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Providing evidence to improve practice

Action: Detect & report dead primates and clinically determine their cause of death to avoid disease transmission Primate Conservation

Key messages

  • One before-and-after study in the Republic of Congo found that most reintroduced chimpanzees survived over five years when dead chimpanzees were examined to determine their cause of death, alongside other interventions.
  • One before-and-after study in French Guiana found that most translocated white-faced sakis survived over four months when dead sakis were examined to determine their cause of death, alongside other interventions.
  • One before-and-after study in Madagascar found that most black-and-white ruffed lemurs did not survive over five years despite the fact that dead lemurs were clinically examined to determine their cause of death, alongside other interventions.
  • One controlled, before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that the population size of mountain gorillas where dead animals were examined to determine the cause of death, alongside other interventions, increased by 168% over 41 years.
  • One before-and-after, site comparison study in Congo and Gabon found that most western lowland gorillas survived over four years when dead individuals were examined to determine their cause of death, alongside other interventions.
  • Two studies, including a before-and-after, in Vietnam and Indonesia found that most reintroduced pygmy slow lorises either died or disappeared despite the fact that dead lorises were examined to determine their cause of death, alongside other interventions.

Supporting evidence from individual studies

1 

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 survived over five years when dead chimpanzees were examined to determine their cause of death alongside 16 other interventions. Out of 20 reintroduced chimpanzees, two juveniles were confirmed dead, and one male and three females disappeared. No statistical tests were carried out to determine whether the population decrease was significant. Chimpanzees were radio-collared and followed at distances of 5-100 m. Rehabilitated orphaned chimpanzees underwent vaccination, parasite treatment and veterinary screens before being translocated in four subgroups from the sanctuary to habitat where resident conspecifics occurred. Staff members were permanently present to monitor primate health and provide with additional food if necessary. The area status was upgraded from reserve to national park in 1999. Local people were relocated to a nearby village. Sick or injured chimpanzees were treated. TV and radio advertisements were used to raise chimpanzee conservation awareness and local people were provided monetary and non-monetary benefits in exchange for their conservation support. The study does not distinguish between the effects of the different interventions mentioned above.

2 

A before-and-after trial in 1994-1995 in tropical forest near Petit-Saut dam, French Guiana found that most of the translocated white-faced sakis Pithecia pithecia survived for at least four months when dead sakis were examined to determine their cause of death along with other interventions. Two out of three translocated sakis survived for at least four months after release, one individual died after circa 22 weeks. One male died following a new world screwworm fly larvae Cochliomya hominivorax that developed under its radio-collar. Veterinary screens included blood and skin biopsy and general health checks. Three out of six translocated wild sakis where monitored over 41 weeks after their release, which took place one day after capture. Monkeys were captured at development sites by nets and tagged with radio transmitters prior to release as single individuals or as a group into habitat already occupied by resident sakis. The study does not distinguish between the effects of the different interventions mentioned above.

3 

A before-and-after trial in 1997-2002 in primary forest in Betampona Reserve, Madagascar  found that more than half of all captive-bred, parent-reared black-and-white ruffed lemurs Varecia variegata variegata did not survive until the end of the study period of five years, although each dead lemur’s cause of death was clinically determined upon its detection alongside ten other interventions. 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 in the wild group. All dead lemurs underwent a post-mortem examination. Released animals were fitted with radio-collars. Captive lemurs had limited semi-free-ranging experience, were quarantined and underwent veterinary screens before their reintroduction in groups into habitat with predators and wild resident lemurs. They were recaptured and treated when sick and provided with supplementary food and water for a certain period. They were allowed to adapt to local habitat conditions before release. The study does not distinguish between the effects of the different interventions mentioned above.

4 

A controlled, before-and-after study in 1967-2008 in tropical moist montane forest in Volcanoes-, Mgahinga-, and Virunga National Parks in Rwanda, Uganda, and the Democratic Republic of Congo, respectively found that a mountain gorilla Gorilla beringei beringei population increased in size over time, when dead individuals were examined and their cause of death investigated alongside ten other interventions,. Annual population growth was 4.1%, resulting in an overall population increase of 168% over 41 years. No statistical tests were carried out to determine whether this difference was significant. When a gorilla death was detected, the cause of death was clinically determined by an on-site vet. The population was continuously monitored by vets and individuals received medical treatment if necessary. As part of an ecotourism- and research project, gorillas were habituated to human presence, where visitors/researchers had to follow strict health procedures; these included keeping a safety distance to the gorillas, wearing face-masks, spending only a limited amount of time with gorillas, ensuring that visitors/researchers were healthy, and disinfecting visitors’/ researchers’ clothes, boots etc. The study does not distinguish between the effects of the other interventions mentioned above.

5 

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 survived over four years when dead individuals were examined to determine their cause of death alongside 14 other interventions. Twenty-one of 25 gorillas (84%) released in 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. Four individuals died at each release site; three individuals died of natural causes, two died after fights with other gorillas and three disappeared and were pressumed dead. Gorillas underwent disease screening and vaccinations during quarantine. Gorillas were released in groups in habitats with no resident gorillas, allowed to adapt to local environment and supplemented with food prior to release. Released gorillas were treated for parasites and when sick. So-called ‘problem-animals’ were removed and relocated. Forty-three individuals were rehabilitated wild-born orphaned gorillas and eight gorillas were ex-situ captive-born. Both sites were proclaimed protected areas before reintroduction procedures. The study does not distinguish between the effects of the different interventions mentioned above.

6 

A site comparison study 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 several pygmy slow lorises Nycticebus pygmaeus, survived reintroduction while dead individuals were examined to determine their cause of death alongside eight other interventions. Four out of eight lorises survived for at least two months post-release. One individual died due to assumed hyperthermia, a predator killed another and the remaining two lost their collar soon after release. Lorises were released as multiple individuals during the wet season after 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 between <2 months and two days, and were subsequently supplemented with food for 7-30 days in DTI and DNBR, respectively. The study does not distinguish between the effects of the different interventions mentioned above.

7 

A site comparison in 2008-2012 in mosaic forest at two sites in Cat Tien National Park, South Vietnam found that all reintroduced pygmy slow lorises Nycticebus pygmaeus either died or disappeared; dead individuals were examined to determine their cause of death along with other interventions. Three individuals were killed by predators and two others disappeared and were assumed dead. All individuals underwent a 6-week quarantine, veterinary screens and treatment for parasites. Lorises were released as multiple individuals during the dry season into habitat with no wild resident lorises but with predators. Another two individuals were held in a semi-wild enclosure for one month to foster behaviour that would facilitate their survival in the wild and were released during the wet season. The study does not distinguish between the effects of the different interventions mentioned above.

8 

A before-and-after trial in 2006-2011 in tropical forest at Gunung Halimun Salak National Park and Batutegi Nature Reserve, Indonesia found that only few reintroduced Javan slow lorises Nycticebus javanicus and greater slow lorises N. coucang survived for at least 146 and 22-382 days, respectively, when dead individuals were examined to determine their cause of death along with other interventions. Out of five reintroduced greater slow lorises, only one survived for at least 146 days and out of 18 reintroduced Javan slow lorises only five individuals (28%) survived for at least 22-382 days. The study did not report more details about survival time. Two Javan slow lorises died of septicemia, one of electrocution and three of unknown causes. Three greater slow lorises were killed by predators and one died of unknown causes. All lorises underwent quarantine and veterinary screens prior to single releases. Sick individuals were recaptured and treated. All but two lorises were held in enclosures at the release site to adapt to local habitat where conspecifics and predators occurred. 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. & Sutherland, W.J. (2018) Primate conservation. Pages 393-445 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2018. Open Book Publishers, Cambridge, UK.