Ground Squirrels and Prairie Dogs: a World Beneath the Ground
Prairie Dogby Nancy Blanton
Chihuahuan Desert Research Institute
Fort Davis, Texas

Beneath the ground, in areas of the Chihuhuan Desert, lives a community of animals that other animals of the desert grassland depend upon for survival. Their world is a world of tunnels, escape hatches, hide and seek from predators, and a place of refuge from the sun and winter cold. It is the underground world of prairie dogs, Cynomys sp., and ground squirrels, Spermophilus sp.

In the northwestern part of the Chihuhuan Desert region are a number of ground squirrels, and two species of prairie dogs. They do not live together in common burrows, but where they do occur, their burrow homes provide protection and habitat for other desert animals. In the case of the prairie dog, ecologists are beginning to better understand its role as a linchpin species in desert grassland and prairie grassland ecosystems.

A linchpin species is a plant or animal within an ecosystem that is a central to the healthy functioning of that ecosystem. Without the presence of the linchpin species, the ecosystem becomes vulnerable to unretriveable negative impacts. Prairie dog and ground squirrels are important to ecosystems for two reasons. Networks of deserted burrows are used as shelter by a variety of animals from salamanders to owls, while prairie dogs and ground squirrels are a major food source for predators including hawks, bobcats, badgers, and coyotes. Contrary to what was thought in the past, when prairie dogs occur in low populations, they are not detrimental to the land. Rather, their burrows are thought to enrich the soil with oxygen through aeration and disturbance. In areas where they consumed much of the grass, the grass returns again, more plentiful and nutrious than before. This can benefit large grass-eating ungulates, such as domestic cattle, horses, pronghorn and deer.

Two common ground squirrels of the Chihuahuan Desert are the Mexican Spotted Ground Squirrel, Spermophilus mexicanus, and the Spotted Ground Squirrel, Spermophilus spilosoma. The physical appearance of the two species is similar, the major difference being coloration and size. Both animals have white rows of spots on the back. However, the Mexican Ground Squirrel is larger and darker brown. The Mexican Ground Squirrel is 11-15 inches long, and has a bushier tail than the tail of the Spotted Ground Squirrel which averages 9 inches. The undersides of both species are white or buff - a common characteristic in desert animals - as a means to reflect ground heat away from the animal’s body. Dry, sandy areas are inhabited by the Spotted Ground Squirrel which will also make burrows in brush and grassy areas, as does the Mexican Spotted Ground Squirrel.

The Spotted Ground Squirrel balances perfectly on it’s hind legs motionless for minutes at a time, watching for danger or another squirrel invading its territory. They signal each other with high-pitched whistles. In the summer of 1998 at the CDRI Headquarters, two Spotted Ground Squirrels were constant rivals for territory nearest the birdseed provided by the Institute’s staff. When frightened, they bolted for the nearest hole, with white tails flagging high in the air.

The underground network for ground squirrels is not as extensive or as complex as for prairie dogs which do not live in extended communities, but establish adjacent territories. Ground squirrels are diurnal animals and are active throughout most of the day except during the hours of most intense sunlight. In the heat of the desert day, they slip into their burrows for a siesta. Through the colder areas of their range, ground squirrels hibernate during winter months, slowing their normally high metabolic rate to very low levels. During this time, they stay within the burrow, seldom venturing out.

In the Chihuahuan Desert, there are two species of prairie dog, the Black-tailed Prairie Dog, Cynomys ludovicianus, and the Mexican Prairie Dog, Cynomys mexicanus. The Black-tailed Prairie Dog, is the more common species. Due to habitat reduction and removal, the Mexican Prairie Dog is endangered.
The prairie dog is a controversial animal because many people perceive them to be a prolific nuisance. Shooting and poisoning has reduced an extremely large population, which once covered most of the western U.S. and northern Mexico. In Texas, the historic population at the turn of the century in 1900 was estimated to be approximately 5.5 billion animals. Today, numbers of Black-tailed Prairie Dogs in Texas are estimated at only 300,000. One of the largest remaining prairie dog towns in the world is found in the Chihuahuan Desert region in Mexico.

The prairie dogs are much larger than ground squirrels. They average nearly 19 inches in length including the tail. Prairie dogs live in family groups called “coteries” made up of multiple females and a single male. Several coteries combine to make up a “ward.” Prairie dog burrows are deeper and more extensive than ground squirrels and they generally choose short grass prairies. Their burrow networks are deep in the ground, between 6 and 20 feet. At the entrance, the praire dogs mound the soil for visibility and to prevent a rain from flooding out the burrow.

Currently, scientists are interested in a variety of communication noises that prairie dogs make. Their vocalization patterns are thought to be as complex as dolphins. Many desert and prairie animals are dependent on shelter provided by “dog towns.” Within a prairie dog community, burrowing owls, rabbits, snakes, and ferrets can find shelter. The endangered Black-Footed Ferret is dependent on the prairie dog for not only shelter, but as prey. Burrowing Owls use abandoned burrows as nests for their young. Badgers and hawks also prey on prairie dogs and ground squirrels. In addition, snakes and salamanders will use the dark moist burrows as a place to retreat from the heat of the desert.

Prairie dogs and ground squirrels are of the same family, along with tree squirrels and chipmunks. Often, ground squirrels are mistakenly called gophers. Gophers are also a common rodent of the Chihuahuan Desert region, but belong to a different family, Geomyidae.

Links to other Ground Squirrel/Prairie Dog sites

Other Discovery articles: