Abstract
The study was conducted on the substrate height and substrate use by the Western Hoolock Gibbon (Hoolock hoolock) between April 2002 and June 2003 at Lawachara National Park, Bangladesh. One gibbon group with three individuals was follwed and a total of 2674 observations were recorded during the study period. Substrate height used by the gibbons ranged between 3m and 28m. They performed most of their activities (84%) between 6m and 20m substrate height. Maximum use of substrate heights in different activities were recorded from 11m to 15m; maximum feeding (34%), moving (40%), resting (32%) calling (45%) and social activities (26%) were recorded between this (11m & 15m) heights. Minimum feeding (6%), moving (5%) and resting (6%) were recorded from 1m to 5m and minimum calling (2%) and social activities (2%) were recorded above 26m substrate height. In substrate use they performed most of the activities on small branches and near the periphery and least on the trunk of trees. Substrate height and substrate use during different activities varied significantly and between different age-sex classes. Gibbons were not found to Perform any activities on the ground.