Use nets to keep primates out of fruit trees

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

40%
Certainty

30%
Harms

20%

Calculating overall effectiveness category

Background information and definitions

Tree nets can be used to close off tree canopy travel pathways of primates in order to protect the fruit from being eaten by the primates. Netting is cheap to install but can be labour intensive for subsistence farmers.

Study locations

Key messages

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.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

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.
Study and other actions tested
Referenced paper
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.

Please cite as:

Junker, J., Kühl, H.S., Orth, L., Smith, R.K., Petrovan, S.O. & Sutherland, W.J. (2020) Primate Conservation. Pages 431-482 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Primate Conservation

Related Actions

Actions	Effectiveness	Category
Use GPS and/or VHF tracking devices on individuals of problem troops to provide farmers with early warning of crop raiding Action Link	No evidence found (no assessment)	Synopsis Link
Strategically lay out the scent of a primate predator (e.g. leopard, lion) Action Link	No evidence found (no assessment)	Synopsis Link
Use loud-speakers to broadcast sounds of potential threats (e.g. barking dogs, explosions, gunshots) Action Link	No evidence found (no assessment)	Synopsis Link