Use non-lethal measures to prevent bats from accessing fruit in orchards to reduce human-wildlife conflict

Overall effectiveness category Likely to be beneficial
Number of studies: 2
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How is the evidence assessed?

Effectiveness

70%
Certainty

50%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Bats may be culled by farmers or injured/killed by entanglement with inappropriately installed nets at fruit orchards. Various non-lethal alternatives have been suggested to prevent bats from accessing fruit in orchards to reduce human-wildlife conflict. These include using fixed nets (that prevent entanglement), netting individual trees or branches, planting decoy crops, picking fruit before peak ripeness and deterring bats with light, noise or unpleasant smells and tastes (see Aziz et al. 2016).

Aziz S.A., Olival K.J., Bumrungsri S., Richards G.C. & Racey P.A. (2016) The conflict between Pteropodid bats and fruit growers: species, legislation and mitigation. Pages 377–426 in: Voigt C.C. & Kingston T. (eds.) Bats in the Anthropocene: Conservation of Bats in a Changing World. Springer International Publishing, Cham.

Study locations

Key messages

Two studies evaluated the effects of using non-lethal measures to prevent bats from accessing fruit in orchards to reduce human-wildlife conflict. The studies were in Madagascar and Mauritius.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (0 STUDIES)

OTHER (2 STUDIES)

Human-wildlife conflict (2 studies): Two replicated, controlled studies (including one randomized study) in Madagascar and Mauritius found that using an organic deterrent spray, hanging plastic flags in trees, or covering individual tree branches with nylon net bags reduced damage to lychees caused by Madagascan flying foxes or Mauritius fruit bats. One of the studies found that ringing bells in lychee trees deterred most Madagascan flying foxes.

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 replicated, randomized, controlled study in 2012–2013 at two lychee Litchi chinensis growing sites in Madagascar (Raharimihaja et al 2016) found that using an organic deterrent or plastic flags reduced lychee damage caused by Madagascan flying foxes Pteropus rufus, and ringing bells caused most bats to fly away. At both sites, the average proportion or number of lychees damaged by flying foxes/fruit cluster was lower with an organic deterrent (Site 1 = 5%; Site 2: two fruit/fruit cluster) or plastic flags (Site 1 = 32%; Site 2 = 0.5 fruit/fruit cluster) than with no deterrent (Site 1 = 62%; Site 2 = 11 fruit/fruit cluster). Across both sites, ringing bells resulted in 35 of 44 (80%) flying foxes flying away. Three deterrents were tested at two sites in 2012 and 2013. An organic deterrent (‘Plantskydd’) made from dried blood and vegetable oil was mixed with water and sprayed onto 19–27 lychee clusters/site (each with 60–125 fruit), 15 days before lychees ripened. Bright pink plastic flags (1 x 0.5 m) were hung 1 m from 18–20 randomly selected lychee clusters/site (each with 100–150 fruit). Controls were 21–32 lychee clusters/site with no deterrents. On three occasions, six bells (12-cm diameter) were hung in two lychee trees for four consecutive nights. Bells were rung using a string between 18:00 and 22:00 h when flying foxes attempted to feed on lychees. Lychee damage caused by flying foxes (identified from teeth marks) was monitored daily until lychees were collected by farmers.
Study and other actions tested
Referenced paper
Raharimihaja T.E.A., Rakotoarison J.L.M. & Andrianaivoarivelo R.A. (2016) A comparison of the effectiveness of methods of deterring pteropodid bats from feeding on commercial fruit in Madagascar. Journal of Threatened Taxa, 8, 9512-9524.
A replicated, controlled study in 2016–2017 of 18 lychee Litchi chinensis trees in three towns in central Mauritius (Tollington et al 2019) found that covering individual branches with nylon net bags reduced damage to lychees, mostly caused by Mauritius fruit bats Pteropus niger. Lychee yield from panicles that were covered with net bags was 33% greater than that from uncovered panicles (data reported as statistical model results) due to reduced damage by Mauritius fruit bats, birds, or other causes. Bats were estimated to damage 42% of lychees, birds 13% and unknown causes or splitting 21%. Up to six individual panicles on each of 18 ‘backyard’ lychee trees were covered with nylon net bags and six were left uncovered (total 75 covered, 81 uncovered). The number of lychees on each panicle and damaged/fallen lychees were counted every 2–3 days over an average of 18 days in November–January 2016/2017. Damage by bats was identified from bite marks or discarded seeds.
Study and other actions tested
Referenced paper
Tollington S., Kareemun Z., Augustin A., Lallchand K., Tatayah V. & Zimmermann A. (2019) Quantifying the damage caused by fruit bats to backyard lychee trees in Mauritius and evaluating the benefits of protective netting. PLoS ONE, 14, e0220955.

Please cite as:

Berthinussen, A., Richardson O.C. and Altringham J.D. (2021) Bat Conservation: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

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This Action forms part of the Action Synopsis:

Bat Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Prevent culling of bats around fruit orchards Action Link	No evidence found (no assessment)	0	Synopsis Link
Use non-lethal measures to prevent bats from accessing fruit in orchards to reduce human-wildlife conflict Action Link	Likely to be beneficial	2	Synopsis Link
Introduce certification for bat-friendly crop harvesting regimes Action Link	No evidence found (no assessment)	0	Synopsis Link