Meeting Abstract
The maintenance of the energetic cost of life within an ecological context, though crucial, remains poorly understood for most animals. Bats are the only truly flying mammals, and execute an explosive switch from immobile states to energetically expensive flight. We took a multi-pronged approach to estimate how tent-making bats (Uroderma bilobatum) manage their high-energy lifestyle fueled primarily by fig juice. We measured instantaneous and total daily energetic expenditure via heart rate telemetry of free-flying bats; how quickly ingested food enters metabolism and is incorporated into fat through carbon dioxide isotopes of breath; and the potential for energy mobilization by glucocorticoids. Daily energetic expenditure of Uroderma is 46 kJ with a sustained metabolic scope 5.39. They maintain this through unusual cyclical depressions in resting heart rate to less than 200 bpm that save 10% of daily expenditure and counter flying heart rates of over 900 bpm. We also found some of the fastest metabolic incorporation rates measured in flying vertebrates, which support the explosive metabolic shift between rest and flight. Finally, these bats elevate circulating cortisol to 10-15 times basal values when restrained. These findings throw new light on how small tropical animal can apply several strategies to fuel dramatically fluctuating daily energetic demands, in this case including ecological specialization on a temporally unpredictable fruit resource.
