Action Synopsis: Bat Conservation About Actions

Restrict artificial lighting in caves and around cave entrances

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • One study evaluated the effects of restricting artificial lighting in caves on bat populations. The study was in the USA.




  • Behaviour change (1 study): One controlled study in the USA found that using low intensity white lights or red lights in caves resulted in fewer bat flights than with full white lighting, but the number of bat movements was similar between all three light treatments.

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

  1. A controlled study in 1997–1998 in one cave in Arizona, USA (Mann et al 2002) found that using low intensity white lights or red lights within the cave resulted in fewer flights by roosting cave myotis bats Myotis velifer than when full white lighting was used, but the number of bat movements was similar between all three light treatments. When compared with full intensity white lighting, low intensity white lights or red lights resulted in fewer take-offs (full white: 23; low white: 12; red: 14) and landings (full white: 20; low white: 11; red: 12). However, the overall activity of the colony (all bat movements) did not differ between the three light treatments (full white: 64% of the colony active; low white: 62%; red: 63%). All three measures of bat activity were lowest when no lighting was used (take-offs: 9; landings: 9; proportion active: 54%). A colony of 1,000 cave myotis bats roosted in a large cluster within one room of the cave. Experimental tours were carried out through the room with five replicates of each of 24 treatment combinations. Treatments included light intensity and colour (no light, low intensity white light, full red light, full white light), size of tour group (0, 1–3 or 6–8 people), and voice intensity (no people talking, all members of group talking). A total of 120 experimental cave tours were carried out between April and September in 1997 and 1998. Bat behaviour was observed with a night-vision video camera and infrared lights.

    Study and other actions tested
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?

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Bat Conservation

This Action forms part of the Action Synopsis:

Bat Conservation
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