The big importance of little towns on the prairie - prairie dogs - includes related information on prairie dog architecture - Cover Story

National Wildlife, June-July, 1996 by Bob Holmes

EVER SINCE PEOPLE first set eyes on prairie dogs, the impulse to anthropomorphize has been irresistible. After all, the sociable rodents greet each other with a "kiss" (touching teeth). They sound alarms when danger approaches. Sometimes they care for one another, and sometimes they are murderous. They form clans, establish boundaries, construct living quarters and live in towns. Listen to the very scientists who study the creatures: "They're just like little people," says prairie dog expert John Hoogland, of the University of Maryland's Appalachian Environmental Laboratory in Frostburg. "Some are aggressive; some are meek. Some get up early, some get up late. They have individual personalities."

And another thing: Prairie dogs radically alter the habitat in and near their underground settlements, as people do with their own towns and cities. Just as we can destroy natural habitat, these sociable rodents ruin the grass for grazing animals--don't they? Haven't cattle ranchers known that to be true ever since they first set sight on the critters' towns, with their barren dirt mounds and mowed landscapes?

Whoa! Hold your horses! The notion of anthropomorphism can only go so far. For one thing, wildlife biologists have long known that prairie dogs (actually a type of ground squirrel) and their modified habitat attract and support many other animals. And recent research has prompted a new appreciation of how important the dogs are to the whole prairie ecosystem. "They're biological hotspots," says Dan Uresk, a research biologist with the U.S. Forest Service's experiment station in Rapid City, South Dakota. Not only that, it turns out that ranchers' bottom lines suffer far less from the dogs' presence than previously assumed. Under the right circumstances, cattle and prairie dogs can even mutually benefit one another.

At the beginning of the twentieth century, black-tailed prairie dogs occupied more than a hundred million acres of the Great Plains down the eastern side of the Rocky Mountains from Canada to Mexico. One town in the Texas Panhandle stretched 250 miles long and 100 miles wide and contained an estimated 400 million animals. In the decades since, ranchers and government agencies have launched massive poisoning campaigns to clear prairie dogs off rangeland. By the 1960s, the rodents occupied less than 2 percent of their original range. Yet even now, remnant populations of black-tailed prairie dogs cover nearly a million acres of prairie, many of them on public land.

Three other prairie dog species--Gunnison's, white-tailed, and the federally threatened Utah prairie dog--occur farther west on the Colorado plateau. All three live in much looser colonies and have much less ecological impact than black-tails. A fifth species, the Mexican prairie dog, inhabits the highlands of central Mexico.

There is no question that black-tailed prairie dogs change their habitat. The animals clip the grasses in and around their town, eating their fill and clearing the rest so they can see one another and approaching predators. "Within a growing season, they can enter an area and make it almost like a golf course," says grassland ecologist James Detling of Colorado State University. In the center of town, this constant clipping eventually kills almost all the grass and allows broadleafed herbs and small shrubs to move in.

Out in their more recently-settled suburbs, prairie dogs have a much different effect. By clipping off older grass blades and stems, they stimulate tender, nutritious new growth and actually raise the quality and diversity of the forage for other grazers (though they decrease its quantity). Cattle and bison prefer feeding on these newer parts of a prairie dog town rather than in undisturbed prairie. Studies have indicated that young bison gain significantly more weight feeding in a prairie dog town than elsewhere. But that does not mean cattle necessarily experience the same benefits from dog proxmimity, especially if they are packed onto a limited amount of land.

Other studies have found that prairie dog towns hold twice the density of wildlife and nearly double the number of species as prairie without the rodents. "I never expected to find so much wildlife associated with prairie dogs," says U.S. Forest Service biologist Uresk, who has studied the animals. Vertebrate species associated with the towns number as high as 170, ranging from mice, to swift foxes, to raptors. Some animals, such as burrowing owls and prairie rattlesnakes, rely on the towns' underground architecture as shelter. A few, such as pronghorns, seek out the broadleafed herbs that grow in the heart of town. And others, such as the mountain plover--a prairie-dwelling shorebird far from any shore--favor the bare terrain where the dogs have their greatest impact.

The best known of prairie dogs' dependents is the critically endangered black-footed ferret. Ferrets live only in prairie dog burrows and eat their hosts, almost exclusively. "The ferrets couldn't exist without the prairie dogs," says ferret specialist Dean Biggins of the National Biological Survey in Fort Collins, Colorado. Biggins has estimated that towns covering fewer than 1,000 acres are too small to support even a minimal ferret population, yet few towns larger than this still exist on the plains.