This study was conducted in Trishna Wildlife Sanctuary(TWS) between November 2001 and July 2005 to know the habitat requirements of the gaur (Bos gaurus gaurus), hoolock gibbon (Bunopithecus hoolock), capped langur (Trachypithecus pileata) and pigtailed macaque (Macaca nemistrina). The study also assessed the forestry resources those are important for the conservation of above species. In total 359 km., effort was made along six line transects during winter and summer. The observed seasonal group size was highest for pigtailed macaque followed by capped langur and hoolock gibbon. During the study the population of non-human primate species decreased in the intensive study area. Results showed that niche limitations are not likely to constrain co-existence of hoolock gibbon, pigtailed macaque and capped langur. Two sub-population of gaur, one inside Sanctuary and other outside (Siddinagar and around) Sanctuary were observed. Group size of gaur varied significantly during different seasons and also for inside and outside Sanctuary sub-population. Highest individual encounter rate for gaur was observed in mixed bamboo forest, where as highest group encounter rate was observed in mixed deciduous forest. The semi-evergreen type of forest was the only habitat occupied by all the study species and observed to be the best habitat for area based conservation approach.

The study recommended total protection of the Sanctuary area especially from the organized illicit fellers and poachers. As the endangered species of the study area are facing high risk of local extinction, we suggest demarcation of about 70 square kilometer area in the centre of southern part of the Sanctuary to be declared as National Park to ensure protection to the existing population. We also recommend the southern part of the outside Sanctuary area near Siddinagar should be included in TWS to ensure protection to gaur population and subsequent corridor improvement programme.
 

Sabyasachi Dasgupta, TA