title: Collateral damage or a shadow of safety? The effects of signalling heterospecific neighbours on the risks of parasitism and predation.
abstract: Although males often display from mixed-species aggregations, the influence of nearby heterospecifics on risks associated with sexual signalling has not been previously examined. We tested whether predation and parasitism risks depend on proximity to heterospecific signallers. Using field playback experiments with calls of two species that often display from the same ponds, túngara frogs and hourglass treefrogs, we tested two hypotheses: (1) calling near heterospecific signallers attractive to eavesdroppers results in increased attention from predatory bats and parasitic midges (collateral damage hypothesis) or (2) calling near heterospecific signallers reduces an individual's predation and parasitism risks, as eavesdroppers are drawn to the heterospecifics (shadow of safety hypothesis). Bat visitation was not affected by calling neighbours. The number of frog-biting midges attracted to hourglass treefrog calls, however, rose threefold when played near túngara calls, supporting the collateral damage hypothesis. We thus show that proximity to heterospecific signallers can drastically alter both the absolute risks of signalling and the relative strengths of pressures from predation and parasitism. Through these mechanisms, interactions between heterospecific guild members are likely to influence the evolution of signalling strategies and the distribution of species at both local and larger scales.
authors.affiliation: Department of Biology, Gettysburg College, Gettysburg, Pennsylvania, USA Smithsonian Tropical Research Institute, Panama City, Panamá ptrillo@gettysburg.edu.
authors.forename: Paula A
authors.identifier: 0000-0001-5994-5189
authors.initials: PA
authors.lastname: Trillo
authors.affiliation: Smithsonian Tropical Research Institute, Panama City, Panamá Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.
authors.forename: Ximena E
authors.initials: XE
authors.lastname: Bernal
authors.affiliation: Department of Biology, Gettysburg College, Gettysburg, Pennsylvania, USA Smithsonian Tropical Research Institute, Panama City, Panamá
authors.forename: Michael S
authors.initials: MS
authors.lastname: Caldwell
authors.affiliation: Smithsonian Tropical Research Institute, Panama City, Panamá Department of Ecological Science, Vrije Universitait, Amsterdam, The Netherlands.
authors.forename: Wouter H
authors.initials: WH
authors.lastname: Halfwerk
authors.affiliation: Smithsonian Tropical Research Institute, Panama City, Panamá Department of Biological Sciences, Butler University, Indianapolis, IN, USA.
authors.forename: Mallory O
authors.initials: MO
authors.lastname: Wessel
authors.affiliation: Smithsonian Tropical Research Institute, Panama City, Panamá
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Page
mesh_terms: D000818:Animals; D001001:Anura / Q000469:parasitology* / Q000502:physiology*; D002685:Chiroptera / Q000502:physiology; D004175:Diptera / Q000502:physiology; D020387:Food Chain; D006790:Host-Parasite Interactions; D008297:Male; D010176:Panama; D011235:Predatory Behavior; D014828:Vocalization, Animal
keywords: Corethrella midges; Trachops cirrhosus; hourglass treefrogs; mating signals; risk; túngara frogs