Measures of Oxygen Consumption and Stroke Frequency of a Captive Subadult Female Polar Bear (Ursus maritimus) while Resting in Water and Swimming and Diving in a Metabolic Water Flume, Oregon Zoo, 2017

Measurements occurred from 4 September to 6 September, 2017. Measurements were made within a sealed metabolic chamber (2.9 m × 1.4 m × 0.6 m) constructed of polycarbonate and reinforced with a steel frame (Carter2Systems, Inc., Hillsboro, OR, USA) that was mounted to the concrete walls of a 1.6 m deep pool. Across the swimming/diving trials, water was circulated at approximately 0.6 km/hr within the chamber using an electric motor (Fastlane, Endless Pools, Inc., Aston, PA, USA). Water was not circulated during resting trials. Fractional concentration of oxygen was measured by an oxygen analyzer. Air was pulled from a metabolic chamber using a vacuum pump (FlowKit Mass Flow Controller, Sable Systems International, Inc., Las Vegas, NV, USA) at 500 L/min. Sub-samples of air from the exhaust port of the chamber were drawn through a series of 6 columns, bi-alternatingly filled with desiccant (Drierite, W. A. Hammond Drierite, Xenia, OH, USA) and scrubbed of carbon dioxide (Sodasorb, W.R. Grace & Co, Chicago, IL, USA) before entering the oxygen analyzer (Sable Systems International, Inc.). The percent of oxygen in the expired air was monitored continuously and values were recorded once per second using Expedata Analysis software (Sable Systems International, Inc.). Air temperature in the chamber, water temperature, and relative humidity were averaged over each measurement session (Artisan Modular Thermo-hygrometer, RS-232, APT Instruments, Omaha, NB, USA). Barometric pressure was similarly averaged over each measurement session (Perception II, Davis Instruments, Hayward, CA, USA). Resting (n = 7 sessions) and swimming/diving (n = 6 sessions) data measurement trials were collected during independent intervals. During each measurement session the bear swam into the chamber and a resting measurement was recorded for a minimum of 10 min with oxygen consumption reported from steady state measurements before each swimming session. Following resting measurements, the water pump was turned on and the bear was enticed to swim and dive by dropping fish into the water column. Each swimming and diving measurement was recorded for a minimum of 10 min (mean = 11 min) with oxygen consumption reported from steady state measurements.

Stroke frequency was measured as the complete power stroke of both forepaws using video from a high-definition video camera (Sony, Tokyo, Japan; HDR-CX260V, 1080 HD, 60p) positioned either above or in front of the flume and a second high-definition video camera (GoPro, San Mateo, CA, USA; Hero 3+, 1080 HD, 60p) positioned in front of the flume at the water line.