关键词: 东黑冠长臂猿, 新群体形成, 种群数量, 保护现状

Abstract: Eastern black crested gibbons (Nomascus nasutus) are listed as Critically Endangered in the IUCN Red List, because of their small population size. The single remaining population is comprised of about 110 individuals living in a karst forest patch along the border of China and Vietnam. We monitored gibbon calls from fixed listening posts to survey the Chinese population in Guangxi Bangliang National Nature Reserve (Bangliang NNR) during May and August of 2015. We found a previously unknown group of eastern black crested gibbons that consists of 1 adult male, 2 adult females, and 1 infant. This is the first discovery of a newly formed group in China since 2006, when the species was rediscovered in Bangliang NNR. The population of eastern black crested gibbons in China is now estimated to have increased from 22 individuals in 3 groups to 26 individuals in 4 groups. The population size is likely limited by available habitat, restoration of which will be vital to future population growth. Presently, livestock grazing is a serious threat to gibbon habitat in Bangliang NNR. Actions must be taken to reduce or even prohibit grazing inside the nature reserve. Given that this population is distributed across the border of China and Vietnam, relevant government departments in both countries need to strengthen cooperation in border management and habitat protection. Fragmentation of this population by the international border would harm its recovery.

Key words: Conservation status, New group formation, Nomascus nasutus, Population quantity