Humpbacks return to the same breeding areas, in warm coastal waters, each year. Solitary males are thought to 'sing' most regularly, perhaps trying to attract a mate. Whales in a breeding stock all tend to sing a very similar song, which is quite different from the songs of whales in other breeding stocks. The songs last from 6-35 minutes, and range in frequency from 40-5,000 Hz.
Mating has never been directly observed, but whales seen diving together and then rising vertically to the surface, belly-to-belly, have been assumed to be mating. Calves stay close to their mothers for at least a year, taking at least 40 litres of milk from them each day for the first five months.