Why do monitor lizards have forked tongues?

Monitor lizards, which belong to the family Varanidae, possess long, forked, and snakelike tongues that serve as essential tools for chemoreception.1

Like snakes, monitor lizards use their tongues to sample the environment for chemical information. By flicking their tongues in and out, they capture scent particles from the air or ground. These particles are then transferred to the Jacobson’s organ—a specialized chemosensory structure located in the roof of the mouth—which analyzes the chemical composition of the surroundings.234

The forked shape of the tongue is significant because it allows the lizard to sample odor molecules from two distinct points in the environment simultaneously. This provides the animal with a directional, or "stereo," sense of smell, helping it track prey, detect predators, or locate mates with greater precision. Because the Jacobson’s organ in monitor lizards is isolated from the nasal cavity, the tongue is the primary mechanism for transporting these environmental chemicals to the sensory receptors.234