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Providing evidence to improve practice

Action: Use nets to keep primates out of fruit trees Primate Conservation

Key messages

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  • One controlled, replicated, before-and-after study in Indonesia found that areas where nets were used to protect crop trees, crop-raiding by orangutans was reduced.

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 tree nets, crop-raiding by orangutans Pongo abelii was reduced. In areas where farmers used no mitigation technique, the frequency of crop-raiding events did not change. Crop yield increased from 69 kg to 176 kg (61% increase) after trials on farms where farmers used tree nets (n=10 farms) and decreased from 64 kg to 47 kg (27% decrease) on farms where no mitigation technique was trialled (n=15 farms). 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. However, all farmers stopped using nets as a mitigation technique five months after the study. Barrier nets of 5 x 5 cm2 mesh stitching nylon rope were placed to partially or entirely cover the canopy of 14 separate jengkol Archidendron pauciflorum trees.

Referenced papers

Please cite as:

Junker, J., Kühl, H.S., Orth, L., Smith, R.K., Petrovan, S.O. & Sutherland, W.J. (2019) Primate conservation. Pages 439-491 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.