A giant squid's eye can reach about 27 centimeters (10.6 inches) across, measured on specimens by scientists, as reported in 2012. Because eyeballs collapse and the head sags after a giant squid dies, scientists have to take some guesses when they measure them.
Giant squid eyes can be as big as a human's head, and compared with a swordfish, a giant squid's eyes are three times as wide and 27 times the volume, relative to body size, said a Duke biologist in 2012, and the eyes let in a lot of light, which helps the squid notice faint shapes in dim water.
Many animals in the deep sea can make their own light, which is called bioluminescence. A moving whale makes tiny sea animals glow, and giant squid eyes may help them see sperm whales coming. Scientists estimate that a giant squid could notice the faint glow of a moving sperm whale from about 120 meters away.
Giant squid see best in blue light, so scientists filming them in the deep sea used red lighting, which is less likely to disturb them. The cameras use lights that the squid cannot see. A camera system called Medusa filmed a giant squid off Japan in 2012 and in the Gulf of Mexico in 2019.
Giant squid live in the deep sea, perhaps 200 to 1,000 meters down, in the twilight zone where light fades quickly. Below 1,000 meters the deep ocean is completely dark, and its average temperature is only 4 degrees Celsius (39 degrees Fahrenheit). Deep-sea pressure is extreme: from about 40 to over 110 times the pressure of Earth's atmosphere. Cameras in a 2021 study recorded giant squid and other deep-sea squid in the Gulf of Mexico and near the Bahamas at depths between 557 and 950 meters.
Scientists can measure chemicals in squid beaks recovered from whale stomachs, and these measurements reflect both what and where the animals ate. eDNA is genetic material that animals naturally shed, through skin, fluids or waste, and scientists can find it in seawater. In a study of seawater from deep canyons off Western Australia, scientists found eDNA from a giant squid. That study collected 178 ten-liter water samples from depths of up to about 14,800 feet.
As of November 2026, scientists do not know how many giant squid there are.
Words to know
- bioluminescence: living light
- specimens: kept examples
- pressure: pushing force
- twilight: dim zone
