title: Crossmodal comparisons of signal components allow for relative-distance assessment.
abstract: Animals have multiple senses through which they detect their surroundings and often integrate sensory information across different modalities to generate perceptions. Animal communication, likewise, often consists of signals containing stimuli processed by different senses. Stimuli with different physical forms (i.e., from different sensory modalities) travel at different speeds. As a consequence, multimodal stimuli simultaneously emitted at a source can arrive at a receiver at different times. Such differences in arrival time can provide unique information about the distance to the source. Male túngara frogs (Physalaemus pustulosus) call from ponds to attract females and to repel males. Production of the sound incidentally creates ripples on the water surface, providing a multimodal cue. We tested whether male frogs attend to distance-dependent cues created by a calling rival and whether their response depends on crossmodal comparisons. In a first experiment, we showed distance-dependent changes in vocal behavior: males responded more strongly with decreasing distance to a mimicked rival. In a second experiment, we showed that males can discriminate between relatively near and far rivals by using a combination of unimodal cues, specifically amplitude changes of sound and water waves, as well as crossmodal differences in arrival time. Our data reveal that animals can compare the arrival time of simultaneously emitted multimodal cues to obtain information on relative distance to a source. We speculate that communicative benefits from crossmodal comparison may have been an important driver of the evolution of elaborate multimodal displays.
authors.affiliation: Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama; Institute of Biology, Leiden University, 2300 RA Leiden, the Netherlands. Electronic address: wouter.halfwerk@gmail.com.
authors.forename: Wouter
authors.initials: W
authors.lastname: Halfwerk
authors.affiliation: Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Page
authors.affiliation: Department of Biology, Salisbury University, Salisbury, MD 21801, USA.
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Taylor
authors.affiliation: Department of Mechanical Engineering, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Preston S
authors.initials: PS
authors.lastname: Wilson
authors.affiliation: Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama; Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ryan
mesh_terms: D000818:Animals; D001001:Anura / Q000502:physiology*; D001307:Auditory Perception; D004215:Distance Perception; D008297:Male; D010176:Panama; D014732:Vibration; D014828:Vocalization, Animal; D014867:Water
chemical_list: D014867:Water