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Endangered Species Research

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ESR 10:269-279 (2009)  -  DOI:

Energetic consequences of plunge diving in gannets

Jonathan A. Green1,5,*, Craig R. White2,3, Ashley Bunce4,6, Peter B. Frappell1,7, Patrick J. Butler2

1Adaptational and Evolutionary Respiratory Physiology, Department of Zoology, La Trobe University, Melbourne, Victoria 3070, Australia
2Centre for Ornithology, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
3School of Integrative Biology, The University of Queensland, St Lucia, Queensland 4072, Australia
4School of Ecology and Environment, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia
5Present address: School of Biological Sciences, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK
6Present address: Centre for Marine Studies, University of Queensland, St. Lucia, Queensland 4072, Australia
7Present address: School of Zoology, University of Tasmania, Hobart, Tasmania 7001, Australia

ABSTRACT: Seabirds that forage by plunge diving dive less frequently than those that dive from the water surface, and spend less time in flight than more generalist foragers. We hypothesised that this is due to foraging by plunge diving entailing a high energetic cost, which in turn is due to high energetic costs of take-off and flight. Using heart rate as a proxy for metabolic rate, we evaluated the energetic costs of foraging by plunge diving in the Australasian gannet Morus serrator. As expected, flight entailed a high energetic cost, and energy expenditure during foraging was equivalent to that during flight and significantly higher than that when animals were resting during foraging trips or were inactive on land. These values represent the highest costs of foraging yet recorded in a seabird, and the low frequency of plunge diving can be attributed to these high costs. On average, Australasian gannets perform 2.6 dives h–1 when foraging, with a mean dive duration of 3.4 s. As a result, they spend <0.25% of the duration of each foraging trip submerged. We combined this information with previously obtained data on diet to calculate an estimated rate of prey capture of ~287 g (min submerged)–1. This rate is at least 7 times greater than rates recorded in other diving birds. For plunge divers, therefore, the high costs of foraging are offset by high rates of energy gain.

KEY WORDS: Energetics · Gannet · Plunge diving · Foraging · Catch per unit effort · CPUE

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Cite this article as: Green JA, White CR, Bunce A, Frappell PB, Butler PJ (2009) Energetic consequences of plunge diving in gannets. Endang Species Res 10:269-279.

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