Radio tracking of Hatinh langurs ( Trachypithecus laotum hatinhensis ) at a semi-wild enclosure in Phong Nha - Ke Bang National Park, Central Vietnam

Summary In 2005 the Frankfurt Zoological Society in cooperation with the Cologne Zoo launched a reintroduction program for two endangered primate species, the Hatinh langur ( Trachypithecus laotum hatinhensis ) and red-shanked douc langur ( Pygathrix nemaeus ) in the Phong Nha ‐ Ke Bang National Park in central Vietnam. As a first step, a semi-wild enclosure was built and in early September 2007 two groups of Hatinh langurs from the Endangered Primate Rescue Center were transferred. All individuals were equipped with radio collars and continuously monitored over a periodofnineweeks.Thelangurssettled-inwellandrapidlyexploredthewholeenclosure.Original group composition was not maintained, but the langurs finally merged into one group. While during the first half of the study, observation conditions were limited as animals were hiding under dense liana covers, later on the langurs gradually exposed themselves in more open areas, allowing extended data sampling periods. Follow-up studies are recommended.