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Providing evidence to improve practice

Individual study: Demographic and Female Life History Parameters of Free-Ranging Chimpanzees at the Chimpanzee Rehabilitation Project, River Gambia National Park

Published source details

Brewer M.S., Marsden D. & Emery T.M. (2006) Demographic and Female Life History Parameters of Free-Ranging Chimpanzees at the Chimpanzee Rehabilitation Project, River Gambia National Park. International Journal of Primatology, 27, 391-410


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

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

A study in 1979-2004 in tropical forest on Baboon Islands, River Gambia National Park, The Gambia found that rehabilitated and reintroduced western chimpanzees Pan troglodytes verus that received periodic deworming alongside other interventions, increased from 50 to 69 chimpanzees over 25 years. No statistical tests were carried out to determine whether this increase was significant. Fertility and mortality rates were similar to that in wild chimpanzees, except for infant mortality (18%), which was lower than in wild populations. Inter-birth interval, average age at first birth, proportion males at birth, age at first sexual swelling in females, and adolescent infertility were similar to that of wild chimpanzees. In total, 50 chimpanzees from various backgrounds were released in groups on three islandsinto habitat with natural predators (although these were rare), but with no wild or previously reintroduced chimpanzees. Chimpanzees were given antibiotic treatment when they suffered from severe colds, and were provided supplementary food every 1-2 days. 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 study in 1979–2004 in tropical forest in The Gambia, found that the population of rehabilitated western chimpanzees Pan troglodytes verus that were reintroduced into habitat with no wild or previously reintroduced chimpanzees, along with other interventions, increased from 50 to 69 over 25 years. No statistical tests were carried out to determine whether this increase was significant. Fertility and mortality rates were similar to wild chimpanzees, except for infant mortality (18%), which was lower than in wild populations. Time between births, average age at first birth, proportion of males at birth, age at first sexual swelling in females, and adolescent infertility were similar to that of wild chimpanzees. In total, 50 chimpanzees from various backgrounds were released on three islands. Individuals were reintroduced in groups and into habitat with small populations of natural predators. They were provided supplementary food daily or on every second day, depending on which one of the islands they lived on. Individuals were periodically dewormed, and given antibiotic treatment when they suffered from severe colds. The study does not distinguish between the effects of the different interventions mentioned above.

Reintroduce primates into habitat with predators Primate Conservation

A study in 1979–2004 in tropical forest in River Gambia National Park, The Gambia found that rehabilitated western chimpanzees Pan troglodytes verus that were reintroduced into habitat with small populations of natural predators, alongside other interventions, increased from 50 to 69 chimpanzees over 25 years. No statistical tests were carried out to determine whether this increase was significant. Fertility and mortality rates were similar to wild chimpanzee populations, except for infant mortality (18%), which was lower. Time between births, average age at first birth, proportion of males at birth, age at first sexual swelling in females, and adolescent infertility, were similar to wild chimpanzees. In total, 50 chimpanzees were released on three islands. Individuals were reintroduced in groups and into habitat with no wild or previously reintroduced chimpanzees. Chimpanzees were provided supplementary food daily or every second day, depending on which one of the islands they lived on. Individuals received periodic deworming, and were given antibiotic treatment when they suffered from severe colds. The study does not distinguish between the effects of the different interventions mentioned above.

Rehabilitate injured/orphaned primates Primate Conservation

A study in 1979-2004 in tropical forest on Baboon Islands, River Gambia National Park, The Gambia found that reintroduced western chimpanzees Pan troglodytes verus that were rehabilitated before releases along with other interventions, increased from 50 to 69 chimpanzees over 25 years. No statistical tests were carried out to determine whether this increase was significant. Fertility and mortality rates were similar to that of wild chimpanzees. However, infant mortality (18%) was lower than in wild populations. Other reproductive parameters were similar to those of wild chimpanzees. In total, 50 chimpanzees with various backgrounds and exposure to human care and handling were released on three islands. Nine of these had been received from traders, nursed back to health, and regularly taken into the forest for five years before being moved to Niokolo Koba National Park in Senegal, where they stayed for five years before being released to River Gambia National Park. Individuals were reintroduced in groups and into habitat with no chimpanzees but with predators (although these were rare) . They were provided with supplementary food daily or every second day. Individuals received periodic deworming, and were given antibiotic for severe colds. 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 study in 1979-2004 in tropical forest on Baboon Islands, River Gambia National Park, The Gambia found that rehabilitated and reintroduced western chimpanzees Pan troglodytes verus that were regularly and continuously provided with supplementary food along with other interventions, increased from 50 to 69 chimpanzees over 25 years. No statistical tests were carried out to determine whether this increase was significant. Fertility and mortality rates were similar to wild chimpanzees, except for infant mortality (18%), which was lower than in wild populations. Inter-birth interval, average age at first birth, proportion males at birth and other reproductive parameters were similar to those of wild chimpanzees. In total, 50 chimpanzees from various backgrounds were released on three islands. Individuals were reintroduced in groups and into habitat with natural predators (although these were rare), but with no chimpanzees. Individuals received periodic deworming, and were given antibiotics for severe colds. The study does not distinguish between the effects of the different interventions mentioned above.

Treat sick/injured animals Primate Conservation

A study in 1979-2004 in tropical forest on Baboon Islands, River Gambia National Park, The Gambia found that rehabilitated and reintroduced western chimpanzees Pan troglodytes verus that were treated when sick alongside other interventions, increased from 50 to 69 chimpanzees over 25 years. No statistical tests were carried out to determine whether this population increase was significant. Fertility and mortality rates were similar to that in wild chimpanzees, except for infant mortality (18%), which was lower than in wild populations. Inter-birth interval, average age at first birth, proportion males at birth, age at first sexual swelling in females, and adolescent infertility were all similar to that of wild chimpanzees. Individuals received periodic deworming and antibiotic treatment for severe colds. Chimpanzees were reintroduced in groups and into habitat with natural predators (although these were rare), but with no other chimpanzees. They were provided supplementary food every 1-2 days. The study does not distinguish between the effects of the different interventions mentioned above.

Reintroduce primates in groups Primate Conservation

A study in 1979-2004 in tropical forest on Baboon Islands, River Gambia National Park, The Gambia found that rehabilitated western chimpanzees Pan troglodytes verus that were reintroduced in groups along with other interventions, increased from 50 to 69 chimpanzees over 25 years. No statistical tests were carried out to determine whether this increase was significant. Fertility and mortality rates were similar to wild chimpanzees, except for infant mortality (18%), which was lower than in wild populations. Inter-birth interval, average age at first birth, proportion males at birth, age at first sexual swelling in females, and adolescent infertility were similar to wild chimpanzees. In total, 50 chimpanzees from various backgrounds were released on three islands. Individuals were reintroduced into habitat with no wild or previously reintroduced chimpanzees and with small populations of natural predators. They were continuously provided supplementary food every 1-2 days. Individuals received periodic deworming and antibiotic treatment when they suffered severe colds. The study does not distinguish between the effects of the different interventions mentioned above.