We augmented food resources to a heteromyid rodent community in the Sonoran Desert of southern California to experimentally ascertain the effect of a resource pulse on rodent abundance, diversity, and home-range dynamics. The same community displayed increased rodent abundance and species diversity in response to the productivity pulse that resulted from the 1997–1998 El Niño Southern Oscillation (ENSO). In marked contrast to the response to the ENSO, our experiment resulted in a decline in rodent diversity because the largest pocket mouse present (Chaetodipus formosus) monopolized the added resources and increased its proportional abundance. In addition, the abundance of adult rodents did not change in response to supplemental resources, even though reproduction, and consequently juvenile abundance, increased greatly. This implies that home-range size and overlap by adult animals remained unchanged despite the greater abundance of food. Among caching species such as pocket mice, this may be an adaptive response to the highly variable and scarce resources of the desert environment. The decline in diversity and lack of change in adult density and home-range dynamics observed with the experimental resource pulse are directly counter to the response of the community to the ENSO resource pulse, and were apparently the result of fine-scale spatial processes. This suggests that the effects of resource pulses are scale-dependent, and that the results of small-scale manipulative experiments may provide limited insight into community responses to large-scale climatic events.