The interplay between individual, social, and environmental influences on chimpanzee food choices.

The foraging activity of chimpanzees requires individuals to balance personal preferences with nutrient requirements, food availability, and interactions with members of their social group. To determine whether chimpanzee food preferences are fixed or malleable across varying socio-ecological contexts, we presented six zoo-housed chimpanzees with pairwise combinations of four different foods under two experimental conditions. First, we individually tested each chimpanzee's choices for the four foods to ascertain individual preferences. Second, we tested the chimpanzees in a situation which more-closely mimicked the foraging pressures experienced by wild chimpanzees. In this second condition, the chimpanzees were tested in a group setting and the food availability was less predictable, such as in a patchy foraging environment. Subjects expressed significant variation in their selection of which foods to consume in the two different contexts and also appeared more willing to consume less-preferred foods in the unpredictable, social environment. These results suggest that chimpanzees' food preferences are not fixed, but change with context and are likely mediated by social facilitation. This is not only important to understand chimpanzees' foraging patterns and dietary requirements, but also has implications for experimental paradigms that rely on food preferences.