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Foraging site fidelity in male Australian fur seals

Abstract

Optimal foraging theory predicts that predators will employ strategies that maximise their net energetic return. Foraging site fidelity (the re-use of a prior foraging area) is assumed to be beneficial, because it facilitates direct travel to foraging areas and familiarity with a foraging area may confer energetic advantages over the lifetime of an animal. In the present study, foraging site fidelity was investigated in 16 male Australian fur seals (Arctocephalus pusillus doriferus) from Kanowna Island (39°10′S, 146°18′E), in northern Bass Strait, south-eastern Australia, during the winters of 2013 and 2014. Male Australian fur seals used several haul-out sites and made relatively short foraging trips (3.4 ± 0.2 days) to nearby foraging areas. Males behaved like central place foragers and foraged exclusively on the continental shelf (modal dive depth range: 70.5–85.5 m). Presumably, short foraging trips enabled males to minimise the metabolic costs of transit, while maximising their net energetic intake. Site fidelity varied considerably between individuals (site fidelity index ranged 0.1–0.6). However, the degree of site fidelity was unrelated to individual morphology parameters (such as body length). While long-term fidelity could make some individuals susceptible to increased environmental variability, the intra-variability in site fidelity reported in the present study suggests that males maximise their fitness by optimizing the time spent in different foraging areas. Variability in male foraging site fidelity highlights behavioural flexibility within Australian fur seals, which could help to reduce intra-specific competition or be a response to environmental variability.

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Acknowledgements

We thank the numerous field volunteers involved in this study; in particular, L. Kernaléguen, M. Rodriguez-Malagon, R. Orben, and L. Quayle for their assistance. We also thank K. Lay and the team at Wildlife Computers for their technical support. We thank G. Boyd of Prom Adventurer Boat Charters, Parks Victoria, R. Knox, and K. and L. Mugford for their logistical support.

Funding

Financial support was provided by research grants from The Winifred Violet Scott Trust and the Holsworth Wildlife Research Endowment.

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Authors and Affiliations

Authors

Contributions

TCK and JPYA conceived the study. TCK, AMMB, and JPYA conducted the fieldwork. TCK analysed the data, with input from AMMB and JPYA. TCK wrote the paper, with assistance from AMMB and JPYA.

Corresponding author

Correspondence to Travis C. Knox.

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Ethical standards

All work was carried out with the approval of the Deakin University Animal Ethics Committee and under the Department of Environment, Land, Water, and Planning (Victoria, Australia) wildlife research permits (B12-2013, 1007153).

Conflict of interest

The authors declare that they have no conflict of interest.

Additional information

Reviewed by S. Simmons and an undisclosed expert.

Responsible Editor: D.E. Crocker.

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Knox, T.C., Baylis, A.M.M. & Arnould, J.P.Y. Foraging site fidelity in male Australian fur seals. Mar Biol 165, 108 (2018). https://doi.org/10.1007/s00227-018-3368-1

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  • DOI: https://doi.org/10.1007/s00227-018-3368-1