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The California sea lions suffer degenerative bone lesions in themasticatory apparatus associated to osteoarthritis and osteomyelitisthat develop during several years and may compromise their ability tocapture prey. To test the potential effect of bone damage in themasticatory apparatus over their feeding habits, we compared ?13Cand ?15N values in tooth collagen along the whole series of dentinegrowth layers. Sea lions with mandible fractures or total absence ofteeth should have difficulties to prey on elusive, rapid or slipperypelagic prey (fish, squid), therefore be forced to prey on slower items(crustaceans and benthic molluscans), which in turn should have acarbon enrichment. Thirty sea lions without bone damage and 23individuals with distinct degree of bone lesions were collected fromBahia Magdalena area (Mexico) in the last 20 years. Collagen wasobtained from de-mineralized dentine samples obtained with a MicromillSystem to construct their ontogenetic isotope patterns. Thedegree of damage was estimated according to the area affected,number of fissures, deformations, fractures, including tooth wear andloss, among other conditions. Values of ?13C and ?15N of toothcollagen were determined with an elemental analyzer interfaced witha mass spectrometer. ?15N values in the last 4 years of life wereindistinguishable in animals with bone damage (19.3 ± 0.9 ‰)compared to normal individuals (19.1 ± 0.7 ‰). Only the fourextreme cases showed significantly lower ?13C values (-12.8 ± 0.4 ‰)than normal (-13.6 ± 0.3 ‰) suggesting a more benthic feeding.Annual growth layers however, may not reflect accurately the effectof a bone lesion in the last months of life, thus a more appropriatetissue to analyze this type of relationships could be the vibrissae.

Palabras clave: feeding habits; Guadalupe fur seal; Osteoarthritis; osteomyelitis

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