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Modelling the effects of prey size and distribution on prey capture rates of two sympatric marine predators

Thaxter, Chris B.; Daunt, Francis; Gremillet, David; Harris, Mike P.; Benvenuti, Silvano; Watanuki, Yutaka; Hamer, Keith C.; Wanless, Sarah. 2013 Modelling the effects of prey size and distribution on prey capture rates of two sympatric marine predators. PLoS One, 8 (11), e79915. 10, pp. 10.1371/journal.pone.0079915

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Abstract/Summary

Understanding how prey capture rates are influenced by feeding ecology and environmental conditions is fundamental to assessing anthropogenic impacts on marine higher predators. We compared how prey capture rates varied in relation to prey size, prey patch distribution and prey density for two species of alcid, common guillemot (Uria aalge) and razorbill (Alca torda) during the chick-rearing period. We developed a Monte Carlo approach parameterised with foraging behaviour from birdborne data loggers, observations of prey fed to chicks, and adult diet from wateroffloading, to construct a bio-energetics model. Our primary goal was to estimate prey capture rates, and a secondary aim was to test responses to a set of biologically plausible environmental scenarios. Estimated prey capture rates were 1.5±0.8 items per dive (0.8±0.4 and 1.1±0.6 items per minute foraging and underwater, respectively) for guillemots and 3.7±2.4 items per dive (4.9±3.1 and 7.3±4.0 items per minute foraging and underwater, respectively) for razorbills. Based on species' ecology, diet and flight costs, we predicted that razorbills would be more sensitive to decreases in 0- group sandeel (Ammodytes marinus) length (prediction 1), but guillemots would be more sensitive to prey patches that were more widely spaced (prediction 2), and lower in prey density (prediction 3). Estimated prey capture rates increased non-linearly as 0- group sandeel length declined, with the slope being steeper in razorbills, supporting prediction 1. When prey patches were more dispersed, estimated daily energy expenditure increased by a factor of 3.0 for guillemots and 2.3 for razorbills, suggesting guillemots were more sensitive to patchier prey, supporting prediction 2. However, both species responded similarly to reduced prey density (guillemot expenditure increased by 1.7; razorbill by 1.6), thus not supporting prediction 3. This bio-energetics approach complements other foraging models in predicting likely impacts of environmental change on marine higher predators dependent on species-specific foraging ecologies.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1371/journal.pone.0079915
Programmes: CEH Topics & Objectives 2009 - 2012 > Biodiversity > BD Topic 1 - Observations, Patterns, and Predictions for Biodiversity > BD - 1.4 - Quantify and model interactions to determine impacts ...
CEH Topics & Objectives 2009 - 2012 > Biodiversity > BD Topic 1 - Observations, Patterns, and Predictions for Biodiversity
CEH Topics & Objectives 2009 - 2012 > Biodiversity
CEH Sections: CEH fellows
Watt
ISSN: 1932-6203
Additional Information. Not used in RCUK Gateway to Research.: Open Access paper - Official URL link provides full text
NORA Subject Terms: Ecology and Environment
Biology and Microbiology
Date made live: 10 Dec 2013 14:35 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/503887

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