Eavesdropping and cue denial in avian acoustic signals

Searcy, William A.; Yasukawa, Ken

doi:10.1016/j.anbehav.2016.07.018

Cited by 17 publications

(6 citation statements)

References 135 publications

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“…Why do so many different species lower the amplitude of their songs during aggressive territorial interactions? One compelling explanation is the eavesdropping avoidance hypothesis (Dabelsteen et al, ), which proposes that individuals sing softly to avoid social eavesdropping by conspecific males or females, or interceptive eavesdropping by predators (McGregor, ; Searcy & Yasukawa, ). Eavesdroppers can impose high costs on signallers, in the case of both social eavesdropping (Mennill, Boag, & Ratcliffe, ) and interceptive eavesdropping (Randall & Matocq, ).…”

Section: Discussionmentioning

confidence: 99%

“…Why do so many different species lower the amplitude of their songs during aggressive territorial interactions? One compelling explanation is the eavesdropping avoidance hypothesis (Dabelsteen et al, 1998), which proposes that individuals sing softly to avoid social eavesdropping by conspecific males or females, or interceptive eavesdropping by predators (McGregor, 1993;Searcy & Yasukawa, 2016).…”

Section: Discussionmentioning

confidence: 99%

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Quiet violence: Savannah Sparrows respond to playback‐simulated rivals using low‐amplitude songs as aggressive signals

et al. 2018

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When animals compete over resources such as breeding territories, they often use signals to communicate their aggressive intentions. By studying which signals are associated with aggressive interactions, we gain a deeper appreciation of animal behaviour. We studied aggressive signalling in male Savannah Sparrows, Passerculus sandwichensis, focusing on signals that precede physical attack against territorial intruders. We simulated intruders using song playback and taxidermic models, and we determined which behaviours were associated with physical attack. Previous studies that have used this approach suggest that many species produce songs of dramatically lower amplitude, or “soft songs,” as signals of aggressive intention. Savannah Sparrows, however, are not known to produce soft songs, and therefore, they provided an interesting system for testing signals that predict attack. Of 93 playback subjects, 23 males attacked the simulated intruder and 70 did not. To our surprise, Savannah Sparrows produced soft songs, and the number of soft songs was a significant predictor of attack on the simulated intruder. Birds also showed a nonsignificant tendency to produce more “chip” calls prior to attack on the simulated intruder, whereas three other measured behaviours (aggressive calls, wing waving and passes over the model) did not predict attack. Our study contributes to the growing body of research on aggressive territorial signals and reveals that soft song is an even more widespread signal of aggression in songbirds than previously recognized.

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Section: Discussionmentioning

confidence: 99%

“…Why do so many different species lower the amplitude of their songs during aggressive territorial interactions? One compelling explanation is the eavesdropping avoidance hypothesis (Dabelsteen et al, 1998), which proposes that individuals sing softly to avoid social eavesdropping by conspecific males or females, or interceptive eavesdropping by predators (McGregor, 1993;Searcy & Yasukawa, 2016).…”

Section: Discussionmentioning

confidence: 99%

Quiet violence: Savannah Sparrows respond to playback‐simulated rivals using low‐amplitude songs as aggressive signals

et al. 2018

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“…The latter type of soft songs tend to have the lowest amplitude and contain alternating sequences of low and high frequency elements covering a broader frequency range (1539-9118 Hz for warbled songs, 1762-8081 for crystallized soft songs and 2038-7999 Hz for broadcast songs, see Table 1 of Anderson et al 2008). Although usually assumed that the acoustic structure of soft song is selected for minimizing transmission distance (which would exacerbate the difficulty of their detection under urban noise), the evidence for this is as yet lacking for song sparrows (Akçay, Anderson, Nowicki, Beecher, & Searcy, 2015; Akçay & Beecher, 2012; Searcy & Yasukawa, 2017). In fact, a recent study found that soft songs (both crystallized and warbled) transmitted slightly better than broadcast songs when played at low amplitudes from a speaker and remeasured at different distances (Niederhauser, DuBois, Searcy, Nowicki, & Anderson, 2018).…”

Section: Discussionmentioning

confidence: 99%

Are signals of aggressive intent less honest in urban habitats?

Akçay

Beck

Sewall

2018

Preprint

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18The effect of urban noise on animal communication systems is one of the best examples of how 19 anthropogenic change affects animal social behaviour. It is well documented that urban noise 20 drives shifts in the acoustic properties of signals but the consequences of noise for the reliability 21 of signalsthat is, how well they predict signaler behaviour, is unclear. Here we examine 22 whether reliability of aggressive signaling in song sparrows (Melospiza melodia) differs between 23 urban and rural habitats. Previous research in this species showed that urban males are more 24 aggressive than rural males. We predicted that the main signal of aggressive intent, low-25 amplitude soft songs, would be less effective in urban noise and that urban birds should signal 26 their aggressive intent via loud songs. We found that while acoustic noise was higher in urban 27 habitats, the urban birds still sang more soft songs and rural birds. Furthermore, high rates of soft 28 songs and lack of loud songs predicted attacks in both habitats. Finally, we found evidence for a 29 potential but incomplete multimodal shift due to urban noise. These results indicate that 30 urbanization, despite the well documented effects on signal structure has a limited effect on the 31 reliability of the signals in song sparrows. 32 33

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“…These strategies involve the use of signal features that minimize cues available to eavesdroppers (i.e. cue denial; Searcy & Yasukawa, 2017), reflecting the intersection between responding to selection to avoid exploitation without overly compromising communication efficacy.…”

Section: (B) Reduction In Signal Ratementioning

confidence: 99%

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

Bernal

Page

2022

Biological Reviews

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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.

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Eavesdropping and cue denial in avian acoustic signals

Cited by 17 publications

References 135 publications

Quiet violence: Savannah Sparrows respond to playback‐simulated rivals using low‐amplitude songs as aggressive signals

Quiet violence: Savannah Sparrows respond to playback‐simulated rivals using low‐amplitude songs as aggressive signals

Are signals of aggressive intent less honest in urban habitats?

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

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