Decreasing overheating risk
- Avoid dark-colored bat boxes as dark colors substantially increase overheating [1,2] and bats may preferentially select dark-colored boxes [3–5], which increases the risk.
- We recommend lighter colors (than have traditionally been recommended) as light colors absorb less solar radiation and will be cooler, thus decreasing overheating risk [1,6].
- High solar exposure can increase bat box temperature and increase overheating risk [1,4,7]. Because bats maternal bats typically select solar exposed bat houses over shaded alternatives [8,9], we recommend that boxes be placed so that they receive some shade during the hottest part of the day.
- Small bat houses with low mass may overheat more readily and not offer bats saftey from high temperatures [10,11]. We recommend tall bat houses with four sides as these structures provide large temperature gradients [7,12,13], which allows bats to move to avoid high temperatures.
- We recommend larger bat boxes for bat species that form larger groups. If a larger group forms in a small bat box, there likely will not be room for some individuals to move down and, thus, bats at the top may be exposed to lethally hot temperatures.
- We also recommend larger bat boxes made of dense materials with low thermal conductance as they will have a higher thermal mass and thus take longer to heat [2,6].
- Adding insulating layers is also a good method to reduce bat box temperatures .
- Adding extra vents to your bat box will reduce overheating risk and make the roost cooler for bats [2,13].
- Adding additional shading features (e.g., large or elevated roof) to your bat house can also reduce overheating risk [13,15].
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