Students of evolutionary biology are involved in testing predictions about how animals make a living. `Making a living` is shorthand for studying how animals search for food, avoid predators, and reproduce successfully. It is assumed that, like us, animals do not have time to perform an infinite variety of tasks; some are more important than others. Finding food and avoiding predators are critical to survival even before reproduction can become an issue, and food fuels all of these activities. Since most primates need to refuel every day, the ability of each individual to find food is an essential daily activity. This study examines how Venezuelan white faced saki monkeys (Pithecia pithecia) solve the problem of finding and using food. White faced sakis live in small social groups that travel together from morning to evening. Finding food is thus both an individual and social problem. We will employ interdisciplinary methods to examine how female sakis, who like all female mammals are under stronger energy constraints than males, balance nutritional needs in different reproductive states (estrous cycles, pregnancy and lactation). Traditional behavioral methods of observation will be combined with recently developed laboratory techniques to help us understand how females make individual choices based on reproductive status and nutritional value of the foods.
