STABLE OXYGEN AND CARBON ISOTOPES IN CETACEAN EAR BONES AND TEETH: PALEOCLIMATIC APPLICATIONS

The oxygen isotopic composition of bioapatite in cetaceans is directly related to the oxygen isotopic composition of seawater. However, this relationship may differ among species due to differences in physiology. To understand if phosphate-δ¹⁸O values of whale teeth and ear bones are a reliable proxy for ocean water δ¹⁸O, oxygen isotopic compositions of bioapatite samples from 23 individuals collected along the Florida coasts were measured. These individuals represent five different species of cetaceans belonging to the suborder Odontoceti, including the sperm whale P. macrocephalus, K. breviceps, O. orca, Z. cavirostris, and G. macrorhynchus. The studied species cover a diversity of habitats, diets, and latitudinal migratory behaviors according to their species and genders. δ¹⁸O data range from 16.7‰ to 21.3‰ averaging 19.6±1.04‰ (n=89) for tooth samples and 15.5‰ to 19.7‰ averaging 19.0±0.93‰ (n=47) for ear bone samples, while the oxygen isotopic ratios of teeth are heavier than those of ear bone samples by 0.7‰ to 2.4‰ with an average of 1.5‰. O. orca has the most depleted δ¹⁸O values while G. macrorhynchus individuals display variations according to their gender. G. macrorhynchus males and females have average tooth enamel δ¹⁸O of 19.8‰ and 20.3‰ respectively. However, average ear bone samples of males are isotopically heavier than females by 1.7‰; δ¹⁸O average for males is 19.6‰ and females is 17.6‰. More depleted δ¹⁸O tooth values may be a result of inhabiting higher latitudes. Serial analysis of tooth samples, displaying intra-tooth variations, may also indicate seasonal migration among habitats.