Timber, Territory, and Tension: Behavioral Responses of Hoolock Gibbons to Human Activity in Assam’s Fragmented Forests

Abstract (English)

In the face of expanding human activity within protected areas, understanding the behavioral responses of wildlife to anthropogenic disturbances is essential for designing effective conservation interventions. This study investigates how the endangered Western Hoolock Gibbon (Hoolock hoolock), India’s only ape species, adapts its behavior in response to increasing human presence — particularly timber poaching and forest resource extraction— in the Hoollongapar Gibbon Wildlife Sanctuary (HGWS), Assam.
Drawing on direct behavioral observations conducted across multiple gibbon groups in 2025, the study documents changes in daily activity patterns in regions with varying levels of human intrusion. In areas affected by active or recent timber poaching, gibbons exhibited elevated rates of vigilance behavior, a notable reduction in resting and grooming time, and an increased frequency of short, fragmented travel bouts. Alarm vocalizations were more common, and group cohesion was periodically disrupted, even in the absence of direct visual encounters with humans. Juvenile individuals in these zones demonstrated reduced play behavior and remained in closer proximity to adult members, a possible indicator of stress or perceived risk. These behavioral changes suggest a breakdown of routines critical for social cohesion, developmental learning, and energetic stability.
The behavioral data were contextualized through semi-structured interviews with local forest guards and residents from adjacent villages. These interviews revealed that while many households depend on the sanctuary for fuelwood and non-timber forest products, some practices—such as covert timber harvesting—exploit legal ambiguities in the Indian Wild Life (Protection) Act. Specifically, poachers often pre-weaken trees by carving notches into trunks, causing them to fall naturally during storms, thus circumventing enforcement. Such tactics make it difficult for frontline forest staff to distinguish between legitimate resource collectors and illegal loggers.
Gibbons appear highly sensitive to direct human presence and indirect cues such as auditory signals, trails, and olfactory traces, which influence their spatial movements and vigilance patterns. These findings highlight that forest integrity alone is insufficient to ensure species survival if the behavioral ecology of resident fauna is not simultaneously considered.
By foregrounding the nuanced behavioral responses of gibbons to human presence, this paper advocates for conservation frameworks that integrate ethological data with socio-economic realities on the ground. Protecting wildlife in rural landscapes like HGWS requires understanding how animals interpret human activity and the socio-legal context in which such activity occurs. Conservation, therefore, must be both ecologically informed and socially attuned.