Using mounting, orientation, and design to improve bat box thermodynamics in a northern temperate environment

Amélie Fontaine,Kyle H Elliott,Bryan Dubois,Julien Dutel,Anouk Simard

doi:10.1038/s41598-021-87327-3

Amélie Fontaine, Kyle H Elliott + Show 3 more

Open Access

https://doi.org/10.1038/s41598-021-87327-3

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Abstract

Wildlife managers design artificial structures, such as bird houses and bat boxes, to provide alternative nesting and roosting sites that aid wildlife conservation. However, artificial structures for wildlife may not be equally efficient at all sites due to varying climate or habitat characteristics influencing thermal properties. For example, bat boxes are a popular measure employed to provide compensatory or supplementary roost sites for bats and educate the public. Yet, bat boxes are often thermally unstable or too cold to fulfill reproductive females needs in northern temperate environments. To help improve the thermodynamics of bat boxes, we tested the effect of (1) three mountings, (2) four orientations, and (3) twelve bat box designs on the internal temperature of bat boxes. We recorded temperatures in bat boxes across a climate gradient at seven sites in Quebec, Canada. Bat boxes mounted on buildings had warmer microclimates at night than those on poles and those facing east warmed sooner in the morning than those facing west or south. Our best new model based on passive solar architecture (Ncube PH1) increased the time in the optimal temperature range (22–40 °C) of targeted species by up to 13% compared to the most commonly used model (Classic 4-chamber) when mounted on a building with an east orientation (other designs presented in the Supplementary Information). Based on bioenergetic models, we estimated that bats saved up to 8% of their daily energy using the Ncube PH1 compared to the Classic 4-chamber when mounted on a building with an east orientation. We demonstrate that the use of energy-saving concepts from architecture can improve the thermal performance of bat boxes and potentially other wildlife structures as well.

Highlights

Birth to the peak of resources[24] or allow bats to save energy on cool days when insects are not available, entering torpor during summer may delay female reproduction by slowing fetal development and reducing milk production[25,26,27], with negative consequences on the probability of survival throughout hibernation for both mother and o ffspring[22,23,28,29]
Despite attempts by conservationists to address the causes of variability listed previously, the colonization rate of bat boxes varies widely[7,16,44,45,46,58], often with low rates in urban or suburban northern temperate environments
The present study aimed to improve the thermal properties of artificial bat boxes to better meet the thermal preferences of reproductive female little brown bats living in Quebec, as estimated via the extended optimal temperature range of 22–40 °C (EOTR)

Summary

Introduction

Birth to the peak of resources[24] or allow bats to save energy on cool days when insects are not available, entering torpor during summer may delay female reproduction by slowing fetal development and reducing milk production[25,26,27], with negative consequences on the probability of survival throughout hibernation for both mother and o ffspring[22,23,28,29]. Passive solar designs take advantage of a building’s geographic location and climatic conditions, building’s shape, orientation, construction materials, openings, and more to minimize energy use for heating and cooling to maintain thermal conditions that are suitable for its inhabitants[51]. The present study aimed to improve the thermal properties of artificial bat boxes to better meet the thermal preferences of reproductive female little brown bats living in Quebec, as estimated via the extended optimal temperature range of 22–40 °C (EOTR). We predicted that external factors, such as an east-facing orientation and mounting on a heated building, could improve thermal properties of bat boxes and favour time spent in the EOTR of 22–40 °C of reproductive female little brown bats. We expected that thermal improvements to bat boxes, as measured during our field experiments, should lower the modelled daily energy expenditure of reproductive female little brown bats. We expected bats to save energy especially at night and in the early morning, when reproductive females are thermally challenged as they rewarm after nightly torpor bouts

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