The susceptibility of bats to a deadly disease is influenced by the humidity of the caves in which they hibernate.

Credit: US FWS/Ryan von Linden, NY Dept of Environ. Conserv./SPL

White-nose syndrome, which has killed millions of bats in North America, is caused by infection with the fungus Pseudogymnoascus destructans. The disease is thought to speed up bats' use of energy reserves during hibernation, putting the animals at risk of starvation.

To find out why only some bat populations survive these infections, David Hayman at Massey University in Palmerston North, New Zealand, and his team used a computer model to predict winter survival times for four species. Humidity significantly reduced survival, which could explain why the little brown bat (Myotis lucifugus; pictured) — a resident of warm, humid caves during hibernation — has been affected more than other bat species.

Larger bats, including some that live in Europe, are more likely to survive the infection.

Sci. Adv. 2, e1500831 (2016)