The fin whale, scientifically known as Balaenoptera physalus, is a large marine mammal often referred to as the finback whale or common rorqual. This baleen whale is the second-largest animal on Earth, surpassed only by the blue whale. Fin whales are widely distributed across the world’s oceans, inhabiting both polar and tropical waters.
Physical Characteristics
The fin whale has a sleek, streamlined body. Adults measure between 20 to 27 meters (65 to 89 feet) in length. Their weight ranges from 70 to 80 metric tons (77 to 88 short tons).
A distinctive feature of the fin whale is its asymmetrical coloration, which serves as countershading. Its dorsal side is dark grey or brownish-black, while the ventral side is white. This asymmetry extends to its jaw: the lower right jaw is white, contrasting with the dark left jaw. The fin whale also has a prominent, backward-pointing dorsal fin, exceeding 60 centimeters (23 inches) in height, positioned about 70% along its back. Its long, tapered flippers can be up to 10% of its body length.
Instead of teeth, fin whales possess 260 to 480 baleen plates used for filter feeding. They also have 50 to 100 long throat pleats that extend to the navel.
Habitat and Diet
Fin whales are found in all major oceans, from polar to tropical regions, though less common in the warmest, equatorial areas. They avoid waters close to the ice pack and smaller, enclosed seas like the Red Sea. Highest population densities are observed in temperate and cool waters.
Fin whales are migratory, moving between high-latitude feeding grounds in summer and lower-latitude breeding grounds in winter. In summer, they migrate to colder, food-rich waters, such as the Chukchi Sea, Gulf of Alaska, and coastal California in the North Pacific, and areas around Greenland, Iceland, and the Barents Sea in the North Atlantic. Breeding and calving occur in warmer, low-latitude seas, primarily from November to January in the Northern Hemisphere and June to September in the Southern Hemisphere.
The diet of fin whales includes small schooling fish like herring, capelin, and mackerel, as well as small squid and planktonic crustaceans, particularly krill. They are considered carnivores. Fin whales employ a lunge-feeding technique, engulfing large volumes of water and prey, then filtering the water through their baleen plates.
Behavior and Conservation Status
Fin whales are observed alone or in small groups, though they can gather in larger aggregations of up to ten, especially in abundant feeding grounds. They communicate using low-frequency vocalizations, ranging from 16 to 40 hertz, which are outside human hearing range. These sounds are among the lowest frequencies produced by any animal and facilitate long-distance communication. Fin whales are also known for their swimming speed.
Historically, commercial whaling impacted fin whale populations, with over 725,000 individuals taken from the Southern Hemisphere between 1905 and 1976. This overharvesting led to a decline in their numbers, with populations dropping to as low as 38,000 by 1997. Commercial whaling of fin whales was banned in 1976 in both the North Pacific and Southern Hemisphere.
The International Union for Conservation of Nature (IUCN) Red List classifies the fin whale as “Vulnerable”. While the global population is estimated at around 100,000 mature individuals and appears to be increasing, full recovery to pre-whaling numbers may take many decades. Ongoing threats include ship strikes, entanglement in fishing gear, and ocean noise pollution from human activities. Climate change also poses a threat by altering their habitat and prey distribution. International conservation efforts, including legal protections in various waters, are in place to support their recovery.