Catastrophic Decline of a Desert Rodent, Dipodomys Spectabilis: Insights from a Long-term Study

We describe the catastrophic decline of a species of keystone rodent at a Chihuahuan Desert site. The population density of Dipodomys spectabilis averaged 7.6 individualslha from 1977 to 1983, but declined to near extinction over the winter of 1983-1984. We propose hypotheses to explain this decline: 1 ) disease; 2) damage to seed stores by heavy precipitation; 3) contamination of seed stores by mycotoxins. Available data cannot conclusively distinguish these possibilities, but they implicate tropical storm Octave and favor hypotheses 2 and 3. The decline of D. spectabilis was followed by increased abundance of three species of a rodents and a sharp decline in another, Perognathus JEavus. Long-term studies can provide unique insights into the nature, magnitude, and consequences of infrequent catastrophic disturbances.