The integral of the dynamic component of acceleration over time has been proposed as a measure of energy expenditure in wild animals. We tested that idea by attaching accelerometers to free-ranging pelagic cormorants (Phalacrocorax pelagicus) and simultaneously estimating energy expenditure using doubly-labelled water. Two different formulations of dynamic body acceleration, VeDBA and ODBA, correlated with mass specific energy expenditure (both R(2)=0.91). VeDBA models combining and separately parameterizing flying, diving, activity on land and surface swimming were consistently considered more parsimonious than time budget models and showed less variability in model fit. Additionally, we observed provisional evidence for the presence of hypometabolic processes (i.e. reduced heart rate and body temperature; shunting of blood away from non-essential organs) that suppressed metabolism in cormorants while diving, which was the most metabolically important activity. We concluded that a combination of VeDBA and physiological processes accurately measured energy expenditure for cormorants.
Bibliographical noteThe doubly-labelled water assays and accelerometers were paid for by the authors. Funding to reach Middleton Island was supported through the Animal Behaviour Society Research Grant and the Northern Scientific Training Program of Indigenous and Northern Affairs Canada.
- doubly-labelled water
- field metabolic rate