TEMPORAL PATTERNS OF ACTIVITY OF THE UNSTRIPED NILE RAT,<i>ARVICANTHIS NILOTICUS</i>

Abstract

Previous descriptions of the daily pattern of activity of the unstriped Nile grass rat (Arvicanthis niloticus) conflict. Researchers have described this species as diurnal, nocturnal, or crepuscular. In our laboratory colony, some animals are diurnal and others are nocturnal in running wheels. We systematically examined activity patterns of free-living grass rats in the Masai Mara National Reserve, Kenya, where the animals in our lab originated. Sherman traps were set at dawn or dusk near animal burrow entrances, and the time of capture was recorded for each animal. Seventy-seven A. niloticus were captured 287 times at 20 different sites. Captures occurred almost exclusively during daylight. In contrast, other small mammals that were trapped on 49 occasions were caught exclusively at night. The temporal pattern of capture of A. niloticus did not vary as a function of age or sex. The diurnal pattern of activity we observed in A. niloticus is unusual among small rodents.