Impact of Habitat Fragmentation on the Demography of Lion-tailed Macaque (Macaca silenus) Populations in the Rainforests of Anamalai Hills, Western Ghats, India

Abstract

Habitat fragmentation is considered the most serious threat to primate conservation in the tropics, and understanding it effects on lion-tailed macaque is very important because most of the populations live in fragmented habitats. We examined demographic parameters of 9 lion-tailed macaque groups in 8 rain forest fragments with reference to fragment area, tree density, canopy cover, tree height, and total basal area of food trees. Group size ranged from 7 to 90 individuals but was not related to habitat variables. Birth and growth rates of groups did not differ significantly between small (n = 4) and large (n = 4) fragments. Tree density, canopy cover, and total basal of food trees all show strong positive correlations with fragment area. Growth rate correlates with tree density, but there are no other significant relationships between birth or growth rate and habitat variables. The percentage of immature individuals in the group is significantly positively associated with the total basal area of food trees, but not with any other habitat variable. Comparison of our data from this study with data available for the same population in 1996 indicates a slight decline in birth rate but an increase in total number of individuals, from 154 to 242. Of the 5 small fragment groups, 3 have increased in size since 1996 while the sizes of the other 2 groups have remained the same. Based on this study, we advocate that to manage the fragile lion-tailed macaque groups the following steps need to be taken: 1) create dispersal corridors between the fragments using fruit trees to facilitate male dispersal, 2) construct canopy bridges across the prevailing roads, 3) protect the fragments from further degradation, and 4) periodically monitor these populations for long-term conservation.