An extrasensory organ in the roof of a snake's mouth sharpens its sense of smell. Called Jacobson's organ, it consists of two hollow, highly sensitive saclike structures. The snake's acute odor perception allows it to track both prey and potential mates.

Pit vipers detect prey using a two-chambered "pit" organ located between the eye and the nostril on each side of the head. Warm-blooded animals give off thermal radiation even when motionless. The snake's brain identifies this heat by comparing the temperatures in the outer and inner chambers. Since the brain distinguishes between input from the right and left pit organs, the snake can tell where the heat source is in relation to itself. It can strike accurately, even in the dark, at prey a fraction of a degree warmer.