Climate anomalies influence tooth growth patterns of South American sea lions

Abstract

El Niño-Southern Oscillation (ENSO) and Southern Annular Mode (SAM) indirectly affect tooth growth of marine mammals, through changes in prey abundance, availability, and composition. This is reflected as variation in the dentine deposition, which determines the formation of annual layers, called growth layer groups (GLGs). The aim of this work was to study potential effects of ENSO and SAM on South American sea lion (Otaria byronia) of Patagonia, by examining interannual variability of GLG width. Adapting dendrochronological techniques, we analyzed 97 individuals (60 females and 37 males) and built six chronologies (three for each sex) by using cubic splines with different rigidity.Chronologies were correlated with MEI (Multivariate ENSO Index) and SAM index time series, considering lags in the biological response. The chronologies of females spanned 39 years and only two of these chronologies showed negative correlation with 1 year lagged SAM events. The chronologies of males spanned 23 years, but none showed significant correlation with these indexes. Our results did not indicate any ENSO effects on this species, while positive SAM events could reduce the abundance or availability of South American sea lion's prey, affecting the nutritional status of females and generating thinner GLGs during the next year.