Arrhythmic breathing, apnea and non-steady-state oxygen uptake in hibernating little brown bats (Myotis Lucifugus)

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Abstract
We measured the breathing pattern and oxygen consumption of hibernating little brown bats {Myotis lucifugus) in open- and closed-circuit metabolic chambers. At 5°C, hibernating M. lucifugus showed bouts of ventilation lasting on average 1.24min and separated by periods of apnea lasting on average 47.59min. The bats consumed 0.014 ml O2g−1 during ventilation bouts and 0.002 ml g−1 during apnea. The total O2 uptake was 0.016 ml g−1 for a complete ventilationapnea cycle, giving a Vo2 of 0.020 ml g−1 h−11. This value is considerably lower than most values previously published for Myotis spp. and we suggest that studies using open-circuit systems that did not account for the intermittent nature of gas exchange during hibernation may be in error. Based on the dimensions of the respiratory tract, we estimate that 0.026 ml O2g−1h−1 and 0.009mlCO2g−1h−1 could diffuse down the tract if the glottis was open. The low O2 uptake during apnea indicates that the glottis was closed. If CO2 retention acts to depress metabolism in hibernators, a closed glottis and arrhythmic breathing may be adaptive strategies in hibernation.