Meeting Abstract
As small-bodied, flying mammals, insectivorous bats experience substantial, but variable, energetic demands. In the summer, females experience the greatest demands during reproduction, particularly due to increases in wing loading and long periods of lactation. Following lactation, there is a period of comparatively lower energy demand prior to fall migration. To compensate for periods of greater energy demand, we hypothesized that bats increase fat storage and lipid oxidative capacity. Using quantitative magnetic resonance, we measured fat mass in a maternity colony of Brazilian free-tailed bats (Tadarida brasiliensis) over the course of the summer active season. We also collected pectoral muscle at multiple time points spanning the reproductive cycle and measured changes in the activity of three catabolic enzymes that are known to be upregulated in bats during migration. We found that fat mass decreased from mid-pregnancy through lactation, suggesting that females rely, at least partially, on stored fat to fuel reproductive events. Males, which don’t experience reproductive costs in the summer, showed little variation in fat mass. Analysis of catabolic enzyme activity in flight muscle is ongoing, and will reveal whether parallel variation in lipid oxidative capacity occurs with the observed variation in fat stores. Unlike running mammals, bats rely on extramuscular fat stores to fuel high intensity exercise, and this research will determine whether bats require additional physiological compensation to continue powering flight during energetically demanding life-cycle stages. More broadly, the present study addresses the ability of animals to maintain energy balance by adjusting flexible physiological and biochemical traits in response to periodic changes in energy demand.
