Flexibility in positional behavior is associated with ecological seasonality in Assamese macaques inhabiting limestone forests

Information on the positional behaviors of primates is essential for understanding the mechanisms of environmental adaptation. From October 2021 to September 2022, we collected data on positional behaviors of Assamese macaques (Macaca assamensis) at Guangxi Nonggang National Nature Reserve, China, using instantaneous scan sampling method. Our results showed that quadrupedal walking (34.99% ± 6.05%) was adopted as their most frequent locomotor mode, followed by leaping (31.54% ± 10.50%), climbing (25.55% ± 11.33%), quadrupedal running (6.55% ± 2.65%) and bridging (1.37% ± 1.19%). The ground (36.83% ± 21.18%) was the most frequently used stratum during moving. Most arboreal locomotion occurred on small (44.06% ± 11.36%) and medium (34.90% ± 11.09%) sized substrates. Sitting (81.19% ± 10.47%) was used as their most common postures, followed by holding (6.38% ± 9.97%), quadrupedal standing (3.70% ± 3.03%), bipedal standing (3.54% ± 1.84%), sprawling (3.17% ± 6.45%), suspending (1.88% ± 1.19%) and lying (0.14% ± 0.21%). Positional behaviors seasonally vary with habitat structure, and distribution of food resources. The macaques used climbing more frequently in the fruit-lean season (dry season) than in the fruit-rich season (rainy season), which could be related to reducing energy expenditure in the dry season. In addition, they adopted holding and lying together to conserve energy and stabilize intergroup relationships. In conclusion, Assamese macaques adapt to limestone forests with positional behavior flexibility in response to seasonality. Our findings highlight the necessity to understand the effects of ecological factors on the behavioral ecology and adaptations of Assamese macaques in their unique limestone forest habitats.