Pulmonary Function and Resting Metabolic Rates in California Sea Lions (Zalophus californianus) on Land and in Water

Respiratory flow, expired O-2, and CO2 were measured during voluntary participation while spontaneously breathing in 13 confirmed healthy, male California sea lions (Zalophus californianus; body mass [M-b] range: 49 to 130 kg). Expiratory and inspiratory flow ((V) over dot(exp) and (V) over dot(insp)), tidal volume ((V) over dot(Texp), and V-Tinsp), and breath durations (T-exp, T-insp and T-tot) were collected on land (lying down in sternal recumbency and sitting up) and floating in water to test the hypothesis that lung function changes with body position and on land versus in water. For sea lions on land, no differences were seen in any of the lung function values when comparing lying down versus sitting up. However, when comparing animals on land versus in water, both T(exp)( )and T-insp decreased and (V) over dot(exp) and (V) over dot(insp) increased, while the V(T)(exp )and V-T(insp) remained the same. The resting mass-specific VT (25.1 +/- 1.7 ml kg(-1)) in the current study was approximately 24 to 30% of the estimated total lung capacity. We also measured breath-by-breath gas uptake to determine the O-2 consumption rates ((V) over dotO(2)) and CO2 production rates ((V) over dotCO(2)) during rest on land and in water. There were no differences in (V) over dotO(2) or (V) over dotCO(2) on land as compared with water, and the average estimated values were 0.58 +/- 0.22 1 O-2 min(-1) (range: 0.24 to 1.01 1 O-2 min(-1)) and 0.50 +/- 0.19 1 CO2 min(-1) (range: 0.22 to 0.89 1 CO2 min(-1)), respectively, which agrees with results from other studies on otariids. Additionally, the allometric mass-exponent for V-T and (V) over dotO(2) were 1.13 to 1.20 and 0.86, respectively. These data are the first reported estimates of metabolic rate and lung function in confirmed healthy California sea lions.