What if you could see in the dark? For some animals, abilities like this are part of life.

Animals use sight to hunt prey, avoid predators, and communicate. Their eyes work in the same basic way as human eyes do. Special cells in the eye collect light from the environment. These cells send signals to the brain, which creates the images we see.

The structure of an animal’s eyes affects how it views the world. So does the number of eyes that it has and where they are placed. 

Read on to meet four animals with unique adaptations for vision. Their eyes let them see things no human could.

Owls: Light Collectors

Human eyes are built to see in daylight. After dark, it’s hard to make out our surroundings. Owls don’t have this problem. They hunt at night. So their eyes are adapted to soak up a lot of light. This gives them vision clear enough to spot prey even in the dim light of the moon and stars.

Owls’ eyes are enormous—much larger compared with their body size than those of many other animals. When it’s dark out, holes called pupils expand to cover the front of the owls’ eyes. The extra-large openings let in a lot of light. Where a human sees a dark forest, an owl sees a scene that’s nearly three times as bright!

Praying Mantises: Seeing All Sides

What if you could see in front of you and behind you at the same time? A praying mantis can! The insect’s head can rotate 180 degrees to view its surroundings and potential prey. Two bulging eyes sit on its swiveling head. In between these big eyes are three much smaller, simpler eyes.

Spiders: Night Vision

Not all spiders have the same number of eyes. Most species of spider have eight eyes. But some spiders have two, four, six, or even zero eyes!

Most spiders have poor eyesight. They rely on other senses—touch, taste, and feel—to hunt prey. But their eyes are well adapted for the dark. They can even sense small changes in light and dark. 

Horseshoe Crabs: Eyes All Over

Horseshoe crabs have been around for millions of years. They’re called living fossils because they haven’t changed much over that time. Horseshoe crabs have eyes all over their bodies, including one on their telsons (tail-like body segments)!

The crab’s two compound eyes are the largest. Compound means the eyes are made up of many tiny lenses. Through these eyes, the horseshoe crab sees multiple images instead of just one. Compound eyes help horseshoe crabs find mates. 

The crab’s other eyes are much smaller. They help the crab sense light and dark, especially when swimming.