Javan Gibbon Rescue and Rehabilitation Centre:
A project report


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Texts and information by Dianne Gates and Christine Baker.
Editing and references by Thomas Geissmann

August 2001


The Javan or silvery gibbon (Hylobates moloch) is endemic to the Indonesian island of Java and one of the most endangered gibbon species. The species has been rated as critically endangered by the criteria of the IUCN (Hilton-Taylor, 2000). The remaining population in the wild has been estimated at between 400 to 3,000 animals in the wild, occurring in about 20 forested areas mainly scattered over West Java (Asquith et al., 1995; Kappeler, 1984; Supriatna et al., 1994). Several of the smaller sub-populations are considered non-viable in the long-term. Although recent discoveries show that the Central Javan population may be larger than previously assumed (Nijman & van Balen, 1998), population estimates still suggest that intervention will be necessary in order to conserve the species. Various conservation strategies and priorities have been discussed by Asquith (2001). The taxonomy also needs to be resolved, because some molecular evidence suggests that there may be two genetically discrete populations which should not be mixed (Andayani et al., 2001).

In addition to gibbons remaining in the wild, approximately 80 gibbons are also kept illegally as pets throughout Java, and it is those animals that are the focus of this project. Conservation International-Indonesia and the Silvery Gibbon Project (Perth, Australia) have agreed to collaborate on an effort that will help maximize the contribution of Javan gibbons illegally held in captivity to the conservation of this species.

The urgent situation for this species has been discussed at a Population and Habitat Viability Analysis (PHVA) workshop in Cisarua in 1994 (Supriatna et al., 1994), at a follow-up meeting in Bogor in 1997 (Supriatna et al., 1999), at a gibbon workshop held at the Great Ape Conference in Chicago in 2000, and at the 18th International Congress of the Primatological Society (IPS) in Adelaide in 2001.

One of the recommendations that have come out of these meetings was to establish a Javan Gibbon Rescue and Rehabilitation Center. This center would house some the gibbons currently held illegally as pets on Java. The Javan Gibbon Captive Breeding Center would also be used for education and raising awareness, and to make the Javan Gibbon an icon for Java, in the same way that awareness is now high for orang utans in Sumatra and Borneo.

The Silvery Gibbon Project (SGP) of Perth, Australia, has made a commitment to fund the Captive Breeding Center. The SGP was established in 1991 to assist the in-situ conservation of the Javan gibbon. Funds are raised through events and activities, generating money from members and other interested people.

Approximately US$30,000 has already been raised by the Silvery Gibbon Project. Conservation International (USA based), in partnership with the Silvery Gibbon Project, then applied to Margot Marsh Biodiversity Fund for US$35,000 and has been successful in receiving matching funding (US$30,000). As a result, the Silvery Gibbon Project will be able to support the construction, administration and staffing of the Javan Gibbon Rescue and Rehabilitation Center.

The projected Javan Gibbon Rescue and Rehabilitation Center

During this project, an International Management Committee for the Javan Gibbon will be formed of Indonesian and foreign experts, a suitable site will be acquired for construction of a Javan Gibbon Rescue and Rehabilitation Center, and illegally-held animals will be confiscated by Indonesian authorities.

The objective of the project is to place donated or confiscated Javan gibbons into a rescue, rehabilitation, breeding and reintroduction program. The aim is to assess their medical and psychological health, and to restore these gibbons to full health. Essentially, the genetic material that these animals represent is considered too important to be lost to efforts aimed at saving this species from extinction. The Center will seek to utilize these animals for captive breeding, non-invasive research and education. Pair formation and breeding of rehabilitated gibbons will be encouraged, as will living in natural family groups following the anticipated breeding success.

As it has been designed initially, the Center could hold up to 16 adult gibbons at one time, 10 in bonding enclosures and six in breeding cages, in addition to any offspring that were produced. Since at least 80 animals are thought to be in private hands on Java, provision will have to be made for the transfer of rehabilitated animals and pairs to other zoological institutions in Indonesia (via the Indonesian Zoo Association, PKBSI), as well as to foreign zoos and breeding programs in Asia, Europe and North America. In addition, it is likely that facilities at the Center will have to be expanded at some later date.

Should reintroduction of captive-bred animals to the wild ever become a possibility, these ex-situ populations could someday provide the stock for such an experiment. This objective however, is not short term as behavioral rehabilitation also involves the gibbons abilities to form family groups. Any re-introductions would be based on IUCN recommendations, along with specific guidelines for gibbon reintroduction based on IUCN/SSC recommendations. As reintroduction of rehabilitated gibbons is one of the final conservation strategies to be used for the conservation of doomed populations, these gibbons should be managed at species level regardless of sub-species. For the foreseeable future, however, successes achieved at this Center in terms of rehabilitation and breeding will be targeted toward expanding the size and distribution of this endangered species' captive population.

The permanent staff for the Javan Gibbon Rescue and Rehabilitation Center will be Indonesian, with the provision for securing the services of expert advisors from abroad, especially during the projectís early stages. Training in captive husbandry techniques will be provided not only to permanent staff, but also to representatives of PKBSI whose institutions are likely to receive captive gibbons via their collaboration with the Center. One important output of this project will be the production of a husbandry manual for distribution to institutions interested in housing and breeding Javan gibbons.

This project will establish an International Management Committee for the Javan Gibbon. Indonesian and foreign stakeholders, experts and interested parties will comprise the Committee, and will represent the authority under which the Javan Gibbon Rescue and Rehabilitation Center interacts with local, regional and national authorities, as well as with foreign institutions, for the integrated management of wild and captive Javan gibbon populations. In the initial stages of the project the Committee will be composed of the following individuals:

Jatna Supriatna: Conservation International - Indonesia
Dianne Gates: Silvery Gibbon Project / Perth Zoo
Leif Cocks: International Studbook Keeper / Perth Zoo
Russell Mittermeier: Conservation International
Wahyudi Wardoyo: Indonesian Ministry of Forestry
Widodo Ramono: Indonesian Directorate of Forest Protection and Nature Conservation
David Ware: Independent Consultant


People interested in receiving additional information, in becoming members of the Silvery Gibbon Project or in financially supporting the project may contact:

Dianne Gates
The Silvery Gibbon Project
PO Box 335
Como, Western Australia 6952
Tel: +61-8-92 93 30 52


Andayani, N., Morales, J.C., Forstner, M.R.J., Supriatna, J. & Melnick, D.J. (2001). Genetic variability in mtDNA of the silvery gibbon: Implications for the conservation of a critically endangered species. Conservation Biology 15: 770-775.

Asquith, N.M. (2001). Misdirections in conservation biology. Conservation Biology 15: 345-352.

Asquith, N.M., Martarinza & Sinaga, R.M. (1995). The Javan gibbon (Hylobates moloch): Status and conservation recommendations. Tropical Biodiversity 3: 1-14.

Hilton-Taylor, C. (compiler) (2000). 2000 IUCN Red List of threatened species. IUCN, Gland, Switzerland and Cambridge, UK.

Kappeler, M. (1984). The gibbon in Java. In Preuschoft, H., Chivers, D.J., Brockelman, W.Y. & Creel, N. (eds.), The lesser apes. Evolutionary and behavioural biology. Edinburgh University Press, Edinburgh, pp. 19-31.

Nijman, V. & van Balen, S. (1998). A faunal survey of the Dieng mountains, Central Java, Indonesia: Distribution and conservation of endemic primate taxa. Oryx 32: 145-156.

Supriatna, J., Tilson, R., Gurmaya, K.J., Manansang, J., Wardojo, W., Sriyanto, A., Teare, A., Castle, K. & Seal, U. (eds.). (1994). Javan gibbon and Javan langur: Population and habitat viability analysis report. IUCN/SSC Conservation Breeding Specialist Group, Apple Valley, Minnesota, 112 pp.

Supriatna, J. & Manullang, B.O. (eds.). (1999). Proceedings of the international workshop on Javan gibbon (Hylobates moloch) rescue and rehabilitation. Conservation International Indonesia Program, and Center for Biodiversity and Conservation Studies, University of Indonesia, Jakarta, 60 pp.


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