Signal recognition by frogs in the presence of temporally fluctuating chorus-shaped noise

The Journal of the Acoustical Society of America

Forester

2012

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An important aspect of hearing and acoustic communication is the ability to discriminate differences in sound level. Little is known about level discrimination in anuran amphibians (frogs and toads), for which vocal communication in noisy social environments is often critical for reproduction. This study used two-choice phonotaxis tests to investigate the ability of females of Cope's gray treefrog (Hyla chrysoscelis) to discriminate between two advertisement calls differing only in sound pressure level by 2, 4, or 6 dB. Tests were conducted in the presence and absence of chorusshaped noise (73 dB) and using two different ranges of signal levels (73-79 dB and 79-85 dB). Females discriminated between two signals differing by as little as 2-4 dB. In contrast to expectations based on the "near miss to Weber's law" in birds and mammals, level discrimination was slightly better at the lower range of signal amplitudes, a finding consistent with earlier studies of frogs and insects. Realistic levels of background noise simulating a breeding chorus had no discernable effect on discrimination at the sound level differences tested in this study. These results have important implications for studies of auditory masking and signaling behavior in the contexts of anuran hearing and sound communication.

Section: B Implications For Studies Of Auditory Maskingcontrasting

confidence: 52%

Sound level discrimination by gray treefrogs in the presence and absence of chorus-shaped noise

Bee

The Journal of the Acoustical Society of America

Forester

2012

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“…The first method was based on response proportions. Using the same general methods and response criterion as in the present study, Vélez and Bee (Vélez and Bee, 2010) estimated a 'false alarm' rate of 20%; i.e. about 2 in 10 females released at the center of our test arena in the absence of any broadcast sound are expected to exhibit behaviors that our criterion would consider to be a response.…”

Section: C Kuczynski and Othersmentioning

confidence: 99%

Sound transmission and the recognition of temporally degraded sexual advertisement signals in Cope's gray treefrog (Hyla chrysoscelis)

Kuczynski

Journal of Experimental Biology

Schwartz

et al. 2010

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SUMMARYAcoustic communication signals degrade as they propagate between signalers and receivers. While we generally understand the degrading effects of sound propagation on the structure of acoustic signals, we know considerably less about how receivers make behavioral decisions based on the perception of degraded signals in sonically and structurally complex habitats where communication occurs. In this study of acoustic mate recognition in Cope's gray treefrog, Hyla chrysoscelis (Cope 1880), we investigated how the temporal structure of male advertisement calls was compromised by propagation in a natural habitat and how females responded to stimuli mimicking various levels of temporal degradation. In a sound transmission experiment, we quantified changes in the pulsed structure of signals by broadcasting synthetic calls during active choruses from positions where we typically encountered signalers, and re-recording the signals from positions where we typically encountered potential receivers. Our main finding was that the silent gaps between pulses become increasingly 'filled in' by background noise and reverberations as a function of increasing propagation distance. We also conducted female phonotaxis experiments to determine the threshold modulation depth required to elicit recognition of the pulsatile structure of the call. Females were surprisingly tolerant of degraded temporal structure, and there was a tendency for greater permissiveness at lower playback levels. We discuss these results in terms of presumed mechanisms of call recognition in complex environments and the acoustic adaptation hypothesis.

“…The slow rate of fluctuation appears to correspond to the call rates and call timing interactions of males in the chorus. The faster rate corresponds to the pulse rate of the advertisement call (V elez and Bee, 2010). Evidence from studies that have measured masked signal-recognition thresholds (Bee and Schwartz, 2009) indicates that thresholds for responding to conspecific calls are significantly lower in temporally modulated, chorus-shaped noise than in unmodulated noise (V elez andBee, 2011, 2013;Schwartz et al, 2013).…”

Section: B Dip Listening In Modulated Noisementioning

confidence: 95%

“…1(a)] that had a long-term frequency spectrum modeled after that of gray treefrog choruses recorded between May and July of 2007, 2008, 2009, and 2010 (additional details of recording protocols can be found in V elez and Bee, 2010Bee, , 2011. Our noises were based on average spectra determined from 90-s digital recordings (44 100 Hz sampling rate, 16-bit resolution) of between 3 and 14 different choruses.…”

Section: Unmodulated Sam and Cam Noisesmentioning

confidence: 99%

See 1 more Smart Citation

Pulse-number discrimination by Cope's gray treefrog (Hyla chrysoscelis) in modulated and unmodulated noise

The Journal of the Acoustical Society of America

Linehan-Skillings

et al. 2013

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In Cope's gray treefrog (Hyla chrysoscelis), thresholds for recognizing conspecific calls are lower in temporally modulated noise backgrounds compared with unmodulated noise. The effect of modulated noise on discrimination among different conspecific calls is unknown. In quiet, females prefer calls with relatively more pulses. This study tested the hypotheses that noise impairs selectivity for longer calls and that processes akin to dip listening in modulated noise can ameliorate this impairment. In two-stimulus choice tests, female subjects were allowed to choose between an average-length call and a shorter or longer alternative. Tests were replicated at two signal levels in quiet and in the presence of chorus-shaped noise that was unmodulated, modulated by a sinusoid, or modulated by envelopes resembling natural choruses. When subjects showed a preference, it was always for the relatively longer call. Noise reduced preferences for longer calls, but the magnitude of this reduction was unrelated to whether the noise envelope was modulated or unmodulated. Together, the results are inconsistent with the hypothesis that dip listening improves a female gray treefrog's ability to select longer calls in modulated compared with unmodulated noise.