Meeting Abstract

P3-10   -   Wingbeat rate and flight characteristics of pregnant and lactating big brown bats (Eptesicus fuscus) Calistri-Yeh, A*; Young, VKH; Kloepper, LN; Northwestern University; Saint Mary's College; Saint Mary's College adriennecy@gmail.com

Volant animals rely on their wings to generate the lift necessary to initiate and maintain flight against the force of gravity. For flying mammals, this demand increases seasonally in females due to increased body mass while pregnant. The extra weight may cause pregnant bats to drop further toward the ground and take more time to generate lift after emerging from a high roost, as well as move more slowly in flight. To test the hypothesis that pregnant bats modify flight behavior to adjust for pregnancy-related increases in mass, we recorded thermal video data from a maternal colony of big brown bats (Eptesicus fuscus) as they emerged from their roost inside a barn at St. Patrick's County Park in South Bend, IN. We tracked the wingtip and center of body locations frame by frame for 28 bats while the colony was heavily pregnant in June 2021, and 24 bats during the lactation period in July 2021. For each individual, we calculated the vertical drop distance before upward motion (lift) was achieved, time from emergence until lift, average speed after lift, and average wingbeat rate per second (WBR). Statistical analysis of the data indicated that pregnant bats had a significantly larger drop distance, longer time until lift, higher flight speed, and higher WBR compared to lactating bats. Our results suggest that pregnancy has a significant effect on flight in female bats, with a particularly strong impact on achieving lift after emergence. However, the higher speed and WBR of the pregnant sample imply that bats can adapt to such changes in body mass by altering their flight mechanics to sustain lift while pregnant.