Contribution to Zoology, 75 (3/4) – 2006Vincent Nijman: In-Situ and Ex-Situ status of the Javan Gibbon and the role of zoos in conservation of the species

To refer to this article use this url:


The wild Javan gibbon population is severely fragmented with many small populations. By and large these fragments are separated from other forests by several kilometer-wide gaps of non-forest, cultivated, land. Natural expansion of the population is not an option as most if not all of the forest areas (including those that are legally protected) are facing encroachment into the remaining forest to some extent. There are no indications of populations being far below the carrying capacity of the forest (i.e. there are no ‘emptied forests’ within the range of the species). Gates (1998) suggested that Mt Halimun National Park had the greatest potential for natural expansion of Javan gibbon population. This would be valid if, indeed, less than a hundred individuals would be present in the 400 km2 large reserve, as implied by Gates (1996, 1998). However, numerous studies have been conducted on the gibbons in Mt Halimun National Park, some with the specific aim to estimate the total population size of the reserve. Kappeler (1981) estimated the population in Mt Halimun National Park at 600-1800 gibbons, Kool (1992) at 850-1320 gibbons, Asquith et al. (1995) at 870 gibbons, Sugarjito and Sinaga (1997) at 864-936 gibbons, Rinaldi (2003) at 456-1149 gibbons, and Djanubudiman et al. (2004) at 2905 gibbons. All these estimates from one forest area (out of 29 inhabited by Javan gibbons) are larger than the total world population presented by Gates (1998). Although Mt Halimun National Park is of major importance to the protection of the Javan gibbon, unfortunately some of the most valuable lowland forests are situated outside the boundaries of the reserve, are discontinuous, and are, therefore, not as secure as it may seem (Whitten et al., 1996). Furthermore, encroachment is threatening the integrity of the park, both from the central enclave (expansion of the tea estate), as well as from the park’s periphery. Conservation (and research) efforts are concentrated in the eastern part of the park, and, although a management plan has been drawn, active protection of the forest receives little attention.

The largest unprotected population of Javan gibbons is found Mts. Dieng, representing the species’ easternmost population with a population of >500 individuals (Nijman, 1995; Nijman and van Balen, 1998; Geissmann and Nijman 2006). As noted by Gates (1998) Mts Dieng may be as significant for the Javan gibbon as the Mt Halimun National Park; it was however not included in the PHVA on which Gates’ (1998) review was based. The forests on Mts. Dieng receive no form of protection, even though proposals for increased protection have been submitted to the authorities. The forest has suffered significantly during and following the economic crisis that hit Indonesia in 1997-1998, and the period of social and political turmoil that followed, with large areas being affected by illegal small-scale logging. No data are available as to what extent the forests in Mts. Dieng have suffered, nor what the effects are on the population of Javan gibbons, but losses must have been significant.

At the PHVA workshop (Supriatna et al., 1994) a substantial proportion of time was spent forcing participants to estimate numbers they had no ability or authority to estimate (Asquith, 2001). The resulting estimate of 400 individuals as the total population of Javan gibbons made during the PHVA workshop was largely based on the number of gibbons that the participants of this workshop had themselves observed. Thus, the population of the 400-km2 Mt Halimun National Park, for which various studies have indicated that the population numbers over 800 gibbons (see references listed above), was estimated at 53 individuals as those attending the workshop had observed a mere 16 groups. The method employed at the PHVA has been criticised (Asquith, 1995, 2001; Nijman, 2004a) and even the senior author of these PHVA proceedings has revised these numbers upward (Supriatna and Wahyono, 2000).

In formulating a conservation strategy for the Javan gibbon, Supriatna (2001) argued that “While conservation programs might focus primarily on the core populations…smaller populations on different sites should not be undervalued since they may function as critical stepping-stones that allow gene exchange and colonization to take place. Establishing habitat corridors among those several small and large protected areas should become the first priority while also establishing a wild sanctuary that brings together individuals from different populations”. Likewise, Gates (1998) and others (Andayani et al., 2001; Ellis, 1996/1997; Supriatna et al., 1994; Supriatna and Manullang, 1999; Malone et al. 2004) have stressed and reiterated the importance of protection of small fragmented populations, and the need for metapopulation management through some form of genetic supplementation, including plans to capture young gibbons preparing to leave their families and take them to other areas (Derr, 2002).

These interventions, and the focus on small populations, were justified by making reference to the small population size (i.e. the purported 400 individuals), that is extremely fragmented, with essentially no viable population (>100 individuals) remaining. If this situation were to be true it is easy to see the importance of the captive population as almost a quarter of the world population of Javan gibbons would indeed be in captivity (Table 1).

With many more gibbons remaining in the wild than presumed by some, the question arises also what is the conservation value of the ex-situ Javan gibbon population and how it can contribute to conservation of wild Javan gibbons? At present, within Indonesia, there is a relatively large captive population of Javan gibbons, in zoological gardens, wildlife rescue centres, and, almost invariably illegally, in private hands. All are directly derived from the wild and, with a few notable exceptions, are currently kept in appalling conditions. A number of initiatives have recently started to improve the lives of these captive animals either by improving conditions in zoos, or even by rehabilitation and release in isolated forest areas without resident gibbons. This may be a way to solve the dilemma of what to do with large numbers of long-lived gibbons held in captivity, but should not be confused with being a conservation strategy for the species. Initiatives to improve the lives of captive Javan gibbons and programmes that enables the Indonesian conservation authorities to house confiscated gibbons properly are to be applauded, but will contribute little to increase the survival chances of gibbons in the remaining forests on Java. If these initiatives would be made an integral part of a larger scheme covering law-enforcement and public-awareness campaigns, they could benefit the wild population by enhanced protection. Current offenders of wildlife laws, however, are rarely prosecuted (despite intensive searches I am not aware of any conviction of someone that illegally killed, caught, kept or traded a Javan gibbon). The current system, where the public can ‘donate’ their pet gibbon to zoos, wildlife rescue centres and rehabilitation programmes, has created too easy a solution for private owners to get rid of their adult gibbon. This has led to a situation where one can renew illegal wildlife (e.g. get a younger individual and dispose of on older one) and has created a loophole for malevolent zoos. Despite the current laissez-faire situation, there are still opportunities for an increased co-operation between Indonesian zoos, wildlife rescue centres and the forestry department with the aim of setting up a co-ordinated captive-management programme within Indonesia. The number of captive gibbons is sufficiently large, and, with the help for foreign zoos and international NGOs husbandry conditions within Indonesia can be improved, with the ultimate outcome of the much desired integrated captive-breeding programme (Gates, 1998; cf. Ware, 2001).

For the real protection of the Javan gibbons, however, we have to focus fully our attention on the remaining forest habitat in which Javan gibbons occur. Gates (1998), and others with him, targeted the relatively small number of individuals that are found in a large number of small populations (including the ex-situ population). Here I would like to argue that the best strategy is to focus on the large number of individuals found in a small number of larger forest blocks. As indeed pointed out by Asquith (2001), the most cost-effective and meaningful strategy for bettering the conservation status of the Javan gibbon is improvement of the protection of the largest remaining forest area which contains significant numbers of Javan gibbons. Secondly, it will be of vital importance to stimulate and continue efforts of including unprotected gibbon populations into the protected-area network (cf. Birkett, 2005). The areas most urgently in need of improved protection are Mts Dieng and Mt Wayang, but in effect all large populations could do with an increase in active field protection.

This increased protection is best achieved by a pragmatic approach involving the different sections of the Ministry of Forestry (Directorate General for Forest Conservation and Nature Protection and Perum Perhutani), local authorities (including those from nearby communities) and local non-governmental organizations (NGOs). The lead in this is best taken by a small, dedicated group that lobbies at the local and regional levels as to get various stakeholders and the local authorities on board. Alongside, campaigning and education to inform on the plight of the Javan gibbon and its habitat should target the local, regional and national level (cf. Wahyono et al., 2000). With their expertise in raising awareness, national zoos, as well as wildlife rescue centres, can take a lead in this. A way to prevent encroachment and illicit logging in selected forest areas is to set up a system where patrol teams involving local community representatives, local NGOs, the forestry department, and police (operating in mixed teams so as to prevent internal collusion) for prolonged periods of time. Institutional and financial support for this could be made available by international donors, including foreign zoos.