Timing of pregnancy, lactation, and female foraging activity in three species of bats in southern Illinois

Abstract

Pregnant Northern Long-eared Bats (Myotis septentrionalis), Red Bats (Lasiurus borealis), and Eastern Pipistrelles (Pipistrellus subflavus) were taken beginning in mid-May in southern Illinois. For Northern Long-eared and Red Bats, pregnant individuals were caught during a two-week period until early June. Pregnancy and lactation in Northern Long-eared and Red Bats were fairly synchronized; both species apparently limited their foraging activity during a one-week period possibly near and immediately after parturition. Pregnancy in Eastern Pipistrelles was much less synchronized. Capture of pregnant females extended over at least an eight-week period from mid-May to mid-July. Volant juvenile Northern Long-eared Bats were taken three weeks earlier than any other species; either parturition was earlier or young developed more rapidly. Pregnant Northern Long-eared Bats foraged primarily in the early evening; early and late activity periods were evident for lactating individuals. Foraging trends for pregnant and lactating Red Bats and Eastern Pipistrelles were less apparent. Significant differences in body mass of Northern Long-eared Bats and Eastern Pipistrelles were evident based on reproductive status. No differences in body mass associated with reproductive condition were found in female Red Bats.