Dear All We are happy to share our new publication looking at lung function and metabolic rate while at rest on land and in water for California sea lions. We investigated how sea lions vary respiratory flow and breath duration on land and in water to keep tidal volume constant. It also confirms that the tidal volume in marine mammals is greater as compared with terrestrial mammals but only about 24-30% of the vital capacity. Abstract: Respiratory flow, expired O2, and CO2 were measured during normal voluntary breathing in thirteen confirmed healthy, male California sea lions (Zalophus californianus), body mass (Mb) range 49-130 kg. Expiratory and inspiratory flow (V), tidal volume (VTexp, VTinsp), and breath durations (Texp, Tinsp, Ttot) 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 vs 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 in water versus on land, both Texp and Tinsp decreased, and expiratory and inspiratory flow increased while the VTexp and VTinsp remained the same. The resting mass specific VT (25.1 ± 1.7 ml kg-1) in the current study was approximately 24-30% of the estimated total lung capacity. We also measured breath-by-breath gas uptake to determine the O2 consumption rate (VO2) and CO2 production rates (VO2) during rest on land and in water. There were no differences in VO2 or VCO2 on land as compared with water, and the average estimated values were 0.58 ± 0.22 l O2 min-1 (range: 0.24-1.01 l O2 min−1) and 0.50 ± 0.19 l CO2 min-1 (range: 0.22-0.89 l CO2 min-1), respectively, which agrees with results from other studies in otariids. Additionally, the allometric mass-exponent for VT and VO2 were 1.13-1.20 and 0.86, respectively. These data are the first reported estimates of metabolic rate and lung function in confirmed healthy California sea lions. Reference: Fahlman, A., Meegan, J., Borque-Espinosa, A., Jensen, E.D., Pulmonary function and resting metabolic rates in California sea lions (Zalophus californianus) in water and on land. 2020. Aquatic Mammals, 46:1, 67-79. DOI 10.1578/AM.46.1.2020.67 The article is open access and can be downloaded at: https://www.aquaticmammalsjournal.org/index.php?option=com_content&view=arti... Or a pdf can be requested through afahlman@whoi.edu