Resource Ramblings 2007-10
Many biologists feel that black-footed ferrets are the most endangered land mammal in North America. Through the efforts of an aggressive captive-breeding and reintroduction program, this species was probably saved from extinction but now is hopefully on its way toward recovery in the wild.
Black-footed ferret released in Wind Cave National Park. The black-footed ferret is a grassland species and depends on prairie dogs for its survival. Prairie dog distribution has continued to decline as a result of habitat alteration, extermination, and disease (i.e., plague). Prairie dog colonies once ranged from southern Canada to northern Mexico and occupied much of the Great Plains of the central United States. Today, they occupy a fraction of their former area. Because of the close relationship between prairie dogs and species that depend upon the habitat created by prairie dogs, these species have declined as well. In 1986, only 18 black-footed ferrets were known to exist in the wild.
Black-footed ferrets are a species dependent on prairie dogs for food and shelter as they eat, sleep, and raise their young in prairie dog burrows. In fact, they cannot survive for extended periods outside of prairie dog colonies. They even spend about 90% of their time underground in prairie dog burrows.
Black-footed ferrets are mustelids, or mammals having scent glands under their tails. They are carnivores, with a diet consisting of almost exclusively prairie dogs. Some of their cousins include mink, weasel, skunk, badger and otter. Black-footed ferrets are different from domestic ferrets, which are of European origin and have been domesticated for centuries.
Black-footed ferrets are 18-24 inches long, including a 5-6 inch tail, and can weigh up to 2½ pounds. Males are a bit larger than females. Ferrets have short, yellow to buff color fur, which is lighter on the belly and nearly white on the face and throat. The fur is also black tipped along the back and they have a black face mask and black feet.
Black-footed ferrets are a nocturnal species, but are sometimes seen during early morning hours. They are less active during the winter, but do not hibernate. They can also spend up to a week below the ground living off of cached food.
The life expectancy for a black-footed ferret in the wild is 3-4 years, while some have lived for 8-9 years in captivity. In 1998, an 8-year old male was found in the Buffalo Gap National Grasslands in South Dakota. He had been released as a 5-year old in 1995, and had not been seen for over 3 years!
Black-footed ferrets move above ground in a series of jumps or a slow "gallop." They can travel at speeds of up to 5-7 miles per hour. Biologists have tracked ferrets moving 6 miles in one night, with one ferret examining over 100 prairie dog burrows in a single night!
Black-footed ferrets communicate with various sounds. When alarmed or excited they chatter loudly or emit several loud barks interrupted by low hissing sounds. Male ferrets "chortle" to females during breeding. Ferret kits emit tiny squeaking sounds. Black-footed ferrets also communicate with scent by rubbing their scent glands on rocks, soil, and vegetation to mark territories.
In the wild, prairie dogs make up 90% of a ferret's diet. A ferret may eat over 100 prairie dogs in one year, and scientists calculate that over 250 prairie dogs are needed to support one ferret family for one year. They may also eat ground squirrels, small rodents, rabbits and birds. Ferrets kill their prey by biting the back of the neck or throat. They do most of their hunting at night inside prairie dog burrows, killing prairie dogs while they sleep. The close confines of the burrow make it difficult for their prey to escape.
The normal gestation period for ferrets is 41-43 days, with baby ferrets being called "kits." The average litter size is 3-4 kits, although single kits and litters of 9-10 have been documented. Kits are born in the spring, and in the wild, they are born underground in prairie dog burrows. Male ferrets play no part in raising kits, but females are excellent parents. Kits are born blind and helpless and stay below ground until they are about 2 months old. At this age, the female begins to take her young on hunting forays and separate the kits into different burrows. By October, the young are completely independent and will disperse to their own territories.
Black-footed ferrets are very playful, especially as kits. They are often observed chasing one another, stalking, or staging mock "attacks" - all valuable skills they will use in hunting. Both wild and captive ferrets do the "ferret dance" with mouths wide open, hopping, leaping, and bucking with total reckless abandon!
The national goal is to establish ten free-ranging populations of black-footed ferrets, across the widest possible area in their former range. Each population will have 30 or more breeding adults. It is hoped that 1,500 free-ranging black-footed ferrets will be established in the wild by the year 2010. (Information source is the Black-footed Ferret Recovery Implementation Team website at www.blackfootedferret.org/)
Comments and feedback about Resource Ramblings are encouraged and should be directed to Dan Foster, in person, or via email.