Food selection of semifree common marmosets (Callithrix jacchus): Indications for optimal foraging

In this investigation a group of common marmosets (Callithrix jacclus) cons isting of two parents and their six progeny of various ages were allowed fr ee access to an open-air enclosure, which was equipped with a heated hut, r oofed veranda, external cage, and a runway system made of roofing slats and a few small trees. Feeding places, sitting boards and sleeping boxes were distributed throughout the whole area. This investigation covered a total o f 254 hours of observation. The hut and its immediate vicinity can be consi dered as being the core area of the home-range, as the maximum frequencies of both feeding and location occurred there. Through the experimental varia tion in the type of foods provided at specific feeding places, it was obvio us that the closeness of the feeding place to the hut was more important to the marmosets than the type of food placed there. The marmosets apparently reduced the energy output when searching for food by minimizing the distan ce to the food patches.