Abstract

The identity, distribution and movements of blue whales Balaenoptera musculus that forage in the Chiloense Ecoregion in Southern Chile remain unclear. Studies of blue whale songs have identified acoustic populations with distinct song types, geographic ranges, migration routes and seasonal residencies-information that is relevant to the conservation of this endangered species. Here, we characterized the song sequences of blue whales that use the Corcovado Gulf based on dipping hydrophone recordings from 3 austral summer field seasons (2008, 2009, 2011), and compare these data to previously described song types for the Southeast Pacific (SEP) in order to better understand meso-scale (versus basin-scale) variation in blue whale song. Two distinct songs, SEP1 and SEP2, emerged from our analysis. Neither of these songs is used by Antarctic blue whales. Although SEP1 was the first song recorded in the Corcovado Gulf area in 1970, we found SEP2 to be the more common song, despite never having been reported previously in this area. Our report of SEP2 adds a new song to the current description of the SEP blue whale repertoire. Our recording of SEP1 reaffirms the acoustic link already established between Chile and the Eastern Tropical Pacific (ETP); our recording of SEP2 establishes a new acoustic link for this song between Chile and the ETP. These findings provide the basis for future passive acoustic studies on the temporal and spatial distributions of endangered SEP blue whales and for understanding how these songs relate to the population structure.