Tactics of evasion: strategies used by signallers to deter eavesdropping enemies from exploiting communication systems

Abstract

Eavesdropping predators, parasites and parasitoids exploit signals emitted by their prey and hosts for detection, assessment, localization and attack, and in the process impose strong selective pressures on the communication systems of the organisms they exploit. Signallers have evolved numerous anti‐eavesdropper strategies to mitigate the trade‐off between the costs imposed from signal exploitation and the need for conspecific communication. Eavesdropper strategies fall along a continuum from opportunistic to highly specialized, and the tightness of the eavesdropper–signaller relationship results in differential pressures on communication systems. A wide variety of anti‐eavesdropper strategies mitigate the trade‐off between eavesdropper exploitation and conspecific communication. Antagonistic selection from eavesdroppers can result in diverse outcomes including modulation of signalling displays, signal structure, and evolutionary loss or gain of a signal from a population. These strategies often result in reduced signal conspicuousness and in decreased signal ornamentation. Eavesdropping enemies, however, can also promote signal ornamentation. While less common, this alternative outcome offers a unique opportunity to dissect the factors that may lead to different evolutionary pathways. In addition, contrary to traditional assumptions, no sensory modality is completely ‘safe’ as eavesdroppers are ubiquitous and have a broad array of sensory filters that allow opportunity for signal exploitation. We discuss how anthropogenic change affects interactions between eavesdropping enemies and their victims as it rapidly modifies signalling environments and community composition. Drawing on diverse research from a range of taxa and sensory modalities, we synthesize current knowledge on anti‐eavesdropper strategies, discuss challenges in this field and highlight fruitful new directions for future research. Ultimately, this review offers a conceptual framework to understand the diverse strategies used by signallers to communicate under the pressure imposed by their eavesdropping enemies.

Assessing patterns of eavesdropper risk on sexual signals and the use of meta-analysis in behavioural ecology: a comment on: ‘The exploitation of sexual signals by predators: a meta-analysis' White et al . (2022)

“…[ 1 ] cover a wide range of literature, drawing on eavesdropping studies that span much of the animal world, to examine how eavesdropping predators impose selection pressure on sexual signallers. This is an interesting phenomenon that has received previous attention but has not been investigated using a quantitative approach [ 2 – 4 ]. We applaud their extensive investigation into this fascinating literature.…”

“…The generalized predictions presented in White et al . 's study may be misleading, as the magnitude of eavesdropping risk is context-dependent and influenced by various factors including signalling environments, the eavesdropper's sensory system and prey signalling strategies (reviewed in [ 4 ]). For instance, one prediction in this review is that visual signals incur low eavesdropper risk, as they propagate in the short/medium range.…”

“…The argument for the lack of evidence of signal saliency driving eavesdropper risk may also be problematic given the vague use of the terms ‘conspicuousness' and ‘saliency’ in the literature [ 4 ]. Conspicuousness and saliency are used as broad concepts that involve differences in signal detectability, localizability or preference by a receiver tapping into a variety of perceptual and cognitive processes that result in increased attractiveness.…”

To call or not to call: Persistence of flexible alternative reproductive tactics in a tree cricket

“…If signalling males attract predators, females are expected to avoid such males due to the predation risk associated with them and may also be less choosy (Sih, 1994). While some studies have focused on change in expression of ARTs when exposed to predators (reviewed in Bernal & Page, 2022), the relationship between expression of ARTs and their corresponding fitness effects under varying predation risk has received little attention.…”

An Invited Reply to: A Comment on: The exploitation of sexual signals by predators: a meta-analysis (2022) White et al.

“…For a deeper discussion, we too refer readers to Bernal et al . 's [ 9 ] excellent recent review on the topic.…”