New findings of the Northern white-cheeked gibbon population in Xuan Lien Nature Reserve
The conservation program for the critically endangered northern white-cheeked gibbon (Nomascus leucogenys) in Vietnam is a long-term conservation program that has been initiated by the Center for Nature Conservation and Development (CCD) with a focus on Xuan Lien and Pu Hoat Nature Reserves (NR). The purpose of this program is to recover the populations of the northern white-cheeked gibbon in their historical distribution areas.
Following the regular monitoring of this species, in December 2019, CCD with the support from Xuan Lien management board and a local forest protection group conducted a gibbon survey in the fixed monitoring area – Suoi Sai So (Cat Trang stream) – where the existence of gibbons was confirmed in 2011 to understand the fluctuation of gibbon groups and individuals. The monitoring resulted in at least 16 gibbon groups of about 43 individuals that were recorded through vocalization and observation. Compared with the 2011-2012 baseline survey data included 10 groups and 29 individuals in the same area (Nguyen et al 2012), the number of gibbon groups and individuals dramatically increased after eight years with additional six groups and 14 individuals.
It is exceptional from this monitoring that gibbon groups were recorded in the mixed bamboo-timber forest type. This finding is new for the northern white-cheeked gibbon in particular and for crested gibbons in general because all the records of habitat types of the northern white-cheeked gibbons so far have only been in primary forests where large timber trees dominate. Therefore, the result provides new information on the habitats of this species.
Gibbon is territorial animals, hence, the monitoring of gibbons in the fixed listening posts can help identify more accuracy of the gibbon population trend. The 2019 surveys showed positive evidence of the recovery and thriving of the northern white-cheeked gibbon population in Xuan Lien NR while their sub-populations are extirpating in many other known habitats. The recovery of the northern white-cheeked gibbon population is also a good indicator to measure the effectiveness of forest protection and conservation efforts that Xuan Lien NR management board and its partners are doing. It is no doubt that Xuan Lien NR is the most important and effective conservation area for Northern white-cheeked gibbon population in Vietnam.
