The current study was conducted among 18 groups of western hoolock gibbon (Hoolock hoolock) in the Hoollongapar Gibbon Wildlife Sanctuary of Assam to understand their behavioural pattern in a wild habitat when influenced by environmental and anthropogenic factors. The study mainly aimed to understand how they adapt to region-specific conditions such as heavy rain, mate selection and protection against predators. Focal animal sampling and all-occurrence sampling were used to record the behavioural patterns during the study. Although the northern region of the forest is rich in biodiversity, it has witnessed heavy wood poaching, which directly affects the movement and territory of the gibbon populations. There is also an acute scarcity of biogeographic corridors, thereby weakening the gibbons’ movement and resulting in the formation of larger groups. This study suggests that the behavioural activities of these gibbons augment most of their requirements without any (visible) need for innovative behaviour, such as the use or manufacture of tools. Also, the forest has witnessed a slow yet gradual decrease in total land cover, and with the increased anthropogenic pressure, the gibbons are being forced towards a particular geographical point, which has raised aggressive behaviour among them.