The brain and behavior of the tentacled snake.

Tentacled snakes (Erpeton tentaculatum) are aquatic predators that feed exclusively on fish. They have a unique pair of tentacles projecting from the face and an unusual J-shaped hunting posture. These features have been the subject of speculation for over a century. In a series of behavioral studies, tentacled snakes were found to exploit fish escape responses by startling fish toward their strike. This remarkable, deceptive behavior takes advantage of the stereotyped C-start escape response of fish. For some fish approach angles, snakes predicted future fish behavior and accurately struck at their moving head. These findings suggest tentacled snakes are acting as "rare enemies"--taking advantage of prey behavior that is usually adaptive for the prey species. Anatomical and physiological analysis showed the tentacles are densely innervated by the trigeminal nerve and are sensitive mechanoreceptors that respond to water movements. Mechanosensory information from the tentacles projects to the optic tectum in approximate register with vision, providing a mechanism for integrating visual and mechanosensory cues for identifying, localizing, and capturing prey.