The demography of the lion-tailed macaque (Macaca silenus) in rain forest fragments in the Anamalai Hills, South India

We examined demographic consequences of habitat fragmentation in the lion-tailed macaque in the Anamalai Hills in southern Western Ghats. The parameters examined were group size, age/sex composition, and birth rate, in relation to various habitat parameters. Demographic parameters were estimated for 11 groups in 8 rain forest fragments, during January to May 1996. Area, tree density, canopy cover, canopy height, and tree basal area were estimated for these fragments. As fragment area decreased, there was a decline in birth rate and proportion of immatures in the group, and an increase in the number of adult males, and the variability in group size and adult sex ratios. A similar pattern was also observed with decreasing values of other habitat variables. Differences in the founder population size and age structure, demographic randomness, and history of poaching have caused greater variability in group size and adult sex ratios in the small fragments. The lack of dispersal in the small fragments is another reason for the high variability.