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One of the greatest surprises for the Spanish conquistadors, priests, and explorers during their discovery of what is now known as the Chihuahuan Desert Region was a harsh but highly diverse land-scape, teeming with unusual wildlife and strange plants. The Camino Real, the historical route that linked Mexico City to Santa Fe in New Mexico, crossed a large part of the Chihuahuan Desert Region. Along that road, the Spaniards marvelled at the sight of apparently endless grasslands, which in fact ex-tended practically uninterrupted from northern Mexico north beyond the Camino Real and the edge of the Chihuahuan Desert Region to southern Canada. Did the pristine grasslands of the Chihuahuan Desert Region also support large populations of the black-tailed prairie dog (Cynomys ludovicianus)? According to Bailey (1932), a prairie-dog town in 1908 covered an estimated 1000 square mile area in the Animas Valley of New Mexico, near the border with Chihuahua. Prairie dogs might initially have increased their range after the introduction of cattle (see Hubbard and Schmitt 1984), but argu-ably they were always a common feature of the Chihuahuan Desert Region grasslands, as they were always a common feature of the Great Plains.

Unfortunately, 5 centuries after the discovery of the New World, grasslands have been massively converted to croplands, rangelands, and urban environments. They are among the most threatened ecosystems in North America. The rate and severity of their disappearance represents a major conservation concern at a landscape, species, and population level (Samson and Knopf 1996; Henwood 1998).