Dietary habit of western hoolock gibbon (Hoolock hoolock Harlan, 1831) in the Inner Line Reserve Forest of southern Assam, India

This study investigates the dietary routines and feeding patterns of the western hoolock gibbon (Hoolock hoolock), a species facing extinction in the Inner Line Reserve Forest (ILRF) of Assam’s Cachar district. The research, essential for effective primate conservation, focuses on a four-member gibbon group that resides in a small, isolated forest patch within the ILRF. Over a period of 12 days each month for a year (December 2011 to November 2012), with a total of 1,008 contact hours, observations reveal the diverse diet of the gibbon group. They allocate 34% of their annual activity budget to feeding, engaging in a varied diet that includes fruits (55.34%), leaves (24.28%), flowers (12.30%), seeds (5.18%), and minimal insect consumption (2.91%). Seasonal fluctuations in the consumption of plant parts are evident. The gibbon group displays extensive plant use, incorporating 56 species from 31 families. Moraceae (21.4%) dominates the diverse vegetation, which includes trees, figs, climbers, and woody lianas. Fruit consumption accounts for a significant portion (75%) of their diet, with Artocarpus, Ficus, Dysoxylum, and Syzygium species identified as preferred food sources. Although the gibbon group uses 56 species, the top 20 contribute approximately 75% to their overall feeding time. This study provides insights into the dietary preferences and plant choices of Hoolock hoolock in the ILRF. Understanding its activity budget, especially feeding time and dietary needs, is crucial for conservation, as it identifies essential food resources and seasonal dependencies. This knowledge can guide habitat management, restoration of preferred food species, and help mitigate habitat fragmentation impacts on the western hoolock gibbon. Keywords: feeding behaviour; Hoo­lock hoolock; seasonal variation; Inner Line Re­serve Rorest; Cachar; Assam