Japanese monkeys (Macaca fuscata) spontaneously associate alarm calls with snakes appearing in the left visual field

Many socially living animals are sensitive to a potential predator as part of their antipredator strategy. Alarm calls function to deter predators and to help other group members detect danger. The left visual field is involved in detection of potential threats or predators in many vertebrates, but it is unclear how alarm calls influence visual detection of a potential predator. Here, we experimentally examined how alarm calls spontaneously influence the search for pictures of a potential predator in captive Japanese macaques. We used an audiovisual preferential-looking paradigm by presenting pictures of a snake and a flower simultaneous with either a recording of alarm calls or contact calls. We found no difference in gaze duration between the 2 picture types when playing back contact calls. Monkeys looked significantly longer at pictures of snakes than at those of flowers when alarm calls were played back if the snake pictures were presented on the left side of the monkey's visual field, indicating right hemispheric bias during processing of predator representations. This is the first laboratory demonstration of auditory enhancement of visual detection of predators in the left visual field in animals, which will contribute to a better understanding of alarm call studies conducted in the wild.