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. Like their cousins, female eastern pipistrelles give birth to twins. The neonates are hairless, but develop rapidly and are able to fly when they are two to three weeks old. Males have been known to live to 15 years of age; the maximum recorded longevity for females is 10 years.

Links:
Mammal Species of the World
Click here for The American Society of Mammalogists species account