Black-crested gibbon  (Nomascus concolor)

The black-crested gibbon is one of the world's most endangered primates and may be on the very brink of extinction (7). Males and females are strikingly different in appearance with males almost completely black, but sometimes with white or buff cheeks, and females a golden or buff colour with variable black patches, including a black streak on the head (2). The common name of this species comes from the tuft of longer fur on the crown of the head (5). Both sexes have the characteristic slender shape of the ‘lesser ape' with long arms and legs, grasping hands and feet, and no tail (4). A variety of calls are produced, which are amplified with the aid of a throat sac below the chin; males and females engage in duets, in which males grunt, squeal and whistle whilst females sing rising notes and twitter (2).

The black-crested gibbon is found in South East Asia, and the greatly reduced and fragmented range includes Vietnam, China and Laos. Much confusion surrounds the taxonomy of this species but at present five different subspecies are recognised (9). The central Yunnan (Nomascus concolor jingdongensis) and the west Yunnan black-crested gibbon (N. c. furvogaster) are both found within the Yunnan Province of China (6). Whilst the Laotian black-crested gibbon (N. c. lu) is found in Laos, the Tonkin black-crested gibbon (N. c. concolor) is found in Northern Vietnam (7) and the Hainan black-crested gibbon (N. c. hainanus) is found on Hainan Island, China (6).

The black-crested gibbon inhabits tropical evergreen broad-leaved forests and semi-deciduous monsoon forests (4).

Gibbons are forest dwellers and are well known for their habit of swinging between the branches of the rainforest on their long arms, a method of locomotion known as brachiation (4). Gibbons are also adept however, at walking upright, both on the ground and in the trees (2). Black-crested gibbons live in small family groups consisting of a monogamous male and female and their offspring, there are also reports that groups may contain additional mature females (4). These apes are predominantly arboreal and the group forages and sleeps amongst the trees (2). Led by the female, the breeding pair partakes in vigorous bouts of singing in the morning, which hauntingly echo through the forest. It is believed that these ‘duets' are essential in pair bond formation and reinforcement, but also serve to advertise the presence of the group within the territory (2). A single young is born every two to three years and the infant is usually weaned once it reaches 2 years old (2).

Black-crested gibbons feed preferentially on ripe sugar rich fruit such as figs (Ficus spp.), although they also supplement their diet with leaves and insects (2).

Deforestation has swept across South East Asia at an alarming rate as trees are logged for timber or to make way for agriculture and development. Gibbons throughout the region have undergone dramatic declines due principally to this habitat loss, but also as a result of hunting (7). The fragmentation of their habitat causes groups to become separated from the remaining population (2), and it is estimated that about 75% of the black crested gibbon's original habitat has already been lost (8). The taxonomic confusion surrounding this species makes population estimates particularly difficult but at least two of the subspecies are today at critically low levels (1).

The black-crested gibbon is protected from international trade by its listing on Appendix I of the Convention on International Trade in Endangered Species (CITES) (3). Fauna and Flora International (FFI) have been studying the species in Northern Vietnam since 1999. They have also been involved in a community awareness programmes in the area and there is pressure to designate the last stronghold of the species (the Che Tao Forest) as a Gibbon Sanctuary (7). In China, the largest population of the Central Yunnan black crested gibbon subspecies occurs within the Wuliang Mountain National Reserve (7). It is vital that any remaining viable populations and habitats are protected or this previously successful ape is in grave danger of disappearing.

Authenticated by Dr David J. Chivers, University of Cambridge.