Eavesdropping avoidance and sound propagation: the acoustic structure of soft song

Vargas-Castro, Luis E.; Sandoval, Luis; Searcy, William A.

doi:10.1016/j.anbehav.2017.10.008

Cited by 20 publications

(18 citation statements)

References 51 publications

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“…In this study, more males intruded on territories when soft songs were sung compared to when songs were broadcast, which contradicts the eavesdropping hypothesis. Males may lower song amplitude to avoid eavesdropping by conspecific females (Dabelsteen, ; Vargas‐Castro, Sandoval, & Searcy, ); to date, no experimental studies have investigated the role of females in the evolution of soft songs.…”

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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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%

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

et al. 2018

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“…We compared the signal degradation and attenuation of calls in the transmission experiments using general linear mixed models (LMM), for each response variable (signal-to-noise ratio, excess attenuation, tail-to-signal ratio, and blur ratio), following the approach used in similar experiments Graham et al, 2017;Nemeth et al, 2006;Sabatini et al, 2011;Sandoval, Dabelsteen et al, 2015;Vargas-Castro et al, 2017). The GLMM included the distance (four levels), speaker position (three levels), and the interaction of these predictor variables as fixed factors.…”

Section: Discussionmentioning

confidence: 99%

“…Hence, sound transmission experiments allow better-controlled hypotheses testing. Furthermore, sound transmission experiments have been widely used to test the transmission properties of several animal sounds (e.g., frogs, birds, and mammals) in different habitats (Boncoraglio & Saino, 2007;Ey & Fischer, 2009;Gerhardt, 1994;Graham et al, 2017;Nemeth et al, 2001;Velásquez et al, 2018), or to compare different call types (Piza & Sandoval, 2016;Sabatini et al, 2011) and song types (Penna & Solís, 1998;Sandoval, Dabelsteen et al, 2015;Vargas-Castro et al, 2017), providing evidence on how sound reverberation improves sound transmission (Nemeth et al, 2006;Slabbekoorn & Smith, 2002), with different vegetations types (Graham et al, 2017;Velásquez et al, 2018), or at different heights Nemeth et al, 2001).…”

Section: Me Thodsmentioning

confidence: 99%

Male orientation on vocalization perches could optimize acoustic signal transmission in anurans

et al. 2020

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Acoustic signals are distorted by vegetation, wind currents, or other sounds when transmitted through the environment. Consequently, vocalizations with features that optimize sound transmission or behaviors that improve the efficacy of communication have evolved in many animal species. Among behavioral strategies, some species call from perches above the ground to increase the propagation distance of their acoustic signals. However, the orientation in the perch also influences the transmission of the vocalizations, so that frogs calling from different orientations (i.e., horizontal, upward, or downward) may affect differently the quality and efficacy of sound transmission. We implemented a sound transmission experiment to test for the effect of calling orientation (upward, downward, and horizontal) and distance on the attenuation and degradation of advertisement calls in the common dink frog Diasporus diastema. We broadcasted and re‐recorded advertisement calls at 2 m height, setting the speaker in three directions (upward, downward, and horizontal) to simulate different signaler orientations. We found that attenuation of the advertisement calls is significantly reduced when the speaker was directed either upward or downward, rather than horizontally. However, the degradation of call is lower when the speaker is direct horizontally. Since calls produced from either upward or downward orientations could travel farther, they could be used to signal male spatial location, while calls produced from a horizontal position could provide information on male quality at shorter distances at advanced phases of courtship.

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“…Low-amplitude vocalizations have been associated with aggressive motivation in a number of bird species, mostly songbirds (Dabelsteen, et al, 1998;Ballentine, et al, 2008) but also in other taxa (Ręk & Osiejuk, 2011;Reichard & Welklin, 2015); for a recent review see (Akçay, et al, 2015). There are several hypotheses that explain "soft calling" as adaptive behaviour (Dabelsteen, et al, 1998;Akçay, et al, 2015;Vargas-Castro, et al, 2017). However, in some situations, loud vocalizations might be difficult to produce because of physical or physiological constraints.…”

Section: Issues and Open Questionsmentioning

confidence: 99%

Pervasive low-frequency vocal modulation during territorial contests in Eurasian Scops Owls (Otus scops)

Grieco¹

2020

Preprint

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In several animal species, including birds, individuals are known to produce low-frequency vocalizations during aggressive interactions with conspecifics. In this study, I investigated territorial interactions between male Eurasian Scops Owls that occupy territories in a densely-packed area. The single-note hoot of the Scops Owl is generally assumed to be highly repeatable, however extensive recording of male-male interactions identified previously unrecognized variation in the hoots’ structure. Male Scops Owls gave hoots at a frequency lower than usual when engaging in short-distance contests with neighbouring males. Within-subject analysis revealed that the caller’s average hoot frequency was positively correlated with the distance from its rival. During contests, males gradually reduced their hoot frequency as they approached one another, perhaps reflecting changes in the degree of escalation. Male Scops Owls reduced their hoot frequency immediately after the rival initiated countersinging, and returned to their usual frequency range at the end of the contest. These findings demonstrate that vocal modulation is pervasive in social contexts in the Scops Owl, and suggests that individuals have full voluntary control of the structure of their vocalizations. This study confirms in part the findings of other authors’ experimental work, where male owls adjusted their vocal frequency when challenged by an opponent. However, that study suggested that vocal frequency would encode information about the caller’s body weight. In contrast, the present study revealed context-dependent fluctuations in hoot frequency, which may suggest that the hoot of the Scops Owl dynamically reflects the current motivational state of the caller during the contest.

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Eavesdropping avoidance and sound propagation: the acoustic structure of soft song

Cited by 20 publications

References 51 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

Male orientation on vocalization perches could optimize acoustic signal transmission in anurans

Pervasive low-frequency vocal modulation during territorial contests in Eurasian Scops Owls (Otus scops)

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