For years, bats in North America have been plagued by a deadly fungal disease called white-nose syndrome. Despite measures to stop its spread, this fungus has swept across the continent, and scientists are monitoring the surviving bat populations to see if they are better equipped to avoid getting sick in the future. Unfortunately, North American bats may be stuck in an "ecological trap" that keeps them returning to the very habitats where the fungus grows best.

According to a recent study in the journal Nature Communications, little brown bats (Myotis lucifugus) in Michigan and Wisconsin choose to hibernate in roosts that stay above 8°C even when colder roosts are available. This is important because the fungal pathogen that causes white-nose syndrome grows best at 12-16°C, so hibernating in colder caves would protect bats from this deadly disease. 

Conservation biologists expected that when white-nose syndrome tore through these populations, the warm-loving bats would die off, leaving only cold-loving survivors behind. And, as bats are known to be fast learners, they could potentially learn to avoid warm roosts in order to stay alive.

However, when the researchers compared the habitat preferences of bat populations before and after the fungus arrived, they only found a minor shift in preference towards colder roosts. The researchers concluded that these little brown bats are not likely to either evolve or learn warmer roosting preferences quickly enough to protect them from the disease. Considering that these bats have evolved for millennia with the risk of wintertime freezing, it makes sense that their desire to seek out warm roosts is difficult to overcome.

While it may not be possible to change the bats’ behavior, it is possible to conserve natural roosting sites that are cold enough to protect them and to restore human-altered sites like mines and tunnels by removing the artificial barriers that insulate them. These conservation measures will be increasingly important as both habitat degradation and climate change continue to worsen.