Spooky Senses

Some snakes can see heat. It helps them spot prey. They can see the heat given off by their prey’s body—even when it’s dark outside.

Pit vipers can do this thanks to holes between their nostrils and eyes. These holes are called pit organs. They act like antennas that detect heat, explains David Julius. He works at the University of California, San Francisco. He studies how animals’ bodies work.

Cells inside the pit organs detect heat. An electrical signal then travels from nerves in the pit organ into the snake's brain. The brain translates the signal into an image. This allows the snake to visualize heat. Scientists don’t know exactly what snakes are seeing. But Julius says it’s likely similar to images people see when using thermal cameras or night-vision goggles.

All spiders have hair on their bodies. But it’s not to keep the animals warm. Most spiders have poor eyesight. They use these body hairs to gather information about their surroundings—day or night.

The hairs detect air movements in the spider's environment. They are so sensitive that they can sense changes in the air caused by the flapping of tiny insect wings. “If anything moves around a spider, they’ll likely feel it,” says Eileen Hebets. She studies spiders at the University of Nebraska-Lincoln. People who study spiders are called arachnologists.

A spider’s exoskeleton, or hard outer shell, also contains thousands of tiny holes. The vibrations from an insect’s movements enter these holes. This triggers a signal through a nerve. The signal travels  to the spider’s brain. This tells it there is something nearby—and SNATCH! The spider catches a meal.