We studied the distribution and ecology of male and female Myotis lucifugus (Little Brown Bats) and M. septentrionalis (Northern Long-eared Bats) on Newfoundland, where conditions (e.g., resource availability, abiotic conditions) were expected to be less favorable than in areas where most studies of conspecifics have occurred. We found that both species were patchily distributed and that Northern Long-eared Bats were more widely distributed across the island than previously documented. We located and characterized 36 roost trees from 14 female (6 lactating and 8 non-lactating) Northern Long-eared bats and found that, relative to conspecific populations on mainland North America, female Northern Long-eared Bats on the northern peninsula of Newfoundland roosted in shorter trees with smaller diameters. We also found that roosts used by lactating Northern Long-eared females were in cavities of large-diameter trees that maintained more stable microclimates compared to roosts used by non-lactating females.