‘Silent’ signals: selective forces acting on ultrasonic communication systems in terrestrial vertebrates

摘要: Through technological innovations, humans have attained the unique ability to observe and study perceptual phenomena occurring outside limits of our own sensory capabilities. In acoustic communication, one such realm is frequency channel above upper limit human hearing (ca. ≥20 kHz), which defined in terms as “ultrasound”. The ultrasonic boundary biologically somewhat arbitrary; hear ultrasound widespread among terrestrial vertebrates, thought be an ancestral trait mammals (Masterton et al. 1968; Sales & Pye 1974). However, within context distinguishing between audible (i.e., range, ca. 20 Hz – kHz) communication provides a foundation upon explore intriguing questions regarding adaptive utility animal systems. ever-expanding selection quality ultrasonically-sensitive microphones recorders provided opportunity address with increasing sophistication. For effective occur, emitted signal must reach receiver enough clarity allow appropriate behavioral and/or physiological decision made. After Endler (1993), we can therefore consider clear reception minimum requirement successful system. With this mind, it becomes apparent that factors inherent transmission properties frequencies place some restrictions on environments social conditions they are useful information-bearing elements (sensu Suga 1972). Higher-frequency sounds attenuate more rapidly distance (Morton 1975; Lawrence Simmons 1982; Surlykke 1988; Romer Lewald 1992) directional than low-frequencies (Kinsler Frey 1962). addition, short wavelengths high-frequency make them susceptible reflection scattering by relatively small objects, twigs, leaves, blades grass (Marler 1955; Thus, interest clarity, may expect animals engaging long-distance or communicating small-scale properties, focus their vocal efforts range; way, ensure calls higher probability maintaining fidelity during from emitter receiver. additional environmental complexities further, cases competing, selective constraints frequency. certain ecological scenarios encourage exploitation ultrasound’s distinctive properties. Herein, will discuss biological evolution favor development system, provide examples vertebrates apparently been subject pressures. We because group expanding field. By defining biophysical, behavioral, under likely evolve well situated identify organisms use similar strategies. discovery communicators run evolutionary spectrum amphibians gain complete understanding foundations communication. comparative studies ultrasonically-communicating taxa give insight into fundamental mechanisms underlie both produce perceive extraordinarily sounds.