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

Alejandro Vélez, Mark A. Bee

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

The background noise generated in large social aggregations of calling individuals is a potent source of auditory masking for animals that communicate acoustically. Despite similarities with the so-called cocktail party problem in humans, few studies have explicitly investigated how nonhuman animals solve the perceptual task of separating biologically relevant acoustic signals from ambient background noise. Under certain conditions, humans experience a release from auditory masking when speech is presented in speech-like masking noise that fluctuates in amplitude. We tested the hypothesis that females of Cope's gray treefrog (Hyla chrysoscelis) experience masking release in artificial chorus noise that fluctuates in level at modulations rates characteristic of those present in ambient chorus noise. We estimated thresholds for recognizing conspecific advertisement calls (pulse rate = 40-50 pulses/s) in the presence of unmodulated and sinusoidally amplitude-modulated (SAM) chorus-shaped masking noise. We tested two rates of modulation (5 and 45 Hz) because the sounds of frog choruses are modulated at low rates (e. g., less than 5-10 Hz) and because those of species with pulsatile signals are additionally modulated at higher rates typical of the pulse rate of calls (e. g., between 15 and 50 Hz). Recognition thresholds were similar in the unmodulated and 5-Hz SAM conditions and 12 dB higher in the 45-Hz SAM condition. These results did not support the hypothesis that female gray treefrogs experience masking release in temporally fluctuating chorus-shaped noise. We discuss our results in terms of modulation masking and hypothesize that natural amplitude fluctuations in ambient chorus noise may impair mating call perception.

Original languageEnglish (US)
Pages (from-to)1695-1709
Number of pages15
JournalBehavioral Ecology and Sociobiology
Volume64
Issue number10
DOIs
StatePublished - 2010

Bibliographical note

Funding Information:
Acknowledgments We are grateful to J. Berrío, H. Chun, L. Corcoran, D. Heil, J. Henderson, J. Henly, M. Kuczynski, J. Lane, A. Leightner, E. Love, R. Olsen, K. Riemersma, D. Rittenhouse, N. Rogers, K. Speirs, E. Swanson, S. Tekmen, A. Thompson, and J. Walker-Jansen for their assistance in collecting and testing frogs; to S. Humfeld and G. Höbel for recordings of green treefrogs included in Fig. 1; to K. Riemersma and K. Speirs for their extensive help analyzing videos; and to two anonymous reviewers for their helpful feedback on an earlier version of the manuscript. This work was conducted under Special Use Permit #14902 from the Minnesota Department of Natural Resources and with Special Use Permits issued by M. Linck at the Three Rivers Park District and John Moriarty at the Ramsey County Department of Parks and Recreation. This research was approved by the University of Minnesota Institutional Animal Care and Use Committee (#0809A46721) and funded by a Grant-in-Aid of Research from the University of Minnesota Graduate School and NIH R03DC008396 to M. Bee and an EEB Block Grant, a UMN Graduate School Thesis Research Grant, and a Florence Rothman Fellowship to A. Vélez. Preparation of the manuscript was further supported by a fellowship from the McKnight Foundation to M. Bee.

Keywords

  • Auditory masking
  • Cocktail party problem
  • Gray treefrog
  • Hyla chrysoscelis
  • Masking release
  • Modulation masking

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