SUMMARY
Brants' whistling rat, Parotomys brantsii, is a gregarious rodent indigenous to the south-west arid biome of southern Africa. However, P. brantsii portrays few physiological adaptations to its semi-arid environment. Consequently behavioural considerations such as use of refuges, diet selection and activity patterns are probably critical to its survival. This field study, based on direct observations of individuals. examines the diurnal activity pattern of these rodents. Despite the negative effect of increasing windspeed on winter activity, ambient temperature did not limit diurnal activity. In contrast, during summer, individuals fed and foraged for shorter period!, than in winter, and spent a greater proportion of their time underground on hotter days. These limitations to ambient environmental conditions suggest that P. brantsii is probably better adapted, due to its physiological limitations, to winter rainfall areas such as Namaqualand and the Little Karoo, than summer rainfall areas such as the southern Kalahari and central Karoo.