Black-footed ferrets (Mustela nigripes) are a federally endangered species and a member of the weasel family, closely related to mink, badgers and otters. Black-footed ferrets are 20 to 24 inches long, including a five to six-inch black-tipped tail, and weigh between one and two pounds. They are best recognized by their black face mask and black feet.

The black-footed ferret is the only native ferret known to North America. The European (or domestic) ferret, which is sold in pet stores, and the Siberian polecat from Asia both resemble black-footed ferrets but are different species. Black-footed ferrets once lived wherever prairie dog colonies thrived throughout the western Great Plains, from northern Mexico to southern Saskatchewan, Canada, and from the foothills of the Rocky Mountains eastward through the grasslands of western Oklahoma, Kansas, Nebraska, and the Dakotas.

Black-footed ferrets are dependent upon prairie dogs (Cynomys spp.) for food and shelter. Prairie dogs are social rodents that live in colonies (or towns) on the Great Plains. The diet of black-footed ferrets consists almost entirely of prairie dogs, and black-footed ferrets are found only on prairie dog colonies. Such a high dependence on prairie dogs was almost the demise of black-footed ferrets as poisoning, land conversion and disease drastically reduced prairie dog populations throughout the 20th century. By 1980, no black-footed ferrets were known to exist and the species was nearly declared extinct until a small population was discovered in Meeteetse, Wyoming in September of 1981.

The Meeteetse black-footed ferrets thrived on white-tailed prairie dogs (Cynomys leucurus) and the population reached as high as 129 individuals. But the population succumbed to a combination of diseases, such as canine distemper (fatal to black-footed ferrets) and sylvatic plague (fatal to both prairie dogs and black-footed ferrets). Biologists removed as many black-footed ferrets as they could find and placed them in captivity. By 1987, the last 18 black-footed ferrets in the world inhabited a captive breeding center near Laramie, Wyoming. Captive breeding was successful and by 1991 enough black-footed ferret kits were produced that some could be released into the wild. Check out black-footed ferrets release sites here.

Releasing black-footed ferrets back into the wild is an important undertaking and much is learned with each reintroduction. One of the most important findings was that when black-footed ferrets receive "pre-conditioning" (i.e. black-footed ferret school) before they are released, they survive much better than black-footed ferrets that do not. Pre-conditioning consists of placing captive-born black-footed ferrets into outdoor pens where they live in dirt burrows and learn to kill prairie dogs. All black-footed ferrets released into the wild today are pre-conditioned for approximately 45 days.

Once black-footed ferrets are released, biologists have several methods of tracking them. The primary method is called spotlighting and uses high-powered lights to see the reflected green eye shine of black-footed ferrets. Once spotted, biologists then use a special reader to identify an individual by its PIT tag. Before release, all black-footed ferrets have a Passive Integrated Transponder (PIT) tag implanted under their skin. The PIT tags do not hinder the animals in any way, have no moving parts or batteries, and generally last the life of the black-footed ferret. Biologists must get the reader within 6 inches of the black-footed ferret in order to get a PIT tag reading, which is made easier by a specialized donut shaped ring that fits over a burrow opening. When the black-footed ferret pops its head through the opening, its PIT tag is read.

The wild-born young of released black-footed ferrets obviously have no PIT tags, so biologists must capture these animals to implant them. A specialized trap, shaped like a square tube, is used to safely capture black-footed ferrets. They are anesthetized and then a PIT tag is inserted. The process of implanting a PIT tag takes approximately 30 minutes and once the black-footed ferret is fully awake it is released back at the capture site.