Diurnal Calling in a Nocturnal Frog: Exceptional Calling Activity of Túngara Frogs (Engystomops pustulosus) on the Panamanian Island of Taboga

Abstract Túngara Frogs, Engystomops pustulosus, are known to reduce the complexity of their calls in the presence of predators. Although complex calls are more attractive to females, they also attract predators, particularly frog-eating bats, and are rarely emitted by solitary males. Therefore, if Túngara Frogs were to be released from predation pressure, as on the island of Taboga in the Gulf of Panama where frog-eating bats are absent, such constraints on calling should be alleviated. We compared the calling behavior of Túngara Frogs on Taboga with the calling behavior of those on Barro Colorado Island, located in central Panama where frog-eating bats are present, using timed video recordings. Compared with Túngara Frogs on Barro Colorado Island, male Túngara Frogs on Taboga called more, emitted consistently more calls in choruses, and called both day and night. On Taboga, even solitary males routinely embellished their calls with chuck elements. These results are consistent with a hypothesis of predator release positively affecting calling behavior.