The goal of this research is to determine the mechanisms underlying predatory and defensive behavior guided by an extraordinarily novel sensor in snakes. Pit vipers, pythons and boas possess special organs that form images in the brain of the thermal environment, much like vision occurs in the human brain. Thus, these snakes see heat, and this amazing system is the most sensitive infrared detector on Earth, natural or artificial. A better understanding of infrared-based thermal imaging in snakes is important not only for understanding complex behavior in these highly efficient predators, but also for understanding the evolution of imaging sensors and the behaviors they support in other animals including people. Part of the National Science Foundation Series “Science Nation.”