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Ontogenetic dietary information of the California sea lion ( Zalophus californianus ) assessed using stable isotope analysis
Author(s) -
Orr Anthony J.,
Newsome Seth D.,
Laake Jeffrey L.,
VanBlaricom Glenn R.,
DeLong Robert L.
Publication year - 2012
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.2011.00522.x
Subject(s) - zalophus californianus , ontogeny , foraging , biology , weaning , juvenile , trophic level , δ13c , isotope analysis , zoology , sea lion , δ15n , predation , ecology , stable isotope ratio , endocrinology , physics , quantum mechanics
We used stable carbon (δ 13 C) and nitrogen (δ 15 N) 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 δ 15 N values and lower δ 13 C 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 δ 15 N values were slightly lower than pup or nearly indistinguishable from adult values depending on the tissue analyzed, indicating a dietary shift from maternal dependency to independent foraging. Juveniles (2–4 yr) and adults (>4 yr) had similar δ 15 N values indicating they fed at a similar trophic level. There did not appear to be a pronounced dietary shift in δ 13 C values. However, δ 13 C values integrated with telemetry data indicated that postweaned individuals fed in similar foraging areas. Dietary changes during early life stages may be due to differences in physiology, morphology, experience, or energetic requirements; however, young animals are able to attain the skills needed to consume adult prey types near the end of their second year of life.