The paradox of hearing at the lek: auditory sensitivity increases after breeding in female gray treefrogs (Hyla chrysoscelis)
Both behavioral receptivity and neural sensitivity to acoustic mate attraction signals vary across the reproductive cycle, particularly in seasonally breeding animals. Across a variety of taxa receptivity to signals increases, as does peripheral auditory sensitivity, as females transition from a non-breeding to breeding condition. We recently documented decreases in receptivity to acoustic mate attraction signals and circulating hormone levels, but an increase in peripheral auditory sensitivity to call-like stimuli following oviposition in Cope’s gray treefrogs (Hyla chrysoscelis). However, it is not known if changes in auditory sensitivity are confined to the frequency range of calls, or if they result from more generalized changes in the auditory periphery. Here, we used auditory brainstem responses (ABRs) to evaluate peripheral frequency sensitivity in female Cope’s gray treefrogs before and after oviposition. We found lower ABR thresholds, greater ABR amplitudes, and shorter ABR latencies following oviposition. Changes were most pronounced and consistent at lower frequencies associated with the amphibian papilla, but were also detectable at higher frequencies corresponding to the tuning of the basilar papilla. Furthermore, only ABR latencies were correlated with circulating steroid hormones (testosterone). Changes in peripheral processing may result from changes in metabolic function or sensorineural adaptation to chorus noise.
KeywordsAuditory brainstem response Corticosterone Estradiol Oviposition Testosterone
We thank members of the Bee lab, and Jessie Tanner in particular, for assistance in collecting frogs and John Moriarty and the Three Rivers Park District for after-hours access to frog ponds.
Funding was provided by the Michener Faculty Fellowship at Swarthmore College to ATB, a National Science Foundation grant to MAB (IOS 1452831), and the Vassar College Dean of Faculty office to MDG.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted. Animal collections were made under Special Permit 21947 from the State of Minnesota Department of Natural Resources. This study was approved by the Institutional Animal Care and Use Committee at the University of Minnesota (Protocol 1701-34456A, approved 3 March 2017). This article does not contain any studies with human participants performed by any of the authors.
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