Slender-tailed meerkats (Suricata suricatta) are small, diurnal, and gregarious mongooses which inhabit the semi-arid regions of southern Africa. In the south-western Kalahari, substantial fluctuations in productivity are caused by extreme seasonality in rainfall and temperatures. We observed the foraging behaviour of habituated meerkats from January to July, a period covering the entire birth season and stages of high and low prey availability. Insects were the most frequently occurring prey class (78.1%), of which larvae (33.4% total frequency) and adult Coleoptera (27.5% total frequency) were the most important prey items throughout the year. Reptiles were heavily utilized in terms of prey bulk-an index of volume-(19.9%), but not by frequency (9.2%). Consumption of Coleoptera was positively correlated with rainfall, and negatively with temperature. Meerkats used a mean of 6.7 ± 1.1 prey categories daily, and there were significant monthly differences in prey diversity in the diet. Dietary shifts were apparently related to fluctuations in prey availability and the presence of preferred prey. There were no differences between the sexes in dietary diversity or niche breadth, but pregnant and lactating females foraged at significantly higher rates than males. The timing of foraging activity altered over the months in response to changes in daylength and thermoregulatory constraints. Foraging behaviour and seasonality in foraging effort are described, and the implications of an insect prey base for meerkat socioecology are discussed.