Action: Humans chase primates using random loud noise
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- One controlled, replicated, before-and-after study in Indonesia found that in areas where noise deterrents were used, along with tree nets, crop raiding by orangutans was reduced.
- One study in the Democratic Republic Congo found that chasing gorillas and using random noise resulted in the return of gorillas from plantations to areas close to protected forest.
Farmers chase primate crop-raiding species out of fields by shouting and banging objects to make loud noises. Farmers may use a range of noise-makers, such as beating drums and tins, bells, fire crackers, and ‘cracking’ whips in addition to yelling and whistling.
Supporting evidence from individual studies
A controlled, replicated, before-and-after trial in 2007-2009 in an agro-forest system in Batang Serangan region, north Sumatra, Indonesia found that in areas where farmers used noise deterrents and tree nets, crop-raiding by orangutans Pongo abelii was reduced, compared to areas where no mitigation was used. Orangutan feeding time on crops was lower on farms that used noise deterrents and tree nets (69 min, n=25) than on farms that did not (81 min, n=25). In addition, interviews with 50 farmers (of which 50% participated in the trials) showed that attitudes towards orangutan management had changed after the study. The proportion of farmers who wanted orangutans removed from their farms decreased from 58% before the study to 28% after the study. Forty per cent of farmers continued to use noise deterrents as a mitigation technique five months after the study. Hand-held firecracker cannons made out of bamboo and tin filled with calcium carbide to produce noise, and hand-held bamboo drums were used on 25 farms.
A study in 1996 in subtropical montane forest and plantation mosaic in Virunga National Park, Democratic Republic of Congo found that one habituated group of mountain gorillas Gorilla beringei beringei that were raiding corn and banana plantations 3 km from the edge of the park were chased back into the forest using random noise. The authors provided no details on the size of the gorilla group. Rangers produced noise by banging on pots and pans to move the entire gorilla group back into the forest. Guards were dressed in civilian clothing and surrounded the group. Chasing was stopped as the gorillas where within 500 m of the park to avoid association of disturbance with the forest. The International Gorilla Conservation Programme purchased large bells for future interventions.
- Campbell-Smith G., Sembiring R. & Linkie M. (2012) Evaluating the effectiveness of human–orangutan conflict mitigation strategies in Sumatra. Journal of Applied Ecology, 49, 367-375
- Lanjouw A. (1995) Gorilla conservation problems and activities in north Kivu, Eastern Zaire. African Primates, 1, 44-46