Behaviour 2019
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Signaling in mixed-species groups: Heterospecific neighbor call type, density, and eavesdropper attraction  
Paula/A Trillo, Brian/F Ruether, Taylor/L Derick. Gettysburg College, Gettysburg, PA, United States

Males of species with similar breeding requirements often display from mixed-species aggregations. While much research explores how signaling conspecific neighbors mediate risks suffered by signalers, less is known about how signaling heterospecifics shape these risks. Previously, we demonstrated a novel mechanism, ‘collateral damage’, by which interactions between heterospecific signalers can substantially influence the attraction of eavesdropping enemies, thereby altering pressures driving signal evolution. Our new work uses playback of calls from species found within the same neotropical ponds, túngara frogs and hourglass treefrogs. We test whether call variants produced by neighbors and the density of those neighbors alter selective pressures imposed by collateral damage. We find that eavesdropper risks to hourglass treefrogs are independent of túngara call type, but that collateral damage resulting from calling close to túngara frogs is reduced within dense aggregations. Together, this work suggests that heterospecific interactions are likely to influence the evolution of signaling strategies, signal structure, and the distribution of species at local and larger scales.