Not as small as its western cousin, the eastern pipistrelle weighs in at 6 to10 g and is comparable in size to many bats in the family Vespertilionidae. Eastern pipistrelles are stronger fliers than western pipistrelles, and some migrate several hundred miles in late summer and early fall, to the caves where they hibernate. Learn more about the Pipistrellus subflavus, more commonly known as an Eastern Pipistrelle, in this easy-to-read species overview by the Smithsonian's National Museum of Natural History.