The fin whale (Balaenoptera physalus), also known as the finback whale or common rorqual, is a species of baleen whale and the second-longest cetacean after the blue whale. The biggest individual reportedly measured in length, with a maximum recorded weight of . The fin whale's body is long, slender, and brownish-gray in color, with a paler underside to appear less conspicuous from below (countershading).
At least two recognized subspecies exist, one in the North Atlantic and one across the Southern Hemisphere. The species is found in all the major oceans, from polar to tropical waters, and is absent only from waters close to the pack ice at the poles and relatively small areas of water away from the open ocean. The highest population density occurs in temperate and cool waters. Its prey mainly consists of smaller schooling fish, small squid, and crustaceans, including copepods and krill. Mating takes place in temperate, low-latitude seas during the winter. Fin whales are often observed in pods of 6–10 animals, with whom they communicate using frequency-modulated sounds, ranging from 16 to 40 hertz.
Like all other large whales, the fin whale was a prized kill during the "heyday" of whaling from 1840 to 1861. This remained so into the 20th century, but decades of overharvesting contributed to declining numbers through the late 20th century. Over 725,000 fin whales were reportedly taken from the Southern Hemisphere between 1905 and 1976. Postrecovery numbers of the southern subspecies are predicted to be less than 50% of the pre-whaling population, even by 2010, due to long-lasting impacts of whaling and slow recovery rates. In the North Atlantic, it is considered to be fully recovered from past exploitation, while in other oceans, it is still in the process of recovery. As of 2018, it was assessed as vulnerable by the International Union for the Conservation of Nature.
Taxonomy
The fin whale was first described by Friderich Martens in 1675 and by Paul Dudley in 1725. The former description was used as the primary basis for the species Balaena physalus by Carl Linnaeus in 1758. In 1804, Bernard Germain de Lacépède reclassified the species as Balaenoptera rorqual, based on a specimen that had stranded on Île Sainte-Marguerite (Cannes, France) in 1798. In 1830, Louis Companyo described a specimen that had been stranded near Saint-Cyprien, southern France, in 1828, as Balaena musculus. Most later authors followed him in using the specific name musculus, until Frederick W. True (1898) showed that it referred to the blue whale. In 1846, British taxonomist John Edward Gray described a specimen from the Falkland Islands as Balaenoptera australis. In 1865, German naturalist Hermann Burmeister described a roughly specimen, found near Buenos Aires about 30 years earlier, as Balaenoptera patachonicus. In 1903, Romanian scientist Emil Racoviță placed all these designations into Balaenoptera physalus. The word physalus comes , referring to the prominent blow of the species.
Fin whales are rorquals, members of the family Balaenopteridae, which includes the humpback whale, blue whale, Bryde's whale, sei whale, and minke whale. The family diverged from the other baleen whales in the suborder Mysticeti in the middle Miocene.
Recent DNA evidence indicates that the fin whale may be more closely related to the humpback whale (Megaptera novaeangliae), and in at least one study, the gray whale (Eschrichtius robustus), two whales in different genera, than it is to members of its own genus, such as the minke whale. As of 2023, four subspecies are named, each with distinct physical features and vocalizations. The northern fin whale, B. p. physalus (Linnaeus 1758) inhabits the North Atlantic and the southern fin whale, B. p. quoyi (Fischer 1829) occupies the Southern Hemisphere. Most experts consider the fin whales of the North Pacific to be a third subspecies—this was supported by a 2013 study, which found that the Northern Hemisphere B. p. physalus was not composed of a single subspecies. A 2019 genetic study concluded that the North Pacific fin whales should be considered a subspecies, suggesting the name B. p. velifera (Scammon 1869). The three groups rarely mix.
Clarke (2004) proposed a "pygmy" subspecies (B. p. patachonica, Burmeister, 1865) that is purportedly darker in colour and has black baleen. He based this on a single physically mature female caught in the Antarctic in 1947–48, the slightly smaller average size of sexually and physically mature fin whales caught by the Japanese around 50°S, and the smaller, darker, sexually immature fin whales caught in the Antarctic, which he believed were a "migratory phase" of his proposed subspecies. The subspecies has not been genetically established, and is not recognized by the Society for Marine Mammalogy.
Hybrids
The genetic distance between blue and fin whales has been compared to that between a chimpanzee and human (3.5 million years on the evolutionary tree). Nevertheless, hybrid individuals between blue and fin whales, with characteristics of both, are known to occur with relative frequency in both the North Atlantic and North Pacific. The substantial overlap in both distribution and diet, and the fact that fin and blue whales often join in mixed schools, likely explains the apparently high frequency of hybridisation.
The DNA profile of a sampling of whale meat in the Japanese market found evidence of blue/fin hybrids. Similarly, a whale caught by whalers off the coast of Iceland in 2018 was found to be a hybrid descended from a female blue whale and a male fin whale. A 2024 genome analysis of North Atlantic blue whales found that about 3.5% of their genome was derived from hybridization with fin whales. The gene flow was determined to be unidirectional from fin to blue whales. Despite their smaller size, fin whales have similar cruising and sprinting speeds to blue whales, which would allow fin males to complete courtship chases with blue females.
Anatomy
The body is relatively slender, with a slim back and a large, hook-shaped dorsal fin measuring , located on the fourth posterior end of the body. It has an elongated ridge on its back and around 260 to 480 baleen plates. It has two blowholes that can squirt up in the air. Like most rorquals, the fin whale has grooves between the tip of the lower jaw and the navel.
Among whale species, the fin whale is exceeded in size only by the blue whale. Adults usually average in weight. Males have a mean length of , and females average . They are sexually dimorphic, with females generally being longer and heavier than males. The largest specimens can attain lengths of over and weights of . The record length was measured at . The Discovery Committee reported lengths up to . However, the longest fin whale ever scientifically measured was a female caught south of Antarctica in the Southern Indian Ocean, as verified by Major F. A. Spencer, a whaling inspector aboard the whaling ship Southern Princess (1936–38). The fin whale is estimated to have weighed up to . Fin whales from the Northern Hemisphere are smaller than their southern counterparts and reach a body length of around for females and for males.
The fin whale is brownish to dark or light gray dorsally and white ventrally. The left side of the head is dark gray, while the right side exhibits a complex pattern of contrasting light and dark markings. The right lower jaw is white or light gray, which sometimes extends laterally and dorsally unto the upper jaw. Dark, oval-shaped areas of pigment called "flipper shadows" extend below and posterior to the pectoral fins.
The skull is long and weighs . The ribs had a maximum straight length of . The liver and heart are the largest of any known animal, weighing between for the liver and for the heart. The kidneys are also large, weighing between , and the right lung is about 10% heavier than the left, weighing between each.
The fin whale's penis typically measures , with a maximum length of ; the testes usually weigh in mature individuals. The oral cavity of the fin whale has a very stretchy or extensible nerve system, which aids them in feeding. An intersex fin whale was caught in South Georgia with several interesting features, including a connected testis and uterus and a severely deformed clitoris.
In one study, a fin whale brain measured long and wide at the tips of the temporal lobes and weighed around . The encephalization quotient (EQ) of the fin whale was measured at 0.14.
Life history
Mating takes place during the winter, in temperate, low-latitude waters, and the gestation period lasts between 11 and 12 months. The length of the young at birth is . At 6 to 7 months of age, when it is in length, a newborn weans from its mother, and the calf accompanies its mother to the summer feeding area. Calves remain with their mothers for about a year. Although reports of up to six foetuses have been made, single births are far more typical. In the Northern Hemisphere, females reach sexual maturity between the ages of 6 and 12, at lengths of , and around in the Southern Hemisphere. Males reach sexual maturity at 6–10 years.
Full physical maturity is attained between 22 and 25 years. Fin whales live, on average, to 75–90 years. The fin whales studied in one 1958 study were estimated to be either 50 years old or 60–67 years old. Three fin whales, killed as part of a commercial hunt in Iceland in 2013 and 2015, were found to be aged 82, 80, and 65. Some studies have recorded individual whales living longer: one, studied near Iceland in 1988, was estimated to be 94 years old; a 1979 study recorded the maximum lifespan as 114 years; and a female specimen, which was found in 2010, measured in length and weighed , was estimated to be 135–140 years old.
The fin whale, one of the fastest cetaceans, can sustain speeds between and . Speeds up to have been recorded, earning the fin whale the nickname "the greyhound of the sea". The maximum speed measured by methods such as satellite tracking or GPS was . The American naturalist Roy Chapman Andrews has pointed out that the fin whale, like the blue whale, has more endurance and power compared to the sei whale.
Fin whales are more gregarious than other rorquals and often live in groups of 6–10, although feeding groups may reach up to 100–250 animals.
Vocalizations
Multimedia relating to the fin whaleThe whale calls have been sped up 10x from their original speed. Like other whales, males make long, loud, low-frequency sounds. The vocalizations of blue and fin whales are the lowest-frequency sounds made by any animal. Most sounds are frequency-modulated (FM) down-swept infrasonic pulses from 16 to 40 hertz frequency; the range of sounds that most humans can hear falls between 20 hertz and 20 kilohertz. Each sound lasts 1-2 seconds, and various sound combinations occur in patterned sequences lasting 7 to 15 minutes each. The whale then repeats the sequences in bouts, which can last for several days. The vocal sequences have source levels of up to 160–186 decibels relative to 1 micropascal at a reference distance of one metre and can be detected hundreds of miles from their source.
When fin whale sounds were first recorded by US biologists, they did not realize that these unusually loud, long, pure, and regular sounds were being made by whales. They first investigated the possibilities that the sounds were due to equipment malfunction, geophysical phenomena, or even part of a Soviet scheme for detecting enemy submarines. Eventually, biologists demonstrated that the sounds were the vocalizations of fin whales.