The prolific Patent at her best, with a succinct, well researched, and informative rundown of the prairie rodent's lifestyle and social organization, plus a clear presentation of its controversial role: knowing that 400 or so prairie dogs eat enough grass to maintain a cow, ranchers (and the US) have exterminated them by the millions (``Their numbers have been reduced by about 90 percent''). But Patent presents recent evidence that their colonies actually enrich the grass enough so that the land's value as pasture is maintained, while a multitude of other species thrive in and around their burrows. Though they're appealing, these little creatures don't lend themselves to dramatic photos; still, Mu§oz contrives a pleasing variety in his color photos, including shots of their neighbors and habitat. Useful and consistently interesting. Bibliography; index. (Nonfiction. 9-14)