Visual and passive acoustic observations of blue whale trios from two distinct populations.

Blue whale populations from both hemispheres are thought to undertake annual migrations between high latitude feeding grounds and low latitude breeding grounds. For individuals of some populations these predetermined movements to and from wintering areas where calving occurs have been confirmed through photo‐identification, satellite‐tracking, and passive acoustic monitoring. However, for many blue whale populations no clear migratory behavior has been reported and locations of respective breeding grounds remain unclear