Invertebrates
Giant Squid
Architeuthis dux · also called kraken (in legend)
The giant squid is the animal behind the kraken myth and one of the last large creatures on Earth that humans have barely observed alive. It lives in the deep ocean, hunts in the dark, and for most of scientific history was known only from the bodies it left behind.
Overview
Giant squid are found in deep water in most of the world’s oceans, usually between about 300 and 1,000 metres down, along the slopes of continents and islands. They are not thought to be rare — sperm whales, which feed on them, are estimated to eat many millions of tonnes of squid a year — but they are dispersed, elusive, and live where people cannot easily go, so almost everything known about them comes from strandings, fisheries bycatch, and whale stomach contents.
Body
A giant squid has the standard squid layout scaled up: a torpedo-shaped mantle, eight arms and two much longer feeding tentacles, a sharp beak at the centre of the arms, a funnel for jet propulsion, and fins at the rear of the mantle. The suckers on the arms and tentacle clubs are ringed with sharp, tooth-like chitin, and it is these that leave the distinctive circular scars found on the skin of sperm whales.
Its most extreme feature is its eyes — up to 27 centimetres across, the largest known in the animal kingdom, apparently evolved to spot approaching sperm whales by the faint light their movement stirs up in the plankton.
Hunting
Giant squid hunt fish and other squid in the deep sea, shooting out the two elastic feeding tentacles to grab prey at a distance and drawing it back to the arms and beak. A rasping tongue-like radula shreds the food before it enters the oesophagus, which — as in other squid — passes through the middle of the brain, limiting how large each swallowed piece can be.
Life cycle
Giant squid are believed to grow fast and live only about five years, reaching their enormous size in that short span and dying after a single breeding effort, like most squid. Females produce a huge egg mass, possibly containing millions of small eggs. Males transfer packets of sperm into the female’s arms with a long muscular appendage. The larvae and juveniles live in shallower water and move deeper as they grow, but this early life stage is very poorly known.
Giant squid and people
The species is listed as Least Concern — there is no targeted fishery and no evidence of decline. Its significance is mostly scientific and cultural: it is a flagship for how little of the deep ocean has been explored, a fixture of maritime legend, and a key player in the deep-sea food web as the sperm whale’s principal large prey.
Giant Squid: common questions
How big is a giant squid, really?
Big, but smaller than the legends. The largest well-documented specimens are around 12–13 metres long for females and about 10 for males, measured with the two feeding tentacles stretched out. The mantle — the main body — is only about 2 metres. Claims of 18-metre squid are unverified and probably exaggerated from stretched, damaged tentacles. The colossal squid, a different species, is shorter but heavier and more massive.
Why does the giant squid have such enormous eyes?
The leading explanation is that dinner-plate eyes are specifically useful for detecting a sperm whale at distance in the deep sea. The whale's approach disturbs bioluminescent plankton, creating a faint glow, and only a very large eye can gather enough light to see that glow far enough away to react. Giant and colossal squid are the whale's main deep-sea prey, so early warning is worth the cost of building such huge eyes.
Has anyone ever seen a live giant squid?
For centuries the species was known only from carcasses washed ashore or hauled up in nets, and from beaks and sucker scars found on sperm whales. The first photographs of a live giant squid in its habitat were taken in 2004 by Japanese researchers, and the first video followed in 2012, filmed from a submersible about 900 metres down off Japan. It has been seen alive only a handful of times since.
Do giant squid attack ships or people?
No. The "kraken" of Norse legend was probably inspired by real giant squid sightings, but giant squid live in the deep ocean, are not aggressive toward large objects, and have never been reliably recorded attacking a vessel or a person. Their main predator is the sperm whale, and their battles are fought kilometres below the surface.