Glimpses of the social structure and behavior of whales can be obtained by study of the acoustic calls and songs of these animals. Songs are repeated patterned groups of sounds which typically have a syntax and are only produced by males in each case where data is available.
Blue whale tagging done by John Calambokidis, John Hildebrand, Erin Oleson, Bill Burgess and myself has shown blue whales sometimes feed more during the day, when the krill are at depth and call more during the night. Calls are illustrated by the circles and asterisks. This work is published in "Behavioral Context of Northeast Pacific Blue Whale Call Production" by Oleson et al. (2007).
Some of the large whales produce sounds frequently while other species are relatively quiet. Of the large whales the sperm whales are the most active acoustically, followed by humpback whales, fin whales, and blue whales. Others which are commonly very active acoustically are bowheads, right and gray. Sei, brydes and minke whales are known to make sounds, but there is relatively little understanding of the settings and seasonality corresponding to when these whales are acoustically active.
Most of the baleen whales produce song as well as relatively simple communication calls. The right whales and gray whales do not sing, while the songs for some other species such as sei whales and minke whales are just beginning to be understood. For some species such as blue whales, the song is stable over decades and can be used as a population discriminator along with genetic sampling and morphology studies. Blue whales songs were divided into nine types worldwide in 2006 (McDonald et al. 2006), but now a 10th type has been discovered from the South Atlantic, an area with very few acoustic recordings.