Population Dynamics of a Lion-Tailed Macaque (Macaca silenus) Population in a Rainforest Fragment in the Southern Western Ghats of India

Abstract

Demographic analysis is often used for the effective management of wildlife, especially for species facing human-caused disturbances to their habitat, such as habitat fragmentation. The objective of this long-term study was, therefore, to gain insights into the status of a lion-tailed macaque (Macaca silenus) population, inhabiting the Puthuthottam estate near Valparai in the Western Ghats of southwestern India, by documenting demographic factors, such as group numbers, group size and age/sex composition, as well as estimating growth, birth, and mortality rates. We documented the demography of five resident groups of this species, comprising 5% of the remaining wild lion-tailed macaque populations. In this paper, we present a demographic history of the Puthuthottam population through comparisons with studies conducted by various research groups, beginning in the 1970s, and report a five-fold increase in population size over a period of four decades. Using Generalized Linear Mixed Models, we analyze and discuss the effects of population demographic parameters on birth rates, including a moderately reduced growth- and birth rate, as compared to previous records for the population. The most frequent contributor to mortality, especially of the vulnerable juvenile age class, was found to be roadkill deaths, followed by other anthropogenic causes, including electrocution on exposed electric lines. We also report a shift in the social system, pervasive across this population, from unimale–multifemale to multimale–multifemale social groups. We strongly believe that the observed drastic alterations to the socioecological profile of the study population, as a result of habitat fragmentation and increased utilization of human habitats, have major implications for the long-term survivability of this macaque population. We hope the information presented in this paper will aid in the effective management of the remaining lion-tailed macaque populations across their distribution range, particularly as they become increasingly exposed to human-altered habitats.