COMMUNITY STRUCTURE AND DEMOGRAPHY OF SMALL-MAMMAL POPULATIONS IN INSULAR MONTANE FORESTS IN SOUTHERN INDIA

Small mammals were studied in insular montane forest patches in the Up per Nilgiris in southern India from February 1994 to September 1996. N ine patches were selected at two sites, one with a single large 600-ha patch, the other with several small patches ranging in size from 0.2 to 60 ha. The population characteristics and community structure of sm all mammals were studied in relation to patch size and habitat structu re within the patches. The two most abundant species were Rattus rattu s (2-36 individuals/ha) and Suncus montanus (0-11 individuals/ha), whi le the abundance of seven other species recorded were very low. The po pulation characteristics of R. rattus examined were density, biomass, proportions of juveniles, sub-adults and adults, mean weight of all an imals, mean weight of adults, sex ratio and persistence. The proportio n of adults, sub-adults, mean weight of animals, and mean weight of ad ult males were correlated with patch size. Persistence of sub-adult fe males in the large patch was especially high. The density and biomass of other small-mammal species were also studied. Two indices of divers ity, species richness and proportion of R. rattus were compared as mea sures of community structure. Seven habitat characteristics were measu red; of these, canopy cover, canopy height and tree density were corre lated with the size of the patch. Density and biomass of species other than R. rattus and proportion of R. rattus were correlated with canop y height. Density and biomass of species other than R. rattus were hig hest in smaller patches. While the population characteristics of R. ra ttus may be affected by patch size, the density of rare species may be influenced by factors related to lower canopy height. Migration betwe en patches may be an important factor in maintaining populations in th ese patches.