We conducted a survey of the distribution and population status of the eastern hoolock gibbon Hoolock leuconedys in non-protected fragmented forest areas of the Lower Dibang Valley district of Arunachal Pradesh, India, during September 2010–June 2011. We estimated the minimum population density at seven study sites by direct observation and by counting the number of vocalizations heard from groups that were out of view. We used 1-ha belt transects (500 × 20 m) to estimate tree diversity in the study area. For two groups of gibbons we recorded their feeding patterns in forest fragments, using focal individual sampling, during May 2011. A total of 54 groups and three solitary individuals were recorded: 39 groups and three individuals through visual encounter and 15 groups through vocalization recognition. The mean group size recorded was 2.89 ± SE 0.11 (range 2–4). We counted a total of 289 trees, of 26 species and 17 families, in 18 belt transect surveys covering all non-protected fragments of the Lower Dibang Valley district. The gibbons' diet consisted of seasonal fruits and figs (29%), leaves (65%), seeds (2%) and flowers (0.5%). The major threats recorded at the study sites were habitat destruction and hunting. To protect the Vulnerable eastern hoolock gibbon, conservation measures will need to involve local communities.

We conducted an intensive survey of the Vulnerable eastern hoolock gibbon Hoolock leuconedys along the west bank of the Salween River in southern China, covering all known hoolock gibbon populations in China. We found 40–43 groups, with a mean group size of 3.9, and five solitary individuals. We estimated the total population to be < 200. In the nine groups for which we recorded composition, seven comprised one adult pair and 0–3 offspring and the other two groups both comprised one adult male and two adult females. The population is severely fragmented, in 17 locations, with the largest subpopulation containing only five family groups. Compared with the population in 1985 and 1994 five subpopulations have declined and gibbons have been extirpated from nine localities, although we discovered two previously unknown subpopulations. Commercial logging, illegal hunting, agricultural encroachment and population fragmentation pose serious threats to the future of H. leuconedys in China. An integrated conservation plan, including nature reserve establishment/expansion, enforcement of existing laws, conservation education, translocation and conservation-oriented research are needed to ensure the survival of H. leuconedys in China.