Abstract:
Reintroduction of the pileated gibbon, an endangered species, was made in order to find a
solution to manage pet and captive gibbons. The study involved collaboration between an
academic institution and conservation management authorities. Literature reviews were made to
seek out best practices for gibbon release. Practical aspects of this reintroduction project were a
compromise between best available science and practicality. The study was conducted during June
2004 – July 2006.
Three pairs of captive pileated gibbons (1 male and female / pair) from Krabok Koo
Wildlife Breeding Center were released at 2 sites in Khao Khieo-Khao Chompoo Wildlife
Sanctuary. Five trials were made: 1) Pair 1 released at Site 1; 2) Pair 1 recaptured and released at
Site 2; 3) Pair 2 released at Site 2, with 2 other gibbons (Pair1) already in the area; 4) Male from
Pair 2 transferred to adjacent area; and 5) Pair 3 released at Site 2 with 4 gibbons as neighbors.
Observation times for each released gibbon varied from 9 to 678 hours. Released gibbons spent
most time resting, followed by traveling and foraging. Trends in time spent in specific activities of
released gibbons could be classified into 3 patterns: 1) increasing; 2) decreasing; and 3) constant.
Trends in activities differed among different gibbon pairs. Gibbons were able to determine which
wild plants to eat. At least 58 plant species were eaten, most of which were Ficus spp. Gibbons did
not produce offspring during the short reintroduction time, although seventeen copulation attempts
were found in Pair 1. The release trials showed partial success in that the gibbons were able to fend
for themselves in the wild, but an extensive survey of the wildlife sanctuary is now required to
locate surviving gibbons and make a complete assessment of reintroduction success. Lessons
learned from this study will help to make future well-planned release programs. The main points
that came out from this study are that sudden stopping of food supplements may cause rapid
gibbon disappearance, and more partnerships with local communities and government, in addition
to those between academic institutions and conservation management authorities, are required to
improve release programs.