Impact of the chorus environment on temporal processing of advertisement calls by gray treefrogs

Abstract

Male gray treefrogs advertise for mates using calls that consist of a series of pulses. Pulse duration, interpulse interval, and pulse shape determine whether a call is recognized as a conspecific signal by females. Females use call rate and call pulse number to assess relative calling performance by males, and prefer males that display high calling efforts. However, within choruses call overlap among males and background noise can compromise the ability of females to detect and correctly interpret temporal information in calls. Phonotaxis tests using calls suffering from different patterns of overlap or with internal gaps were used to investigate specific consequences of interference and masking as well as mechanisms that might alleviate such problems. Our data indicate that females do not employ a process analogous to phonemic restoration to ‘‘fill in’’ missing call segments; however, if a sufficient percent of call elements fall within species-specific ranges, females may ignore call anomalies. Additional findings are generally consistent with those from a recent study on anuran auditory midbrain neurons that count and indicate that inappropriate pulse intervals can reset the pulse counting process. [Work supported by NSF and a Pace University Eugene M. Lang Research Fellowship.]

Sound Processing in Real-World Environments

“…Because of this, there is a need to determine whether frogs perceive calls of individual males in a chorus as separate auditory streams, or whether the complete scene contributes to a single stream. Preliminary studies from Schwartz et al (2004) indicate that frogs lack the ability to "restore" signal, that is, to fill in signal elements that are missing or inaudible due to the presence of masking noise (see Section 5.2 of Wells and Schwartz, Chapter 3). If their result is validated, the frog's perceptual ability would be in line with that of insects.…”