Jito Sugardjito

Residential status and seasonal movements of wild orang-utans in the Gunung Leuser Reserve (Sumatera, Indonesia)

Data on the presence of wild orang-utans, Pongo pygmaeus, in the Ketambe area (Sumatera, Indonesia), collected over 12 consecutive years, were analysed to study population structure and residential status. Forty-three individuals could be identified during the study period. The socionomic sex ratio was close to unity, at least when subadault and adult males were considered as one category. The adult sex ratio was skewed towards females. A clear distinction between residents and non-residents could be made, but there was apparently no transient sex and no positive correlation between the densities of non-resident males and local females capable of conceiving. Hence, the hypothesis that non-resident males wander to locate receptive females was not supported. Instead, the data reveal seasonal movements and show that non-residents of both sexes are equally attracted to the study area when food is abundant. Two (not mutually exclusive) mechanisms that may explain how ranging of non-residents is tuned to food available are proposed.

Selecting nest-sites of Sumatran orang-utans, Pongo pygmaeus abelii in the Gunung Leuser National Park, Indonesia

In the Gunung Leuser National Park of Indonesia a population of orang-utans has been observed. The location of 172 night-nest sites has been examined with respect to their position in relation to the last food tree visited during the preceding day and with respect to their height above the ground. There were significant differences between the sex-age classes in the distribution of distances between nest-sites and the last visited food tree. The more vulnerable animals nested at greater distances and also tended to nest at greater height. These aspects of nest-sites selection have been interpreted in terms of an anti-predator strategy: the more vulnerable animals avoid nesting in fruit trees; instead they prefer more cryptic, unpredictable and inaccessible sites.

Meat-eating behaviour in wild orang utans,Pongo pygmaeus

Meat-eating was observed for the first time among a population of wild orang utans at Gunung Leuser National Park, Sumatra. An adult female who was consorting with an adult male consumed a gibbon (Hylobates lar) carcass. There was no food sharing between the consort pair. The absence of food sharing is interpreted as indicative of the anti-social attitude of adult orang utans.

Assessment and Management Options of Human-Tiger Conflicts in Kerinci Seblat National Park, Sumatra, Indonesia

Abstract. This paper aimed to investigate human-tiger conflict during the year 2000–2004 and has reviewed a number of potential measures for resolving the conflicts as part of conserving the Sumatran tigers which can be applied in the study area. These include technical measures which deal mainly with the individual ‘problem’ animal that comes into conflict and human dimension measures which focus on raising human tolerance toward tigers and reducing the negative effects of co-existence between human and tigers. Some of the measures namely, disruptive stimuli modification, raising tolerance through education and cultural perspective approaches had been tried for a short period. The success or otherwise of these measures in the field have also contributed to the conclusions drawn and the recommendations made as a result. The data are supplemented with more information, including the insight on the effect of conflicts between inhabitant and wildlife, the perspectives of villagers regarding human-tiger conflicts and the causal factors of individual conflict incidents. The reluctance of local community to report incidents prevents conservation agencies for delivering an immediate and effective response and it stimulates the killing of Sumatran tigers that benefits both hunters and livestock owners through the sale of tiger derivatives. This study also proposed a procedure for handling human-tiger conflict that hopefully may be tested in any other area.

Biology and behaviour of reintroduced gibbons

We observed and recorded the behaviours of gibbons undergoing rehabilitation, before and after release, to document the behavioural and social changes of gibbons in the rehabilitation program and develop criteria for determining the suitability of a pair of gibbons for release. Hylobates albibarbis were observed at the Kalaweit Gibbon Rehabilitation Project in Kalimantan, Indonesia. Data were collected on animals both pre- and post-release and on wild gibbons for comparison. Data presented here show that reintroduced gibbons are capable of surviving without human intervention. In addition, their behaviour is similar to that of wild gibbons in terms of activity budgets, position in the canopy, body posture, pair association (PA) and diet. Prior to this study, no attempt has been made to quantify the rehabilitation process for gibbons, and rehabilitation project personnel require data reporting all aspects of a release so that improvements can be made. It is important to report these data for the benefit of future releases. Criteria, based on the behaviour of wild gibbons, are proposed to assist rehabilitation centers in assessing the suitability of gibbon pairs for release.

Measuring Performance of Orangutan Protection and Monitoring Unit: Implications for Species Conservation

The orangutan is the only great ape species that inhabits Asia. During the Pleistocene, they occurred throughout Southeast Asia, from Southern China in the North to Java in the South (Hooijer 1948; von Koeningswald 1981). Current distribution of this species is limited to the northern part of Sumatra and fragmented forest areas in Borneo (Reijksen and Meijaard 1999). Recently, experts have suggested that the orangutan populations on each island represent unique species (Pongo abelii on Sumatra and P. pygmaeus on Borneo; Groves 2001; Warren et al. 2001). The Bornean species is generally divided into three subspecies: P. p. pygmaeus, Pongo p. wurmbii, and P. p. morio (Groves 2001).