Evaluating bat boxes: design and placement alter bioenergetic costs and overheating risk

Area of Science:

• Ecology
• Bioenergetics
• Conservation Biology

Background:

• Bat box microclimates exhibit spatial and temporal temperature variations.
• This heterogeneity poses thermoregulatory challenges, including heat and cold stress, for roosting bats.
• Understanding factors influencing bat box suitability is vital for effective conservation of bat species.

Purpose of the Study:

• To assess how bat box designs, landscape placements, weather, and bat usage impact temperature suitability and energy expenditure.
• To model overheating risk and energy costs for both endothermic and heterothermic bats using artificial roosts.
• To evaluate the conservation value of different bat box strategies.

Main Methods:

• Deployed 480 temperature dataloggers across 40 rocket box style bat boxes of 5 designs.
• Monitored bat abundance and used bioenergetic models to estimate energy expenditure and overheating risk.
• Analyzed data based on box design, placement, bat numbers, and weather conditions.

Main Results:

• Solar-exposed placements and designs with higher thermal mass reduced energy expenditure for endothermic bats.
• Shaded placements benefited heterothermic bats by providing suitable torpor microclimates, irrespective of box design.
• Overheating risk increased with solar exposure, lack of thermal buffering, higher bat abundance, warmer temperatures, and lower wind speeds.

Conclusions:

• The external water jacket design, offering high thermal mass, reduced overheating risk and endothermic energy expenditure.
• Assessing bat box suitability from both physiological perspectives (endothermy and heterothermy) provides a robust conservation evaluation.
• Future research should focus on manipulating thermal mass and conductance to mitigate overheating and enhance social thermoregulation.