Some snakes can see heat in total darkness using special holes on their faces called pit organs.

Pit organs are very sensitive. They can detect temperature changes as small as 0.003 degrees Celsius. In 2010, Dr. David Julius found a protein called TRPA1 in these organs. This protein acts like a sensor that sends a signal to the brain when it feels heat.The pit works like a pinhole camera. Heat enters the hole and hits a thin membrane full of nerves. These nerves send information to the same part of the brain that handles regular sight. This allows the snake to combine what it sees with its eyes and what it feels with its heat pits.This system is very accurate. A blindfolded rattlesnake can hit a moving target 98% of the time. The Western Diamondback Rattlesnake uses this to hunt mice in dark burrows. Pythons and boas have similar pits along their lips. This helps them tell the difference between a warm animal and a warm rock.The system does not need any light to work. A snake can still see its prey even if its eyes are closed. This gives nocturnal hunters a big advantage in the dark.