HABITAT RELATIONS WITHIN LOWLAND GRASSLAND RODENT COMMUNITIES IN TAIWAN

Patterns of habitat use by murid rodents were examined in lowland gras slands in Taiwan. Fifteen grassland sites were live-trapped in 1990, a nd 16 microhabitat variables were measured at each of 539 trap station s in the sampling sites. Mus caroli, Apodemus agrarius, Rattus losea, and Bandicota indica were captured regularly during the sampling. Ratt us norvegicus and Niviventer coxingi were captured infrequently. The a nalysis focused on the four common species. Mus caroli, R. losea, and B. indica have been considered to be commensals of humans and to be la rgely dependent upon agricultural crops. However, these species were c aptured in natural habitats, often far from agricultural areas. M. car oli and R. losea were by far the most abundant species. Vertical strat ification of the habitat did not increase the number of species or ove rall rodent abundance. Rather, sites with well-developed grass cover a nd little vertical development of vegetation above the grass layer had the highest overall densities of rodents. Use of habitat was very sim ilar among the four common species and was concentrated in areas with dense grass cover. Overlap in habitat use was particularly extensive i n the core areas of greatest occupancy. Relative population abundances (number of individuals captured per trap station) of the four species were related weakly to the microhabitat variables. These variables we re better predictors of capture probabilities of M. caroli and R. lose a at individual trap stations, as revealed by multiple logistic regres sion. Abundances and capture probabilities did not appear to be affect ed by the presence or abundance of other species. It is suggested that body size differences may facilitate coexistence of these four specie s of ecologically similar murids. Beginning with the smallest species (M. caroli), body masses of each subsequent species in the series diff er by at least a factor of two. These grassland communities may be som ewhat resistant to invasion by more similar-sized species of murids.