Impact of habitat disturbance on the distribution of endemic species of small mammals and birds in a tropical rain forest in Sri Lanka

Abstract

We tested whether species endemic to Sri Lanka were less able than non-endemics to tolerate disturbed habitats. Small mammals were surveyed in four habitat types along a disturbance gradient (unlogged forest, selectively logged forest, cultivated areas and areas abandoned after cultivation) within and around the Sinharaja rain forest in south-west Sri Lanka. Twenty 90-m×40-m plots were live trapped in each of these habitat types. Twelve taxa: nine rodents (Srilankamys ohiensis, Rattus rattus kelaarti, R. r. kandianus, Mus mayori, M. cervicolor, Bandicota indica, Funambulus layardi, F. sublineatus and F. palmarum) and three insectivores (Crocidura miya, Suncus zeylanicus and Feroculus feroculus) were recorded. Of these, five were endemic to Sri Lanka at the species level (species confined to the island) and six at subspecies level (subspecies confined to the island; other subspecies occurring on the Indian subcontinent). Species richness of small mammals decreased with the magnitude of forest disturbance. The endemic species selectively utilized sites within the forest whilst the majority of the other taxa used both forest and non-forest habitat types or were restricted to the latter. Bird surveys were carried out in the same plots, using sightings and calls. Sixty-six bird species were recorded, of which 21 were endemic species. Twenty endemic bird species preferentially used sites within the forest. The findings suggest that the forest-dwelling endemic species of both small mammal and bird encounter difficulties in tolerating modified landscapes, whilst other taxa are less affected. This highlights the vulnerability of endemic species to forest conversion.