On the Trail of the Black-Footed Ferret
While domestic ferrets are common pets, black-footed ferrets (Mustela nigripes)are one of North America’s most endangered mammals. Sometimes called "prairie bandits," nocturnal ferrets spend 70 to 80 percent of their time underground. Federal wildlife biologist Randy Matchett, who has been working with ferrets since 1991, says, "Black-footed ferrets have an incredibly fine-tuned niche with prairie dogs. Such specialization is risky should your prey and habitat be greatly reduced."
As semi-nomadic predators, black-footed ferrets wander among numerous burrows on prairie dog towns, and are found at night by the green glow reflected from their eyes by a spotlight. The ferrets live in tunnels abandoned by prairie dogs. Sometimes a mother ferret will distribute her litter of two to three kits among several burrows while she is out hunting—if predators such as badgers or coyotes lurk around one entranceway at least all of her kits are not in danger. One female requires 100 acres of dense prairie dog habitat to feed her litter for a year.
Despite their three-pound weight and two-foot maximum length, these docile-looking members of the weasel family are quite voracious in taking on prairie dogs that often are larger, weigh more and put up a fight. Mating season for black-footed ferrets occurs throughout March and early April. Kits stay underground until July and leave in their first fall. In captivity, ferrets can live up to eight or nine years. Three to four years in the wild is old for a ferret.
Largely because they are so nocturnal and since they require such specific habitat characteristics, black-footed ferrets have been difficult for scientists to study. Historic specimen records were widespread throughout the ranges of three prairie dog species from Canada to Mexico. Because of small populations and the mass die-off of prairie dogs through poisoning, shootings and diseases, black-footed ferrets have been pushed to the brink.
In fact, until 1981 when a small black-footed ferret population was discovered in Meeteestse, Wyoming, they were thought to be extinct. Eighteen individuals were captured, raised, and bred in captivity. Consequently, every black-footed ferret in existence today can be traced to seven founders, which raises concerns regarding inbreeding. While ferret reintroduction has been quite successful in South Dakota, ferret populations in eastern Montana have not flourished. However, after 2004 spring field counts, 19 individuals were identified, which is the highest success rate since the animals were reintroduced in 1994.
Matchett says, "Anything less than 100 breeding females in a wild ferret population would not persist over the long-term. Some geneticists and population viability experts suggest 300 to 400 breeding females are needed. To get even close to that number, we need 10,000 acres of healthy prairie dog populations."