Record number of Big Brown Bat (Eptesicus fuscus) overwintering in a building at the northern limit of their range in eastern Canada

Abstract

Big Brown Bat (Eptesicus fuscus) is believed to overwinter typically in heated buildings at the northern limit of its range, often singly and generally fewer than 12 per building, as well as in underground environments. As the species is a relatively recent arrival in Maritime Canada, little information is available on its natural history in the region. Here we report a case from New Brunswick, where it appears that at least 122 Big Brown Bats overwintered together in the attic of a brick building constructed in 1947. Exit from this winter hibernaculum occurred abruptly, with a peak in mid-March and a secondary, but lower, peak in mid-April.