The Fin Whale (Balaenoptera physalus) is the second-largest animal on Earth. This baleen whale belongs to the rorqual family, characterized by throat pleats that allow the mouth to expand dramatically during feeding. Found in all major oceans, Fin Whales migrate vast distances between feeding and breeding grounds. They are also known as the Finback Whale or the Razorback, referencing their prominent dorsal fin and slender profile.
Defining the Fin Whale’s Size
The physical dimensions of the Fin Whale place it second only to the Blue Whale. Lengths vary significantly by population, with those in the colder Southern Hemisphere growing larger than their Northern counterparts. Northern Hemisphere Fin Whales average 20.5 to 22.5 meters (67 to 74 feet) for females and 19 to 21 meters (62 to 69 feet) for males.
In the Southern Ocean, Fin Whales can reach a maximum recorded length of about 27 meters (89 feet). The largest individuals are always females, a form of sexual dimorphism. An adult Fin Whale weighs between 45 and 75 tonnes, though the largest recorded specimens have weighed over 80 tonnes.
The whale’s weight fluctuates seasonally, as they accumulate significant blubber reserves during summer feeding periods. The total mass of a Fin Whale can reach upwards of 120 tonnes in exceptional cases.
Distinctive Physical Features
The Fin Whale has a sleek and slender body shape, earning it the nickname “The Greyhound of the Sea.” This hydrodynamic form allows the animal to achieve bursts of speed up to 35 kilometers per hour. Its dorsal coloration is dark brownish-gray, contrasting with a white underside. This countershading helps conceal the whale from predators above and below.
The most unique physical feature is the asymmetrical pigmentation on its head. The left side of the lower jaw is dark gray or black, while the right side is white or light gray. This pattern extends to the baleen plates inside the mouth, where the right side is mostly creamy-yellow.
The species name is derived from its prominent, curved dorsal fin, which is tall and located about two-thirds of the way down its back. The head is V-shaped and relatively flat, featuring 50 to 100 ventral grooves, or pleats, that run from the chin to the navel. These specialized anatomical features play a direct role in the whale’s feeding mechanism.
Feeding Habits Supporting Massive Size
The Fin Whale sustains its enormous size through lunge feeding, a specialized method of consumption. This technique involves accelerating rapidly into dense patches of prey with the mouth wide open. The whale’s throat grooves expand dramatically, allowing the engulfment of an immense volume of water and prey.
The primary diet consists of small schooling fish, such as herring and capelin, and small crustaceans like krill and copepods. Once engulfed, the whale uses its tongue to force the water out through the fringed baleen plates that hang from its upper jaw. The baleen acts as a sieve, trapping the small organisms for swallowing.
This feeding strategy requires a high caloric intake, satisfied by consuming up to 1.8 to 2.8 tonnes of food per day during peak feeding seasons. The unique asymmetrical coloration, particularly the white right jaw, is theorized to help herd or disorient schooling fish as the whale circles and lunges, often turning on its right side.