Mammalian Biology

, Volume 77, Issue 4, pp 271–280 | Cite as

Foraging behavior and prey of sea otters in a soft- and mixed-sediment benthos in Alaska

  • Ryan C. Wolt
  • Frances P. Gelwick
  • Frederick Weltz
  • Randall W. DavisEmail author
Original Investigation


Sea otter (Enhydra lutris kenyoni) foraging behavior and prey preference were studied from June to August 2001–2004 in Simpson Bay, Prince William Sound, Alaska. The study area has an average water depth of 30 m and a benthos primarily of soft- and mixed-sediment with no canopy-forming kelps. A total of 1816 foraging dives from 211 bouts were recorded. Overall, dives ranged in depth from <5 to 82 m; most dives were less than 15 m (40%) with smaller, secondary peaks at 25–30 m (10%) and 50–55 m (7%). Average dive depth and duration were 27 m ± 19.5 and 1.89 min ± 0.88, respectively. Dive durations were all significantly different: male > unknown > female. Dive depths reflected the bathymetry (percentage of the bay within a depth range) of Simpson Bay but favored shallow areas. 87% of foraging dives were successful, and 44% of the prey was positively identified: 75% clams, 9% Pacific blue mussels, 6% crabs, 2% Reddish scallops and a variety of other invertebrates. There was no evidence for prey specialization among the sexes. Although sea otters in Simpson Bay rely heavily on bivalves, their diet has remained unchanged for the past 18 years, and the minimum summer population has been constant for at least the past nine years. It appears that bivalves are the predominant and stable component of the diet, and their productivity is sufficient to sustain a stable population of sea otters with a minimum peak summer density of 4.3 adult otters km−2 and an average annual density of ca. 2.9 adult otters km−2 for the past nine years and probably longer.


Sea otter Enhydra lutris Foraging behavior Prey Soft- and mixed-sediments 


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  1. Bodkin, J.L., Ballachey, B.E., Dean, T.A., Fukuyama, A.K., Jewett, S.C., McDonald, L., Monson, D.H., O‘Clair, C.E., VanBlaricom, G.R., 2002. Sea otter population status and the process of recovery from the 1989 ‘Exxon Valdez’ oil spill. Marine Ecology-Progress Series 241, 237–253.CrossRefGoogle Scholar
  2. Bodkin, J.L., Esslinger, G.G., Monson, D.H., 2004. Foraging depths of sea otters and implications to coastal marine communities. Marine Mammal Science 20, 305–321.CrossRefGoogle Scholar
  3. Calkins, D.G., 1978. Feeding-behavior and major prey species of sea otter (Enhydra lutris), in Montague Strait, Prince William Sound, Alaska. Fishery Bulletin 76, 125–131.Google Scholar
  4. Costa, D.P., 1982. Energy, nitrogen and electrolyte flux and sea-water drinkingin the sea otter (Enhydra lutris). Physiological Zoology 55, 35–44.CrossRefGoogle Scholar
  5. Davis, R.W., Williams, T.M., Thomas, J.A., Kastelein, R.A., Cornell, L.H., 1988. The effects of oil contamination and cleaning on sea otters (Enhydra lutris). 2. Metabolism, thermoregulation, and behavior. Canadian Journal of Zoology – Revue Canadienne De Zoologie 66, 2782–2790.CrossRefGoogle Scholar
  6. Doroff, A.M., Estes, J.A., Tinker, M.T., Burn, D.M., Evans, T.J., 2003. Sea otter population declines in the Aleutian archipelago. Journal of Mammalogy 84, 55–64.CrossRefGoogle Scholar
  7. Doroff, A.M., Bodkin, J.L., 1994. Sea otter foraging behavior and hydrocarbon levels in prey. In: Louglin, T. (Ed.), Marine Mammals and the Exxon Valdez. Academic Press, San Diego, CA, USA, pp. 193–208.CrossRefGoogle Scholar
  8. Ensminger, A.H., Ensminger, M.E., Konlande, J.E., Robson, J.R.K., 1994. Food & Nutrition Encyclopedia. CRC, Press, Inc., Boca Raton, FL.Google Scholar
  9. Estes, J.A., 1977. Population estimates and feeding behavior of sea otters. In: Merritt, M.L., Fuller, R.G. (Eds.), The Environment of Amchitka Island, Alaska. National Technical Information Service, Springfield, VA, pp. 511–526.Google Scholar
  10. Estes, J.A., Jameson, R.J., M, J.A., 1980. Food selection and some foraging tactics of sea otters. In: Worldwide Furbearer Conference, Frostburg, MD.Google Scholar
  11. Estes, J.A., 1990. Growth and equilibrium in sea otter populations. Journal of Animal Ecology 59, 385–401.CrossRefGoogle Scholar
  12. Estes, J.A., Duggins, D.O., 1995. Sea otters and kelp forests in Alaska – generality and variation in a community ecological paradigm. Ecological Monographs 65, 75–100.CrossRefGoogle Scholar
  13. Estes, J.A., Bodkin, J.L., 2002. Otters. In: Perrin, W.F., Wursig, B., Thewissen, J.G.M. (Eds.), Encyclopedia of Marine Mammals. Academic Press, San Diego, CA, USA, pp. 842–858.Google Scholar
  14. Estes, J.A., Riedman, M.L., Staedler, M.M., Tinker, M.T., Lyon, B.E., 2003. Individual variation in prey selection by sea otters: patterns, causes and implications. Journal of Animal Ecology 72, 144–155.CrossRefGoogle Scholar
  15. Finerty, S.E., Hillman, G.R., Davis, R.W., 2007. Computer matching of sea otter (Enhydra lutris) nose scars: a new method for tracking individual otters. Aquatic Mammals 33, 349–358.CrossRefGoogle Scholar
  16. Finerty, S.E., Wolt, R.C., Davis, R.W., 2009. Summer activity pattern and field metabolic rate of adult male sea otters (Enhydra lutris) in a soft sediment habitat in Alaska. Journal of Experimental Marine Biology and Ecology 377, 36–42.CrossRefGoogle Scholar
  17. Finerty, S.E., Pearson, H.C., Davis, R.W., 2010. Interannual assessment of territory quality for male sea otters (Enhydra lutris) in Simpson Bay, Prince William Sound, Alaska. Canadian Journal of Zoology – Revue Canadienne De Zoologie 88, 289–298.CrossRefGoogle Scholar
  18. Garshelis, D.L., 1983. Ecology of sea otters in Prince William Sound, Alaska. Ph.D. Thesis. University of Minnesota, Duluth, MN, USA.Google Scholar
  19. Garshelis, D.L., Garshelis, J.A., Kimker, A.T., 1986. Sea otter time budgets and prey relationships in Alaska. Journal of Wildlife Management 50, 637–647.CrossRefGoogle Scholar
  20. Gilkinson, A.K., Pearson, H.C., Weltz, F., Davis, R.W., 2007. Photo-identification of sea otters using nose scars. Journal of Wildlife Management 71, 2045–2051.CrossRefGoogle Scholar
  21. Gilkinson, A.K., Finerty, S.E., Weltz, F., Dellapenna, T.M., Davis, R.W., 2011. Habitat associations of sea otters (Enhydra lutris) in a soft- and mixed-sediment benthos in Alaska. Journal of Mammalogy 92, 1278–1286.CrossRefGoogle Scholar
  22. Kenyon, K.W., 1975. The Sea Otter in the Eastern Pacific Ocean. Dover Publications, New York.Google Scholar
  23. Kenyon, K.W., 1981. Sea Otter, Enhydra lutris. London, Academic Press Inc.Google Scholar
  24. Kvitek, R.G., Oliver, J.S., 1992. Influence of sea otters on soft-bottom prey communities in Southeast Alaska. Marine Ecology Progress Series 82, 103–113.CrossRefGoogle Scholar
  25. Kvitek, R.G., Oliver, J.S., Degange, A.R., Anderson, B.S., 1992. Changes in Alaskan softbottom prey communities along a gradient in sea otter predation. Ecology 73, 413–428.CrossRefGoogle Scholar
  26. Kvitek, R.G., Bowlby, C.E., Staedler, M., 1993. Diet and foraging behavior of sea otters in Southeast Alaska. Marine Mammal Science 9, 168–181.CrossRefGoogle Scholar
  27. Laidre, K.L., Jameson, R.J., 2006. Foraging patterns and prey selection in an increasing and expanding sea otter population. Journal of Mammalogy 87, 799–807.CrossRefGoogle Scholar
  28. Lee, O.A., Galwick, F., Davis, R.W., 2010. Summer foraging tactics in sea otters (Enhydra lutris): maintaining foraging efficiencies in a stable population in Alaska. Aquatic Mammals 36, 351–364.CrossRefGoogle Scholar
  29. Lepš, J., Šmilauer, P., 2003. Multivariate Analysis of Ecological Data Using CANOCO. Cambridge University Press, Cambridge, UK.Google Scholar
  30. Miller, D.J., 1974. The sea otter Enhydra lutris: it’s life history, taxonomic status and some ecological relationships. Marine Resources Leaflet No. 7, California Department of Fish and Game.Google Scholar
  31. Nickerson, R.B., 1977. A study of the littleneck clam (Protothaca staminea conrad) and the butter clam (Saxidomus giganteus Deshayes) in a habitat permiting coexistence. In: Proceedings of the National Shellfisheries Association 67, Prince William Sound, AK.Google Scholar
  32. Noll, C.J., Dellapenna, T.M., Gilkenson, A., Davis, R.W., 2008. A high-resolution geophysical investigation of sediment distribution controlled by catchment size and tidesinamulti-basin turbid outwash fjord: Simpson Bay, Prince William Sound, Alaska. Geo-Marine Letters, 1–16.Google Scholar
  33. O‘Clair, R.M., O‘Clair, C.E., 1989. Southeast Alaska’s Rocky Shores Animals. Auke Bay, Plant Press.Google Scholar
  34. Osterrieder, S.K., Davis, R.W., 2009. Summer foraging behaviour of female sea otters (Enhydra lutris) with pups in Simpson Bay, Alaska. Aquatic Mammals 35 (9), 481–489.CrossRefGoogle Scholar
  35. Osterrieder, S.K., Davis, R.W., 2011. Sea otter female and pup activity budgets, Prince William Sound, Alaska. Journal of the Marine Biological Association of the United Kingdom 91, 882–892.CrossRefGoogle Scholar
  36. Pearson, H.C., Davis, R.W., 2005. Behavior of territorial male sea otters (Enhydra lutris) in Prince William Sound, Alaska. Aquatic Mammals 31 (2), 226–233.CrossRefGoogle Scholar
  37. Pyke, G.H., 1984. Optimal foraging theory – a critical-review. Annual Review of Ecology and Systematics 15, 523–575.CrossRefGoogle Scholar
  38. Rotterman, L.M., Simon-Jackson, T., 1988. Sea Otter. In: Lentfer, J.W. (Ed.), Selected Marine Mammals of Alaska: Species Accounts with Research and Management Recommendations. Marine Mammal Commission, Washington, DC, pp. 237–271.Google Scholar
  39. Tinker, M.T., Costa, D.P., Estes, J.A., Wieringa, N., 2007. Individual dietary specialization and dive behaviour in the California sea otter: using archival time-depth data to detect alternative foraging strategies. Deep-Sea Research Part Ii-Topical Studies in Oceanography 54, 330–342.CrossRefGoogle Scholar
  40. Tinker, M.T., Bentall, G., Estes, J.A., 2008. Food limitation leads to behavioral diversification and dietary specialization in sea otters. Proceedings of the National Academy of Sciences of the United States of America 105, 560–565.CrossRefGoogle Scholar
  41. VanBlaricom, G.R., 1988. Effects of foraging by sea otters on mussel-dominated intertidal communities. In: VanBlaricom, G.R., Estes, J.A. (Eds.), The Community Ecology of Sea Otters. Springer-Verlag, Berlin, pp. 48–91.Google Scholar
  42. Williams, T.M., Kastelein, R.A., Davis, R.W., Thomas, J.A., 1988. The effects of oil contamination and cleaning in sea otters (Enhydra lutris). Thermoregulatory implications based on pelt studies. Canadian Journal of Zoology 66, 2776–2781.Google Scholar

Copyright information

© Deutsche Gesellschaft für Säugetierkunde 2012

Authors and Affiliations

  • Ryan C. Wolt
    • 1
  • Frances P. Gelwick
    • 2
  • Frederick Weltz
    • 3
  • Randall W. Davis
    • 1
    Email author
  1. 1.Texas A&M University, Dept. of Marine Biology, Ocean and Coastal Studies Bldg.Texas A&M UniversityGalvestonUSA
  2. 2.Texas A&M University, Dept. of Wildlife and Fisheries SciencesTexas A&M UniversityCollege StationUSA
  3. 3.Alice Cove ResearchCordovaUSA

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