A precedence effect underlies preferences for calls with leading pulses in the grey treefrog, Hyla versicolor

The temporal relationship between signals often has strong and repeatable influences on receiver behaviour. While several studies have shown that receivers prefer temporally leading signals, we show that the relative timing of signal elements within overlapping signals can also have repeatable influences on receiver responses. Female grey treefrogs, Hyla versicolor, preferred overlapping conspecific advertisement call alternatives in which pulses were in the leading position relative to pulses in an alternative. The preference was maintained even when the first pulse of the stimulus with leading pulses began after that of the call with following pulses. To rule out the possibility of masking interference of the pulse pattern, we used a split-pulse design in which the playback of two nonoverlapping pulse elements were synchronized from spatially separated speakers. Females were attracted to the source of the short (6 ms) leading pulse element, which did not attract females in isolation, even though its amplitude was 24 dB lower than the long (24 ms) following element, which did attract females in isolation. Taken together, our results fall within a range of phenomena that have been classified as precedence effects. However, to our knowledge, showing localization based on successive leading pulses rather than the very first-arriving pulse is a novel discovery for nonhuman animals. (C) 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.