Why signal softly? The structure, function and evolutionary significance of low-amplitude signals. (July 2015)

• Record Type: Journal Article
• Authors: Reichard, Dustin G.; Anderson, Rindy C.
• Is Part Of: Animal behaviour. Volume 105(2015)
• Page Start: 253
• Page End: 265
• Publication Date: 2015-07
• Subjects: communication -- eavesdropping -- sexual selection -- short-range song -- social behaviour -- soft song; Animal behavior -- Periodicals; 591.5
• DOI: 10.1016/j.anbehav.2015.04.017
• Languages: English
• ISSNs: 0003-3472

Abstract

Abstract : Acoustic signalling is a taxonomically widespread form of animal communication consisting of long-range, high-amplitude signals and short-range, low-amplitude signals. Research on acoustic communication has emphasized high-amplitude signals and often overlooked low-amplitude signals, even though they are produced in behavioural contexts that directly influence fitness. Low-amplitude signals are referred to by a variety of names such as soft songs, courtship songs, whispers, close calls, contact calls, grunts and moans, but all of these signals share a reduced amplitude and an active space that is limited to close-proximity receivers. In this review, we establish a general definition for low-amplitude signals and investigate the similarities and differences between low- and high-amplitude signals with respect to their acoustic structure and function. Then, we critically evaluate some proximate and ultimate evolutionary mechanisms that may explain why these signals are produced at low amplitude using examples from a variety of taxa. We conclude by suggesting priorities for future research on low-amplitude signals and highlighting how studying these signals will lead to a more complete understanding of how and why animals communicate acoustically. Highlights: Low-amplitude signalling is a common but understudied form of communication. These signals can be both structurally and functionally distinct from loud signals. Eavesdropping avoidance may select for low-amplitude signals in many contexts. Costs enforcing signal reliability may not apply to some low-amplitude signals. We highlight priorities for future research on low-amplitude communication.