Many people in the northern United States and the mountains of the Southwest are familiar with little, tunnel-like runways through the grass. These beaten pathways sometimes contain clippings of vegetation and often mouse droppings. To the naturalist, this advertises the presence of one of the many species of voles, mice that graze much as do horses and cattle.
In the northern lowlands of the Chihuahuan Desert, grassy areas likewise reveal runways. But the vole runways of the Pleistocene ice ages have been replaced by those of larger rodents moving in from the south. Cotton rats, larger than voles and without the specialized grazing dentition of those mice, nevertheless play much the same role.
Vole or cotton rat, these little passageways are miniature highways
through the tangled grasses to all small creatures—open to unimpeded passage, yet
concealing from the watchful eyes of predators. Wait by one, and observe the small
world passing by—other rodents, shrews, insects, even the occasional snake. Hopefully,
the freeloaders are thankful for the runway engineers who make this possible.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Findley, J. S. 1987. The natural history of New Mexican mammals. University of New Mexico Press, Albuquerque, 164 pp.
University of Michigan Museum of Zoology. Photographs of voles and links to other information; includes a photograph of a runway.