The fin whale, known scientifically as Balaenoptera physalus, is a marine mammal that is the second-largest animal on Earth. This streamlined giant of the ocean has earned the nickname “greyhound of the sea” due to its impressive speed and agility. Its presence across the world’s oceans makes it a widespread, yet often elusive, inhabitant of marine ecosystems.
Size and Appearance
Fin whales have a long, sleek, and streamlined body, allowing swift movement through the water. Adult fin whales typically reach lengths between 22.9 to 27.4 meters (75 to 90 feet), with females generally being slightly larger than males. They weigh between 67 to 103 metric tons (74 to 114 tons).
The coloration of a fin whale’s body is dark grey to brownish-black on its back and sides, contrasting with a paler, almost white, underside. Their head coloration is uniquely asymmetrical. The left side of the lower jaw is dark, while the right side, and sometimes the upper lip, is white or light gray. This unusual pigmentation also extends to their baleen plates, which are creamy-yellow on the front right side and striped yellowish-white and bluish-gray on the left.
Habitat and Migration Patterns
Fin whales are found in all major oceans, from polar to tropical regions. Their highest population densities are typically observed in temperate and cool waters. They are generally absent from waters very close to the ice pack at both the North and South Poles.
These whales undertake extensive seasonal migrations. During summer, fin whales primarily feed in cold, high-latitude waters near the poles. As winter approaches, they migrate to warmer, lower-latitude waters in tropical or subtropical regions for breeding and calving. Although the precise locations of their winter breeding grounds remain largely unknown, some populations, such as those in the Gulf of California and the Mediterranean Sea, may be resident year-round.
Diet and Feeding Methods
Fin whales are filter feeders, consuming small marine organisms. Their primary food sources include small schooling fish like herring, capelin, and sand lance, as well as squid and various crustaceans such as krill and copepods. Depending on their geographical location, their diet can vary, with krill often being the predominant prey in Antarctic waters.
Lunge-feeding is their most notable feeding technique. This involves accelerating at high speed and engulfing enormous volumes of water and prey, which can be up to 70 cubic meters (18,000 US gallons) in a single gulp. Their accordion-like throat pleats, numbering between 50 and 100, allow their mouths and throats to expand dramatically to accommodate this large intake. Once the water and food are engulfed, the whale closes its jaws and uses its 260 to 480 baleen plates, which are long, flat, keratinous structures, to strain the water out, trapping the food inside for consumption.
Conservation and Human Impact
The fin whale is classified as “Vulnerable” on the IUCN Red List, an improvement from its previous “Endangered” status. Commercial whaling in the 20th century severely depleted fin whale populations, with hundreds of thousands taken from the Southern Hemisphere alone between 1905 and 1976. The introduction of modern whaling techniques, such as steam-powered ships and explosive harpoons, made it possible to target these fast-swimming whales.
Following the 1986 International Whaling Commission (IWC) moratorium on commercial whaling, fin whale populations have shown signs of recovery. Despite this global ban, some countries have resumed limited whaling activities. Today, the main threats to fin whales include vessel strikes (collisions with large ships) and underwater noise pollution, which can interfere with their communication and navigation. The recovery of fin whale numbers since the moratorium demonstrates the positive impact of international conservation efforts.