- We studied dietary intakes and time budgets in two desert gerbillids, Psammomys obesus, a diurnal herbivore, and Meriones crassus, a nocturnal granivore. P. obesus was offered fresh leaves of Atriplex halimus while M. crassus was offered millet seeds and Atriplex halimus, mainly as a source of water. We predicted that the (1) nocturnal rodent will feed mainly at night and the diurnal rodent mainly during the day; and (2) the herbivore consuming a relatively low energy diet will spend more time feeding than the granivore consuming a relatively high energy diet. The latter prediction was confirmed in that P. obesus spent more time feeding than M. crassus. Number of feeding sessions in M. crassus was the same as in P. obesus but each feeding session was shorter. However, the former prediction was only partially confirmed. Feeding during the dark phase was significantly longer than the light phase in the nocturnal M. crassus, as predicted; but feeding did not differ between diel phases in the diurnal P. obesus. The large amount of forage required by P. obesus necessitated consumption throughout the light and dark phases at the same rates of intake.