Factors Affecting the Diet and Activity Budget of Wild Tibetan Macaques (<i>Macaca thibetana</i>)

Behavioral and dietary flexibility allow primates to effectively exploit resources that fluctuate in time and space. Here we examined monthly variation in the diet and activity budget of a wild nonprovisioned group of Tibetan macaques inhabiting Mt. Huangshan, China. From October 2022 to September 2023, we recorded the behavior of a group of wild macaques and collected data on food availability, temperature, rainfall, and day length. We found that over a 12-month period, the Tibetan macaques fed on 109 plant species. The main food types consumed were fruits (54.5%), leaves (24.3%), seeds (7.7%), stems (6.5%), flowers (4.0%), and buds (2.5%). Tibetan macaques were found to target fruits as a main resource during months in which fruits were most abundant. During months when fruits were scarce, they increased their consumption of leaves, seeds, and stems. The top three plant species each month accounted for 70.7% of total feeding time indicating that their foraging effort focused on a small number of highly productive plant species each month. The Tibetan macaque daily activity budget was dominated by feeding (3.98 h or 33.7%) and resting (3.81 h or 32.8%), followed by traveling (2.40 h or 20.9%) and socializing (1.45 h or 12.6%). When time spent feeding on leaves increased, the Tibetan macaques experienced a significant increase in time spent resting and a significant decrease in time spent feeding. In addition, during the months of December and January, pine seeds were found to be an important food for Tibetan macaques. It is possible that increasing lipid consumption during the cold winter months serves to offset the additional costs of thermoregulation. Our results indicate that Tibetan macaques flexibly adjusted their diet and activity patterns in response to monthly variation in temperature, rainfall, and food availability across a range of forest types in east-central China.