**Abstract**

The population density, structure, and biomass of mammal species were investigated in the tropical forest of Southern India. The population of large mammals was estimated using distance sampling methods at the Mudumalai Tiger Reserve in the dry seasons from 2004 to 2007. The estimated densities of larger ungulate species such as elephant and gaur were 4.8/sqkm and 7.9/sqkm. Medium-sized ungulate species such as sambar, chital, barking deer, and wild pig densities were 7.1, 27.9, 1.1, and 0.4/sqkm, respectively. The estimated density of primate species, *i.e.*, common langur, was 14.9/sqkm. The smaller rodent species, black-naped hare, had a lower density of 1.3/sqkm, which could be attributed to the nocturnal behaviour of hares. Among these mammal species, barking deer and black-naped hare are solitary species, while others are gregarious. The study area supports herbivore biomass density of 15,198 kg/sqkm. Comparison with earlier estimates, the densities of elephant and gaur is increasing in the study area. The population density of large mammals is compared to other areas and discussed.

**Keywords:** large mammal population, Mudumalai Tiger Reserve, ungulate densities in tropical forest, elephant, gaur, chital
