Adult size is 15 to 18m. The large head is up to one forth the body length. This bonnet is the result of lice and barnacles that live on the whales and cause a yellowish callosity to grow from the skin. Right whales lack a dorsal fin, have a long narrow upper jaw that arches forward, and a large fleshy lower lip. The wide tail is composed of the two caudal flukes joining together with a deep notch where they join.
Juveniles are blueish in color, and as they mature they become dark grey to black.
Irregular white patches on the throat to belly are often found. These animals feed by filtering small marine animals out of the water with their baleen plates. Reproduction Mating and birthing occurs Feburary to April in the warmer southern waters. Young are born the following spring after a gestation period of a year and measure about 5.5m at birth. Behavior Right whales often travel in slow moving, small groups of six or less.