Golden-headed Langur

The golden-headed langur, Trachypithecus p. poliocephalus, is probably the most endangered of the Asian colobines. This species only occurs on the Island of Cat Ba in the Gulf of Tonkin, northeastern Vietnam. The Cat Ba Archipelago is in the world-famous Ha Long Bay, a spectacular karst formation that was invaded by the sea. The golden-headed langur inhabits tropical moist forest on limestone karst hills, and shares this habitat preference with the six to seven taxa of the T. francoisi group. Among these so called karst langurs, the Cat Ba langur and its closest relatives, the white-headed langur, T. p. leucocephalus Tan, 1955, in southern China, and the wide-ranging Francois’ langur, T. francoisi (Pousargues, 1898), the northernmost representative of the genus, display the strictest behavioral adaptations to their karst habitat.

There are no systematic and reliable data available on the historic density of the langur population on Cat Ba Island. According to reports of indigenous people the entire island of Cat Ba (140 km²) and some smaller offshore islands were previously densely populated by langurs. Hunting has been the sole cause for the dramatic and rapid population decline from an estimated 2,400–2,700 in the 1960s to only 53 individuals by 2000. The langurs were poached mainly for trade in traditional medicines. Since the implementation of strict protection measures towards the end of 2000, the langur population on Cat Ba Island increased to a current 65 individuals (+22.5%).

Although the growth of the population is encouraging, the overall status of the species is most critical. As a result of habitat fragmentation, the remaining population is now divided into seven isolated sub-populations, five of which include or consist of all-female groups, thus non-reproducing social units. The estimated effective population size is 29 individuals at most. Only three groups are currently reproducing, and the total reproductive output in this species is accordingly low. Since a peak in births in 2003, the reproductive output of the Cat Ba Langur has stagnated at 1-2 offspring per year.

Cat Ba Island and the surrounding area are nationally and internationally recognized for their importance to biodiversity conservation. Cat Ba National Park was established in 1986. It presently covers more than half of the main island. The Cat Ba Archipelago (some 1500-2000 large and small islands, cliffs and rocks) was designated a UNESCO Man and Biosphere Reserve in 2004.

Despite this, nature and wildlife protection on Cat Ba Island is deficient. Efforts to effectively conserve the langurs and their habitat face major obstacles because of the lack of partnership and commitment with the local communities and the need to better address their aspirations for development, and due to the steadily increasing human population, besides persistent, severe deficiencies in law enforcement. As elsewhere in the region, poaching is driven by increasingly attractive commercial gains in satisfying the immense local and regional demand for wildlife. The strictest protection regime possible is necessary for the survival of all the mammals and other species on Cat Ba that are, like the langurs, targeted by the Asian wildlife trade.

A conservation program for the golden-headed langur on Cat Ba was initiated in November 2000 by the Zoologische Gesellschaft für Arten- und Populationsschutz (ZGAP), München, in cooperation with Allwetterzoo, Münster, Germany. The aim is to provide for their protection, reduce population fragmentation, and contribute to the conservation of the biodiversity on Cat Ba Island in collaboration with Vietnamese authorities.