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Desert Diary


Ecologists have something that they call "density-dependent" factors, processes that change their effects according to the number of organisms in an area. As population sizes grow, so do some problems, such as disease transmittal, pollution, food scarcity, and aggression between members of the population. As population density decreases, social interactions become difficult, as may even finding a mate.

Density-dependent problems aren't limited to humans, however. In truth, most species run into difficulties if their population density gets too great or too small. Even prairie dogs, renowned for their large towns and sociability, suffer at times. For example, there is evidence that the number of external parasites, such as fleas, increases much more rapidly than do the prairie dogs. Even aside from the discomfort caused by fleas and lice, this increased parasite burden may increase the likelihood of transmittal of bubonic plague, endemic in the Southwest. Among spread out populations of rodents, occasional deaths by the plague occur. Periodically, though, the disease sweeps through prairie dog towns, decimating them. Just as not enough may be bad, so may too much.
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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.