- Conservation of the Javan gibbon Hylobates moloch: population estimates, local extinctions, and conservation priorities
- The Raffles Bulletin of Zoology
- Volume | Issue number
- 52 | 1
- Pages (from-to)
- Document type
- Faculty of Science (FNWI)
- Institute for Biodiversity and Ecosystem Dynamics (IBED)
The Javan gibbon is one of the rarest species of gibbons, restricted as it is to the western half of the densely populated island of Java, Indonesia. Based on a study from 1994-2002 it was found that the Javan gibbon has a larger distribution range than previously assumed. It is not restricted to the forests of the province of West Java and significant populations occur in the central part of the island. To establish the presence of gibbons in an area focused research is needed and in the past certain populations were missed in rapid presence-absence surveys. Javan gibbons occur in population densities of c. 2.6 groups km-2 (or c. 8-9 individuals km-2) in lowland and hill forest <1000 m asl and less than one group km-2 (or c. 1.5 individuals km-2) in montane forest between 1000-1750 m asl. Based on the extent of remaining habitat in 15 of the largest populations of Javan gibbons, a conservative density estimate of one group km-2, and exclusion of floaters (sub-adults that have not yet established a territory), it is estimated that some 4000-4500 gibbons remain in the wild. This conservative estimate is considerable higher than assumed by conservation authorities. Given that large-scale deforestation on Java (the main threat to the survival of the species) dates back more than a century and has slowed down over the last decades, this suggests that the present IUCN status of Critically Endangered seems untenable. As still considerable populations remain in unprotected areas of natural forest it is argued that, in order to effectively protect the species and in an attempt to increase its survival prospects, increased protection of these forest areas is the key to the survival of the species. It is recommended not to resort to expensive and intrusive captive breeding programmes and reintroduction initiatives as this will inevitably divert the attention away from in-situ conservation. Any programme that costs a great deal of money over the years will inevitably seek to portray itself as necessary and relevant, and if caution is needed it is in the evaluation of current management options, based on the best possible information irrespective of previous investments.
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