Fin whale (Balaenoptera physalus) — the fast rorqual

Physical characteristics

Fin whales have a long, slender body with a small dorsal fin set far back on the rump. Key features include a series of ventral pleats or throat grooves that expand during lunge feeding, a mouth lined with baleen plates rather than teeth, and a striking asymmetry in coloration: the right lower jaw and adjacent area are often pale while the left side is darker. This species can reach great lengths and substantial mass, making it one of the largest marine animals.

Behavior and ecology

Fin whales are powerful swimmers and can reach high short-burst speeds. They feed primarily by gulping and filtering large volumes of water to capture krill and small schooling fishes. Individuals are typically seen alone or in small groups, though they may gather in larger concentrations in rich feeding areas. They produce low-frequency vocalizations used for communication across long distances.

Distribution, migration and life history

Fin whales are cosmopolitan, occurring in most of the world’s temperate and polar oceans. Many populations undertake seasonal migrations between high-latitude feeding grounds in summer and lower-latitude breeding or overwintering areas. Reproduction follows a typical large-whale pattern: females bear a single calf after a gestation of roughly a year and invest extended parental care.

Conservation and human interactions

Historically, fin whales were heavily targeted by commercial whaling, which caused large declines in many populations. Today they benefit from international protections but still face threats from ship strikes, fishing gear entanglement, ocean noise, and changes in prey distribution linked to climate change. Conservation efforts include population monitoring, ship-speed regulations in busy corridors, and measures to reduce bycatch. The species remains an important subject for ecological research and whale-watching tourism.

Notable facts

• Second largest living animal after the blue whale.
• Sometimes called the "greyhound of the sea" for its speed.
• Distinctive asymmetrical jaw coloration helps with field identification.