The mixed-species chorus as public information: tungara frogs eavesdrop on a heterospecific

Multispecies choruses represent a promising but uninvestigated forum for public information. Although frogs exposed to a potential predator call more readily in the presence of conspecific calls than in their absence, none are known to make comparable use of heterospecific calls. To test for heterospecific eavesdropping, we isolated calling male tungara frogs (Physalaemus pustulosus), presented them with a potential predator, and recorded their responses to playbacks of 1 of 4 stimuli: calls of a conspecific, a sympatric heterospecific (Leptodactylus labialis), an allopatric congener (Physalaemus enesefae), or silence. We found that males called more in response to the L. labialis call than to either the silent stimulus or the P. enesefae call. In contrast, the P. enesefae call did not result in significantly more calling than the silent stimulus. The conspecific call was the most effective at promoting calling. The data indicate that tungara frogs selectively attend to the call of a heterospecific. We hypothesize that such heterospecific eavesdropping contributes to the emergent behavior of mixed-species choruses.