Few studies of venomous snakes have addressed how anti-predator behavior may be affected by experience with a potential predator. Because defensive strikes may be costly to snakes, individuals with the ability to learn to discriminate among potentially harmful and non-harmful predatory stimuli should be favored by natural selection. In large venomous snakes, adults are capable of successfully defending themselves against most potential predators, whereas neonates suffer higher predator-induced mortality and are faced with a large diversity of predators. Consequently, we hypothesized that the relative costs of habituation to potential predatory stimuli should vary ontogenetically. This hypothesis predicts that adults should habituate rapidly to non-harmful predatory stimuli, whereas neonates should consistently employ active defensive displays (e.g. striking) because they are at higher risk. To test this prediction, we examined daily changes in the defensive behavior of adult and neonate cottonmouths (Agkistrodon piscivorus) towards a standardized non-harmful predatory stimulus. As predicted, adults and neonates differed in their tendencies to habituate: adults decreased defensiveness over days while neonates did not. Adults showed habituation of striking components but not of warning displays. Our results support the hypothesis that there may be ontogenetic differences in predator perception.