Centennial Museum gecko logo

Desert Diary


Competition—as well as cooperation—is a fact of life in nature as in human affairs. Unlike much of human competition, most organisms don't realize that they are competing, except possibly during the winning of mates. Competition is most fierce within a species, for over the long term, only a relatively few of those conceived survive to produce the next generation.

The next strongest competition tends to be between members of closely related species. Sharing a large part of their genetic makeup inherited from their common ancestor, they often require many of the same resources. One result of competition between closely related species is the dividing up of the landscape, the various species adapting to different ecological aspects. For example, Deer Mice of the genus Peromyscus are common in the Chihuahuan Desert. In the El Paso region, the Cactus Mouse chooses rocky slopes and sand dunes; the Brush Mouse patches of oak and shrub; the Rock Mouse, mountain-top rocky slopes; the White-footed Mouse, vegetation-choked arroyos; and the Deer Mouse whatever patch is unoccupied by the other species.
pen and ink


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.



Smartt, R. A. 1978. A comparison of ecological and morphological overlap in a Peromyscus community. Ecology, 59:216-220.

Strickberger, M. W. 2000. Evolution. Third Ed., Jones and Bartlett Publishers, Sudbury, MA. 721 pp. rule