Providing evidence to improve practice

Individual study: The release of wild-born orphaned chimpanzees Pan troglodytes into the Conkouati Research, Republic of Congo

Published source details

Goossens B., Ancrenaz M., Vidal C., Latour S., Paredes J., Vacher-Vallas M., Bonnotte S., Vial L., Farmer K., Tutin C.E.G. & Jamart A. (2001) The release of wild-born orphaned chimpanzees Pan troglodytes into the Conkouati Research, Republic of Congo. African Primates, 5, 42-45


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

Rehabilitate injured/orphaned primates Primate Conservation

A before-and-after trial in 1996-1999 in tropical rainforest in Conkouati Reserve, Republic of Congo found that 14 out of 20 (70%) reintroduced wild-born orphaned chimpanzees Pan troglodytes troglodytes that were rehabilitated were still alive 3.5 years after release. Estimated mortality was 10-30%. None of the adult females reproduced. Chimpanzees fed on 137 different plant species, a variety similar to wild chimpanzees, and had activity budgets that resembled those of wild chimpanzees. No statistical tests were carried out to determine whether similarities were statistically valid. Orphan chimpanzees were rehabilitated and fostered at a sanctuary. Chimpanzees underwent veterinary screens, endoparasite treatments, and were vaccinated for poliomyelitis and tetanus. Before reintroduction in groups into habitat with low densities of resident wild chimpanzees, individuals spent 6-9 years on one of three forested islands in the region to acclimatize. Researchers were permanently on-site and monitored chimpanzees with radio-collars. The study does not distinguish between the effects of the different interventions mentioned above.

Preventative vaccination of habituated or wild primates Primate Conservation

A before-and-after trial in 1996-1999 in a tropical rainforest in Conkouati Reserve, Republic of Congo found that 14 out of 20 (70%) reintroduced wild-born orphaned chimpanzees Pan troglodytes troglodytes that were vaccinated against poliomyelitis and tetanus alongside eight other interventions were still alive 3.5 years post-release. None of the adult females produced offspring. Chimpanzees underwent veterinary screens and were treated for internal parasites. Before reintroduction in groups into habitat with low densities of wild chimpanzees, they spent six to nine years on one of three forested islands in the region to acclimatize. Orphan chimpanzees were rehabilitated and fostered at a nearby sanctuary. Researchers were permanently present on-site and monitored released chimpanzees with radio-collars. The study does not distinguish between the effects of the different interventions mentioned above.

Remove/treat external/internal parasites to increase reproductive success/survival Primate Conservation

A before-and-after trial in 1996-1999 in a tropical rainforest in Conkouati Reserve, Republic of Congo found that 70% of reintroduced wild-born orphaned chimpanzees Pan troglodytes troglodytes that were treated for internal parasites alongside eight other interventions, were still alive 3.5 years after release. Confirmed mortality was 10%, with a possible 30%. None of the adult females reproduced. Chimpanzees fed on 137 different plant species, a variety in diet similar to that of wild chimpanzees and had activity budgets that resembled those of wild conspecifics. No statistical tests were carried out to determine whether differences were insignificant. Chimpanzees underwent veterinary screens and vaccinations for poliomyelitis and tetanus. Before reintroduction in groups into habitat with low densities of wild chimpanzees, they spent 6-9 years on forested islands in the region to acclimatize. Orphan chimpanzees were rehabilitated and fostered at a nearby sanctuary. Researchers were permanently present on-site and monitored released chimpanzees using radio-collars. The study does not distinguish between the effects of the different interventions mentioned above.

Fostering appropriate behaviour to facilitate rehabilitation Primate Conservation

A before-and-after trial in 1996-1999 in tropical rainforest in Conkouati Reserve, Republic of Congo found that 70% of reintroduced wild-born orphaned chimpanzees Pan troglodytes troglodytes that were fostered behaviour to facilitate survival in the wild along with eight other interventions, were still alive 3.5 years after release. Estimated mortality was 10-30%. None of the adult females reproduced. Chimpanzees fed on 137 different plant species, a diet similar to wild chimpanzees. They also had activity budgets that resembled those of wild conspecifics. No statistical tests were carried out to determine whether these similarities were statistically valid. Orphan chimpanzees were rehabilitated and fostered at a nearby sanctuary and accompanied to the forest to help to aid to recover from capture and create social bonds. Chimpanzees underwent veterinary screens, endoparasite treatments and were vaccinated. Before reintroduction in groups into habitat with low densities of resident wild chimpanzees, they spent 6-9 years on one of three forested islands in the region. Researchers were present on-site and monitored chimpanzees with radio-collars. The study does not distinguish between the effects of the different interventions mentioned above.

Run research project and ensure permanent human presence at site Primate Conservation

A before-and-after trial in 1996-1999 in a tropical rainforest in Conkouati Reserve, Republic of Congo in which researchers were permanently based alongside eight other interventions, found that 70% of reintroduced wild-born orphaned chimpanzees Pan troglodytes troglodytes were still alive 3.5 years after release. No chimpanzees were illegally hunted, which the authors ascribe to the permanent research presence in the area. Estimated mortality was 10-30%. None of the adult females reproduced. Chimpanzees fed on 137 different plant species, a diet variety similar to wild chimpanzees, and had activity budgets that resembled those of wild conspecifics. No statistical tests were carried out to determine whether differences were insignificant. Chimpanzees underwent veterinary screens, were treated for endoparasites and vaccinated. Before reintroduction in groups into habitat with low densities of resident wild chimpanzees, they spent 6-9 years on one of three forested islands in the region to acclimatize. Orphan chimpanzees were rehabilitated and fostered at a nearby sanctuary. Researchers monitored released chimpanzees using radio-collars. 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 before-and-after trial in 1996–1999 in a tropical rainforest in Conkouati Reserve, Republic of Congo found that reintroduction of wild-born orphaned chimpanzees Pan troglodytes troglodytes alongside eight other interventions resulted in 70% survival after three and a half years. Ten percent of reintroduced chimpanzees were confirmed to have died after three and a half years but this was possibly as high as 30%. No adult females produced offspring. Chimpanzees fed on 137 different plant species, a variety in diet similar to wild chimpanzees, and had activity budgets that resembled those of wild chimpanzees. However, no tests were carried out to determine whether differences were statistically significant or not. Adult females associated regularly with wild males during periods of oestrus. Before reintroduction in groups, they spent 6–9 years on one of three forested islands in the region to acclimatize. Orphan chimpanzees were rehabilitated and fostered at a nearby sanctuary. After this, chimpanzees were screened by vets, were treated for endoparasites, and vaccinated. 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 before-and-after trial in 1996-1999 in tropical rainforest in Conkouati Reserve, Republic of Congo found that 14 of 20 reintroduced wild-born orphaned chimpanzees Pan troglodytes troglodytes that were allowed to acclimatize to the local environment before their release along with other interventions, survived over three and a half years. Estimated mortality was 10-30%. None of the adult females reproduced. Chimpanzees fed on 137 different plant species, a variety similar to wild chimpanzees, and had activity budgets that resembled those of wild chimpanzees. No statistical tests were carried out to determine whether differences were statistically insignificant. Before reintroduction in groups into habitat with low densities of wild chimpanzees, individuals spent 6-9 years on one of three forested islands in the region to acclimatize. Chimpanzees underwent veterinary screens, were treated for endoparasites, and vaccinated for poliomyelitis and tetanus. Orphan chimpanzees were rehabilitated and fostered at a nearby sanctuary. Researchers were permanently on-site and monitored chimpanzees with radio-collars. The study does not distinguish between the effects of the different interventions mentioned above.

Reintroduce primates in groups Primate Conservation

A before-and-after trial in 1996-1999 in tropical rainforest in Conkouati Reserve, Republic of Congo found that 70% of reintroduced wild-born orphaned chimpanzees Pan troglodytes troglodytes that were released in groups along with eight other interventions, were still alive 3.5 years after release. Estimated mortality was 10-30%. None of the adult females reproduced. Chimpanzees fed on 137 different plant species, a variety similar to that of wild chimpanzees. They also had activity budgets that resembled those of wild chimpanzees. No statistical tests were carried out to determine whether these similarities were statistically valid. Before reintroduction into habitat with low densities of wild chimpanzees, they spent 6-9 years on one of three forested islands in the region to acclimatize. Release groups were small and composed of individuals that had formed strong associations during acclimatization. Chimpanzees underwent veterinary screens, were treated for endoparasites and vaccinated for poliomyelitis and tetanus. Orphan chimpanzees were rehabilitated and fostered. Researchers were permanently present on-site and monitored released chimpanzees using radio-collars. The study does not distinguish between the effects of the different interventions mentioned above.