The Conservation Status of Gibbons in Vietnam
2.2.1
Decree 32/2006/NP-CP on Management of Endangered, Precious and Rare Forest Plants and Animals
Prime Minister’s Decree 32/2006 classifies and defines the level of protection for protected wild animals and plants in Vietnam within two groups; I and II. Gibbons are classified under IB, the highest level of protection for animals which are “strictly banned from exploitation and use for commercial purposes, including plants and animals of scientific or environmental value or high economic value, with very small populations in nature or in high danger of extinction”. Nomascus concolor, N. leucogenys, N. nasutus and N. gabriellae are all explicitly listed and it may be assumed that the listing of N. leucogenys covers N. siki as the sub-species N. leucogenys siki, as it is recorded in the Vietnam Red Data Book and elsewhere in literature from that time. This decree is soon to be supplemented by a decree on “Criteria for Species Identification, Management and Protection of Species listed as Endangered, Precious, Rare and Prioritized for Protection”, which brings formal levels of protection more into line with the categories and criteria of the Vietnam Red Data Book.
2.2.2
Vietnam Red Data Book
All gibbon taxa listed in the current 2007 Vietnam Red Data Book come under the category Endangered with the criteria A1cd C2a, which broadly indicates that there has been a 50% decline and severe fragmentation of the population of each species, and that the species is facing a very high risk of extinction in the wild. N. nasutus and N. annamensis are not directly referred to. N. nasutus falls within the distribution map presented for N. concolor and N. annamensis was not described as a distinct species at the time. However, the actual population status and levels of threat of extinction vary widely for the different gibbon species in Vietnam, and with the more comprehensive information now available it is clear that this one category and set of criteria is inappropriate for all species. The national Red Data Book should clearly indicate relative levels of threat to each species and so support prioritisation of conservation measures through policy and direct action. A more appropriate categorisation for each gibbon species following the criteria of the Vietnam Red Data Book (See Annex 2) is proposed here. It is not intended to be definitive but to provide a starting point for future revisions of the Vietnam Red Data Book. In proposing these categories and criteria, certain assumptions have to be made where there is large uncertainty in the available data. This uncertainty is compounded by the fact of a gibbon generation being long compared to most mammals. In this document a gibbon generation is considered to be about 15 years, following the standard used for gibbons on the IUCN Red List of Threatened Species. The low fecundity of gibbons means long periods of time need to be considered in order to track declines and forecast potential recovery. One generation, i.e. 15 years, is already long enough that sufficient records are not available to make quantitative analyses of population trends based on existing data, so past population trends need to be inferred. However, overall it is assumed with confidence that there have been drastic declines in gibbon populations within the last few gibbon generations, based upon the previous known extent of gibbon occurrence, land-use change and past and present levels of hunting pressure. Eastern Black Gibbon - Nomascus nasutus Proposed category and criteria: Critically Endangered A1cd, B1+2cd The current population of N. nasutus in Vietnam is well documented. There has been a decline in the population of this species over the past three generations greater than 80%, based on the area of occupancy and extent of occurrence being reduced to one population in an area of about 1000 ha. Recent likely local extirpations, such as at Kim Hy and Than Sa-Phuong Hoang Nature Reserves, have no doubt been due to hunting and indicate continued recent declines. N. nasutus thus certainly qualifies for the status of Critically Endangered in Vietnam.
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