|Scientific Name:||Nomascus hainanus (Thomas, 1892)|
|Taxonomic Notes:||Nomascus hainanus has been variously considered either a species in its own right or as a subspecies of N. concolor or N. nasutus; it is here recognized as a distinct species based on differences in vocalizations and fur coloration (T. Geissmann pers. comm. 2006).|
|Red List Category & Criteria:||Critically Endangered A2acd; B1ab(iii,v)+2ab(iii,v); C2a(ii); D ver 3.1|
|Assessor(s):||Geissmann, T. & Bleisch, W.|
|Reviewer(s):||Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)|
Listed as Critically Endangered because of an observed decline of at least 80% over the past 45 years (three generations) due primarily to hunting and habitat loss; and because its extent of occurrence is less that 100 km² and its area of occupancy is less than 10 km², all individuals are in a single subpopulation, and there has been a continuing decline in the number of locations and the number of mature individuals; and because its population size is less than 250 mature individuals, with all individuals in a single subpopulation, and it is experiencing a continuing decline; and because its population size is less than 50 mature individuals.
|Previously published Red List assessments:|
|Range Description:||This species is endemic to Hainan Island, China (Chan et al. 2005). It is currently confined to the Bawangling Nature Reserve on the western side of the island of Hainan (Chan et al. 2005). Before the 1960s it was widely distributed across the island.|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||In the late 1950s, the population was estimated to be over two thousand individuals (Liu et al. 1984). In 1993 there were three groups with less than 20 individuals (Geissmann et al. 2000). During a comprehensive survey in 2003, only 13 individuals were recorded, consisting of two groups, in addition to two solitary individuals (Chan et al. 2005; Geissmann 2005b). Since 2003 an intensive monitoring work showed that the population of Hainan Gibbon has increased in the past five years. The two groups have produced newborn infants every two years, as previously noted (Liu et al. 1989), while a single individual departed from each group during the same period. These changes brought the composition of the two groups to nine and six individuals respectively. At present the there could be also up to five solitary individuals, reaching so a total of 20 individuals (Fellowes et al. 2008).|
|Current Population Trend:||Stable|
|Habitat and Ecology:||This species inhabits remnant forest. It is diurnal, arboreal, and mostly frugivorous (Geissmann et al. 2000). The most difficult time for the gibbons to find food in Bawangling Nature Reserve is between February and April, when only seven of 40 known food-plant species are available for the gibbons (Chan et al. 2005). The species occurs at altitudes ranging from 650 to 1,200 meters (Chan et al. 2005; Geissmann et al. 2000) but in the past probably preferred lowland forest.|
Group size has been reported to range from 4-8 individuals, with an average of 5.3-5.5 individuals, depending on the year of the study (Geissmann et al. 2000). Home range size ranges from 100 to 500 ha (Liu and Tan 1990; Liu et al. 1989; Zhou pers. comm. 2006), with an average of about 360 ha (Liu et al. 1989).
|Major Threat(s):||There is still pressure from hunting. In recent years the core remaining habitat has been protected, although the currently occupied habitat may be in suboptimal (Geissmann 2005a; T. Geissmann pers. comm.). This species is threatened from problems intrinsic to extremely small population size such as inbreeding effects, poor mate-choice, and human or natural disaster (Chan et al. 2005). There are some reports of a sex bias in births, but it is not possible to identify the sex of young crested gibbons in the field, because immature individuals do not differ in fur coloration or calls, and sexual organs of males and females resemble each other (T. Geissmann pers. comm. 2006).|
This species is listed on CITES Appendix I. As far as known it is entirely confined to Bawangling Nature Reserve in Hainan Island (Chan et al. 2005; Geissmann et al. 2000) and is the most critically endangered primate in the world (Geissmann 2005a). There is suitable gibbon habitat outside of the known Nature Reserve, and there is a need to survey for any surviving individuals or groups not yet accounted for, especially in Diaoluoshan Nature Reserve, Yinggelin Nature Reserve, and Jianfenglin Nature Reserve (B. Chan and T. Geissmann pers. comm. 2006).
In terms of the Bawangling population, there should be intensive monitoring of the remaining two groups, and survey of the remaining subadults (Chan et al. 2005; Fellowes et al. 2008). There is a need for continued gun confiscation in the area, which has already been done once in the area (W. Bleisch pers. comm. 2006). The most important thing is to protect all of the remaining habitat and individuals. Captive breeding does not appear to be a wise strategy for this species because (1) there are no captive individuals, (2) earlier attempts to capture wild gibbons alive has not been very successful and may reduce the viability of the few remaining individuals, and (3) captive breeding of crested gibbons has not been highly successful.
|Citation:||Geissmann, T. & Bleisch, W. 2008. Nomascus hainanus. The IUCN Red List of Threatened Species 2008: e.T41643A10526461.Downloaded on 21 January 2018.|