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An increase in minimum metabolic rate and not activity explains field metabolic rate changes in a breeding seabird
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posted on 2013-01-01, 00:00 authored by J Green, E Aitken-Simpson, C White, Ashley Bunce, P Butler, P FrappellThe field metabolic rate (FMR) of a free-ranging animal can be considered as the sum of its maintenance costs (minimum metabolic rate, MMR) and additional costs associated with thermoregulation, digestion, production and activity. However, the relationships between FMR and BMR and how they relate to behaviour and extrinsic influences is not clear. In seabirds, FMR has been shown to increase during the breeding season. This is presumed to be the result of an increase in foraging activity, stimulated by increased food demands from growing chicks, but few studies have investigated in detail the factors that underlie these increases. We studied free-ranging Australasian gannets (Morus serrator) throughout their 5 month breeding season, and evaluated FMR, MMR and activity-related metabolic costs on a daily basis using the heart rate method. In addition, we simultaneously recorded behaviour (flying and diving) in the same individuals. FMR increased steadily throughout the breeding season, increasing by 11% from the incubation period to the long chick-brooding period. However, this was not accompanied by either an increase in flying or diving behaviour, or an increase in the energetic costs of activity. Instead, the changes in FMR could be explained exclusively by a progressive increase in MMR. Seasonal changes in MMR could be due to a change in body composition or a decrease in body condition associated with changing the allocation of resources between provisioning adults and growing chicks. Our study highlights the importance of measuring physiological parameters continuously in free-ranging animals in order to understand fully the mechanisms underpinning seasonal changes in physiology and behaviour.
History
Journal
Journal of experimental biologyVolume
216Issue
9Pagination
1726 - 1735Publisher
Company of BiologistsLocation
Cambridge, EnglandPublisher DOI
ISSN
0022-0949eISSN
1477-9145Language
engPublication classification
C1 Refereed article in a scholarly journalUsage metrics
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basal metabolic ratedivingenergeticsflightgannetheart rate methodseasonal changeScience & TechnologyLife Sciences & BiomedicineBiologyLife Sciences & Biomedicine - Other TopicsPHALACROCORAX-CARBO-CARBODAILY ENERGY-EXPENDITUREBLACK-LEGGED KITTIWAKESGEESE BRANTA-LEUCOPSISHEART-RATEGREAT CORMORANTSOXYGEN-CONSUMPTIONMACARONI PENGUINSBODY CONDITIONFORAGING EFFICIENCY
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