Centennial Museum gecko logo

Desert Diary


Oh, look, a mouse! Or maybe not. Like many things, the looks of an animal can be deceiving—and often, the common names make it worse (for example, a common name for the bat is "raton volador" in Spanish, which translates as flying mouse). Lots and lots of things that look like mice aren't related closely at all.

Biologists have learned the hard way to beware of superficial characteristics and look more deeply—like into a rodent's mouth. When we do, we see that they have only one pair of upper and one pair of lower front teeth—the incisors. Moreover, these chisel-like teeth grow for as long as the animal lives, wearing down at the same rate that they grow.

The jaws and teeth are fashioned exquisitely for gnawing, and whether a tiny pocket mouse or a 60-pound Beaver, all rodents share these two characteristics that they inherited from their long-ago common ancestor. And considering there are more kinds of rodents than any other kind of mammal, the gnawing way of life has paid off big.
pen and ink

Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.


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.

Chinchilla skull

Chinchilla skull: oblique view from below to show the paired incisors and also to demonstrate the gap between the incisors and the cheek teeth, another characteristic of rodents (but not unique to them). Specimen scanned by A.H. Harris.



Vaughan, T. A., J. M. Ryan, N. J. Czaplewski. 2000. Mammalogy. 4th Edition. Saunders College Publishing, Philadelphia, 565 pp.

Wilson, D. E., and D. M. Reeder. 1993. Mammal species of the world, a taxonomic and geographic reference. 2nd edition. Smithsonian Institution Press, Washington. 1206 pp.

Web Resources

Animal Diversity, University of Michigan. Good introduction to rodents.