Geissmann, T.; Nguyen Xuan Dang; Lormée, N. & Momberg, F. (2000). [Vietnam primate conservation status review 2000 - Part 1: Gibbons.] Fauna & Flora International, Indochina Programme, Hanoi. 142 pp. ISBN: 1-903703-03-4. Vietnamese edition.

Summary

by Thomas Geissmann
Gibbon Research Lab., Hannover

Although several faunistic surveys have been carried out in Vietnam in recent years, survey results have rarely been published. Research results, too, are often preliminary reports published in little-known local journals. A critical reassessment of the gibbon populations, their size and their phylogenetic affinities is urgently required.

The Vietnam Primate Conservation Status Review began implementation in July 1999 with the objective of collating a comprehensive data set for leaf monkeys and gibbons. The results on gibbons have now been published (Geissmann et al., 2000). This is not only the first nation-wide status review of Vietnamese gibbons, but also the first book publication on gibbons since several years. An edition in Vietnamese language has also been published.

Recent research results suggest that the diversity of Indochinese gibbons is larger than previously assumed. All Vietnamese gibbons are members of the genus Nomascus (crested gibbons). The affinities of populations in central Vietnam and southern Laos appear to be particularly complex.

Based on earlier reports, museum specimens or forest quality, we were able to identify 87 potential gibbon areas in Vietnam. During the last 5 years, however, the occurrence of gibbons was only confirmed for 21 of these areas. In 17 additional areas, the occurrence of gibbons is probable, albeit not reliably documented. In 49 areas (56.3%), gibbons are possibly or probably extinct. The proportion of these areas is particularly high in northern Vietnam: Nomascus concolor 61.1%, N. leucogenys leucogenys 74.1%, and N. sp. cf. nasutus 75%. The situation is particularly alarming for N. sp. cf. nasutus which has no reliably confirmed populations in Vietnam (12 localities evaluated). The only confirmed observations of this species were made on the Chinese island of Hainan (population: less than 20 individuals), and this species appears to exhibit the sad distinction of being the most critically endangered primate species world-wide. Other gibbons in the northern half of Vietnam are also critically endangered: N. concolor was confirmed in only 2 of 18 localities, and N. leucogenys leucogenys in only 4 of 27.

Contents   1. Introduction   2. Gibbons (Family: Hylobatidae) 2.1 An Introduction to the Gibbons (Family Hylobatidae) 2.2 Splitting the Gibbons 2.3 An Introduction to the Crested Gibbons (Genus Nomascus)   3. Distribution 3.1 Distribution of the Genus Nomascus 3.2 Eastern Black Crested Gibbon Nomascus sp. cf. nasutus 3.3 Western Black Crested Gibbon Nomascus concolor 3.4 Northern White-Cheeked Crested Gibbon Nomascus leucogenys leucogenys 3.5. Southern White-Cheeked Crested Gibbon Nomascus leucogenys siki 3.6 Yellow-Cheeked Crested Gibbon Nomascus gabriellae   4. Ecology and Behavior 4.1 Ecology 4.2 Habitat 4.3 Diet 4.4 Songs   5. Species Descriptions 5.1 Eastern Black Crested Gibbon Nomascus sp. cf. nasutus 5.2 Western Black Crested Gibbon Nomascus concolor 5.3 White-Cheeked Crested Gibbon Nomascus leucogenys 5.4 Yellow-Cheeked Crested Gibbon Nomascus gabriellae 5.5. What Goes On Between N. l. siki and N. gabriellae?   6. Crested Gibbon Records in Vietnam 6.1 Eastern Black Crested Gibbon Nomascus sp. cf. nasutus 6.2 Western Black Crested Gibbon Nomascus concolor 6.3 Northern White-Cheeked Crested Gibbon Nomascus leucogenys leucogenys 6.4. Southern White-Cheeked Crested Gibbon Nomascus leucogenys siki 6.5. White-Cheeked Crested Gibbon Nomascus leucogenys siki or Yellow-Cheeked Crested Gibbon N. gabriellae? 6.6 Yellow-Cheeked Crested Gibbon Nomascus gabriellae   7. Status 7.1 Eastern Black Crested Gibbon Nomascus sp. cf. nasutus 7.2 Western Black Crested Gibbon Nomascus concolor 7.3 Northern White-Cheeked Crested Gibbon Nomascus leucogenys leucogenys 7.4. Southern White-Cheeked Crested Gibbon Nomascus leucogenys siki 7.5. Yellow-Cheeked Crested Gibbon Nomascus gabriellae   8. Threats to Gibbons in Vietnam 8.1 Hunting and Wildlife Trade 8.2 Habitat Disturbance   9. Recommendations 9.1 Hunting and Wildlife Trade 9.2 Population Management 9.3 Habitat Disturbance 9.4 Protected Areas System Review 9.5 Education and Awareness Raising 9.6 Research and Field Surveys 9.7 Species-Specific Recommendations 9.8 General Recommendations   References   Appendix 1. Gibbon Species in the Protected Area Network of Vietnam Appendix 2. Localities List