Alarm response in larval western toads,Bufo boreas: release of larval chemicals by a natural predator and its effect on predator capture efficiency

An alarm response in larvae of the western toad, Bufo boreas, was examined in the laboratory. A natural predator, the giant water bug, Lethocerus americanus, while capturing and feeding on a tadpole, can cause sufficient damage for the release of toad alarm substance and subsequent alarm response in prey conspecifics. Larvae increased their activity and avoided the side of the tank that had a predator feeding on a conspecific tadpole in a visually isolated but interconnected container. Larvae did not increase activity or avoid the side of the tank that had a predator feeding on a heterospecific tadpole. Performance of the alarm response in conspecifics increased survivorship. The capture efficiency of predators (naiads of the dragonfly Aeshna umbrosa) hunting larvae that had been exposed to the alarm substance of conspecifics was reduced: predators required more capture attempts per successful attack compared to control tests.