...Keep bats warm

http://www.defenders.org/bats/bats

Bats are the only mammals capable of true flight. With extremely elongated fingers and a wing membrane stretched between, the bat’s wing anatomically resembles the human hand. Almost 1,000 bat species can be found worldwide. In fact, bats make up a quarter of all mammal species on earth!

http://www.livescience.com/52626-adorable-bats-conjure-more-than-fear.html

And bats are susceptible to disease. White-Nose Syndrome (WNS), a fungal disease of hibernating bats that was first discovered in 2006, has had a major impact. The fungus that grows on their noses and other exposed flesh on their bodies is fatal, and can wipe out up to 99 percent of bats in single colony.