Dip listening and the cocktail party problem in grey treefrogs: signal recognition in temporally fluctuating noise

Dip listening refers to our ability to catch brief ‘acoustic glimpses’ of speech and other sounds when fluctuating background noise levels momentarily decrease. Exploiting dips in natural fluctuations of noise contributes to our ability to overcome the ‘cocktail party problem’ of understanding speech in multitalker social environments. We presently know little about how nonhuman animals solve analogous communication problems. Here, we asked whether female grey treefrogs, Hyla chrysoscelis, might benefit from dip listening in selecting a mate in the noisy social setting of a breeding chorus. Consistent with a dip-listening hypothesis, subjects recognized conspecific calls at lower thresholds when the dips in a chorus-like noise masker were long enough to allow glimpses of nine or more consecutive pulses. No benefits of dip listening were observed when dips were shorter and included five or fewer pulses. Recognition thresholds were higher when the noise fluctuated at a rate similar to the pulse rate of the call. In a second experiment, advertisement calls comprising six to nine pulses were necessary to elicit responses under quiet conditions. Together, these results suggest that in frogs, the benefits of dip listening are constrained by neural mechanisms underlying temporal pattern recognition. These constraints have important implications for the evolution of male signalling strategies in noisy social environments.

► Dip listening describes our ability to catch ‘glimpses’ of target signals when background noise dips to low levels. ► We asked whether female grey treefrogs benefit from dip listening to recognize mating calls in the presence of noise. ► Compared to nonfluctuating noise, signal recognition thresholds were lower in slowly fluctuating noise. ► Dip listening occurred when nine or more consecutive pulses of the mating call fell in dips of fluctuating noise. ► In quiet conditions, mating calls of at least nine pulses were necessary for call recognition.