Fin whale

Name and taxonomy

The name fin whale refers to the tall, curved dorsal fin set far back on the body. Other names are finback, common rorqual and razorback, for the ridge along the tail stock. Carl Linnaeus named it Balaena physalus in 1758, and physalus comes from a Greek word for breath, after its tall blow. The species has been renamed many times, and in 1903 Emil Racovita gathered the scattered names into Balaenoptera physalus.

It belongs to the rorquals, the family Balaenopteridae, with the blue, humpback, sei, Bryde's and minke whales. Rorquals have throat grooves that let the mouth expand like a balloon. Four subspecies are now named: one in the North Atlantic, one in the North Pacific, one in the Southern Hemisphere and a disputed pygmy form. A 2019 genetic study confirmed that the North Pacific whales are a subspecies of their own. The three main groups rarely mix.

Evolution and relatives

The rorquals split from the other baleen whales in the middle Miocene. DNA suggests the fin whale is closer to the humpback whale, and perhaps the gray whale, than to the minke whale in its own genus. The genetic gap between fin and blue whales is about the same as that between people and chimpanzees. Even so, the two species breed together fairly often in the North Atlantic and North Pacific.

A whale caught off Iceland in 2018 had a blue whale mother and a fin whale father. A 2024 genome study found that about 3.5 percent of the North Atlantic blue whale genome comes from fin whales. The gene flow runs one way, from fin whales into blue whales. Fin whales probably manage this because they match blue whales for speed and can keep up in a courtship chase.

Appearance

The fin whale is slender for its size, with a flat head that takes up about a fifth of the body. A single ridge runs along the top of the head from the snout to the two blowholes. The blow rises 4 to 6 metres and is easy to see from a distance. The dorsal fin stands about 61 centimetres tall and curves like a hook. The back is brownish or dark grey and the belly is white. The colouring is lopsided: the right lower jaw is white and the left is dark grey. Pale chevrons sweep back from the head on the right side.

Adults measure 19 to 27 metres, and the longest whale ever measured by a scientist was a 25.9 metre female. Males average 21 metres and females 22, so the female is the larger sex. Northern whales are smaller than southern ones. Weight is usually 36 to 45 tonnes, and the largest whales are put at 120 tonnes. The mouth holds 262 to 473 baleen plates on each side, each up to 76 cm long. The heart weighs 130 to 290 kilograms and the liver 230 to 600 kg, the largest organs of any animal.

Habitat and range

The fin whale is found in every major ocean, from polar to tropical water. It avoids the pack ice itself and small enclosed seas such as the Red Sea. It is most common in temperate and cool water and scarce near the equator. It is the only rorqual that lives year round in the Mediterranean. GBIF holds records from 88 countries.

Most populations migrate between summer feeding grounds near the poles and winter breeding waters at lower latitudes. In the North Atlantic the whales summer from Newfoundland to Svalbard and move south in autumn past Bermuda to the West Indies. In the North Pacific they feed from Baja California north to the Chukchi Sea. They crowd into the Gulf of Alaska and the Bering Sea from May to October. Southern whales feed near Antarctica and breed somewhere in the open ocean, in places that are still unknown. Resident groups stay all year in the Gulf of California and the Mediterranean, where food is steady.

Fin whales favour deep water over the continental slope and shelf, beyond the 200 metre line. Calves learn their mother's migration route and return to her feeding ground in later years.

Diet and feeding

The fin whale is a filter feeder. It eats krill, copepods, small schooling fish such as herring, capelin and anchovy, and squid. In the Southern Ocean it lives almost entirely on Antarctic krill. Of 1,609 stomachs checked at an Icelandic whaling station, 96 percent held only krill. Off Newfoundland the whales eat mostly capelin instead.

To feed, the whale swims into a swarm at about 11 kilometres an hour and drops its jaw. The throat grooves stretch, and the mouth takes in up to 70 cubic metres of water. The whale then shuts its jaws and forces the water out through the baleen, which traps the prey. Each gulp brings in about 10 kilograms of food. On a feeding dive it goes below 200 metres and makes about four lunges. A whale can eat up to 1,800 kg a day, which takes about three hours of feeding.

When it hunts fish, a fin whale circles the school at speed to pack it into a ball. Then it rolls on its side and engulfs the ball. The white right jaw may help to frighten the fish into a tighter ball, though this is not proven. Feeding dives last about 6 minutes on average, with a maximum of 16.9 minutes.

Behaviour and social life

Fin whales are the most sociable of the rorquals. They often travel in pods of 6 to 10 animals. On rich feeding grounds, groups of 100 to 250 whales can gather. The only lasting bond is between a mother and her calf, and that ends at weaning. Migrations run in order: pregnant females go first, then adult males, then mothers with calves.

When a fin whale feeds it blows five to seven times in quick succession, then dives. While travelling it blows once every minute or two. On the last blow it arches its back high but seldom lifts its flukes. Feeding dives reach 316 metres, and travelling dives about 100 m. By day the whales follow their prey into deep water, and at night they rise with it toward the surface.

The fin whale is one of the fastest of all whales. It cruises at 37 to 41 kilometres an hour and has been clocked at 46 to 50 km/h in a sprint. In the days of sail it simply outran the whaling boats.

Communication and senses

Male fin whales make some of the lowest sounds of any animal. The calls are down-swept pulses of 16 to 40 hertz, below the range that most people can hear. Each pulse lasts 1 to 2 seconds, and a patterned sequence runs 7 to 15 minutes. A male repeats these sequences in bouts that can last for days. The sounds reach 160 to 186 decibels at the source and can be picked up hundreds of miles away.

When US biologists first recorded the calls, they suspected faulty equipment, an earthquake or a Soviet submarine detector. Only males sing, and they sing in the breeding season, so the song is thought to be a mating display. The pulses pass more than 2,500 metres into the seabed, and seismologists now use them to map the crust. Ship noise over the past 100 years may have slowed the species' recovery by drowning out the males. Whales also answer each other's calls, and the delay and echo probably tell them about the water around them.

Reproduction and life cycle

Mating takes place in winter in warm, low-latitude water. Fin whales have no fixed breeding ground, so males sing to draw females from afar. A female carries her calf for 11 to 12 months and gives birth in the same warm water the next winter. Twins are very rare, though up to six foetuses have been recorded. A female calves every 2 to 3 years.

A newborn measures 6 to 6.5 metres. It swims at once and nurses for 6 to 7 months, until it is 11 to 12 metres long. It then travels with its mother to the summer feeding ground and learns to feed itself. Northern females mature at 6 to 12 years and males at 6 to 10. Whaling drove the age of maturity down, from 10 to 12 years to 6 or 7 in the north. Full size comes only at 22 to 25 years.

Fin whales live for 75 to 90 years on average. Three whales killed off Iceland in 2013 and 2015 were aged 82, 80 and 65. A 1979 study put the maximum lifespan at 114 years. A female found in 2010 was estimated at 135 to 140 years old, though that figure is less certain.

Predators and threats

The orca is the fin whale's only known predator. At least 20 attacks or chases have been recorded, and only a few ended in a kill. In 2005, 16 orcas chased a fin whale for about an hour in the Gulf of California and killed it. In 2012 a pod killed a 15 metre whale in La Paz Bay after more than an hour. A fin whale usually flees rather than fights, though one in 2019 slapped an orca with its tail.

Today the main killer is the ship. Fast, large vessels over the continental shelf strike whales, and collisions cause many strandings. In 2014 a container ship arrived in New York Harbor with an 18 metre fin whale across its bow. Fishing gear entangles a few whales each year. Military sonar and seismic surveys disturb the whales and can mask the males' songs. A kidney worm, Crassicauda boopis, infected 94 percent of North Atlantic whales in one study and can kill.

Population and conservation

The IUCN listed the fin whale as Vulnerable in 2018. The world population is put at 100,000 to 140,000 mature whales. The North Atlantic holds about 70,000, the North Pacific about 50,000 and the Southern Hemisphere about 25,000. The North Atlantic population is thought to have recovered fully from whaling. The southern population was still under half its pre-whaling size in 2010.

The International Whaling Commission banned fin whaling in the Southern Hemisphere and North Pacific in 1976. A moratorium on all commercial whaling followed in 1986. Greenland keeps a quota of 19 fin whales a year for subsistence hunters. Iceland lodged an objection and still hunts fin whales under national quotas. Japan left the commission in 2019 and took 30 fin whales in 2024. The species is also protected under CITES Appendix I and the US Endangered Species Act.

Relationship with humans

For most of history the fin whale was too fast to catch. Steam ships and the exploding harpoon changed that in the late 19th century. As blue whales ran out, the whalers turned to fin whales for oil, blubber and baleen. Factory ships with stern slipways arrived in 1925 and raised the catch again. Some 874,000 fin whales were taken in the 20th century, 726,000 of them in the Southern Hemisphere. The Soviet Union also killed protected whales and hid the totals under false fin whale counts.

Today the fin whale earns money alive. Whale-watching boats meet it off California, in the Gulf of St Lawrence, the Bay of Biscay and the Mediterranean. Off Palos Verdes it can be seen lunge feeding from the shore. Hybrid fin and blue whale meat has turned up on sale in Japan. No fin whale has ever lived in captivity, and probably none could.

In culture and myth

No myth names the fin whale, but it lives inside the older lore of whales. In Icelandic folklore, the sword whale was an evil whale with a blade of a dorsal fin that slashed ships and other whales. Its rival was the blue whale, and Icelanders refused to eat the flesh of any evil whale. The fin whale itself, the langreydur, counted as a good whale that could be eaten. The Book of Jonah has a great fish swallow the prophet, and Christian art later turned the fish into a whale.

Arctic peoples such as the Inuit hold that a whale gives itself to the hunter, who must thank it. In Maori tradition the ancestor Paikea rides a whale to New Zealand. Chinese myth tells of the kun, a sea creature many thousands of li in length, which turns into a bird. Modern seafarers gave the fin whale its own legend as the greyhound of the sea. Its song added a Cold War myth, when the US Navy took the 20 hertz pulses for a Soviet device. Spirit-animal websites tie the fin whale to Poseidon, but no classical text does, so the link is probably modern.