Differences in diurnal activity patterns exist between blue wildebeest Connochaetes taurinus and red hartebeest Alcelaphus buselaphus. Seasonality also appeared in the patterns of each species. In summer, wildebeest spend less time grazing and more time lying and standing than do hartebeest and this difference is emphasized in winter. Wildebeest also spend more time in the shade whereas hartebeest do not show any regular pattern in their use of shade. These results are discussed in relation to thermoregulatory adaptations and the possible divergence in methods of satisfying energy requirements in the two species. Keywords: Activity patterns, Blue wildebeest, Red hartebeest, Shade-seeking and Thermoregulatory behaviour.