Validating the relationship between 3-dimensional body acceleration and oxygen consumption in trained Steller sea lions
We tested the ability of overall dynamic body acceleration (ODBA) to predict the rate of oxygen consumption ($$s\dot{V}_{{{\text{O}}_{2} }}$$sV˙O2) in freely diving Steller sea lions (Eumetopias jubatus) while resting at the surface and diving. The trained sea lions executed three dive types—single dives, bouts of multiple long dives with 4–6 dives per bout, or bouts of multiple short dives with 10–12 dives per bout—to depths of 40 m, resulting in a range of activity and oxygen consumption levels. Average metabolic rate (AMR) over the dive cycle or dive bout calculated was calculated from $$s\dot{V}_{{{\text{O}}_{2} }}$$sV˙O2. We found that ODBA could statistically predict AMR when data from all dive types were combined, but that dive type was a significant model factor. However, there were no significant linear relationships between AMR and ODBA when data for each dive type were analyzed separately. The potential relationships between AMR and ODBA were not improved by including dive duration, food consumed, proportion of dive cycle spent submerged, or number of dives per bout. It is not clear whether the lack of predictive power within dive type was due to low statistical power, or whether it reflected a true absence of a relationship between ODBA and AMR. The average percent error for predicting AMR from ODBA was 7–11 %, and standard error of the estimated AMR was 5–32 %. Overall, the extensive range of dive behaviors and physiological conditions we tested indicated that ODBA was not suitable for estimating AMR in the field due to considerable error and the inconclusive effects of dive type.