Abstract
This paper investigates population fluctuations of five rodent taxa across a habitat gradient in areas within and adjacent to the Sinharaja rainforest in Sri Lanka. Live trapping was conducted monthly during a continuous period of 13 months in 1998 and 1999. Four habitat types, ranging from undisturbed forest to habitats subject to varying levels of human disturbance were selected. The five taxa investigated were Srilankamys ohiensis, Rattus rattus kelaarti, R. r. kandianus, Mus mayori and M. booduga. Srilankamys ohiensis and Mus mayori are endemic species. The populations of these rodents were relatively stable, with fluctuations being of small magnitude. The densities were low, with the densities of rat species fluctuating between 0-5/ha and the densities of mouse species ranging from 0-10/ha during most of the survey period. Population sizes generally synchronized with rainfall patterns, being higher during the wetter season when fruits were abundant. Recapture rates of all taxa were quite low and this was seen to be the case in all of the four habitat types sampled. Differences were evident in the distribution patterns of the taxa, the most striking observation being the restriction or the predominance of the endemic species in the forest habitats. Monthly habitat usage patterns further indicated that none of the taxa exhibited seasonal migration between the different habitat types, implying that the populations of these rodents were largely insular.