Responses to Seasonal Changes in Nutrient Quality and Patchiness of Food in a Multigroup Community of Tibetan Macaques at Mt. Emei

Provisioning along pedestrian trails by tourists much increased the nutrient quality and patchiness of food (NqPF) for Tibetan macaques (Macaca thibetana) at Mt Emei in spring and summer. In the habitat at a temperate-subtropical transition zone, the macaque's NqPF could be ordered in a decreasing rank from spring-summer to autumn to winter. With the aid of a radio-tracking system, I collected ranging data on a multigroup community in three 70-day periods representing the different seasons in 1991–92. Rank-order correlation on the data show that with the decline of NqPF, the groups tended to increase days away from the trail, their effective range size (ERS), their exclusive area (EA) and the number of days spent in the EA, and reduced their group/community density and the ratio of the overlapped range to the seasonal range (ROR). In icy/snowy winter, the macaques searched for mature leaves slowly and carefully in the largest seasonal range with a considerable portion that was not used in other seasons. Of the responses, the ROR decreased with the reduction in group/community density; and the ERS was the function of both group size (+) and intergroup rank (−) when favorite food was highly clumped. All above responses were clearly bound to maximize foraging effectiveness and minimize energy expenditure, and their integration in term of changes in time and space leads to better understanding macaque ecological adaptability. Based on this study and previous work on behavioral and physiological factors, I suggest a unifying theory of intergroup interactions. In addition, as the rate of behavioral interactions was also related to the group density, Waser's (1976) gas model probably applies to behavioral, as well as spatial, data on intergroup interactions.