We measured respiratory flow rates, and expired O2 in 32 (2-34 years, body mass [Mb] range: 73-291 kg) common bottlenose dolphins (Tursiops truncatus) during voluntary breaths on land or in water (between 2014 and 2017). The data were used to measure the resting O2 consumption rate ([Formula: see text], range: 0.76-9.45 ml O2 min-1 kg-1) and tidal volume (VT, range: 2.2-10.4 l) during rest. For adult dolphins, the resting VT, but not [Formula: see text], correlated with body mass (Mb, range: 141-291 kg) with an allometric mass-exponent of 0.41. These data suggest that the mass-specific VT of larger dolphins decreases considerably more than that of terrestrial mammals (mass-exponent: 1.03). The average resting [Formula: see text] was similar to previously published metabolic measurements from the same species. Our data indicate that the resting metabolic rate for a 150 kg dolphin would be 3.9 ml O2 min-1 kg-1, and the metabolic rate for active animals, assuming a multiplier of 3-6, would range from 11.7 to 23.4 ml O2 min-1 kg-1.\absbreak Our measurements provide novel data for resting energy use and respiratory physiology in wild cetaceans, which may have significant value for conservation efforts and for understanding the bioenergetic requirements of this species.
Keywords: diving physiology; field metabolic rate; marine mammals; pulmonary function test; spirometry; tidal volume.