Reptilian species distribution in response to habitat fragmentation and microhabitats in the rainforests of southern Western Ghats, India.

Abstract

Habitat fragmentation has long been recognized as a threat to biological diversity and a major cause in the sudden increase in the extinction rates of species. Demographic and environmental stochasticity, habitat degeneration, the decrease in genetic variability and the influx of secondary forest species all lead to the extinction of forest species in the forest fragments. The forests in the various hill ranges in the Western Ghats are under anthropogenic pressure, mainly due to commercial plantations like tea, coffee, cardamom and spices and timber. The construction of dams for irrigation and hydroelectric power projects and roads and rapid urbanization are other ways by which the once contiguous middle elevation rainforests of the Western Ghats have been dismembered into scattered fragments. The rainforests of the Western Ghats is one of the richest biogeograpic zones in the country with more than 50% of the reptiles reported from the area being endemic to these forests. The most serious problem that is faced by the wildlife managers in the Western Ghats is that the remaining forests, especially the rainforests, occur in a highly fragmented state. The effect of rainforest fragmentation has taken its toll on the overall biological diversity with declines in reptile species contributing to this loss. Addressing this conservation problem becomes difficult in any forum, as studies on reptiles are few and poorly represented in literature. In this background, the objectives of the present study broadly defined here were to understand 1) the factors that govern the distribution of reptiles in the rainforests. The factors include both macro and microhabitat variables that the reptiles are know to respond to; and 2) to see if the process of rainforest fragmentation has affected the reptilian distribution and community structure, and to understand the direction of this impact. The study was divided in to two phases, the first phase was devoted to understanding the factors that were likely to influence the distribution of rainforest reptiles, while the second phase looked into the effects of rainforest fragmentation on reptiles. A combination of sampling techniques that included the adaptive cluster sampling (for leaf litter reptiles), the forest transects (for arboreal reptiles), stream surveys (for nocturnal stream dwelling reptiles) and opportunistic sampling was used to sample rainforest reptiles. Three sites in the contiguous rainforests of Kalakad-Mundanthurai . Tiger Reserve (KMTR), that broadly represented the altitude range and the different drainages, formed the site for the first phase of the fieldwork. The fourteen rainforest fragments in the Anamalai Hills were the study sites for the second phase of fieldwork where the effects of rainforest fragmentation were enumerated explore in detail the two major points expressed above, and detailed assessment of what is needed to promote reptile conservation is provided at the end.