Macroecology of terrestrial herpetofauna in Andaman and Nicobar Archipelago

Abstract

The islands arc system of Andaman & Nicobar Islands situated in the Bay of Bengal is a major contributor to the overall high biodiversity figures of India. These islands are part of two global biodiversity hotspots and contain an impressive array of endemic flora and fauna. The herpetofauna of these islands have been the subject of explorations since the 19th century when European naturalists started natural history collections in these islands. However, our understanding of the terrestrial herpetofauna of these islands has been restricted to anecdotal observations, field records and taxonomic studies.. We conducted a four year survey of terrestrial herpetofauna in Andaman & Nicobar Islands. During this period 24 islands were surveyed for terrestrial herpetofauna. For the sake of completion, data from prior surveys and museum records were also compiled. We recorded 65 species of terrestrial reptiles and 17 species of amphibians from across the Andaman & Nicobar Islands. We present a presence absence matrix for all species recorded from various islands. As expected, the largest islands had the highest number of species and smaller islands within an island groups tended to have communities that were subsets of the larger island community. Several new records and some new species were discovered during our surveys. We found that the terrestrial herpetofauna in Andaman & Nicobar Islands occur in relatively high densities in undisturbed habitats, reaching as high as 3630 individuals per hectare in Little Andaman Island. Patterns in body size distributions were mostly right skewed, but inter taxa differences were observed in this. The shape of body size distribution did not change between Andaman Islands and Nicobar Islands. Distribution of body sizes within communities of co-existing species of frogs and lizards revealed a highly structured distribution, but not in the case of snakes. Species cooccurrence patterns showed inter taxa and inter island group differences. Differences in biogeographic and colonization histories of both groups of islands are suspected to be the reasons behind the observed species co-occurrence patterns. Abundance and geographic distribution patterns were less clearly defined for both frogs and lizards. We suspect that introduced species such as chital and Indian bullfrog might have adverse impacts on native herpetofauna in the Andaman & Nicobar Islands. We attempt a classification of island herpetofauna according to their vulnerability to extinction. We also assess the current conservation status according to the IUCN criteria and legal protection status according to WPA, 1972, and show that majority of species occurring in the Andaman & Nicobar Islands have not yet been assessed properly. We conclude this report by providing a checklist of the herpetofauna, other than turtles and crocodiles, of Andaman & Nicobar Islands.