Food limitation leads to behavioral diversification and dietary specialization in sea otters

doi:10.1073/pnas.0709263105

Food limitation leads to behavioral diversification and dietary specialization in sea otters

*Department of Ecology and Evolutionary Biology, University of California, Center for Ocean Health, 100 Shaffer Road, Santa Cruz, CA 95060;
^‡Sea Otter Research and Conservation, Monterey Bay Aquarium, 886 Cannery Row, Monterey, CA 93940; and
^§U.S. Geological Survey, Western Ecological Research Center, Long Marine Laboratory, 100 Shaffer Road, Santa Cruz, CA 95060

Edited by Robert T. Paine, University of Washington, Seattle, WA, and approved November 28, 2007 (received for review September 28, 2007)

Abstract

Dietary diversity often varies inversely with prey resource abundance. This pattern, although typically measured at the population level, is usually assumed to also characterize the behavior of individual animals within the population. However, the pattern might also be produced by changes in the degree of variation among individuals. Here we report on dietary and associated behavioral changes that occurred with the experimental translocation of sea otters from a food-poor to a food-rich environment. Although the diets of all individuals were broadly similar in the food-rich environment, a behaviorally based dietary polymorphism existed in the food-poor environment. Higher dietary diversity under low resource abundance was largely driven by greater variation among individuals. We further show that the dietary polymorphism in the food-poor environment included a broad suite of correlated behavioral variables and that the individuals that comprised specific behavioral clusters benefited from improved foraging efficiency on their individually preferred prey. Our findings add to the growing list of examples of extreme individuality in behavior and prey choice within populations and suggest that this phenomenon can emerge as a behavioral manifestation of increased population density. Individuality in foraging behavior adds complexity to both the fitness consequences of prey selection and food web dynamics, and it may figure prominently as a diversifying process over evolutionary timescales.

Footnotes

^†To whom correspondence should be addressed. E-mail: tinker{at}biology.ucsc.edu
Author contributions: M.T.T., G.B., and J.A.E. designed research; M.T.T., G.B., and J.A.E. performed research; M.T.T. and G.B. analyzed data; and M.T.T., G.B., and J.A.E. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0709263105/DC1.