Constrained by consistency? Repeatability of foraging behavior at multiple timescales for a generalist marine predator
Marine predators frequently exhibit consistency in foraging behaviors despite the dynamic nature of marine ecosystems, which has the potential for ecological and evolutionary implications depending on the timescale at which it persists. We examined behavioral consistency in movements and diving behavior of adult female California sea lions (Zalophus californianus), which are abundant, generalist central-place foragers inhabiting an ecosystem characterized by small- and broad-scale oceanographic variability. We used biologging devices to measure repeatability of behavior within a season and stable isotope analysis of whiskers to quantify behavior across a 2-year period associated with anomalous environmental conditions that affected prey availability. Sea lions were significantly repeatable in all variables across multiple timescales (Radj = 0.26–0.82), although repeatability estimates were generally higher for variables related to characteristics of individual dives (e.g., dive depth) than those that described dive bouts (e.g., bout duration) or spatial use (e.g., volume of 3D utilization distribution). These differences may result from the fact that diving behaviors vary with prey type, whereas spatial use and bout variables may reflect the foraging success within prey patches or movement among patches. There was variation in how predictable individual sea lions were in their diving behaviors, which was largely unrelated or negatively related to foraging site fidelity. The strength of behavioral consistency decreased with time yet persisted across the 2-year period, suggesting that while sea lions alter their behavior in response to environmental change, the behavioral flexibility of individuals may ultimately be constrained by consistency.
We would like to acknowledge the US Navy and John Ugoretz for logistical support, S. Simmons, C. Kuhn, P. Robinson, M. Fowler, S. Peterson, L. Hückstädt, and the numerous field volunteers that helped with data collection. We also thank the reviewers whose comments improved the manuscript. Much of the data collection for this project was part of the Tagging of Pelagic Predators (TOPP) project, which was funded by Grants from the California Sea Grant Program, National Oceanographic Partnership Program, the Office of Naval Research, and the Moore, Packard, and Sloan Foundations. A Grant from the E & P Sound and Marine Life Joint Industry Programme (#22 07-23) to DPC and the Earl and Ethel Myers Oceanographic and Marine Biology Trust to EAM funded the remainder of this effort.
This study was funded by the E & P Sound and Marine Life Joint Industry Programme, the California Sea Grant Program, National Oceanographic Partnership Program, the Office of Naval Research, and the Moore, Packard, and Sloan Foundations.
Compliance with ethical standards
Animal handling was permitted under appropriate permits (NMFS #87-1593, 1851, 17952) and approved by the University of California Santa Cruz Institutional Animal Care and Use Committee. All applicable, international, national, and/or institutional guidelines for the care and use of animals were followed.
Conflict of interest
The authors declare that they have no conflict of interest.
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