Control of Breathing and Adaptation to High‐altitude Hypoxia in Deer Mice (Peromyscus maniculatus)

High‐altitude environments pose multiple challenges, such as cold temperatures and low partial pressures of oxygen. This study compared the control of breathing and pulmonary gas exchange in populations of deer mice with highland and lowland ancestry to determine the physiological specializations important for living in high‐altitude environments. The hypoxic ventilatory response was measured using whole‐body plethysmography in response to step‐wise decreases in inspired oxygen fraction, from 21% to 8%, in mice acclimated to normoxia or hypobaric hypoxia (simulating the hypoxia at ~4300 m elevation). Total ventilation was similar between populations, but highland mice acclimated to normoxia had a more effective breathing pattern than lowland mice acclimated to normoxia, characterized by deeper less frequent breaths at a given total ventilation. Hypoxia acclimation had no effect on breathing pattern in highland mice, but it increased tidal volume and decreased breathing frequency in lowland mice. Highland ancestry and hypoxia acclimation also affected respiratory water loss and thermoregulatory responses to hypoxia. Therefore, both highland ancestry and hypoxia acclimation influence the control of breathing and pulmonary gas exchange in deer mice. Supported by NSERC of Canada.