Black-tailed prairie dogs (Cynomys ludovicianus) once ranged the Great Plains from southern Saskatchewan to northern Mexico. Originally named "petits chiens," or "little dogs," by early French explorers, these highly social animals are not really dogs, but rodents. They are members of the Sciuridae or squirrel family, closely related to ground squirrels, chipmunks, woodchucks and marmots. There are five species of prairie dogs in North America, but only the black-tailed prairie dog inhabits Theodore Roosevelt National Park.
Named for their bark-like calls and black-tipped tail, black-tailed prairie dogs are small, short-tailed animals with eyes and small ears set far back on their heads. Their light-brown fur blends well with the dirt of their mounds except when the animal has been blackened by burrowing into coal seams. Prairie dogs average 14 to 17 inches in length and weigh 1 to 3 pounds. With short, muscular legs and long-nailed toes on their front and hind feet, they are well equipped for a burrowing lifestyle.
A prairie dog colony or "town" consists of a large number of closely spaced burrows, each comprising an elaborate network of tunnels and multiple entrance holes that provide escape routes from pursuing predators. The primary prairie dog social unit is the "coterie," an acre or so of territory with 50 to 60 burrow entrances that is occupied by a single family group. A coterie typically consists of one adult male, several adult females, and their offspring. Members of a coterie are a closely knit group, recognizing each other by an identifying kiss or sniff. Their cohesiveness is maintained by the cooperative activities of raising young, constructing burrows, grooming, playing, and defending the coterie territory. The dominant male is typically the most active in the defense of the coterie, patrolling its invisible borders and challenging all comers. Prairie dogs warn of territorial trespassers from adjacent coteries or approaching danger by emitting a series of "barks," which sound more like high-pitched squeaks. Specific threats are associated with distinctive vocalization patterns that serve to alert all residents of a town to the common threat.
Prairie dogs feed primarily on plants, selecting forbs and grasses high in moisture content and nutritive value to supply their needs for water and energy. Grasses, far less resistant to foraging pressure than forbs, quickly disappear from the town, which takes on a barren and overgrazed appearance. The open, closely-cropped terrain promotes easier social contacts and enables the collective "thousand eyes" of the residents to better spot approaching danger. With reduced competition from grass species, forbs begin to increase in abundance, and soon are joined by invading "weedy" plants like thistle and sage. Pronghorn and bison are attracted to feed in this modified community, their trampling and wallowing further compacting the soil to maintain forb growth. Varying its diet so as not to feed on one species of plant exclusively, the prairie dog practices its own brand of crop rotation. Forage pressure on preferred plants is kept at tolerable levels and the community thrives. This balance may be upset by climatic changes that, if persistent, could force prairie dogs to abandon a town. Recolonization may recur later when a more favorable environment has allowed the former plant community to recover.
Prairie dogs build up large stores of body fat to carry them through the fall and winter months. Unlike most other members of their family, black-tailed prairie dogs do not hibernate. They may remain underground for several days during periods of harsh weather, but milder winter conditions allow for towns bustling with activity.
Mating occurs from March to early April. After a month-long gestation period, the female bears a litter of one to six young. Born blind and hairless, the pups stay in the burrow for about six weeks while they develop fully. Emerging from the burrow, young prairie dogs are initially protected by their mothers. Weaning occurs shortly thereafter, when the pups have begun to forage for themselves. Most animals spend their brief five- to seven-year existence within the coteries of a single town.