Action: Provide supplementary food for a certain period of time only
- One study in Tanzania found that a chimpanzee population increased after supplementary feeding for two months immediately after reintroduction, alongside other interventions.
- One before-and-after study in Brazil found that a golden lion tamarin population declined after one year following supplementary feeding, alongside other interventions. One study in Brazil found that an abandoned infant muriqui was retrieved by its mother and rejoined the wild group after supplementary feeding, alongside other interventions.
- Four studies in Brazil, Madagascar, and South Africa found that only a minority of reintroduced primates survived after supplementary feeding, alongside other interventions.
- One study in Guinea found that the majority of introduced chimpanzees survived for at least 27 months following supplementary feeding, alongside other interventions..
- Three studies in Gabon, South Africa and Vietnam found that a majority of primates survived reintroduction while being supplimentry fed alongside other interventions.
- Two studies in Gabon and the Republic of Congo found that the majority of lowland gorillas survived for at least nine months to four years after provision of supplementary food, alongside other interventions.
Supporting evidence from individual studies
A study in 1966-1985 in Rubondo National Park, a forested island in Lake Victoria, Tanzania found that reintroduced eastern chimpanzees Pan troglodytes schweinfurthii that were supplemented with food for two months after the first release along with other interventions, bred and increased in numbers from 17 to at least 20 individuals over a 16-year time period. However, no statistical tests were carried out to determine whether this increase was significant. Only the first out of four release groups received supplementary food. At least two males were shot after attacking game scouts. Two new-born infants were observed in 1968 and in 1985. All of the 17 reintroduced chimpanzees were wild-born and spent various amounts of time in captivity. Their age at the time of release ranged from 4-12 years and their health from good to poor. Chimpanzees were released in four lots in 1966-1969) with considerable time intervals in between release events, and only a few had met before. The island was free of predators. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after trial in 1954-1985 in degraded rainforest in Poço das Antas Reserve, Brazil found that a translocated captive-born golden lion tamarin Leontopithecus rosalia population that received supplementary food for ten months after release along with nine other interventions, decreased by more than half (57%) within the first year of release. No statistical tests were carried out to determine whether this decrease was significant. Of the 14 individuals released, seven (50%) died and two (14%) were removed. Three infants were born, one of which died due to illness. Eight individuals were released as a family group and six individuals were released as pairs one month later. Tamarins spend an unknown amount of time in 15 x 4.5 x 3 m outside enclosures to acclimatize. They were habituated to humans and fostered to facilitate survival in the wild. The reserve included natural predators. Sick or injured tamarins were captured and treated in a nearby rehabilitation centre. Artificial nesting boxes, which were hollow logs provided to them during training, were also set up in the reserve. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after trial in 1984-1991 in coastal forest in Poço das Antas Reserve, Brazil found that the majority of reintroduced golden lion tamarins Leontopithecus rosalia, which were supplemented with food along with 14 other interventions, did not survive over a study period of seven years. Fifty-eight out of 91 (64%) reintroduced tamarins did not survive in the wild. However, 57 infants were born (reproductive rate=63%) during the study period, of which 38 (67%) survived. Supplementary feeding platforms were moved further from the tamarins to encourage them to increase their foraging range. Different groups of captive-bred or orphaned tamarins were introduced in different years into habitat with resident tamarins and predators. Some groups were provided with supplementary water and nesting boxes, and allowed to adapt to local habitat conditions before release. Tamarins were quarantined, underwent veterinary checks and parasite treatment before release. Sick or injured animals were recaptured, treated and rereleased. The reserve became officially protected in 1983 and a long-term research study was implemented. The study does not distinguish between the effects of the different interventions mentioned above.
A study in 1994 in a tropical dry forest in the Caratinga Biological Station in Minas Gerais, Brazil found that an abandoned infant muriqui Brachyteles arachnoides that was retrieved, supplemented with food and then returned along with other interventions was reunited with its mother and re-joined the wild group. Twenty-seven hours after detection and removal of the infant, it was released in the vicinity of its mother, who retrieved it immediately. In addition to being fed milk and mashed apple, the 4-months old female infant muriqui was also given a blanket for warmth before being released again. Furthermore, some ectoparasites were collected for study. The mother answered to the infant’s cries and retrieved it immediately and rejoined the group. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after trial in 1997-2002 in primary forest in Betampona Reserve, Madagascar found that less than half of all captive-bred, parent-reared, reintroduced black-and-white ruffed lemurs Varecia variegata variegata that were provided with supplementary food for a certain period of time along with ten other interventions, survived for five years. Five of 13 individuals (38.5%) survived in the wild and six individuals were born, of which only four survived. One female and one male of the group reproduced with wild lemurs and the male became fully integrated into the wild group. Supplementary feeding was provided for three months after release, meeting approximately 75% of each animal’s daily nutritional requirements. Feeding took place in the forest canopy using suspending feeding baskets and platforms. Released animals were monitored using radio-collars. Captive lemurs had limited semi-free-ranging experience, were quarantined and underwent veterinary screens before reintroduction in groups into habitat with predators and wild resident lemurs. They were recaptured and treated when sick and provided with supplementary water for a certain period of time. They were allowed to adapt to local habitat conditions before release. Dead lemurs were examined. The study does not distinguish between the effects of the different interventions mentioned above.
A study in 2002–2006 in tropical forest in Lékédi Park, Gabon found that one third of captive-bred mandrills Mandrillus sphinx that were provided with supplementary food along with other interventions, died within the first year post-release. Twelve out of 36 mandrills (33%) died within one year post-reintroduction, particularly dependent infants. Fertility rate was 42% (five of 12 females gave birth) and two of the five infants survived longer than six months. Mortality decreased to 4% in the second year and fertility rate remained at 42%, but all five infants born survived for over six months. Their range remained limited during the first two years post-release. In 2006, the group numbered 22 individuals, including 12 translocated mandrills, all in good physical condition. Eight weeks after release, food provisioning commenced daily from non-fixed feeding locations for one month and continued twice weekly until September 2005. The amount of food provided varied with physiological requirements and ecological conditions. Mandrills were dewormed, allowed to adapt to local conditions and reintroduced as a group into habitat with resident mandrills and predators. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after trial in 2007-2008 in dry forest-grassland mosaic near Richmond, KwaZulu-Natal, South Africa found that a small proportion of vervet monkeys Chlorocebus aethiops, which were provided with supplementary food after release along with other interventions, survived for at least 10 months. Out of 35 monkeys released as a first troop, six (17%) survived, 22 (63%) went missing, and seven (20%) individuals died. Two infants were born 10-11 months after release. Of 24 vervets released as a second troop, 12 (50%) survived, seven (29%) went missing and five (21%) died. Both troops were supplemented with food twice a day for 2-3 weeks, after which feeding intensity was decreased until it ceased, after three months. Monkeys underwent veterinary checks and were allowed to adapt to local environmental conditions before their release in groups into habitat with resident vervets. Supplementary water was provided post-release. The study does not distinguish between the effects of the different interventions mentioned above.
A study in 2007-2010 in subtropical forest-shrubland mosaic in Mondi forests, KwaZulu-Natal, South Africa found that only a small portion of the 31 rehabilitated and reintroduced vervet monkeys Chlorocebus aethiops that were provided with supplementary food along with other interventions, survived for at least 12 months. Twelve months post-release, ten individuals (32%) had survived and 20 (65%) disappeared. One individual was euthanized three days after release after raiding houses and acting aggressively towards people. Supplementary food was given twice a day for 19 days, subsequently decreasing over eight weeks. The release group included both wild captured (due to injury) (61%) and hand-raised orphaned (39%) monkeys. Monkeys underwent veterinary screens, were held in an enclosure at the release site to adapt to local habitat conditions, and were released as a group. Eleven individuals were fitted with radio-collars.. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after trial in 2008-2010 in forest-savanna in Haut Niger National Park, Guinea found that the majority of wild-born orphaned western chimpanzees Pan troglodytes verus that were supplemented with food for a certain period of time along with other interventions, survived reintroduction and remained free-living over 27 months. One out of 12 released chimpanzees died from anaesthesia during a recovery mission. One female returned to the sanctuary voluntarily and one male was returned after suffering injuries. Two females gave birth and both offspring survived. Another female integrated into a wild chimpanzee community and three chimpanzees moved to a new area. Although nutritionally independent, chimpanzees were initially supplemented with food on a daily-, and later on, a weekly basis to encourage them to remain in the area and to facilitate visual monitoring. All chimpanzees were screened for diseases before their collective release into habitat with wild chimpanzees and predators. Some chimpanzees were allowed to acclimatize to local habitat conditions prior to release. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after trial in 2009-2010 in coastal forest in Ntendeka Wilderness Area, Kwazulu-Natal, South Africa found that over half of the reintroduced, captive, wild-born vervet monkeys Chlorocebus aethiops that were supplemented with food along with other interventions, survived for at least six months post-release. Three individuals (19%) died, two killed by predators and one by domestic hunting dogs Canis lupus familiaris. Four individuals (25%) disappeared. One female gave birth to an infant two weeks after release. Supplementary food was provided from feeding stations twice per day for two weeks daily for a further three weeks. Food resembled the diet provided at the rehabilitation centre. Monkeys were introduced as one troop of 16 individuals into vacant habitat with predators. To acclimatize, monkeys spent one day in a release enclosure (49 m2). The release site was nationally protected as a wilderness area. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after, site comparison study in 1996-2006 in tropical forests of Lesio-Louna Wildlife Reserve, Republic of Congo (Congo) and Batéké Plateau National Park, Gabon found that most reintroduced western lowland gorillas Gorilla gorilla gorilla that were provided with food during the release phase along with 14 other interventions, survived for at least four years. Twenty-one (84%) of 25 gorillas released in Congo and 22 (85%) of 26 gorillas released in Gabon survived for at least four years. Nine females produced 11 infants, of which nine survived. In Gabon, gorillas received daily supplementary feeding for 23 months and then for another 16 months post-release. Congo groups received minimal supplementary food. During quarantine, gorillas underwent disease screening and vaccinations. Gorillas were released in groups into habitat with no resident gorillas and allowed to adapt to local environment prior to release. Released gorillas were treated for parasites and when sick. So-called ‘problem’-animals were removed and relocated and dead gorillas were examined. Forty-three individuals were rehabilitated wild-born orphaned gorillas and eight gorillas were ex-situ captive-borns. Both sites became protected areas before reintroduction. The study does not distinguish between the effects of the different interventions mentioned above.
A site comparison in 2008-2012 in bamboo thicket-dominated forest at Dao Tien Island (DTI) and mixed forest in Dong Nai Biosphere Reserve (DNBR), South Vietnam found that half of reintroduced pygmy slow lorises Nycticebus pygmaeus that were supplemented with food for a certain period of time along with eight other interventions, survived for over two months. Four out of eight lorises survived at least two months after release, whereas others either died or their radio-collar signal was lost. Lorises were kept in a cage for between two days and 2 months and were subsequently supplemented with food for 7-30 days. Lorises were released during the wet season after a 6-week quarantine, veterinary screens and parasite treatment. Both release sites were protected, no wild resident lorises occurred there and predators were present. Bodies of dead animals were investigated to determine the cause of death. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after trial in 2008-2010 in a tropical forest-grassland mosaic at Batéké Plateau National Park, Gabon found that the majority of western lowland gorillas Gorilla gorilla gorilla that were provided with supplementary food for some time along with ten other interventions, survived for at least nine months. Four (80%) out of five juvenile gorillas survived for at least nine months after release. Depending on their age and ability to feed on forest vegetation, gorillas were either fed milk products developed for human infants, or cereal and milk meals, provided 3 times/day. Three captive-bred and two orphaned wild-born individuals were reintroduced as a group into habitat with predators and without resident wild gorillas after being allowed to adapt to local habitat conditions. They spent the night in an enclosure equipped with nesting platforms, nesting material and water. Gorillas were dewormed regularly. Caretakers guided them into different forest patches on a daily basis. The study does not distinguish between the effects of the different interventions mentioned above.
- Borner M. (1985) The rehabilitated chimpanzees of Rubondo Island. Oryx, 19, 151-154
- Dietz L.A. (1985) Captive-born lion tamarins released into the wild: a report from the field. Primate Conservation, 6, 21-27
- Beck B., Dietz J., Castro L., Carvelho C., Martins A. & Rettberg-Beck B. (1991) Losses and reproduction of reintroduced golden lion tamarins Leontopithecus rosalia. Dodo, 50-61
- Nogueira C.P., Carvalho A.R.D., Oliveira L.P., Veado E.M. & Strier K.B. (1994) Recovery and release of an infant muriqui Brachyteles arachnoides, at the Caratinga Biological Station, Minas Gerais, Brazil. Neotropical Primates, 2, 3-5
- Britt A., Welch C., Katz A., Iambana B., Porton I., Junge R., Crawford G., Williams C. & Haring D. (2004) The re-stocking of captive-bred ruffed lemurs (Varecia variegata variegata) into the Betampona Reserve, Madagascar: methodology and recommendations. Biodiversity and Conservation, 13, 635-657
- Peignot P., Charpentier M.J.E., Bout N., Bourry O., Massima U., Dosimont O., Terramorsi R. & Wickings E. J. (2008) Learning from the first release project of captive-bred mandrills Mandrillus sphinx in Gabon. Oryx, 42, 122-131
- Wimberger K., Downs C.T. & Perrin M.R. (2010) Postrelease Success of Two Rehabilitated Vervet Monkey (Chlorocebus aethiops) Troops in KwaZulu-Natal, South Africa. Folia Primatologica, 81, 96-108
- Guy A.J., Stone O.M.L. & Curnoe D. (2011) The release of a troop of rehabilitated vervet monkeys (Chlorocebus aethiops) in KwaZulu-Natal, South Africa: outcomes and assessment. Folia Primatologica, 82, 308-320
- Humle T., Colin C., Laurans M. & Raballand E. (2011) Group release of sanctuary chimpanzees (Pan troglodytes) in the Haut Niger National Park, Guinea, West Africa: ranging patterns and lessons so far. International Journal of Primatology, 32, 456-473
- Guy A.J., Stone O.M. & Curnoe D. (2012) Assessment of the release of rehabilitated vervet monkeys into the Ntendeka Wilderness Area, KwaZulu-Natal, South Africa: a case study. Primates, 53, 171-9
- King T., Chamberlan C. & Courage A. (2012) Assessing Initial Reintroduction Success in Long-Lived Primates by Quantifying Survival, Reproduction, and Dispersal Parameters: Western Lowland Gorillas (Gorilla gorilla gorilla) in Congo and Gabon. International Journal of Primatology, 33, 134-149
- Kenyon M., Streicher U., Loung H., Tran T., Tran M., Vo B. & Cronin A. (2014) Survival of reintroduced pygmy slow loris Nycticebus pygmaeus in South Vietnam. Endangered Species Research, 25, 85-95
- Le Flohic G., Motsch P., DeNys H., Childs S., Courage A. & King T. (2015) Behavioural ecology and group cohesion of juvenile western lowland gorillas (Gorilla g. gorilla) during rehabilitation in the Batéké Plateaux National Park, Gabon. PLoS ONE, 10