Modifying mines to be cooler may help bats survive white-nose syndrome.
By Kristen Pope
Cold air sinks, warm air rises. It’s a simple concept, but one that is now being tested to improve hibernating bat habitat. White-nose Syndrome has decimated bat populations across North America, killing over 90% of some species. The fungus that causes the deadly bat disease, Pseudogymnoascus destructans, thrives in temperatures ranging from 46-57 degrees Fahrenheit, growing slower when it’s colder. Now, Pennsylvania researchers are testing cooling down habitats to slow the fungus’s spread. Pennsylvania Game Commission wildlife biologist Greg Turner led an experiment with BCI scientists to cool abandoned mines and see how the bats responded.
Contrary to what it may sound like, cooling abandoned mines does not involve lugging in a massive air conditioner to reduce the cave’s temperature. Rather, the modifications create a range of microclimates so bats can choose where they would like to hibernate.
Since cold air sinks, the researchers chose abandoned mines and caves that were previously unsuitable for bats with inclines, modifying them to create natural cooling systems. Building earthen mounds in front of the entrances blocked air flow but allowed bats to pass in and out of the mines. Colder air was trapped inside, settling in lower spots and pushing warmer air up. And creating vents on top of the mine allowed warm air to rise and escape, while colder air was trapped in pockets where the fungus couldn’t incubate as well.
Turner and colleagues published a paper in Conservation Biology in 2022 focusing on five mines and caves, along with an abandoned railroad tunnel, which were all modified to create cooler microclimates. They also studied 25 subterranean areas that were not modified.
They found that Endangered little brown bats (Myotis lucifugus) are choosing sites that are a little colder than their previous hibernation choices when given the option. Endangered northern long-eared bats (Myotis septentrionalis), big brown bats (Eptesicus fuscus), and eastern small-footed myotis (Myotis leibii) also preferred cooler areas (around 37-43 degrees Fahrenheit) over warmer ones (44-51 degrees Fahrenheit).
It’s a fine balance for bats to find the right area to hibernate. If it’s too cold, they’ll wake more frequently which could cost them too much energy until they starve. If it’s too warm, the fungus will grow quicker, waking them more often, causing them to expend too much energy until they starve.
The hope is that bats will inhabit a “goldilocks” area that is not too cold or too hot in order to give the bats a fighting chance to survive the winter.