Habitat use and documentation of a historic decline of western Hoolock Gibbon (Hoolock hoolock) in Dampa Tiger Reserve, Mizoram, India

Abstract

The western hoolock gibbon Hoolock hoolock is globally threatened because of a combination of habitat loss, fragmentation and hunting. Most remaining populations are isolated and contain few individuals. We studied a small population of western hoolock gibbons in Dampa Tiger Reserve in Mizoram, India, an area with a deep-rooted tradition of hunting wildlife. We quantified differences in 35-ha sites that were used by gibbons (n = 9) with those that were not (n = 6). We found no statistical differences with respect to canopy continuity, distance to the nearest village or levels of habitat disturbance, but were not able to quantify levels of hunting. Interviews with local villagers (n = 53) from seven villages distributed throughout the reserve suggests that gibbon numbers declined progressively from the early 1970s to the present day, possibly from >100 to <50 individuals. Interviewees pointed at the combined result of fire (from, for instance, slash-And-burn cultivation), reduction of the available habitat, and hunting, exacerbated by an increase in the human population, as possible causes. This corresponds well with our analysis of vegetation maps of the reserve based on satellite imagery, that show a decline in suitable habitat from 63% of the reserve in 1978, to 59% in 1989, and 50% in 2005. We strongly recommend a greater emphasis on quantifying the impacts of hunting on the distribution and persistence of hoolock gibbons.