An Observation of Spring Mating in Silver-Haired Bats (Lasionycteris noctivagans)

Abstract. The mating behavior of North American tree bats (Lasiurus spp. and Lasionycteris noctivagans) is not well understood. The majority of records suggest that this group of species mates during the autumn migratory period and that females store sperm throughout the winter before resuming the reproductive cycle in spring. On 16 May 2019, while mist-netting in Bernalillo County, New Mexico, USA, we observed a male and female silver-haired bat (Lasionycteris noctivagans) copulating on the ground. Both individuals were captured and processed to obtain further details on reproductive status. To our knowledge this is the first published record of a silver-haired bat copulation event, and its occurrence during the spring migratory period challenges long-held assumptions about the reproductive cycle of the species and tree bats in general.