Utilization of stable isotopes in teeth to investigate pygmy sperm whales (<i>Kogia breviceps)</i> in the southeastern United States

Abstract The pygmy sperm whale (Kogia breviceps) is currently the second‐most stranded cetacean in the southeastern United States (SEUS), but information concerning their population structure is severely limited. This study used stable isotope analysis to investigate the isotopic niches and population structure of K. breviceps among three regions in the SEUS determined by the distance of the continental shelf break and a fourth region in the Gulf of Mexico. Teeth from stranded individuals were subsampled via dental drill at four separate areas on each tooth, representing four different age classes: calf, juvenile, subadult, and adult. Stable isotope ratios of carbon and nitrogen were measured in the organic component of 42 teeth, and oxygen isotope ratios were measured in the inorganic (hydroxyapatite) component of 19 teeth. No differences were found in δ 13 C, δ 15 N, or δ 18 O values between regions. However, differences between age classes were significant for adults and subadults for δ 13 C and adults and juveniles for δ 15 N. Differences between males and females were also significant for δ 15 N. Results from this study provide the first carbon and nitrogen isotope values from different age classes of pygmy sperm whales as well as the first reported oxygen isotope values for this species.