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Oecologia

, Volume 182, Issue 4, pp 995–1005 | Cite as

Foraging strategies of a generalist marine predator inhabiting a dynamic environment

  • E. A. McHuron
  • P. W. Robinson
  • S. E. Simmons
  • C. E. Kuhn
  • M. Fowler
  • D. P. Costa
Behavioral ecology – original research

Abstract

Intraspecific variability is increasingly recognized as an important component of foraging behavior that can have implications for both population and community dynamics. We used an individual-level approach to describe the foraging behavior of an abundant, generalist predator that inhabits a dynamic marine ecosystem, focusing specifically on the different foraging strategies used by individuals in the same demographic group. We collected data on movements and diving behavior of adult female California sea lions (Zalophus californianus) across multiple foraging trips to sea. Sea lions (n = 35) used one of three foraging strategies that primarily differed in their oceanic zone and dive depth: a shallow, epipelagic strategy, a mixed epipelagic/benthic strategy, and a deep-diving strategy. Individuals varied in their degree of fidelity to a given strategy, with 66 % of sea lions using only one strategy on all or most of their foraging trips across the two-month tracking period. All foraging strategies were present in each of the sampling years, but there were inter-annual differences in the population-level importance of each strategy that may reflect changes in prey availability. Deep-diving sea lions traveled shorter distances and spent a greater proportion of time at the rookery than sea lions using the other two strategies, which may have energetic and reproductive implications. These results highlight the importance of an individual-based approach in describing the foraging behavior of female California sea lions and understanding how they respond to the seasonal and annual changes in prey availability that characterize the California Current System.

Keywords

Individual variability Dive behavior Sea lion Zalophus californianus California Current 

Notes

Acknowledgments

We thank Seth Newsome for helpful suggestions that improved the quality of this manuscript, the US. Navy for logistical support, and all of the field volunteers, without which this research would not have been possible. Data collection was part of the Tagging of Pelagic Predators (TOPP) project, and funded by the California Sea Grant Program, National Oceanographic Partnership Program, the Office of Naval Research, and the Moore, Packard, and Sloan Foundations. EAM was supported on a grant from the E & P Sound and Marine Life Joint Industry Programme (#22 07–23). Animal handling was permitted under NMFS permit #87-1593, 1851 and approved by the University of California Santa Cruz Institutional Animal Care and Use Committee.

Author contribution statement

EAM and DPC conceived the study, DPC, PWR, SES, CEK, and MF lead fieldwork, EAM and PWR analyzed the data, EAM wrote the manuscript, with contributions from all authors.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

442_2016_3732_MOESM1_ESM.docx (19 kb)
Supplementary material 1 (DOCX 19 kb)
442_2016_3732_MOESM2_ESM.xlsx (122 kb)
Supplementary material 2 (XLSX 121 kb)
442_2016_3732_MOESM3_ESM.docx (25.9 mb)
Supplementary material 3 (DOCX 26499 kb)

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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • E. A. McHuron
    • 1
  • P. W. Robinson
    • 1
  • S. E. Simmons
    • 2
  • C. E. Kuhn
    • 3
  • M. Fowler
    • 4
  • D. P. Costa
    • 1
  1. 1.Department of Ecology and Evolutionary BiologyUniversity of California Santa CruzSanta CruzUSA
  2. 2.Marine Mammal CommissionBethesdaUSA
  3. 3.National Marine Mammal LaboratoryAlaska Fisheries Science Center/NOAASeattleUSA
  4. 4.Springfield CollegeSpringfieldUSA

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