URBANA, Ill. – Imagine if you had to catch every bite of your dinner with your mouth, while flying, in the dark. You’d be exhausted, and probably pretty hungry. Though some bats go for sedentary insects, most catch their food on the wing every single night. Let that sink in.

Because they expend so much energy this way, bats switch among a couple energetic strategies. The most energy-conserving of these is heterothermy. It involves lowering body temperature and metabolism to match the environment in cold weather. Endothermy, maintaining a constant internal temperature, requires more energy.

Either way, the outside temperature is important. During heterothermic periods, bats and developing pups could suffer if their environment cools off too much or too quickly. Excessive heat or cold can also impact energy reserves during endothermic phases. New University of Illinois research looks at the effect of bat box design and placement on the energetic balance of endangered Indiana bats.

“The temperature of the roost is really important because it influences the energetic expenditure of the bat during the summer. When reproductive females are rearing a pup, really cold roosts either force them into torpor (heterothermy) or make them increase their energetic expenditure to try and stay warm,” says Reed Crawford, a doctoral student in the Program in Ecology, Evolution, and Conservation Biology at Illinois and lead author on a new paper in Conservation Physiology. “Additionally, bats have to pant, spread saliva, wing fan, or move locations to cool themselves in overly hot roosts, and that takes energy too.”

The energy a mother bat expends can affect pup development and influences both the mom and pup’s survival over the winter. If bats use too much energy staying warm, that energy can’t go towards growth or building fat reserves needed to get through hibernation. When roosts are too cold, pup development slows down. With deadly white-nose syndrome affecting bats during their winter sleep, it’s important they enter hibernation in tip-top shape.

Crawford and co-author Joy O’Keefe, an assistant professor and wildlife extension specialist in the Department of Natural Resources and Environmental Sciences at Illinois, tested five bat box designs and four landscape placements to determine how they affected endangered Indiana bats during heterothermic and endothermic periods.

Read more from the College of Agricultural, Consumer & Environmental Sciences

The Department of Natural Resources and Environmental Sciences is in the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois Urbana-Champaign.

The research team with newly installed rocket boxes. Pictured, left to right: Joy O’Keefe, Francis Tillman, Reed Crawford, Luke Dodd, and Evan Moser.