Giant and colossal squids have the largest eyes of any animal—orbs as big as basketballs—but it’s not like the sea creatures have X-ray vision. So why the big eye?
Associate professor of biology Sonke Johnsen says it’s all about defense. “They’re most likely using their huge eyes to spot and escape their predators, sperm whales,” says Johnsen, who collaborated with a group of biologists to model how the giant eyes work.
The team found the design and size of the eye maximize a squid’s ability to detect tiny contrasts in the dimly lit waters of the deep ocean. This enables squids to see approaching sperm whales as they disturb bioluminescent organisms from as far away as 120 meters. That’s not far enough to avoid a whale’s sonar, but it may offer enough time to plot an escape.