Why do snakes have forked tongues?

Snakes are deaf and unable to hear air-borne sounds. Instead, they detect vibrations on the ground through their bodies. A two-tip tongue enables snakes to track other animals far more accurately by sweeping across trails left by their quarry and gauging very accurately where they lead. Snakes flick their tongues in and out incredibly quickly to taste the chemical environment in front of them. The tongue tips sample the environmental chemicals mostly from air, but also from the ground. Each individual tip picks up odour molecules and, when the tongue reacts, it delivers them to two chemosensors called ero nasal organ through separate holes in the top of the palate. As long as both tips are on the odour trail, the snake keeps going straight. But, when the tongue diverts from the trail, the snake veers in the opposite direction in order to put itself back on track. If neither of them is on the trail, the snake stops and waves its head back and forth to pick up the odour again.