title: Validating accelerometry estimates of energy expenditure across behaviours using heart rate data in a free-living seabird.
abstract: Two main techniques have dominated the field of ecological energetics: the heart rate and doubly labelled water methods. Although well established, they are not without their weaknesses, namely expense, intrusiveness and lack of temporal resolution. A new technique has been developed using accelerometers; it uses the overall dynamic body acceleration (ODBA) of an animal as a calibrated proxy for energy expenditure. This method provides high-resolution data without the need for surgery. Significant relationships exist between the rate of oxygen consumption (V̇O2) and ODBA in controlled conditions across a number of taxa; however, it is not known whether ODBA represents a robust proxy for energy expenditure consistently in all natural behaviours and there have been specific questions over its validity during diving, in diving endotherms. Here, we simultaneously deployed accelerometers and heart rate loggers in a wild population of European shags (Phalacrocorax aristotelis). Existing calibration relationships were then used to make behaviour-specific estimates of energy expenditure for each of these two techniques. Compared with heart rate-derived estimates, the ODBA method predicts energy expenditure well during flight and diving behaviour, but overestimates the cost of resting behaviour. We then combined these two datasets to generate a new calibration relationship between ODBA andV̇O2that accounts for this by being informed by heart rate-derived estimates. Across behaviours we found a good relationship between ODBA andV̇O2Within individual behaviours, we found useable relationships between ODBA andV̇O2for flight and resting, and a poor relationship during diving. The error associated with these new calibration relationships mostly originates from the previous heart rate calibration rather than the error associated with the ODBA method. The equations provide tools for understanding how energy constrains ecology across the complex behaviour of free-living diving birds.
authors.affiliation: Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK och@liv.ac.uk.
authors.forename: Olivia
authors.identifier: 0000-0002-6938-9670
authors.initials: O
authors.lastname: Hicks
authors.affiliation: Centre for Ecology & Hydrology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Burthe
authors.affiliation: Centre for Ecology & Hydrology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK.
authors.forename: Francis
authors.initials: F
authors.lastname: Daunt
authors.affiliation: Biomathematics and Statistics Scotland, James Clerk Maxwell Building, The King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
authors.forename: Adam
authors.initials: A
authors.lastname: Butler
authors.affiliation: School of Biological Sciences, Bangor University, Gwynedd LL57 2UW, UK.
authors.forename: Charles
authors.initials: C
authors.lastname: Bishop
authors.affiliation: Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Green
mesh_terms: D061725:Accelerometry / Q000379:methods*; D000818:Animals; D001717:Birds / Q000502:physiology*; D002138:Calibration; D004242:Diving / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005426:Flight, Animal / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D012146:Rest / Q000502:physiology
keywords: Diving; Dynamic body acceleration; Field metabolic rate; Flying; Phalacrocorax aristotelis; Shag