Status and Conservation of Yellow-Cheeked Crested Gibbons (Nomascus gabriellae) in the Seima Biodiversity Conservation Area, Mondulkiri Province, Cambodia

Abstract

The yellow-cheeked crested gibbon (Nomascus gabriellae) occurs east of the Mekong River in southern Vietnam, northeastern Cambodia, and possibly southernmost Lao PDR (2000, Nomad RSI unpubl. data). The northern distributional limit is unclear as it either borders or intergrades with the southern white-cheeked crested gibbon,N. siki (Duckworth et al. 1995, 1999; Geissmann et al. 2000; Konrad 2004). N. gabriellae is currently listed as Endangered in the IUCN Red List of Threatened Species (IUCN 2008). Little behavioral or ecological work was conducted on the species until recent years; however, a picture of the species is beginning to emerge with current studies, particularly in the SBCA (Rawson 2004) and Ratanakiri province, Cambodia (Traeholt et al. 2006), and Cat Tien National Park (NP) in Vietnam (M. Kenyon pers. comm.). It appears that N. gabriellae generally prefers undisturbed evergreen forest with a reasonably high canopy (Nguyen Xuan Dang and Osborn 2004; Traeholt et al. 2006) although the species inhabits other habitat types such as semi-evergreen, mixed deciduous, and even bamboo forest (M. Kenyon pers. comm., this paper). The species can apparently survive a reasonably high degree of habitat and incidental disturbance, persisting in selectively logged habitats and close to human habitation when not hunted to extirpation (Duckworth et al. 1999; Polet et al. 2004, BMR and TC pers. obs.). It has wide altitudinal limits, occurring from 100 m above sea level (m asl) in Cat Tien NP (Eames and Robson 1993) to above 2000 m asl on the Da Lat plateau, Vietnam (Eames and Nguyen Cu 1994). N. gabriellae, like other gibbon species, is territorial and monogamous (Traeholt et al. 2006), with mated individuals producing loud vocal duets