The humpback whale is named for the hump in its dorsal fin, which is accentuated by gray or black. Humpbacks are gray or black, except for the flippers, parts of the chest and belly, and the underside of the tail flukes.
Females are generally larger than the males.
The average weight for a mature adult is 35 to 40 tons. In the North Pacific, where their populations reach 10,000, humpbacks feed in the summer along the coast from California to Alaska. In the winter, they migrate to breeding grounds off of Hawaii, Mexico, Costa Rica, and Japan. Scientists believe these activities are forms of communication because they create a great deal of noise which can be heard at long distances underwater. Humpbacks swim in groups or pods of up to a dozen at calving grounds, and in smaller groups of three to four during migration.