Black-tailed Prairie Dog
Order Rodentia : Family Sciuridae : Cynomys ludovicianus (Ord)

Description. A rather large, chunky, ground-dwelling squirrel with upperparts pinkish cinnamon mixed with buff; tail sparsely haired, tipped with black, and about one-fifth of total length; eyes large; ears short and rounded. Dental formula: I 1/1, C 0/0, Pm 2/1, M 3/3 X 2 = 22. External measurements average: total length, 388 mm; tail, 86 mm; hind foot, 62 mm. Weight, 1-2 kg.

Distribution in Texas. Historically occurs in western one-half of state from north of Rio Grande Plains; easternmost records from Montague and Tarrant counties in north and Bexar County in south; now extirpated over much of its former range.

Habits. Black-tailed prairie dogs typically inhabit short-grass prairies; they usually avoid areas of heavy brush and tall grass, possibly because visibility is considerably reduced. In Trans-Pecos Texas, favored habitat sites are alluvial fans at the mouths of draws, "hard pan" flats where brush is sparse or absent, and the edges of shallow valleys.

The term "prairie dog" is an unfortunate misnomer because the animal is not even remotely related to a dog. It is a ground squirrel with a superficial resemblance to a small, fat pup. These squirrels are sociable creatures and live in colonies, or "towns," that may vary in size from a few individuals to several thousand animals. Vernon Bailey recorded that at the turn of the century an almost continuous and thickly inhabited dog town extended in a strip approximately 160 km wide and 400 km long on the high plains of Texas. This "city" had an estimated population of 400 million prairie dogs. Such large concentrations are now a thing of the past, due to the extensive use of poisoned grain to kill the animals and land conversion for agriculture.

Their homes consist of deep burrows 7-10 cm in diameter. The entrances are funnel-shaped and usually descend at a steep angle for 2-5 m before leveling off. One described burrow dropped nearly vertically for 4.5 m, then turned abruptly and became horizontal for 4 m. From the lower part extended blind side tunnels and nest chambers. The main entrances are made conspicuous by the mounds and parapets constructed around them. These craterlike "dikes" are often 30 cm or more in height and doubtless serve to keep flash floods from inundating the burrows and also as lookout points for the animals. Those who have hunted prairie dogs know how effective the craters are, both as vantage points and as retreats for the animals.

They are strictly diurnal and are most active in the morning and evening periods. The midday hours are usually spent sleeping below ground. In summer the animals store up reserves of fat to tide them over the winter months. In the northern part of Texas they begin hibernating in November. Hibernation seems to be less complete in prairie dogs than in true ground squirrels.

Their food is chiefly plant materials, particularly low-growing weeds and grasses. In Trans-Pecos Texas, burrow grass and purple needle grass are especially favored foods. Their year-round diet as determined by one investigator is made up about as follows: grasses (61.6%), goosefoot family (12.7%), mustard family (4.5%), prickly pear (6.0%), other plants (14.0%). Animal matter, chiefly cutworms, accounted for only 1.4% of the total diet. They are voracious eaters. According to C. Hart Merriam, 32 prairie dogs consume as much food per day as one sheep and 256 eat as much as one cow!

Prairie dog populations are comprised of several small "coteries," or harems, of two to eight females that are defended by a single dominant male. In turn, coteries are organized into larger population units called "wards," which are separated by unoccupied areas of unsuitable habitat or other such barriers. Activity and breeding are usually conducted within the coteries; however, dispersal between coteries and wards occasionally occurs, usually by young males. This complex social structure is thought to contribute to increased genetic variability between both coteries and wards.

One litter of four or five young is born in March or April. At birth the youngsters are blind and hairless and weigh about 15 g. At 13 days fine hair covers the cheeks, nose and parts of the body; the weight is then about 40 g. At 26 days, the body is well-haired and they can crawl awkwardly. Their eyes open at the age of 33-37 days, at which time the young squirrels are able to walk, run, eat green food, and "bark." They first appear above ground when about 6 weeks of age and are weaned shortly after that. The family unit remains intact for almost another month, but the ties are gradually broken and the family disperses. Sexual maturity is reached in the second year.

These squirrels have been displaced by livestock and farming interests for the past 50 years or more. Consequently, their former range and numbers have been considerably reduced. That large concentrations of prairie dogs can damage cultivated crops or compete seriously with livestock cannot be questioned, but the desirability of eliminating them entirely from rangelands has not been satisfactorily demonstrated. Stockmen in certain parts of Texas, for example, claim that removal of prairie dogs has had some direct association with the undesirable spread of brush. This has had detrimental effects on the livestock industry which far outweighs the damage prairie dogs might do.

Photo courtesy of U.S. Fish and Wildlife Service.