Control of nursery colony populations of bats by artificial light

  • Published source details Laidlaw G.W.J. & Fenton M.B. (1971) Control of nursery colony populations of bats by artificial light. Journal of Wildlife Management, 35, 843-846.


This study is summarised as evidence for the following.

Action Category

Leave bat roosts and roost entrances unlit

Action Link
Bat Conservation
  1. Leave bat roosts and roost entrances unlit

    A replicated, controlled study in 1970 of 11 bat colonies within buildings in Ontario, Canada (Laidlaw & Fenton 1971) found that when bat roosts were left unlit, numbers of big brown bats Eptesicus fuscus and little brown bats Myotis lucifugus increased, whereas numbers decreased when roosts were illuminated with artificial lights. The number of big brown bats at a roost that was left unlit increased by 97%, whereas numbers decreased by 41–96% at illuminated roosts. The same was true for little brown bats (unlit roost: 57% increase; illuminated roosts: 53–89% decrease). Two bat roosts (one big brown bat, one little brown bat) were left unlit, and nine roosts (six big brown bat, three little brown bat) were illuminated with artificial lights. All 11 bat roosts were in attics and contained nursery colonies. Three types of light were used: safety lamps (60 or 100-W incandescent bulbs), cool fluorescent lamps (40-W tubes) or spotlights (150 W). Emerging bats were counted at each of the 11 roosts during 46 nights in May–August 1970.

    (Summarised by: Anna Berthinussen)

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