Foraging ecology of mature male Antarctic minke whales (Balaenoptera bonaerensis) revealed by stable isotope analysis of baleen plates

The Antarctic minke whale (Balaenoptera bonaerensis) is a seasonal migrator that feeds mainly on Antarctic krill at higher latitudes during the summer and travels to lower latitudes to breed in winter. A previous study using δ13C and δ15N values of baleen plates showed that pregnant Antarctic minke whales feed on Antarctic krill in the foraging season, with less feeding during the breeding season. However, long-term changes in the habitat use and diet of males remain unknown. In this study, we estimated the foraging habits of nine mature male Antarctic minke whales using the stable isotope signatures of baleen plates. From Bayesian stable isotope mixing models, it was found that Antarctic krill was the predominant prey of male whales, and prey species in lower latitudes were rarely incorporated into the baleen plates. This result is consistent with that of female Antarctic minke whales. Eight whales showed at least one oscillation in δ13C and δ15N values, whereas one whale (AM246) showed no variation in δ15N values. This possibly indicates that AM246 remained in the Antarctic water year-round. Our results suggest multiple migration patterns of male Antarctic minke whales.