Meeting Abstract
Bats (Order Chiroptera) are heavily impacted by habitat loss. Cavity and crevice roosting bats, >50% of bat species worldwide, are losing roost sites to deforestation. Artificial roosts might serve as alternatives, but comparative evaluations of different designs are few. Our comparisons of 3 common designs — synthetic rubber “bark”, a typical flat bat box, and a tall, square “rocket box” — found Indiana bats (Myotis sodalis) strongly preferred the rocket box design. The proximate factors responsible for this preference are not clear, as the 3 designs differed in total volume, roosting surface area, odor, predator protection, and thermal characteristics. Neither do we know if preference translates into reproductive success. To better define causal factors, we exploit parallels with lizard studies to evaluate thermal conditions as related to variations in rocket box construction. Notably, solar radiation and rising warm air creates a vertical thermal gradient in the box. Thus, as do lizards in a gradient experiment, bats may move vertically to select a temperature. Further, many bat species are gregarious, so the amount of space (roosting surface area or volume) available within a temperature range is likely to be important. We compared microclimates in 20 designs differing in height, volume, heat storage, insulation, and air vents; boxes were closed to bats. Regressions to temperatures recorded at 3 heights were used to compute a thermal habitat suitability index established for reptile studies: the integrated product of space × time available at temperatures weighted by a physiological value factor. We found biologically significant differences among designs using ad hoc value factors. However, well-justified physiological and reproductive value factors are also needed.
