Action: Run research project and ensure permanent human presence at site
Key messagesRead our guidance on Key messages before continuing
- Two before-and-after studies in Rwanda, Uganda and Congo found that numbers of mountain gorillas increased over 5-41 years while gorillas were continuously monitored by researchers, alongside other interventions. One review on mountain gorillas in Uganda found that no gorilla was killed over one year while gorillas were continuously monitored by researchers, alongside other interventions.
- One before-and-after study in Brazil found that most reintroduced golden lion tamarins did not survive over seven years post-release despite being permanently monitored by researchers, alongside other interventions, yet tamarins reproduced succesfully.
- One before-and-after study in Belize found that numbers of black howler monkeys increased by 138% over 13 years after being permanently monitored by researchers, alongside other interventions.
- One before-and-after study in the Republic of Congo found that most reintroduced chimpanzees permanently monitored by researchers, alongside other interventions, survived over 3.5 years.
- One before-and-after study in Kenya found ‘problem’ olive baboon troops still survived over 17 years post-translocation while being permanently monitored by researchers, alongside other interventions.
Supporting evidence from individual studies
A before-and-after trial in 1984-1987 in tropical montane forests in the Virunga ecosystem found that mountain gorilla Gorilla beringei beringei populations that were regularly monitored by research staff since 1973 along with other interventions, increased from 242 to 279 individuals (15% increase) in 1981-1986. In addition, average group size increased by 17% (8.5 to 9.2 individuals) and the proportion of immatures increased by 8% (39.7 to 48.1) over the same period. In the same area, some groups were part of a gorilla viewing tourism program started in 1985. Anti-poaching guards regularly patrolled the area and removed snares. Guards were provided with better equipment, which allowed them to increase patrol frequency and effectiveness. An additional multi-organisational conservation project was initiated in 1979. The study does not distinguish between the effects of the different interventions mentioned above.
A review on the status of mountain gorillas in 1972-1989 in tropical montane forest in Eastern Virungas Conservation Area, Uganda found that no mountain gorillas Gorilla beringei beringei were killed in 1989-1990 when a permanent research project was established in the area along with other interventions. In 1989, the game guard force was also increased from three to 13 men and was trained and provided with better equipment. Some locals were resettled from an area (3 km2 in size) that represented the most important gorilla habitat within the Gorilla Game 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 monitored regularly as part of a long-term research program alongside 14 other interventions, did not survive over seven years. Fifty-eight out of 91 (64%) reintroduced tamarins did not survive post-reintroduction. However, 57 infants were born (reproductive rate=63%) of which 38 (67%) survived. In 1983, a long-term study of the wild tamarin population was implemented. 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. Tamarins were quarantined, underwent veterinary checks and parasite treatments before release. Reintroduced sick or injured animals were recaptured, treated and rereleased. The reserve became officially protected in 1983. 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 at Community Baboon Sanctuary, Belize found that when permanent research staff were employed 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 (138% increase), although no statistical tests were carried out to determine whether this difference was significant. Additional interventions included the protection of the sanctuary by the local communities, 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 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 1996-1999 in a tropical rainforest in Conkouati Reserve, Republic of Congo in which researchers were permanently based alongside eight other interventions, found that 70% of reintroduced wild-born orphaned chimpanzees Pan troglodytes troglodytes were still alive 3.5 years after release. No chimpanzees were illegally hunted, which the authors ascribe to the permanent research presence in the area. Estimated mortality was 10-30%. None of the adult females reproduced. Chimpanzees fed on 137 different plant species, a diet variety similar to wild chimpanzees, and had activity budgets that resembled those of wild conspecifics. No statistical tests were carried out to determine whether differences were insignificant. Chimpanzees underwent veterinary screens, were treated for endoparasites and vaccinated. Before reintroduction in groups into habitat with low densities of resident 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 monitored released chimpanzees using radio-collars. The study does not distinguish between the effects of the different interventions mentioned above.
A controlled, before-and-after trial in 1973-2001 in savannah at Chololo ranch, Laikipia Plateau, Kenya found that two troops of translocated crop-raiding olive baboons Papio anubis were still surviving over 16 years post-translocation while being permanently observed by researchers, along with other interventions. The size of the translocated population consisting of two troops totalling 94 baboons in 1984, was 62 individuals in 2001. However, this decrease was not statistically significant. Both troops were observed continuously for 18 years post-translocation. No further details on this intervention were reported. 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. Study groups were observed 265 days/year on average in 1985-2001. Both troops were released into a habitat with resident baboons and predators. Prior to translocation of these so-called ‘problem’-animals, individuals underwent veterinary screens and sick baboons were treated. Translocated baboons were briefly provided with food during periods of drought but not after 1986. The study does not distinguish between the effects of the different interventions mentioned above.
A controlled, before-and-after study in 1967-2008 in tropical 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 that was continuously monitored by researchers alongside ten other interventions, increased in size over time. Annual population growth was 4.1%, resulting in an overall population increase of 168% in 41 years. No statistical tests were carried out to determine whether this increase was significant. Gorillas were habituated to human presence and monitored by researchers for four hours during mid-day. An ecotourism project was subsequently implemented. Visitors/researchers followed strict health procedures, included keeping a safety distance to the gorillas, wearing face-masks, spending only a limited amount of time with gorilla groups, ensuring that visitors/researchers were healthy, and disinfecting visitor’s/researcher’s clothes, boots etc. The population was continuously monitored by vets and individuals were treated if necessary. Dead gorillas in the treatment population were examined and the cause for their death determined. The study only tests for the effect of veterinary interventions, but does not distinguish between the effects of the other interventions mentioned above.
- Aveling R. & Aveling C. (1987) Report from the Zaire Gorilla Conservation Project. Primate Conservation, 8, 162-164
- Butynski T.M., Werikhe S.E. & Kalina J. (1990) Status, distribution and conservation of the mountain gorilla in the Gorilla Game Reserve, Uganda. Primate Conservation, 11, 31-41
- 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
- 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.
- Goossens B., Ancrenaz M., Vidal C., Latour S., Paredes J., Vacher-Vallas M., Bonnotte S., Vial L., Farmer K., Tutin C.E.G. & Jamart A. (2001) The release of wild-born orphaned chimpanzees Pan troglodytes into the Conkouati Research, Republic of Congo. African Primates, 5, 42-45
- Strum S.C. (2005) Measuring success in primate translocation: A baboon case study. American Journal of Primatology, 65, 117-140
- Robbins M.M., Gray M., Fawcett K.A., Nutter F.B., Uwingeli P., Mburanumwe I., Kagoda E., Basabose A., Stoinski T.S., Cranfield M.R. & Byamukama J. (2011) Extreme conservation leads to recovery of the Virunga mountain gorillas. PLoS ONE, 6