Acoustic interactions among male gray treefrogs, Hyla versicolor , in a chorus setting

Abstract

We assembled groups of up to eight male gray treefrogs, Hyla versicolor, in an artificial pond and examined vocal behavior under conditions of different chorus size. Males avoided call overlap when calling in groups of two, but not in larger choruses. The pattern of interference failed to reveal selective attention based on intermale separation, and males in close spatial proximity tended to overlap calls more than more widely separated individuals did. Males were sensitive to the removal of males from or the addition of males to an aggregation, often responding to a change of just one individual with shifts in call duration and rate. Nevertheless, males tended to maintain their relative position in a hierarchy based on call duration following changes in chorus size. We hypothesize that adjustments in gross temporal properties are a response to the increased probability of call interference in larger choruses. Finally, we calculated repeatabilities of call duration, calling rate, and pulse effort within nights using sliding-analysis windows of 30 s to 29.5 min. The change in repeatabilities with window duration suggests that a female could best distinguish among males by assessing their performance for between 4 and 14 min, depending on the measure of calling behavior. However, because the magnitude of change was relatively small, our data do not lend strong support to the hypothesis that there is an optimum time period over which females should assess the calling of males in order to maximize their ability to discriminate among males.

Advertisement-call modification, male competition, and female preference in the bird-voiced treefrog Hyla avivoca

“…The response of female H. avivoca to orient towards longer calls suggest an open-ended preference within the biological maxima of the calling behavior observed in the populations studied, a preference pattern that is typical for dynamic call properties (Gerhardt and Huber, 2002). As stated above, the production of longer calls in chorusing situations should benefit the male by increasing his detectability to females in noisy choruses (Schwartz et al, 2002; but see Passmore and Telford, 1981). However, females preferred long to short calls in the relatively quiet testing situations we used for our playback experiments.…”

“…Direct effects, which are the focus of this study, are alterations occurring during vocal interactions that increase the attractiveness of the signal to females (e.g. Klump and Gerhardt, 1987;Gerhardt, et al, 1996;Hill, 1998;Schwartz et al, 2002).…”

“…We focused on modifications in advertisement calls such as changes in call duration and call rate, and the patterns of call overlap and alternation that arise in the presence of neighbors (e.g., Wells and Taigen, 1986;Schwartz et al, 2002). We then tested how such changes are likely to affect a male's chances of attracting a female.…”

Keeping up appearances: male fiddler crabs wave faster in a crowd

“…Several studies in acoustic signalling systems have shown that males alter call rate, duration and/or complexity in response to the presence and/or calling of other males [4][5][6][7][8][9][10]. Surprisingly, few studies have, however, examined how competing sexual signals influence male behaviour in a visual signalling context [11][12][13].…”

“…For instance, on detecting another male's courtship signal, competing males may alter specific properties of their own signals, such as the rate of production, so as to increase their relative attractiveness and thereby their chance of obtaining a mate [4]. For example, in the grey treefrog (Hyla versicolor), males increased their call rate with an increase in chorus size [5].…”