Abstract
The purpose of this study was to describe pulmonary function in California sea lions (Zalophus californianus) to serve as a baseline model for diagnostic respiratory monitoring, improve anesthetic ventilation, and provide a comparison between wild and managed populations.
Fifteen healthy, male California sea lions (Zalophus californianus), managed under human care, body mass range (49–130 kg), participated in a total of 88 voluntary breathing trials. Breaths were collected on land (lying down and sitting up) and floating in water to evaluate how lung function changes with body position. Respiratory flow rates, expired O2, and CO2 were measured during normal voluntary breathing as well as during maximal expirations. The data were used to measure tidal volume (VT), breath duration, O2 consumption rate (VO2) and CO2 production rates (VCO2) during rest. Breath-by-breath gas uptake was also measured, to assess gas exchange and metabolic rate.
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 expiratory and inspiratory breath durations decreased, and expiratory and inspiratory flow rates increased while the tidal volumes remained the same, respectively. The average estimated VO2 and VCO2 using breath-by-breath respirometry were 0.575±0.217 L O2 min-1 (range: 0.244–1.011 L O2 min−1) and 0.501±0.193 L CO2 min-1 (range: 0.225–0.887 L CO2 min-1), respectively, which is similar to previously published metabolic measurements from California sea lions, Patagonia (Southern) sea lions and Steller sea lions using conventional flow-through respirometry.1,2,3,4,5 Additionally, the results suggest that VT, respiratory flow, and metabolic rate change with body mass. The resting VT in California sea lions is approximately 24–30% of the estimated total lung capacity, suggesting that the mass-specific tidal volume is significantly higher as compared to terrestrial mammals, but similar to other pinnipeds.5,6,7,8
Acknowledgements
The authors would like to thank all the sea lion trainers and animal care staff at the National Marine Mammal Foundation and the U.S. Navy Marine Mammal Program who through their immense dedication, patience and professionalism made this work possible. A special thanks to Celeste Parry, Risa Daniels, Mark Baird, Erin Brodie, Jammy Eichman, Valerie McCants, and Veronica Cendejas for their assistance with data collection and veterinary care for the animals that participated.
This project was funded by the Office of Naval Research (ONR YIP Award # N-000141410563) and was approved by the U.S. Navy Marine Mammal Program’s Institutional Animal Care and Use Committee (IACUC, Approval No. 117-2016), the IACUC at Texas A&M University - Corpus Christi (TAMUCC-IACUC AUP # 04-11), and the Navy’s Bureau of Medicine and Surgery (BUMED NRD-1024).
* Presenting author
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