Acoustic monitoring and radio-tracking were used to study the nocturnal activity of adult female Indiana bats Myotis sodalis at a maternity site in Michigan, U.S.A. Pregnant bats did not use the day roost at night, but lactating females returned 2–4 times/night for 32±7 (se) min/visit, presumably to feed their young. Both pregnant and lactating females night roosted as solitary individuals in trees within their foraging areas; night roosting occurred 0–6 times/night for 14±1 min each time. Bats foraged for most of the night, with the total duration of flight equalling 375±16 min/night. The bats used 13 different foraging areas that were located 0.5–4.2 km from the day roost. Bats did not fly over open fields but travelled along wooded corridors, even though such behaviour increased commuting distance by 55±11%. Current models of habitat suitability for this endangered species should be modified, taking into account the use of wooded commuting corridors and the large home range of these bats.