This text presents the results of a research project carried out on foraging behaviour among African baboons and its consequences for survival and reproduction. Detailed data is provided on the feeding habits of each baboon, with an analysis of its nutrient intake. These figures are then compared with those in optimum diets. The most striking result of this study is that the baboon's subsequent survival and reproductive success could be accurately predicted from what they had eaten as yearlings. The animals with energy intakes closest to the optimum and protein intakes furthest above their requirements were most likely to survive to adulthood and to successfully produce offspring.