REDISCOVERY OF THE CRITICALLY ENDANGERED EASTERN BLACK CRESTED GIBBON Nomascus nasutus (HYLOBATIDAE) IN CHINA, WITH PRELIMINARY NOTES ON POPULATION SIZE, ECOLOGY AND CONSERVATION STATUS

Abstract

The Critically Endangered Eastern Black Crested Gibbon Nomascus nasutus is rediscovered in China. Acoustic records and direct observation confirmed gibbon occurrence in the Bangliang Limestone Forest of Jingxi County in Guangxi Zhuang Autonomous Region of southwest China, along the Sino-Vietnam border. We recorded a total of 19 gibbon groups including three family groups plus a solitary male over a five-day survey; all groups had two females in adult pelage and carried infants, and at least one group was bigynous with both adult females carrying infants. Vocalizations were concentrated in the early hours from dawn till 07:00, especially immediately after sunrise (71% of total song bouts). The average length of a song bout was 22.4 minutes (n = 14 song bouts), and a single song bout comprised up to 11 female great calls. The Bangliang Limestone Forest constitutes about one-third of a contiguous transboundary limestone forest block, and two of the three groups were observed traveling between China and Vietnam, making collaborative transboundary conservation imperative. Priority conservation actions to preserve this population should focus on (1) establishing a protected area in Bangliang Limestone Forest; (2) forming a close working relationship with Vietnamese counterparts; (3) strengthening the enforcement of forest and wildlife protection regulations inside the gibbon forest; and (4) restoring degraded areas inside and around the gibbon forest to accommodate expected population expansion. Very little is known about the ecology of this species; a better understanding of its life with studies on its social, breeding and feeding ecology should be a priority.