Little brown bat ( Myotis lucifugus ): Common throughout the state. Most frequently reside in attics and buildings. About as long as your thumb.
Northern long-eared bat ( M. septentrionalis ): Roosts by day in summer in buildings, under shutters and under tree bark. Uses caves for night roosts. Much more solitary than other members of the Myotis family. Found in small groups on forested hillsides, along streams or lakeshores.
Indiana bat ( M. sodalis ): An endangered species that is difficult to disinguish from other species. Hibernates in a colony.
Big brown bat ( Eptesicus fuscus ): A larger bat about twice the size of a little brown bat. Found throughout the state but is more common in the south. Roosts in buildings and hibernates in colonies.
Silver-haired bat ( Lasionycteris noctivagans ): Bigger than the little brown but smaller than the big brown bat, the silver-haired has fur that is nearly black and tipped with white. Comes to Wisconsin seasonally and migrates south in the winter.
Eastern pipistrella bat ( Pipistrellus subflavus ): The state's smallest bat is yellowish brown in color and prefers to live in caves, abandoned mines and rock crevices.
Red bat ( Lasiurus borealis ): About the size of the big brown bat. Its fur is a rusty red color that looks washed in white. Roosts in trees during the day and is a solitary species that migrates south.
Hoary bat ( Lasiurus cinereus ): Larger than the big brown and weighs about an ounce. Fur ranges from a grayish yellow-brown to gray with grayish-white overtones. Prefers northern forests and migrates south in the winter.