Temporal variability in stable isotope ratios of C and N in the vibrissa of captive and wild adult South American sea lions Otaria byronia : More than just diet shifts

CARDONA, LUIS; VALES, DAMIÁN GUSTAVO; AGUILAR, ALEX; CRESPO, ENRIQUE ALBERTO; ZENTENO, LISETTE

MARINE MAMMAL SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Año: 2017

0824-0469

We analyzed the δ13C and δ15N values in the vibrissae of captive adult breeding South American sea lions (Otaria byronia) fed at a constant diet and then used this information to analyze the change in stable isotope values along the vibrissae from wild individuals. The overall diet-to-vibrissa discrimination factor of the captive animals was 3.0? ± 0.1? for δ13C and 3.6? ± 0.1? for δ15N, but the stable isotope ratios fluctuated periodically despite constant diet. The δ13C and δ15N values of the captive male declined at the end of the breeding season, whereas the δ13C values of the female increased during the central part of pregnancy and the δ15N values peaked during lactation. The δ13C and δ15N values of adult wild specimens also fluctuated periodically and vibrissae growth rate (0.15 mm/d in both sexes) was slightly lower than in captivity (0.17 mm/d), assuming an annual periodicity for oscillations. Similarities in the amplitude of the cycles of captive and wild males suggested that fasting was probably the main source of periodic variability in the δ15N of wild males, whereas pregnancy and lactation were probably the main source of periodic variability for the δ13C of wild females.