Providing evidence to improve practice

Individual study: Adaptation to Forest Life During the Reintroduction Process of Immature Pongo abelii

Published source details

Riedler B., Millesi E. & Pratje P.H. (2010) Adaptation to Forest Life During the Reintroduction Process of Immature Pongo abelii. International Journal of Primatology, 31, 647-663


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Limit time that researchers/tourists are allowed to spend with habituated animals Primate Conservation

A controlled study in 2004-2005 in a mosaic of logged and secondary tropical forest in Bukit Tigapuluh National Park, Indonesia found that reintroduced Sumatran orangutans Pongo abelii that spent only a limited amount of time with their caretakers along with other interventions, acted more like wild orangutans after release compared to individuals that had regular and close contact to caretakers. The behaviour of the three non-habituated orangutans with minimal human contact resembled that of wild orangutans more than that of the five habituated individuals in the way that they built nests, their food choice and canopy use. Furthermore, the former spent more time interacting socially with previously released orangutans. Non-habituated orangutans were released after they spent 6-month at a sanctuary to acclimatize. Human-habituated individuals were kept in semi-free conditions for 7-9 months prior to release where staff members guided them to the forest on a daily basis and tried to foster natural behaviour. The study does not distinguish between the effects of the different interventions mentioned above.

Implement quarantine for primates before reintroduction/translocation Primate Conservation

A controlled study in 2004-2005 in secondary tropical forest in Bukit Tigapuluh National Park, Central Sumatra, Indonesia found that all reintroduced Sumatran orangutans Pongo abelii that underwent quarantine prior to release alongside other interventions, survived for at least three months. Al eight captive orphaned orangutans with largely unknown histories survived for at least three months post-release. Before transportation to the reintroduction centre, orangutans were quarantined and underwent medical screens and clearance at a quarantine centre. All activities and procedures at the quarantine and reintroduction centres followed national and international regulations and guidelines, including IUCN reintroduction guidelines. Orangutans were released into habitat where previously-released orangutans lived to re-establish populations. Supplementary food was provided regularly. One group was directly released into the forest after a 6-month acclimatization phase at a sanctuary. Another group was kept in semi-free conditions for 7-9 months prior to release and allowed to overnight in the enclosure. Staff members guided daily the latter group to the forest. The study does not distinguish between the effects of the different interventions mentioned above.

Fostering appropriate behaviour to facilitate rehabilitation Primate Conservation

A controlled study in 2004-2005 in secondary tropical forest in Bukit Tigapuluh National Park, Indonesia found that reintroduced Sumatran orangutans Pongo abelii that were not fostered natural behaviour along with other interventions, acted more like wild orangutans after release than individuals that had been fostered. The behaviour of the three non-fostered orangutans resembled that of wild orangutans more than that of the five fostered individuals in the way that they built nests, selected food and used the canopy. Non-fostered individuals spent more time interacting socially with previously released orangutans. However, some individuals of the fostered group learned some natural behaviour by watching orangutans that were reintroduced earlier. Individuals in this group were guided daily from night enclosures to the forest and were shown how to handle wild food. They acclimatized to local conditions for 7-9 months before release and were free to overnight in the enclosure. The study does not distinguish between the effects of the different interventions mentioned above.

Reintroduce primates into habitat where the species is absent Primate Conservation

A controlled study in 2004–2005 in tropical forest in Sumatra, Indonesia found that all reintroduced Sumatran orangutans Pongo abelii that were released into habitat where the species was absent, along with other interventions, survived for at least three months. All eight captive orphaned orangutans survived for at least three months after release. Orangutans underwent quarantine and were medically screened before being released into habitat. One group was directly released into the forest after a 6-month acclimatization phase at a sanctuary. Another group of individuals was kept in semi-free conditions for 7-9 months prior to release and allowed to overnight in the enclosure. Staff members guided the latter to the forest on a daily basis. Supplementary food was provided regularly. The study does not distinguish between the effects of the different interventions mentioned above.

Rehabilitate injured/orphaned primates Primate Conservation

A controlled study in 2004-2005 in secondary tropical forest in Bukit Tigapuluh National Park, Central Sumatra, Indonesia found that all reintroduced orphaned Sumatran orangutans Pongo abelii that were rehabilitated before reintroduction into the wild along with other interventions, survived for at least three months. All eight captive orphaned orangutans survived for at least three months after release. Orangutans underwent quarantine and health checks before being released to re-establish populations in habitat where previously-released orangutans occurred. Supplementary food was provided regularly. One group was released after a 6-month acclimatization phase at a sanctuary. Another group was kept in semi-free conditions for 7-9 months prior to release and could overnight in the enclosure. Staff members guided the latter to the forest on a daily basis. The study does not distinguish between the effects of the different interventions mentioned above.

Regularly and continuously provide supplementary food to primates Primate Conservation

A controlled study in 2004-2005 in secondary tropical forest in Bukit Tigapuluh National Park, Central Sumatra, Indonesia found that all captive Sumatran orangutans Pongo abelii that were regularly provided with food alongside other interventions, survived for at least three months post-reintroduction. Orangutans were supplemented with food during the reintroduction process at the release site. One group was guided into the forest on a daily basis where new food items were offered and their handling was demonstrated. All eight orphaned orangutans with largely unknown histories survived for at least three months post-release after which monitoring ceased. Orangutans underwent quarantine and health checks before being released into habitat to re-establish populations where previously released orangutans already occurred. One group was released after a 6-month acclimatization at a sanctuary. Another group was kept in semi-free conditions for 7-9 months prior to release and allowed overnight in the enclosure. Staff members guided the latter daily into the forest. The study does not distinguish between the effects of the different interventions mentioned above.

Allow primates to adapt to local habitat conditions for some time before introduction to the wild Primate Conservation

A controlled study in 2004-2005 in a mosaic of logged and secondary tropical forest in Bukit Tigapuluh National Park, Sumatra, Indonesia found that reintroduced Sumatran orangutans Pongo abelii that were directly released into the forest along with other interventions, performed better after release than individuals that were allowed to adapt to local habitat conditions for some time at the release site. The behaviour of the three orangutans that were released directly into the new habitat resembled that of wild conspecifics more than that of the five individuals that were allowed to adapt for 7-9 months prior to release to local habitat conditions to adjust and learn how to built nests, select food and use the canopy. In addition to the adaptation period on-site, the latter group was guided daily into the forest by rangers trying to foster natural behaviour. The group directly released into the forest spent more time interacting socially with previously released orangutans. The group directly released into the forest spent more time interacting socially with previously-released orangutans. The orangutans in this group were housed at a sanctuary for 6-month before release. The study does not distinguish between the effects of the different interventions mentioned above.

Conduct veterinary screens of animals before reintroducing/translocating them Primate Conservation

A controlled study in 2004-2005 in secondary tropical forest in Bukit Tigapuluh National Park, Indonesia found that all reintroduced Sumatran orangutans Pongo abelii that underwent veterinary screens prior to release alongside other interventions, survived for at least three months. All eight captive orphaned orangutans with largely unknown histories survived for at least three months post-introduction, after which monitoring ceased. Before transportation to the reintroduction centre, orangutans were quarantined and underwent medical screens and clearance. Quarantine and reintroduction followed guidelines, including relevant IUCN guidelines. Orangutans were released to re-establish populations into habitat where previously-translocated orangutans occurred. Supplementary food was provided regularly. One group was directly released into the forest after a 6-month acclimatization phase at a sanctuary. Another group of individuals was kept in semi-free conditions for 7-9 months prior to release and allowed to overnight in the enclosure. Staff members guided the latter to the forest on a daily basis. The study does not distinguish between the effects of the different interventions mentioned above.

Reintroduce primates in groups Primate Conservation

A controlled study in 2004-2005 in secondary tropical forest in Bukit Tigapuluh National Park, Central Sumatra, Indonesia found that all reintroduced Sumatran orangutans Pongo abelii that were released in groups along with other interventions, survived for at least three months. Eight captive orphaned orangutans with largely unknown histories were released in two groups and all survived for at least three months post-release. One group was directly released into the forest after a 6-month acclimatization phase at a sanctuary. Another group of individuals was kept in semi-free conditions for 7-9 months prior to release and allowed to overnight in the enclosure. Staff members guided the latter group daily to the forest. Orangutans underwent quarantine and were medically screened before being released to re-establish populations in habitat where previously released orangutans occurred. Supplementary food was provided regularly. The study does not distinguish between the effects of the different interventions mentioned above.