All individuals are dark gray to brownish black on the back and sides with none of the mottling present on blue whales and are rarely as heavily scarred as sei whales. Along the back, just behind the head, there is a grayish-white chevron, with the apex along the midline of the back and the arms of the chevron oriented posteriorly, which is sometimes distinctive and may be visible as the animals surface to breathe. The undersides, including the undersides of the flukes and flippers, are white. On the head, the dark coloration is markedly asymmetrical, reaching farther down on the left than on the right side. The right lower lip, including the mouth cavity, and the right front baleen (approximately one-fifth to one-third) are yellowish white. Occasionally the right upper lip is also white. The remainder of the plates on the right side and all those on the left side are striped with alternate bands of yellowish white and bluish gray. The fringes of the plates are brownish gray to grayish white.
Natural History Notes
Fin whales are one of the most common baleen whale species in the world and constitute a major portion of the whaling catch. They are reportedly one of the fastest of the big whales (sei whales may be slightly faster) possibly reaching burst speeds in excess of 20 knots, and were not an important commercial species until the comparatively recent development of fast catcher boats and the depletion of blue whale stocks.
A fin whale's blow can be from 15 to 20 feet (4.6 to 6.1 m) tall and has been described as an inverted cone or an elongated ellipse.
Fin whales dive to at least 755 feet (230.1 m). This depth is probably deeper than that of either blue or sei whales, a factor usually reflected in differences among the surfacing, blowing, and diving characteristics of these three species. When they are moving leisurely at the surface, fin whales expose the dorsal fin shortly after the appearance of the blowholes, slightly later than that of the sei whales. When they are surfacing from a deeper dive, however, they surface at a steeper angle, blow, submerge the blowholes, and then arch the back and dorsal fin high into the air before beginning another long dive. In this species it can be generally stated that the maximum amount of the back in the area of the dorsal fin which is exposed above the surface as the animal sounds is approximately 2 times the height of the dorsal fin. Fin whales do not show their tail flukes when beginning a dive.
Unlike blue or sei whales, fin whales do breach on occasion. When they do leap clear of the water, fin whales usually reenter with a resounding splash, like that made by humpback and right whales and not smoothly, head first, as minke whales often do.
Fin whales are sometimes found singly or in pairs but more often occur in pods of six or seven individuals and many pods consisting of as many as 50 animals may be concentrated in a small area.
Fin whales calve and breed in winter, mostly in temperate waters.
Atlantic fin whales eat a wide variety of foods, including krill, capelin, squid, herring, and lanternfish.