Evaluating the relative importance of intrinsic and extrinsic factors on the foraging activity of top predators: a case study on female little penguins |
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Authors: | I Zimmer Y Ropert-Coudert N Poulin A Kato A Chiaradia |
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Institution: | 1.Université de Strasbourg, IPHC,Strasbourg,France;2.CNRS, UMR7178,Strasbourg,France;3.National Institute of Polar Research,Tachikawa,Japan;4.Research Department,Cowes,Australia |
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Abstract: | A complex interaction of biotic and abiotic factors influences animal foraging activity. It is often difficult to understand
which factors may affect animals’ foraging and how it is affected. For instance, whereas the effect of sexual dimorphism on
foraging activity has been reported in several species, little is known of the complex interactions between variables acting
at a finer scale, e.g. the variability of body mass within a sex. Evaluating the importance of these finer scale factors is
also essential to the understanding of foraging behaviour. We propose here a simple approach by applying principal component
analysis (PCA) in a novel way to examine relationships between biotic and abiotic factors affecting foraging behaviour of
top predators. We studied female little penguins (Eudyptula minor) of known age, carrying miniature accelerometers during the guard stage of breeding. Surprisingly, the body mass of the females
did not influence any of the foraging parameters, but females foraging later in the breeding season dived shallower and more
often, showing a strong correlation with laying date. Similarly, the diving effort of females was greater with increasing
chick age within the same breeding stage. These results indicate that for female little penguin, the relationship between
changes in prey availability and hunting effort can change at a fine scale, within a breeding stage. Therefore, any analysis
of little penguin foraging behaviour during breeding should consider the timing in relation to the breeding season. We encourage
researchers to develop the use of this PCA approach as it could help clarify the complexity of the underlying mechanisms determining
foraging activity and we propose that it should be used as a first step of foraging behaviour analysis, before examining a
particular relationship. |
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