The little brown bat, Myotis lucifugus, is one the most common bats in North America. But it and other species of bat could possibly become extinct from white nose syndrome (WNS). WNS is a fungus that grows on the nose, muzzle, ears and wings of bats during hibernation. Large numbers of bats are infected, and perhaps a million have already died.

Scientists do not know yet if it is actually the fungus that kills the bat. The fungus could be an opportunistic infection appearing when a bat’s immune system was impaired from another cause. Because the little brown bat lives in caves in large colonies of up to 20,000, it is especially susceptible. Whatever the actual cause of death, once a cave population is infected, high mortality of the population (up to 90%) follows quickly.

Bats are beneficial to our ecosystem, controlling many species of insects, and the loss of the little brown bat could be devastating. There is some good news. Our other common bat species here in New England, the big brown bat, Eptesicus fuscus, appears to have escaped this pandemic. The reason may be that the big brown bat hibernates in smaller colonies and tends to go into hibernation later and comes out earlier, thus giving the syndrome less time to take hold.

The big brown bat is the most common bat that nests in homes in our area. This year we have seen a significant increase in calls for live removal of this species. It’s certainly possible that the big brown bat population is increasing and filling the void left by the demise of the little brown bat. At this point, the best hope for survival for the little brown bat is that some individual bats will have a natural defense to the syndrome, and the population will have a chance to rebuild. Even if true, this will take decades.