International audienceIn the Southern Indian Ocean, 2 subspecies of blue whales Balaenoptera musculus spp. occur, the Antarctic B. m. intermedia and the pygmy blue whale B. m. brevicauda. Until the present study was conducted it was assumed that the distribution of these 2 subspecies was delimited by the Antarctic Convergence (52° to 56° S) during the austral summer. Here, we report results from the first year-long, continuous acoustic monitoring of blue whales in mid-latitude waters off the Crozet Islands (46° 25' S, 51° 40' E). Using acoustic data from an International Monitoring System hydroacoustic station, we found that Antarctic and pygmy blue whales occur sympatrically in this area based on detection of their stereotyped calls. Antarctic blue whale calls were recorded year-round, indicating continuous presence in the region, which contradicts the migration paradigm attributed to this subspecies. Three geographically distinct types of pygmy blue whale calls were recorded during the summer and autumn only. The Madagascan call type was the most frequently recorded, while Sri Lankan and Australian call types recorded in this area suggest basin-scale longitudinal and latitudinal movements. During spring and summer, blue whale calls were often associated with higher frequency sounds (D calls), which have been attributed to feeding activity. The summer co-occurrence of blue whale subspecies highlights the importance of this productive sub-Antarctic area as a blue whale hotspot and provides new insights into blue whale seasonal distribution and segregation

North Atlantic humpback whales (Megaptera novaeangliae (Borowski, 1781)) migrate from high-latitude summer feeding grounds to low-latitude winter breeding grounds along the Antillean Island chain. In the winters and springs of 2008 through 2012, satellite tags were deployed on humpback whales on Silver Bank (Dominican Republic) and in Guadeloupe (French West Indies) breeding areas. Whales were monitored, on average, for 26 days (range = 4-90 days). Some animals remained near their tagging location for multiple days before beginning their northerly migration, yet some visited habitats along the northwestern coast of the Dominican Republic, northern Haiti, the Turks and Caicos islands, and off Anguilla. Individuals monitored during migration headed towards feeding grounds in the Gulf of Maine (USA), Canada, and the eastern North Atlantic (Iceland or Norway). One individual traveled near Bermuda during the migration. This study provides the first detailed description of routes used by North Atlantic humpback whales towards multiple feeding destinations. Additionally, it corroborates previous research showing that individuals from multiple feeding grounds migrate to the Antilles for the breeding season. This study indicates that North Atlantic humpbacks use an area broader than the existing boundaries of marine mammal sanctuaries, which should provide justification for their expansion.