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Providing evidence to improve practice

Action: Use light/lasers to deter crop damage by mammals to reduce human-wildlife conflict Terrestrial Mammal Conservation

Key messages

Read our guidance on Key messages before continuing

  • Two studies evaluated the effects of using light or lasers to deter crop damage by mammals to reduce human-wildlife conflict. Both studies were in the USA.





  • Human-wildlife conflict (2 studies): A replicated, randomized, controlled study in the USA found that red lasers did not disperse white-tailed deer from fields at night whilst a study in India found that spotlights directed at the eyes of Asian elephants did reduce the probability of crop damage.

Supporting evidence from individual studies


A replicated, randomized, controlled study in 2001 in arable fields on two adjacent wildlife refuges straddling Nebraska and Iowa, USA (VerCauteren et al. 2003) found that red lasers did not disperse white-tailed deer Odocoileus virginianus from fields at night. No differences were found in flight response between two different lasers (deer fled in 2–3% of encounters) or between these lasers and the control without lasers (3% fled). Thirty-two crop fields were randomly assigned one of two lasers, shone from a vehicle, or as the control (vehicle without laser). The two red lasers were the Desman® (633 nm, 5 mW, 12 mm beam) and Dissuader™ (650 nm, 68 mW, variable beam). Deer behaviour was monitored using night-vision binoculars on eight consecutive nights in July 2001 (total 177 deer encounters). Deer were initially located with a spotlight. Lasers were used for 2 minutes/deer, first on adjacent vegetation, then in a zig-zag manner, then on the body.


A study in 2006–2009 in two areas of Assam, India (Davies et al. 2011) found that using spotlights directed at the eyes of Asian elephants Elephas maximus reduced the probability of elephants causing crop damage. The chance of crop damage occurring was lower when spotlights were used to deter crop-raiding elephants compared to a range of other interventions or no intervention (results presented as statistical model coefficients). Only installing fences reduced crop raiding to a greater extent. Using loud noises alongside spotlighting reduced its effectiveness. Within two study areas, 33 community members were trained as monitors to record the 1,761 crop-raiding incidents, from 1 March 2006 to 28 February 2009. A range of deterrents were used, singly or in combination, including spotlights, chili smoke (from burning dried chilies, tobacco, and straw), two-strand electric fences, chili fencing (engine grease and ground chili paste, on a jute or coconut rope), elephant drives (using domesticated elephants to repel wild elephants), fire and noise.

Referenced papers

Please cite as:

Littlewood, N.A., Rocha, R., Smith, R.K., Martin, P.A., Lockhart, S.L., Schoonover, R.F., Wilman, E., Bladon, A.J., Sainsbury, K.A., Pimm S. and Sutherland, W.J. (2020) Terrestrial Mammal Conservation: Global Evidence for the Effects of Interventions for terrestrial mammals excluding bats and primates. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.