Which disease is a major threat to little brown bats during hibernation?

The major hibernation threat to little brown bats is white-nose syndrome. This fungal disease is caused by Pseudogymnoascus destructans and attacks bats during their winter torpor.

The fungus grows on exposed skin, including the muzzle, ears, and wing and tail membranes. Infection disrupts the bat’s physiology and can cause abnormal arousals from torpor. Each arousal consumes precious fat reserves, and affected bats may burn through energy stores roughly twice as fast as healthy bats, eventually dying from starvation or related stress.

White-nose syndrome was first documented in New York during the winter of 2006–2007 and spread widely through North American hibernacula. Little brown bats were among the species hit hardest: more than one million died in the northeastern United States from 2006 to 2011, and some surveyed populations fell by about 90%. Rabies can affect bats, but it is not the disease most strongly associated with mass winter mortality in this species.