Wheel-running activity patterns of five species of desert rodents

In contrast to the extensive laboratory data on activity patterns in rodent species inhabiting temperate zones, much less is known about the activity patterns of desert rodents. In order to address this issue, we measured whe el-running activity patterns in males and females of five species of wild-t rapped desert rodents (Dipodillus dasyurus, Gerbillus andersoni, Gerbillus pyramidum, Meriones shawi, and Acomys cahirinus) in long 'summer-like' and short,'winter-like' day lengths. The specific goals of the present study we re to characterize activity patterns in several desert rodent species in th e laboratory and to determine if activity patterns are expressed in a seaso nal or sexually dimorphic manner. Specifically, wheel-running was measured for 11 weeks in long days followed by II weeks in short days to test for ph otoperiodic entrainment as well as responsiveness to changes in the light-d ark cycle. All animals exhibited rhythmic patterns of wheel-running with co nsistent onsets and offsets that had well-defined relations with the light- dark cycle. All individuals of G. andersoni showed nocturnal activity patte rns. Most individuals of G. pyramidum had nocturnal activity patterns, but some individuals showed a short bout of activity at the beginning of the li ght period. Most individuals of D. dasyurus and M. shawi showed bimodal (i. e., nocturnal and diurnal) activity patterns, although some showed markedly nocturnal activity patterns. There was no sexual dimorphism in wheel runni ng activity rhythms in any of the species examined. As expected decreases i n day length resulted in an overall increase in the duration of activity in all species. Collectively, these data provide an initial characterization of activity patterns within desert rodents in a controlled laboratory setti ng.