Action: Limit time that researchers/tourists are allowed to spend with habituated animals
- One controlled study in Indonesia found that reintroduced Sumatran orangutans that spent limited time with caretakers acted more similar to wild orangutans than orangutans that spend more time with caretakers, alongside other interventions.
- One before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that numbers of mountain gorillas increased by 168% over 41 years while being visited by researchers and visitors during a restricted amount of time, alongside other interventions.
This intervention aims to prevent the spread of viral and bacterial diseases from humans to primates and can be implemented in situations where humans regularly come into close contact with primates, such as when researchers or tourists observe habituated primates in their natural habitat. Another argument for limiting human-primate interactions is that regular contact with humans may influence the behaviour of primates. For example, Riedler et al. (2010) could show that Sumatran orangutans Pongo abelii that were allowed to spend only a limited amount of time with the caretakers, acted more like wild orangutans after release than individuals that had regular and close contact to them.
Other means of preventing the spread of bacterial and viral diseases from researchers/tourists/managers to primates is discussed under ‘Wear face-masks to avoid transmission of viral and bacterial diseases to primates’, ‘Keep safety distance to habituated animals’, ‘Implement quarantine for people arriving at, and leaving the site’, ‘Ensure that researchers/tourists are up-to-date with vaccinations and healthy’, ‘Regularly disinfect clothes, boots etc.’, and ‘Wear gloves when handling primate food, tool items, etc.’.
Riedler B., Millesi E. & Pratje P.H. (2010) Adaption to forest life during the reintroduction process of immature Pongo abelii. International Journal of Primatology, 31, 647–663.
Supporting evidence from individual studies
A controlled study in 2004-2005 in a mosaic of logged and secondary tropical forest in Bukit Tigapuluh National Park, Indonesia found that reintroduced Sumatran orangutans Pongo abelii that spent only a limited amount of time with their caretakers along with other interventions, acted more like wild orangutans after release compared to individuals that had regular and close contact to caretakers. The behaviour of the three non-habituated orangutans with minimal human contact resembled that of wild orangutans more than that of the five habituated individuals in the way that they built nests, their food choice and canopy use. Furthermore, the former spent more time interacting socially with previously released orangutans. Non-habituated orangutans were released after they spent 6-month at a sanctuary to acclimatize. Human-habituated individuals were kept in semi-free conditions for 7-9 months prior to release where staff members guided them to the forest on a daily basis and tried to foster natural behaviour. 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 found that the mountain gorilla Gorilla beringei beringei population that was regularly visited by tourists and researchers that were restricted in the amount of time they were allowed to spend with them alongside ten other interventions, increased over time. 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 increase was significant. One-hour visits were made to each gorilla group daily by tourists. Researchers typically spent no more than four hours with the research-habituated groups. As part of the ecotourism- and research programmes, 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, ensuring that visitors/researchers were healthy, disinfecting visitor’s/researcher’s clothes, boots etc. Gorillas were continuously monitored by vets and received medical treatment if necessary. When gorillas died, their cause of death was clinically determined. The study does not distinguish between the effects of the different interventions mentioned above.
- Riedler B., Millesi E. & Pratje P.H. (2010) Adaptation to Forest Life During the Reintroduction Process of Immature Pongo abelii. International Journal of Primatology, 31, 647-663
- 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