Ambient noise causes independent changes in distinct spectro-temporal features of echolocation calls in horseshoe bats

Hage, Steffen R.; Jiang, Tinglei; Berquist, Sean; Jiang, Feng; Metzner, Walter

doi:10.1242/jeb.102855

Cited by 14 publications

(11 citation statements)

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“…Previous research has demonstrated that spectral shifts in human speech are dependent on the spectral content of the noise [ 6 ]. However, recent data from noise exposure experiments with avian and mammalian taxa show that some vertebrate species are capable of immediate and independent changes to the amplitude and spectral characteristics of vocalizations during increased noise [ 16 – 18 ], suggesting that spectral modifications may serve a communicative function during increased noise. This view accords with the recent suggestion that multiple levels of vocal control may be active during Lombard vocalizations.…”

Section: Introductionmentioning

confidence: 99%

Noise-Induced Frequency Modifications of Tamarin Vocalizations: Implications for Noise Compensation in Nonhuman Primates

2015

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Previous research suggests that nonhuman primates have limited flexibility in the frequency content of their vocalizations, particularly when compared to human speech. Consistent with this notion, several nonhuman primate species have demonstrated noise-induced changes in call amplitude and duration, with no evidence of changes to spectral content. This experiment used broad- and narrow-band noise playbacks to investigate the vocal control of two call types produced by cotton-top tamarins (Saguinus Oedipus). In ‘combination long calls’ (CLCs), peak fundamental frequency and the distribution of energy between low and high frequency harmonics (spectral tilt) changed in response to increased noise amplitude and bandwidth. In chirps, peak and maximum components of the fundamental frequency increased with increasing noise level, with no changes to spectral tilt. Other modifications included the Lombard effect and increases in chirp duration. These results provide the first evidence for noise-induced frequency changes in nonhuman primate vocalizations and suggest that future investigations of vocal plasticity in primates should include spectral parameters.

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Section: Introductionmentioning

confidence: 99%

Noise-Induced Frequency Modifications of Tamarin Vocalizations: Implications for Noise Compensation in Nonhuman Primates

2015

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“…The FM component in horseshoe bat echolocation pulses functions in determining target distance [ 42 , 64 , 65 ]. The spectral and temporal features of the FM component have been shown to vary depending on a number of external factors, including the level of ambient noise [ 66 ] as well as the presence of other bats, both con- and heterospecifics [ 67 ]. The spectral features of the CF component are restricted by the acoustic fovea, limiting their ability to be adjusted to facilitate communication (but see [ 63 , 67 , 68 ]).…”

Section: Discussionmentioning

confidence: 99%

It’s not all about the Soprano: Rhinolophid bats use multiple acoustic components in echolocation pulses to discriminate between conspecifics and heterospecifics

2018

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Acoustic communication plays a pivotal role in conspecific recognition in numerous animal taxa. Vocalizations must therefore have discrete acoustic signatures to facilitate intra-specific communication and to avoid misidentification. Here we investigate the potential role of echolocation in communication in horseshoe bats. Although it has been demonstrated that echolocation can be used to discriminate among con- and hetero-specifics, the specific acoustic cues used in discrimination are still relatively unknown. Furthermore, the Acoustic Communication Hypothesis proposes that in multispecies assemblages, in which echolocation frequencies are likely to overlap, bats partition acoustic space along several dimensions so that each species occupies a discrete communication domain. Thus, multiple echolocation variables may be used in discrimination. The objective of this study was to investigate the potential of various echolocation variables to function as discriminatory cues in echolocation-based species discrimination. Using habituation–dishabituation playback experiments, we firstly tested the ability of Rhinolophus clivosus to discriminate between echolocation pulses of heterospecifics with either discrete or overlapping frequencies. Secondly, to determine whether R. clivosus could use echolocation variables other than frequency, we investigated its ability to discriminate among echolocation pulses differing in only one manipulated parameter. These test variables were identified by their contribution to the dissimilarity among pulses. Our results suggest that R. clivosus could discriminate readily between species using echolocation pulses with discrete frequencies. When frequencies overlapped, the ability of bats to discriminate was dependant on additional acoustic variables that defined the acoustic space occupied by the test signal. These additional acoustic variables included, but may not be restricted to, sweep rate of the FM and duty cycle. Thus, when echolocation pulses share a similar acoustic domain, bats use several cues to reliably discriminate among heterospecifics.

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“…Independent adjustments of signal amplitude and spectral parameters have also been documented in a horseshoe bat species (Hage et al, 2013(Hage et al, , 2014. Independent control of different signal parameters might be a crucial feature for echolocating bats, which deal with moving prey and/or acoustically challenging environments in the dark.…”

Section: Biomechanical Link Underlying Signal Plasticitymentioning

confidence: 96%

Biomechanical control of vocal plasticity in an echolocating bat

Luo

Wiegrebe

2016

Journal of Experimental Biology

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Many animal species adjust the spectral composition of their acoustic signals to variable environments. However, the physiological foundation of such spectral plasticity is often unclear. The sourcefilter theory of sound production, initially established for human speech, applies to vocalizations in birds and mammals. According to this theory, adjusting the spectral structure of vocalizations could be achieved by modifying either the laryngeal/syringeal source signal or the vocal tract, which filters the source signal. Here, we show that in pale spear-nosed bats, spectral plasticity induced by moderate level background noise is dominated by the vocal tract rather than the laryngeal source signal. Specifically, we found that with increasing background noise levels, bats consistently decreased the spectral centroid of their echolocation calls up to 3.2 kHz, together with other spectral parameters. In contrast, noise-induced changes in fundamental frequency were small (maximally 0.1 kHz) and were inconsistent across individuals. Changes in spectral centroid did not correlate with changes in fundamental frequency, whereas they correlated negatively with changes in call amplitude. Furthermore, while bats consistently increased call amplitude with increasing noise levels (the Lombard effect), increases in call amplitude typically did not lead to increases in fundamental frequency. In summary, our results suggest that at least to a certain degree echolocating bats are capable of adjusting call amplitude, fundamental frequency and spectral parameters independently.

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Ambient noise causes independent changes in distinct spectro-temporal features of echolocation calls in horseshoe bats

Cited by 14 publications

References 11 publications

Noise-Induced Frequency Modifications of Tamarin Vocalizations: Implications for Noise Compensation in Nonhuman Primates

Noise-Induced Frequency Modifications of Tamarin Vocalizations: Implications for Noise Compensation in Nonhuman Primates

It’s not all about the Soprano: Rhinolophid bats use multiple acoustic components in echolocation pulses to discriminate between conspecifics and heterospecifics

Biomechanical control of vocal plasticity in an echolocating bat

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