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Ontogenetic Dietary Information Of The California Sea Lion (Zalophus Californianus) Assessed Using Stable Isotope Analysis, Anthony J. Orr, Seth D. Newsome, Jeffrey L. Laake, Glenn R. Vanblaricom, Robert L. Delong

United States Department of Commerce: Staff Publications

We used stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes to examine ontogenetic dietary changes in 289 California sea lions (Zalophus californianus) at San Miguel Island, California during 2004–2007. Tissues analyzed included fur, red blood cells, plasma, and serum. For all tissues, pups had higher δ¹⁵N values and lower δ¹³C values compared to adults, which indicated that pups were feeding higher trophically than older conspecifics and on a lipid-rich milk diet prior to weaning. Yearling δ¹⁵N values were slightly lower than pup or nearly indistinguishable from adult values depending …