Providing evidence to improve practice

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

Key messages

  • One before-and-after study in Brazil found that most reintroduced golden lion tamarins did not survive over seven years, despite undergoing pre-release veterinary screens, alongside other interventions. One study in Brazil found that most reintroduced black lion tamarins that underwent veterinary screens, alongside other interventions, survived over four months.
  • One before-and-after study in Malaysia found that 90% of reintroduced Müller's Bornean gibbons did not survive despite undergoing veterinary screens, alongside other interventions. One controlled study in Indonesia found that reintroduced Bornean agile gibbons that underwent veterinary screens, alongside other interventions, behaved similarly to wild gibbons.
  • Two studies, including one controlled, in Malaysia and Indonesia found that most translocated orangutans that underwent veterinary screens, along with other interventions, survived translocation and the first three months post-translocation. One controlled study, in Malaysia, found that the population size of reintroduced orangutans decreased despite individuals undergoing pre-release veterinary screens, alongside other interventions.
  • Four studies, including three before-and-after studies, in Liberia, the Republilc of Congo and Guinea found that most reintroduced chimpanzees that underwent veterinary screens, alongside other interventions, survived over 1-5 years. One before and after study in Uganda found that a reintroduced chimpanzee repeatedly returned to human settlements after undergoing pre-release veterinary screens, alongside other interventions.
  • Five studies, including four before-and-after studies, in Belize, French Guiana, Madagascar, Congo and Gabon found that most reintroduced or translocated primates that underwent veterinary screens, alongside other interventions, survived at least four months or increased in population size.
  • Seven studies, including four before-and-after studies, in French Guiana, Madagascar, South Africa and Vietnam found that most reintroduced or translocated primates were assumed to have died post-release despite undergoing pre-release veterinary screens, alongside other interventions.
  • One controlled study in Kenya found that a population of translocated olive baboons were still surviving 16 years after translocation when veterinary screens were applied alongside other interventions.

Supporting evidence from individual studies

1 

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 underwent extensive veterinary screens before release alongside 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, of which 38 (67%) survived. Tamarins were screened and treated for parasites, communicable diseases, possible genetically-based defects, injuries, and diaphragmatic thinning and only released if they were clear untreatable conditions. Different groups of captive-bred or orphaned tamarins were introduced in different years into habitat already occupied by the species and predators. Groups were provided with supplementary food, water and nesting boxes, and allowed to adapt to local habitat conditions before release. All tamarin groups were quarantined before release. Reintroduced sick or injured animals were rescued, treated and re-released. In 1983 the reserve became officially protected and a long-term research study was implemented. The study does not distinguish between the effects of the different interventions mentioned above.

2 

A before-and-after trial in 1976-1988 in a degraded tropical forest in Semenggoh Forest Reserve, Malaysia (2) found that at least 77 of 87 (90%) reintroduced captive, wild-born Müller's Bornean gibbons Hylobates muelleri that underwent veterinary checks before release along with other interventions, did not survive after release. Confiscated gibbons were placed in holding cages in a forest clearing for an unknown amount of time prior to release. Where possible, males and females were paired in cages before release into habitat without resident gibbons. Müller's Bornean gibbons were fully protected under the Wild Life Protection Ordinance in Sarawak. Surveys of direct sightings and gibbon calls along grid squares (500 x 500 m) covering a total of 9.5 km were conducted simultaneously by 3-4 observers on non-rainy days on eight mornings in February-March 1988. The study does not distinguish between the effects of the different interventions mentioned above.

3 

A replicated study in 1992-1993 in tropical forest at Cockscomb Basin Wildlife Sanctuary (CBWS) in Belize found that the majority of translocated black howler monkeys Alouatta pigra that underwent veterinary checks prior to release alongside other interventions, survived for at least ten months and reproduced. Twelve out of 14 reintroduced monkeys (86%) survived for at least ten months after release. One male and one juvenile disappeared two months post-release. Two infants were born, in each of two of the three release groups. Veterinary screens included blood tests and general health checks. Wild howlers had been captured at the Community Baboon Sanctuary and were translocated to CBWS. Three groups were released into habitat without resident howlers. They were allowed to adapt to local conditions before release. Six individuals were fitted with ball-chain radio-collars and six others were implanted with radio-transmitters. Radio-collars worked for 6-10 months, but transmitter signals got lost six weeks after release. The study does not distinguish between the effects of the different interventions mentioned above.

4 

A study in June-September 1993 in three fragmented tropical forests in the State of Sabah, Malaysia found that 78 of 80 (98%) translocated orangutans Pongo pygmaeus morio that underwent veterinary screens before their release at Tabin Wildlife Reserve along with other interventions, survived translocation. Four individuals escaped from their temporary holdings before transport to the release site. Of these, three individuals suffered minor injuries and one individual sustained major injury during capture. Individuals were either immobilized in trees or captured manually on the ground with nets. Individuals were treated before they were released individually into habitat already occupied by other orangutans. To avoid injury due to post-traumatic stress, females were kept in separate (but adjacent) cages from their offspring and adequate space was maintained between occupied cages during temporary holdings and transportation. The study does not distinguish between the effects of the different interventions mentioned above.

5 

A before-and-after trial in 1992-1997 in tropical forest in Cockscomb Basin Wildlife Sanctuary in Belize found that the population of introduced wild black howler monkeys Alouatta pigra that underwent extensive veterinary screens before release into the wild along with other interventions, increased in size over time. By 1997, the population increased by 61% (62 to >100 individuals). No statistical tests were carried out to determine whether this increase was significant. One-month-, 6-month-, 1-year, and 2-year survival rates for the different cohorts released in the dry seasons of 1992, 1993, and 1994, were 81-100%. Birth rate was 20% (n=12) and infant survival rate was 75% (n=9). Entire social groups were reintroduced at once over a two-year period. Ten of the 14 groups were held in cages for 1-3 days before release with a distance of 700-1000 m to the neighbouring troop. All individuals were permanently marked and adults were radio-collared. Hunting was largely controlled in the sanctuary and the local community was educated about the reintroduction project and black howler conservation through multimedia campaigns. The study does not distinguish between the effects of the different interventions mentioned above.

6 

A before-and-after study in 1995 in Kibale National Park, Uganda found that a female captive, 4-6 year old wild-born chimpanzee Pan troglodytes schweinfurthii that underwent veterinary screens alongside other interventions, repeatedly returned to human settlements after her release and was subsequently returned to captivity. Eight days after her initial release, she left the forest and was brought back into the forest. The following ten days, she travelled, fed, nested and engaged in social activities with the wild community. During this time, she increased ranging distance to humans and use of height, and visually monitored humans less regularly. However, the proportion of adult males in her vicinity decreased and she increasingly spent time alone. She was returned to captivity six weeks after her release. A veterinary team administered a test of skin reactivity to tuberculin antigen to which she tested negative prior to her release. She underwent pre-release training for three weeks before reintroduction into habitat with a resident wild community. During this time, she was also quarantined. At least ten community members worked on the project. The study does not distinguish between the effects of the different interventions mentioned above.

7 

A study in 1987-1988 on an island in tropical forest in Liberia, West Africa found that the majority of reintroduced western chimpanzees Pan troglodytes verus that underwent veterinary screens prior to release along with other interventions, survived for at least one year post-release. Seven out of 30 released chimpanzees had difficulties to adjust to the new social environment and were brought back to captivity. Prior to release, individuals were screened for diseases and only healthy chimpanzees were released. Chimpanzees were released in groups. Furthermore, they were socialized in naturalistic enclosures and were taught behaviour to facilitate their survival in the wild. On site, primates were allowed to adapt to the local habitat in enclosures for some time; younger and low-ranking individuals were released earlier to reduce stress. Released chimpanzees were continuously provided with food. Sick and injured animals were temporarily removed and treated. The study does not distinguish between the effects of the different interventions mentioned above.

8 

A study in 1994-1995 in primary forest at the Petit Saut hydroelectric dam in French Guiana found that less than half of the translocated red howler monkeys Alouatta seniculus that underwent veterinary screens alongside other interventions, survived for at least 18 months. Of the 16 females monitored, seven (44%) females survived to the end of the study with a possible survival rate of 63%. Deaths related to the translocation process included screwworm fly larvae infestations under radio-collars (n=2) and trauma (n=1). Three (19%) females gave birth after release, but all infants disappeared and probably died. All females studied for longer than three months (50%) settled within the release area. Of the 122 captured and translocated howlers from 28 different troops, ten out of 11 (91%) documented troops broke apart post-release. All animals were anesthetized and examined by a veterinarian. After taking biological samples, all individuals were confirmed as healthy. Monkeys were translocated and reintroduced in groups into habitat already occupied by the species. They were allowed to adapt to local habitat conditions before their release. The study does not distinguish between the effects of the different interventions mentioned above.

9 

A study in 1999 in tropical forest of Morro do Diabo State Park, São Paulo, Brazil found that only two of three reintroduced wild and captive-bred black lion tamarins Leontopithecus chrysopygus that underwent health checks prior to release along with other interventions, survived for at least four months. One tamarin underwent medical tests including both blood and faecal analyses, and a tuberculin test prior to transport. Prior to release, blood tests were conducted for all tamarins. Tamarins were held in an enclosure to adapt to the local environment where predators occurred. The group consisted of two wild females and one captive-born male, bred in a free-ranging environment, where natural behaviour was fostered to facilitate reintroduction. The male was treated after he was detected sick. Monkeys were fitted with radio transmitters and continuously supplemented with food until the end of the study. The study does not distinguish between the effects of the different interventions mentioned above.

10 

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 central chimpanzees Pan troglodytes troglodytes that underwent veterinary screens along with eight other interventions, were still alive 3.5 years post-release. Confirmed mortality was 10%, with a possible 30%. None of the adult females produced offspring. Chimpanzees fed on 137 different plant species, diversity in diet similar to that of wild chimpanzees, and had activity budgets that resembled those of wild chimpanzees. No statistical tests were carried out to determine whether similarities were significant. Chimpanzees were treated for internal parasites and vaccinated for poliomyelitis and tetanus. Before reintroduction in groups into habitat with low densities of 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 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.

11 

A before-and-after trial in 1994-1999 in mixed tropical forest in Conkouati-Douli National Park, Republic of Congo found that the majority of reintroduced central chimpanzees Pan troglodytes troglodytes that underwent health screens prior to release alongside 16 other interventions, survived for at least five years. Out of 20 reintroduced chimpanzees, whose body conditions were visually assessed and blood, faecal, and hair samples examined for diseases, fourteen (70%) survived. Individuals were radio-collared and followed at distances of 5-100 m. Rehabilitated orphaned chimpanzees underwent vaccination and parasite treatment before being translocated in four subgroups from the sanctuary to the release site where resident conspecifics occurred. Staff members were permanently present to monitor primate health, provide animals with additional food if necessary and examine dead animals when needed. The area status was upgraded from reserve to national park in 1999. Local people were relocated from the release site to a nearby village. Some chimpanzees were treated when sick or injured. TV and radio advertisements were used to raise chimpanzee conservation awareness and local people were provided monetary and non-monetary benefits to support conservation. The study does not distinguish between the effects of the different interventions mentioned above.

12 

A before-and-after trial in 1994-1995 in tropical forest near Petit-Saut dam, French Guiana found that two out of three translocated white-faced sakis Pithecia pithecia that underwent veterinary screens prior to release alongside other interventions, survived for at least four months. Three (two males and one female) out of six translocated sakis were monitored intensively for 41 weeks after release using radio-collars. Two of these survived for at least four months post-release, and one male died after 22 weeks due to a screwworm fly larvae infestation under his collar. Veterinary screens included blood and skin biopsy and general health condition checks. When dead sakis were detected, the cause of death was clinically determined. Sakis were captured at development sites using nets and released the next day as single individuals or as a group into primary rainforest habitat already occupied by wild resident sakis. The study does not distinguish between the effects of the different interventions mentioned above.

13 

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 underwent veterinary screens before their release alongside ten other interventions, survived over 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 resident lemurs and the male became fully integrated into the wild group. Veterinary examinations included physical examinations, complete blood cell count, serum biochemical profile, viral serology, Toxoplasma antibody level, trace mineral determination, fat soluble vitamin determination, faecal parasite examination, and faecal culture. Released animals were radio-collared. Captive lemurs had limited semi-free-ranging experience and were quarantined before their reintroduction in groups into habitat with predators and wild conspecifics. They were recaptured and treated when sick and provided supplementary food and water. They were allowed to adapt to local habitat conditions before release. Dead lemurs were clinically examined. The study does not distinguish between the effects of the different interventions mentioned above.

14 

A controlled, before-and-after trial in 1973-2001 in savannah at the Chololo ranch, Laikipia Plateau, Kenya found that the populations of translocated crop-raiding olive baboons Papio anubis had survived over 17 years when individuals underwent veterinary screens prior to release, alongside other interventions. Survival rate of individuals in two translocated troops of a total of 94 baboons in 1984 was 66%, where 62 individuals remained in 2001. One wild troop at the capture site and another resident troop at the release site served as control groups. Survival rates did not differ between control and study groups. Both troops, regarded as ‘problem animals’ by farmers, were translocated into habitat with resident wild baboons and predators. A long-term research project studied these animals. After their release, baboons were frequently monitored by researchers and were briefly provided with food during periods of drought. Some sick baboons were treated. The study does not distinguish between the effects of the different interventions mentioned above.

15 

A controlled study in 2002-2003 in swamp forest on Mintin Island, Borneo, Indonesia found that wild-born, captive-raised Bornean agile gibbons Hylobates albibarbis that underwent veterinary screens before reintroduction alongside other interventions, shared a similar diet, spent similar amounts of time feeding, resting, and arm-swinging and at similar canopy heights as wild gibbons. However, wild gibbons spent more time singing and socializing and travelling, which can be explained by the fact that the reintroduced gibbon pair split up almost immediately after their release. Gibbons were quarantined for at least 12 months before reintroduction. They were kept in enclosures (3 x 3 x 3 m) to socialize and acclimatize to the natural environment and were supplemented with vitamins and leaves once a week. They were introduced in pairs and into habitat in which wild gibbons were present. Only one reintroduced pair of gibbons was compared to a pair of wild gibbons at another site. The study does not distinguish between the effects of the different interventions mentioned above.

16 

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.

17 

A before-and-after study in 2006-2007 in rainforest in Analamazaotra Special Reserve, Madagascar found that black-and-white ruffed lemurs (BWRL) Varecia variegata variegata and diademed sifakas Propithecus diadema survived for at least 30 months and reproduced after they underwent veterinary screens 2-8 months before release along with other interventions. No mortalities were recorded for BWRL over a 30-month observation period, and only one diademed sifaka died from natural causes. Two sets of BWRL twins (reproductive rate=57%) and seven diademed sifaka infants were born (reproductive rate=26%), the latter of which only two survived. A total of seven BWRL and 27 diademed sifakas were captured at four disturbed forest sites and released in their social units to the reserve where the species had locally gone extinct and that included natural predators. Released primates were habituated to human presence and relocated and monitored using radio-collars. The study does not distinguish between the effects of the different interventions mentioned above.

18 

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.

19 

A before-and-after trial in 2007-2008 in forest-grassland mosaic near Richmond, KwaZulu-Natal, South Africa found that only a small proportion of vervet monkeys Chlorocebus aethiops that underwent veterinary checks prior to their release in two troops along with other interventions, survived for at least 10 months. Out of 35 monkeys released in troop one, only six (17%) survived for 10 months after release, after which monitoring ceased. Twenty-two (63%) vervets went missing and seven (20%) died. However, two infants were born ten and 11 months post-release. Out of 24 vervets released in troop two, 12 (50%) survived, seven (29%) went missing and five (21%) died. Two blood samples were taken for haematological and biochemical analysis. Monkeys underwent veterinary checks, and were allowed to adapt to local environmental conditions before their release in groups into habitat already occupied by conspecifics. All monkeys were supplemented with food after release and one troop also received water. The study does not distinguish between the effects of the different interventions mentioned above.

20 

A study in 2007-2010 in forest-shrubland mosaic within the Mondi forestry in KwaZulu-Natal, South Africa found that only a small portion of the 31 rehabilitated and reintroduced vervet monkeys Chlorocebus aethiops that underwent veterinary screens alongside other interventions, survived for at least one year. One year post-release, ten (32%) individuals had survived and 20 (65%) could not be tracked. One individual was euthanized three days after release after raiding houses and acting aggressively towards people. Veterinary screens included physical examination to determine health condition. The release group included both wild captured (61%) (due to injury) and hand-raised orphaned (39%) vervets. They were held in an enclosure at the release site to adapt to local habitat, released as a group, and supplemented with food for eight weeks. Eleven individuals were fitted with radio-collars that worked nine months after release. The study does not distinguish between the effects of the different interventions mentioned above.

21 

A before-and-after trial in 2008-2010 in forest-savanna mosaic in Mafou forest in Haut Niger National Park, Guinea found that the majority of wild-born orphaned western chimpanzees Pan troglodytes verus that underwent veterinary screens prior to release alongside other interventions, survived reintroduction and remained free-living for at least 27 months. Only one out of 12 (8.3%) released chimpanzees died from anaesthesia during a recovery. One female returned to the sanctuary voluntarily and one male was returned after suffering injuries during another recovery mission. Five chimpanzees (42%) remained together at the release site and two females gave birth to an infant, both of which survived. Health checks included examination of faecal samples for parasites, tuberculosis tests and haematological and serotological analyses. All chimpanzees were released together into habitat with resident wild chimpanzees and predators. Some chimpanzees were allowed to acclimatize to local habitat conditions prior to release. Chimpanzees were initially daily supplemented with food and later on, weekly. The study does not distinguish between the effects of the different interventions mentioned above.

22 

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 the majority of reintroduced western lowland gorillas Gorilla gorilla gorilla that underwent veterinary checks prior to release alongside 14 other interventions, survived over four years. Twenty-one of 25 gorillas (84%) released in the Congo and 22 of 26 gorillas (85%) released in Gabon survived for at least four years. Nine females gave birth to 11 infants, of which nine survived. Gorillas underwent disease screening and vaccinations during quarantine. Gorillas were released in groups and allowed to adapt to local environment and supplemented with food before release into habitat with no resident gorillas. Released gorillas were treated for parasites and when sick. So-called ‘problem-animals’ were removed and relocated and bodies of dead gorillas were examined to determine their cause of death. Forty-three individuals were rehabilitated wild-born orphaned gorillas and eight were ex-situ captive-born gorillas. Both sites became protected areas before reintroduction. The study does not distinguish between the effects of the different interventions mentioned above.

23 

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 the pygmy slow lorises Nycticebus pygmaeus that were screened for diseases before translocation alongside eight other interventions, survived for at least two months. Four out of eight lorises survived for at least two months post-release, whereas remaining individuals either died or their radio-collar signal was lost at an early stage. Lorises were released in groups during the wet season after all monkeys had undergone a 6-week quarantine, veterinary screens and treatment for parasites. Both release sites were protected, no wild resident lorises occurred there and predators were present. Lorises were kept in an in situ cage for between < 2 months or two days, and were subsequently supplemented with food for 7-30 days in DTI and DNBR, respectively. Bodies of dead animals were examined to determine the cause of death. The study does not distinguish between the effects of the different interventions mentioned above.

24 

A site comparison in 2008-2012 in mosaic forest at two sites in Cat Tien National Park, South Vietnam found that all pygmy slow lorises Nycticebus pygmaeus that were screened for diseases prior to their translocation alongside other interventions either died or disappeared. All five lorises died or their radio collar signal was lost at an early stage after release. Each loris was examined under anaesthesia and an intradermal tuberculosis test was conducted. All monkeys underwent a 6-week quarantine and treatment for parasites. Lorises were released in groups into habitat with no wild resident lorises. Three lorises were released at Cat Tien National Park during the dry season. Two other individuals were held in a semi-wild enclosure for one month to foster behaviour that would facilitate their survival in the wild. The latter were released during the wet season. Bodies of dead animals were detected and examined to determine the cause of death. The study does not distinguish between the effects of the different interventions mentioned above.

Referenced papers

Please cite as:

Junker, J., Kühl, H.S., Orth, L., Smith, R.K., Petrovan, S.O. and Sutherland, W.J. (2017) Primate conservation: Global evidence for the effects of interventions. University of Cambridge, UK