Hot houses: the race to save bats from overheating as temperatures rise

Chimneys for bat boxes and a flying fox heat stress forecaster are among efforts to prevent deaths from effects of climate crisis

Steve Latour and his wife were enjoying their usual early morning coffee in the sun outside their lake house in the Kootenay region of British Columbia when they heard noises coming from the bat box attached to the side of the house. Every summer, about 150 Yuma myotis bats return to the box, using it as a maternity colony to give birth to pups and take care of them until they are ready to leave for hibernation in the autumn.

“We noticed that as soon as the sun hit the bat box, they would become agitated. We could see them come down to the bottom of the box, trying to cool down and get fresh air,” says Latour.

One summer morning, he discovered 28 dead pups underneath the box and realised they had succumbed to excessive heat. So Latour initially draped the box with a bed sheet to shade it, and later installed a blind that he could open and close to keep the sun off the box in the early morning. The fix worked. “Once they were back in the shade, everybody would shut up for the day and we did not hear them move around in the morning any more.”

Bats play an important role in the ecosystem. As voracious predators of insects, for example, they help to control crop pests, reducing the need for pesticides on agricultural land. So, over the years, animal lovers, conservation organisations and naturalist groups have installed artificial bat boxes to replace lost buildings and natural roosts where the bats come back year after year.

But scientists are now discovering that in a rapidly warming climate, overheating bat boxes can be a death trap.

Female bats rely on the surrounding air temperature to maintain their body heat and need a warm environment to raise their pups. “Bat boxes can be beneficial as they can help pups grow faster and females gather the energy they need for lactation,” says Joy O’Keefe, an assistant professor who studies the roosting and ecology of bats at the University of Illinois department of natural resources and environmental sciences.

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