Iguanas Have a Third ‘Eye’ On Top of Their Heads

Human psychics may claim to have a figurative third eye, but iguanas have a very literal third eye atop their heads — though it doesn’t work like their two front-facing eyes. It’s a pale protrusion called the “parietal eye,” and it offers a key defense against avian predators.

Iguanas have extremely keen vision, though their front-facing eyes only provide them with a view of what’s in front of them. The parietal eye, however, allows iguanas to detect predators from above. This eye is incapable of detecting color or vivid detail, but it does perceive changes in movement and light. Iguanas use it to sense nearby birds of prey, allowing them to scurry to safety before an attack.