining population of Black-footed ferrets can eventually be established in the wild.

Acknowledgements:
Thanks to Mike Lockhart, USFWS