Action: Permanent presence of staff/manager
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- One before-and-after study in Kenya found that numbers of Tana River red colobus and crested mangabeys decreased despite permanent presence of reserve staff, alongside other interventions.
- One study in Thailand found that a reintroduced population of lar gibbons declined over three years despite permanent presence of reserve staff alongside other interventions.
- One before-and-after study in Belize found that numbers of black howler monkeys increased by 138% over 13 years after introducing permanent presence of reserve staff, alongside other interventions.
- One before-and-after study in Congo found that most reintroduced central chimpanzees survived over five years after being accompanied by reserve staff, alongside other interventions.
- One before-and-after study in Gabon found that most reintroduced western lowland gorillas survived over nine months, after being accompanied by reserve staff, alongside other interventions.
Supporting evidence from individual studies
A before-and-after trial in 1975-1985 in swamp and riverine forest in Tana River Primate Reserve, Kenya found that despite permanent presence of reserve staff along with other interventions, Tana River red colobus Colobus badius rufomitratus and crested mangabeys Cercocebus galeritus galeritus decreased over a ten year period. Overall population size decreased from 1,200-1,800 to 200-300 individuals (83% decrease) for colobus and from 1,100-1,500 to 800-1,100 individuals (25% decrease) for mangabeys. The number of forest patches inhabited by these two species also decreased over time. No statistical tests were carried out to determine whether this decrease was significant. Results of total counts in 1985 and in 1973-1975 were compared to estimate population change. A permanent ranger post to house junior reserve staff was built in 1976. In the same year, the area became a National Reserve and from 1977-1981, a tourism enterprise with a permanent lodge was established and maintained in the reserve. The study does not distinguish between the effects of the different interventions mentioned above.
A study, which was included in a review, in 1976-1977 in dry evergreen forest in Sai Yok National Park, Thailand on reintroduced captive lar gibbons Hylobates lar in areas with permanent presence of area managers along with other interventions found that their population decreased by 6% and no infants were born 17 months post-release. No statistical tests were carried out to determine whether this decrease was significant. Four gibbons joined wild groups. The permanent presence of area managers and other staff appeared to ensure protection from hunters. A total of 31 gibbons were introduced as individuals, pairs, or family groups into habitat with wild conspecifics. Anaesthetized gibbons were either kept in separate cages from which they could hear, but not see each other for 14 days before release, or laid out on the forest floor. Injured animals were recaptured and treated. In 1961, gibbons were protected in Thailand. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after trial in 1985-1998 in riparian forest in the Community Baboon Sanctuary, Belize, South America found that when staff were permanently present along with ten other interventions, the sanctuary’s black howler monkey Alouatta pigra population increased by 138% over 13 years. The population increased from 840 to over 2,000 individuals, although no statistical tests were carried out to determine whether this increase was significant. Additional interventions included the protection of the sanctuary by the communities surrounding it, preserving forest buffer strips along property boundaries and a forest corridor along the river, constructing pole bridges over man-made gaps, involving local communities in the management of the sanctuary, preserving important howler food trees in large clearings, an eco-tourism and research program, creation of a museum for education purposes, and monetary benefits (income from tourism and craft industries) to local communities for sustainably managing their forest and its wildlife communities. The study does not distinguish between the effects of the different interventions mentioned above.
A before-and-after trial in 1994-1999 in mixed tropical forest in Conkouati-Douli National Park, Democratic Republic of Congo found that the majority of reintroduced central chimpanzees Pan troglodytes troglodytes that were permanently monitored by staff alongside 16 other interventions, survived over five years. Out of 20 reintroduced chimpanzees whose health condition was monitored by permanently present staff during the study, fourteen (70%) survived. No statistical tests were carried out to determine whether the population decrease was significant. Individuals were radio-collared. Rehabilitated orphan chimpanzees underwent vaccination, parasite treatments and veterinary screens before being translocated in four subgroups from the sanctuary to the release site where resident conspecifics occurred. Staff members provided supplementary food if necessary and examined dead animals. The area status was upgraded from reserve to national park in 1999. Local people were relocated from the release site. Some individuals 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 in exchange for their conservation support. 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 accompanied by caretakers during the day alongside ten other interventions, survived for at least nine months. Four (80%) out of five juvenile gorillas survived for at least nine months after release when caretakers guided them into different forest patches on a daily basis. Three captive-bred and two orphan wild-born individuals were reintroduced as a group into habitat with predators and without resident gorillas after they were allowed to adapt to local habitat conditions for some time. They spent the night in an enclosure equipped with nesting platforms, nesting material, supplementary food and water. Gorillas were dewormed regularly on-site. The study does not distinguish between the effects of the different interventions mentioned above.
- Else J.G. (1987) Conservation efforts at the Tana River Primate Reserve, Kenya. Primate Conservation, 8, 165-166
- Eudey A.A. (1991) Captive gibbons in Thailand and the option of reintroduction to the wild. Primate Conservation, 12, 34-40
- Horwich R.H. & Lyon J. (1998) Community-based development as a conservation tool: The Community Baboon Sanctuary and the Gales Point, Manatee project. in: Timber, tourists and temples. Conservation and development in the Maya Forest of Belize, Guatemala and Mexico. Island Press, Covelo, CA.
- Tutin C.E.G., Ancrenaz M., Paredes J., Vacher-Vallas M., Vidal C., Goossens B., Bruford M.W. & Jamart A. (2001) The conservation biology framework of the release of wild-born orphaned chimpanzees into the Conkouati Reserve, Congo. Conservation Biology, 15, 1247-1257
- 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