Geissmann, T., Vu Ngoc Thanh, Dine, M. C., and Tu Minh Tiep (2009). Results of a gibbon survey in the Kim Hy Nature Reserve (Bac Kan province) in northeastern Vietnam. People Resources Conservation Foundation (PRCF), Vietnam Programme, Hanoi, 25 pp.

Results of a gibbon survey in the Kim Hy Nature Reserve (Bac Kan province) in northeastern Vietnam

Thomas Geissmann¹, Vu Ngoc Thanh² , Michael C. Dine³ and Tu Minh Tiep^3
1 Anthropological Institute, University Zürich-Irchel,
Winterthurerstr. 190, CH-8057 Zürich, Switzerland.
E-mail: thomas.geissmann@aim.uzh.ch
² Zoological Museum, Hanoi University of Science, Vietnam National University,
334 Nguyen Trai Street, Thanh Xuan District, Hanoi, Vietnam.
E-mail: vnthanh@fpt.vn
³ People Resources and Conservation Foundation Vietnam, Hanoi, Vietnam.
E-mails: michael.prcf@gmail.com; and: minhtiep@prcfunion.org

Abstract: The cao-vit crested gibbon (Nomascus nasutus) is one of the wold's most endangered primate species, with one single protected forest patch in the border area between Cao Bang province (Vietnam) and Guangxi province (China) supporting the last known population. No other locality is known to support a population of this species, however, some gibbons are rumoured to have survived in Kim Hy Nature Reserve of Bac Kan province (northeastern Vietnam). Although several previous surveys in Kim Hy failed to find direct evidence for the continued occurrence of gibbons there, each provided interview information indicating that Kim Hy still supported a few gibbons. In order to resolve the contradiction, we conducted a two-week survey in Kim Hy in June 2009. We recorded intrusion of agriculture in the periphery of the nature reserve, massive logging going on mostly, but not exclusively, in the periphery of the reserve, and hunting and gold mining in all areas including the core zone of the reserve. The gold mining in particular had taken on enormous dimensions, with some valleys in the centre of the primary forest reported to harbour over 100 miners. We manned four listening posts in each of two survey areas in the very centre of the remaining forest in the core zone and monitored gibbon calls. The habitat consisted of steep karst hills covered with primary and secondary forest. Much of the forest in the survey area was selectively logged. Gunshots from illegal hunters were heard almost daily. Explosions from gold mining were heard daily and in large numbers from up to three different directions per listening post. In addition, motors of water pumps used for gold mining were also audible from some listening posts. No gibbons were seen or heard calling. In contrast to earlier surveys in Kim Hy, several interviewees suggested that gibbons were extinct in the area. On average, their most recent evidence for the occurrence of gibbons in Kim Hy dated from 2001. The only interviewee who reported having heard gibbon calls one year ago may not have been reliable as he claimed that gibbons occurred in groups of 30-40 individuals. As a result, we conclude that cao-vit crested gibbons of the Kim Hy Nature Reserve probably became extinct early in this century. On the other hand, we found that macaques - probably stump-tailed macaques (Macaca arctoides) - and Francois's leaf monkeys (Trachypithecus francoisi) still occur in Kim Hy.