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Providing evidence to improve practice

Individual study: Reproductive parameters over a 37-year period of free-ranging female Borneo orangutans at Sepilok Orangutan Rehabilitation Centre

Published source details

Kuze N., Sipangkui S., Malim T.P., Bernard H., Ambu L.N. & Kohshima S. (2008) Reproductive parameters over a 37-year period of free-ranging female Borneo orangutans at Sepilok Orangutan Rehabilitation Centre. Primates, 49, 126-134


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

Ensure that researchers/tourists are up-to-date with vaccinations and healthy Primate Conservation

A controlled study in 1967-2004 in tropical forest in Kabili-Sepilok Forest Reserve, Malaysia found that rehabilitated and reintroduced orangutans Pongo pygmaeus morio decreased by 33% over 33 years (1964-1997), although staff and volunteers received medical checks to avoid disease transmission alongside eight other interventions. In addition, infant mortality (57%) was higher than in other wild and captive populations, and the sex ratio at birth was strongly biased towards females (proportion males=0.11) compared to other wild and captive populations. Inter-birth-interval (6.1 years) was similar to wild populations of the same subspecies. Mean age at first reproduction (11.6 years) was lower than in other wild and captive populations. Orangutans were daily provided supplementary food from 2-7 feeding platforms. Individuals underwent in-depth veterinary checks and were kept in quarantine for 90 days before release into the reserve, in which other rehabilitated orangutans lived. Sick or injured individuals were captured and treated. Tourists had to keep safety distances (>5 m) at all times. The study does not distinguish between the effects of the different interventions mentioned above.

Keep safety distance to habituated animals Primate Conservation

A controlled study in 1964-2004 in tropical forest in Kabili-Sepilok Forest Reserve, Malaysia (2) found that rehabilitated and reintroduced orangutans Pongo pygmaeus morio that were visited by tourists that had to keep safety distances to the animals along with eight other interventions, decreased by 33% over 33 years (1964-1997). Infant mortality (57%) was higher than in other wild and captive populations, and the sex ratio at birth was strongly biased towards females (proportion males=0.11) compared to other wild and captive populations. Inter-birth-interval (6.1 years) was shorter than in other orangutan subspecies or species in the wild and in captivity, but similar to wild populations of the same subspecies. Mean age at first reproduction (11.6 years) was lower than in other wild and captive populations. More than 100 tourists/day visited the rehabilitation centre, but were prohibited from touching orangutans and had to keep a minimum distance of 5 m at all times. Orangutans were provided with daily supplementary food from 2-7 feeding platforms. Individuals underwent in-depth veterinary checks and were kept in quarantine for 90 days before release into the reserve, in which other rehabilitated orangutans lived. Staff and volunteers underwent medical checks. 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 1964-2004 in tropical forest in Kabili-Sepilok Forest Reserve, Malaysia found that rehabilitated orangutans Pongo pygmaeus morio that were kept in quarantine for 90 days before their reintroduction along with eight other interventions, decreased in numbers by 33% over 33 years (1964-1997). Infant mortality (57%) was higher than in other wild and captive populations, and the sex ratio at birth was strongly biased towards females (proportion males=0.11) compared to wild and captive populations. Orangutans were daily provided with supplementary food from 2-7 feeding platforms. Inter-birth-interval (6.1 years) was similar to wild populations of the same subspecies. Mean age at first reproduction (11.6 years) was lower than in other wild and captive populations. Individuals underwent in-depth veterinary checks before release into the reserve, where other rehabilitated orangutans lived. Individuals were captured and treated when injured or sick. Staff and volunteers received medical checks and tourists had to keep safety distances (>5 m) at all times. 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 1967-2004 in tropical forest in Kabili-Sepilok Forest Reserve, Malaysia found that rehabilitated and reintroduced orangutans Pongo pygmaeus morio that were continuously provided with daily supplementary food alongside eight other interventions, decreased by 33% over 33 years (1964-1997). Infant mortality (57%) was higher than in other wild and captive populations, and the sex ratio at birth was strongly biased towards females (proportion males: 0.11) compared to other wild and captive populations. However, inter-birth-interval (6.1 years) was similar to wild populations of the same subspecies. Mean age at first reproduction (11.6 years) was lower than in other wild and captive populations. Individuals underwent in-depth veterinary checks and were quarantined for 90 days before release into the reserve, where other rehabilitated orangutans lived. Individuals were captured and treated when injured or sick. Staff and volunteers received medical checks and tourists had to keep safety distances (>5 m) at all times. The study does not distinguish between the effects of the different interventions mentioned above.

Rehabilitate injured/orphaned primates Primate Conservation

A controlled study in 1967-2004 in tropical forest in Kabili-Sepilok Forest Reserve, Malaysia found that reintroduced orangutans Pongo pygmaeus morio that were rehabilitated before release into the wild along with eight other interventions, decreased by 33% over 33 years (1964-1997). Infant mortality (57%) was higher than in other wild and captive populations, and the sex ratio at birth was strongly biased towards females (proportion males: 0.11) compared to other wild and captive populations. However, inter-birth interval (6.1 years) was similar to wild populations of the same subspecies. Mean age at first reproduction (11.6 years) was lower than in other wild and captive populations. Orangutans were provided with daily supplementary food. Individuals underwent veterinary checks and 90 days of quarantine before being released into the reserve, where other rehabilitated orangutans lived. Injured or sick individuals were captured and treated. Staff and volunteers received medical checks and tourists had to keep safety distances (>5 m) at all times. The study does not distinguish between the effects of the different interventions mentioned above.

Reintroduce primates as single/multiple individuals Primate Conservation

A controlled study in 1967-2004 in tropical forest in Malaysia found that rehabilitated and individually reintroduced orangutans Pongo pygmaeus morio decreased in numbers by 33% over 33 years. Infant mortality (57%) was higher than in other wild and captive populations, and the sex ratio at birth was strongly biased towards females (proportion males=0.11) compared to other wild and captive populations. Time between births (6.1 years) was shorter than for other orangutan subspecies or species in the wild and in captivity, but similar to wild populations of the same subspecies. Average age at first reproduction (11.6 years) was lower than in other wild and captive populations. Orangutans were continuously provided with supplementary food. Before release at the site which contained other orangutans individuals underwent in-depth veterinary checks and were kept in quarantine for 90 days before they were released into the reserve. Individuals were captured and treated when they displayed signs of injury or illness. Staff and volunteers received medical checks and tourists were told to keep >5 m from animals at all times. The study does not distinguish between the effects of the different interventions mentioned above.

Treat sick/injured animals Primate Conservation

A controlled study in 1967-2004 in tropical forest in Kabili-Sepilok Forest Reserve, Malaysia found that rehabilitated and reintroduced orangutans Pongo pygmaeus morio, which were captured and treated for injury or illness alongside eight other interventions, decreased by 33% over 33 years (1964-1997). Infant mortality (57%) was higher than in other wild and captive populations, and the sex ratio at birth was strongly biased towards females (proportion males=0.11). However, inter-birth-interval (6.1 years) was similar to wild populations of the same subspecies. Orangutans were provided with daily supplementary food from 2-7 feeding platforms. Mean age at first reproduction (11.6 years) was lower than in other wild and captive populations. Individuals underwent in-depth veterinary checks and were kept in quarantine for 90 days before they were released into the reserve, in which other rehabilitated orangutans lived. Staff and volunteers received medical checks and tourists had to keep safety distances (>5 m) at all times. 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 1967-2004 in tropical forest in Kabili-Sepilok Forest Reserve, Malaysia found that a rehabilitated orangutan Pongo pygmaeus morio population that underwent in-depth veterinary checks before their reintroduction alongside eight other interventions, decreased by 33% over 33 years (1964-1997). Infant mortality was higher (57%) than in other wild and captive populations, and the sex ratio at birth was strongly biased towards females (proportion males=0.11) compared to other wild and captive populations. Orangutans were provided daily with supplementary food from 2-7 feeding platforms. Inter-birth-interval was (6.1 years) similar to wild populations of the same subspecies. Mean age at first reproduction was lower (11.6 years) than in other wild and captive orangutan populations. Individuals were kept in quarantine for 90 days before they were released into the reserve, in which other rehabilitated orangutans lived. Individuals were captured and treated when injured or ill. Staff and volunteers received medical checks and tourists had to keep safety distances (> 5 m) at all times. The study does not distinguish between the effects of the different interventions mentioned above.

Reintroduce primates into habitat where the species is present Primate Conservation

A controlled study in 1967–2004 in tropical forest in Kabili-Sepilok Forest Reserve, Malaysia found that reintroduction, along with eight other interventions, resulted in a 33% decline in the population of reintroduced, rehabilitated orangutans Pongo pygmaeus morio after 33 years. Infant mortality (57%) was higher than in other wild and captive populations, and sex ratio at birth was strongly biased towards females (proportion of males=0.11) as compared to other wild and captive populations. However, the time between births (6.1 years) was shorter than in other orangutan subspecies or species in the wild and in captivity, but similar to wild populations of the same subspecies. Average age at first reproduction (11.6 years) was lower than in other wild and captive populations. Orangutans were continuously provided with supplementary food from 2-7 feeding platforms. Before release individuals underwent in-depth veterinary checks and were kept under quarantine for 90 days. Individuals were captured and treated when they displayed signs of injury or illness. Tourists were informed to keep >5 m from animals at all times. The study does not distinguish between the effects of the different interventions mentioned above.