Giant Squid (Architeuthis dux): Facts, Size and Sightings

What does a giant squid look like?

Like all squid, the giant squid has a long, tube-shaped body called the mantle, with a pair of small fins at the rear. The mantle holds the gills, hearts and other organs. In front of it is the head with two enormous eyes, surrounded by eight thick arms and two much longer, thinner feeding tentacles. In the center of the arms sits a hard, parrot-like beak.

The arms and tentacles are lined with hundreds of cup-shaped suckers, each 2–5 cm (0.8–2 in) across and edged with a ring of sharp, finely serrated teeth made of chitin. The suckers are concentrated on the arms and on the broad, flattened club at the end of each tentacle. Giant squid have no hooks, which separates them from some other large squid.

Its skin contains color cells called chromatophores. Dead specimens usually look reddish or pinkish, while the squid filmed alive in 2012 shimmered silver and gold in the lights of the submersible. Inside, a giant squid keeps itself buoyant with a solution of ammonium chloride spread through its tissues, which is lighter than seawater. This gives the flesh a bitter, salty taste, so people have never fished for it as food.

How big is a giant squid?

Giant squid size has been exaggerated for centuries. Studies of more than 100 specimens give a much smaller, but still impressive, picture.

Most of the length is in the two feeding tentacles, which are elastic and easily stretched when a dead squid is measured on a beach or a ship’s deck. That is the main reason why older reports of 18–20 m (60–66 ft) squid are no longer accepted. Females grow larger than males. Records, famous specimens and the reasons for exaggeration are covered in how big is a giant squid?, and its heavier Antarctic relative is compared in giant squid vs colossal squid.

The largest eyes in the animal kingdom

The giant squid’s eyes reach at least 27 cm (11 in) across, about the size of a dinner plate, with a pupil about 9 cm (3.5 in) wide. Only the colossal squid has eyes of similar or larger size, and among animals of the past only the extinct ichthyosaurs are known to have had bigger ones.

Why so big? Little sunlight reaches the depths where the giant squid lives, and most of the light there comes from bioluminescence, the glow produced by living things. A 2012 study calculated that eyes this large would be especially good at detecting large, glowing disturbances in the water at a distance of more than 120 m (390 ft). A diving sperm whale sets off the glow of tiny plankton as it moves, so huge eyes may give the squid an early warning of its main predator.

Habitat and range

The giant squid lives in all the world’s oceans but is most often found in temperate waters over continental and island slopes. Specimens have come especially from the North Atlantic, around Newfoundland, Norway, the northern British Isles, northern Spain, the Azores and Madeira, and from southern Africa, Japan, New Zealand and southern Australia. It is rare in tropical and polar seas.

It is a deep-water animal. Evidence from trawled specimens and from the diving depths of sperm whales that eat it suggests that it usually lives at about 300–1,000 m (1,000–3,300 ft), in the dark twilight and midnight zones. Genetic studies published in 2013 found very little difference between giant squid from around the world, showing that there is only one species rather than the several that had been named.

What do giant squid eat?

Giant squid are carnivores. Stomach contents show that they eat deep-sea fish, such as orange roughy, and other squid. There is also evidence of cannibalism: beak fragments from other giant squid have been found in giant squid stomachs, and a squid stranded in Spain in 2016 bore injuries apparently inflicted by another giant squid.

A giant squid catches prey by shooting out its two long tentacles and gripping it with the toothed suckers on the clubs. The tentacles pull the prey to the arms, which hold it while the beak cuts it into pieces. The radula, a tongue-like ribbon of small teeth, shreds the pieces further before they are swallowed. Photographs taken in 2004 showed a giant squid attacking a baited line, suggesting that it is an active hunter rather than a slow drifter that waits for food to come by.

Sperm whales and other predators

The main predator of adult giant squid is the sperm whale, which dives hundreds or even thousands of meters to hunt squid. Giant squid beaks, which cannot be digested, are regularly found in sperm whale stomachs, and many sperm whales carry circular scars from the toothed suckers of struggling squid.

Pilot whales and southern sleeper sharks also eat giant squid, and in some regions killer whales may do so too. Young squid are eaten by many deep-sea fish. The popular image of an even battle between a whale and a squid is misleading: a male sperm whale weighs many tonnes, and the squid is its prey. The evidence is explained in do sperm whales fight giant squid?

Reproduction and life cycle

Much of the giant squid’s life cycle is still a mystery. Males reach maturity at a smaller size than females. A mature male has a muscular penis more than 90 cm (3 ft) long, and two of his arms are modified for mating. Females found with small sperm packets embedded in the skin of their arms suggest that the male injects the sperm directly into the female’s body.

Females carry huge numbers of tiny eggs; one had more than 5 kg (11 lb) of eggs in her ovary, each only about 0.5–1.4 mm long. The eggs are probably released in a large gelatinous mass that drifts in the open ocean, but this has never been observed. Newly hatched young, called paralarvae, have been caught near the surface off New Zealand and Japan. Growth rings in the ear stones, or statoliths, suggest that giant squid grow very fast and may reach adult size in about three years. How long they live is not known.

How scientists first saw a live giant squid

For most of history, giant squid were known only from dead or dying animals washed ashore, floating at the surface or taken from the stomachs of sperm whales. About 700 specimens had been recorded by the 2010s, many of them from Newfoundland and New Zealand in the 19th century and from Japan in recent years.

The first photographs of a live giant squid in its natural habitat were taken on 30 September 2004 by the Japanese scientists Tsunemi Kubodera and Kyoichi Mori, using a camera and baited line lowered to about 900 m (3,000 ft) off the Ogasawara Islands south of Tokyo. In July 2012 a team including Kubodera filmed a giant squid from a submersible in the same area, and in 2019 another team filmed one in the Gulf of Mexico. The full story is told in has anyone filmed a live giant squid?

Giant squid, sea monsters and the kraken

Sailors’ tales of giant squid go back to ancient times. The Greek philosopher Aristotle described a large squid in the 4th century BC, and stranded giant squid may lie behind several sea-monster legends, including the kraken of Norwegian folklore. The Danish zoologist Japetus Steenstrup gave the giant squid its scientific name in 1857, and a wave of strandings in Newfoundland in the 1870s helped convince scientists that the animal was real.

Giant squid have since starred in fiction from Jules Verne’s Twenty Thousand Leagues Under the Seas (1870) to modern films. Whether the kraken was a giant squid is discussed in is the kraken real?

Conservation status

The IUCN Red List classifies the giant squid as Least Concern, in an assessment published in 2014. It is not fished, lives in a vast and remote habitat and has a worldwide range. It is occasionally caught by accident in deep-water trawls, especially off New Zealand and in the North Atlantic.

No one knows how many giant squid there are. Estimates based on the number of beaks in sperm whale stomachs suggest that sperm whales eat millions of giant squid each year, implying a large population, but the figures are very uncertain. Giant squid cannot be kept alive in aquariums, so preserved specimens in museums such as the Natural History Museum in London and the Smithsonian’s National Museum of Natural History in Washington, D.C., remain the closest most people will come to one.