Demography and Post-Sterilization Behaviour of Rhesus Macaques (Macaca mulatta) in Himachal Pradesh

Abstract

Encounters between non-human primates and humans are prevalent due to their increasing adaptability in human-made environments. Rhesus macaque (Macaca mulatta) exists alongside humans in the Northern and Central regions of India. Sharing space with humans has led to increased intolerance in the past two decades. Birth control is considered an ethical alternative to culling to limit population growth of them (Sharma, 2020). Therefore, the Himachal Pradesh State Government and Forest Department initiated the 'Monkey Sterilisation Programme' to limit population outbreaks and counter human-macaque conflicts. This study aims to assess the impact of long-term sterilization on social organization and intergroup interactions of rhesus macaques. I found that the mean group size composition of rhesus macaque in Himachal Pradesh was relatively lower than the control population in Hoshiarpur and also previous studies done in Himachal Pradesh and neighboring Bangladesh. The size of the sterilized group in the population was positively skewed and much smaller than the control population. Age-sex class composition and various age-sex ratios within the sterilized population exhibited a remarkable variation from the control population. The behavioral study done on inter- group interactions between two sterilized troops showed that the encounters varied from mutual avoidance to aggressive vocal calls and chase with higher encounter rate than expected. Often, the interactions occurred in a particular geographical area within their overlapping home ranges. However, the study is transient and requires a fair bit of time to determine the factors and reasons that influence the outcomes of encounters.