Population, distribution, vocalization and conservation of the gaoligong hoolock gibbon (Hoolock tianxing) in the Tengchong section of the gaoligongshan national nature reserve, China

摘要

We conducted surveys to estimate the current population and distribution of the recently described Gaoligong hoolock gibbon (Hoolock tianxing) in Yunnan Gaoligongshan National Nature Reserve Tengchong Bureau (TC-GLGS). The reserve supports the northernmost known population of the species in China. A total of 17-20 gibbons in 6-7 family groups were recorded in TC-GLGS in a population census conducted in 2016. The mean group size was 2.8-2.9 individuals (range 2-4) with a population density of 0.18-0.21 groups/km2. All groups contained a single adult pair, and juveniles and/or infants were observed in all but two. Mean dawn time was 07:26 h during the survey, and vocalizations were concentrated in the first hour after dawn (57.9 of total song bouts), with an average song bout duration of 25.7 min (n = 19). Four other primate species occurred in sympatry with the gibbons in the study area, with Macaca arctoides and M. assamensis being the most abundant. TC-GLGS appears to support the single largest subpopulation of H.Tianxing in China, but the population density was very low, despite the presence of large areas of healthy, closed-canopy forest, suggesting that the population may have been well below carrying capacity. The suppressed population size is a combined result of rampant hunting in the past, loss of lower elevation forest, and ongoing disturbance by cattle grazing in the remaining gibbon habitat. Long-Term conservation challenges facing the Gaoligong hoolock gibbon in China include the prevention of poaching and disturbance, restoration of deforested areas <2,000 m asl, and the establishment of biological corridors between forest fragments. Translocation to areas contiguous with larger subpopulations should be considered for single groups in isolated forest fragments.