A FUNCTIONAL ANALYSIS OF THE MATING CALLS OF THE NEOTROPICAL FROG GENERA OF THE LEPTODACTYLUS COMPLEX (AMPHIBIA, LEPTODACTYLIDAE)

Ian R. Straughan and W. Ronald Heyer

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Abstract: Functional characteristics or design features of mating calls for 19 species in the complex are given and analysed for patterns of relationship and convergences due to functional constraints. Two basic ' mating

call patterns can be defined. The first, a quiet, incessant popping produced by exploding a burst of air through the glottis usually with little amplification by secondary structures, is characteristic of riparian species that call resident females over short distances. The second call consists of a single tone burst (note) produced by passing a pulsed stream, of air through the glottis. Often a change in tension of laryngeal musculature produces frequency modulation through the note. In the latter call, resonance in the vocal sacs provides finer frequency tuning and better radiation of the call for attracting females over much longer distances. Patterns of structural similarities in calls are consistent with relationships based on morphology in some instances and apparently contradict morphological evidence in others, indicating that convergence in mating call characters may occur.

Call Trait Variation in Morelett's Tree Frog, Agalychnis moreletii, of Belize

Venetia S. Briggs

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Abstract: Calling behavior and the properties of a male’s call directly affect mate choice and mating success in frogs. In this study, I investigated the difference in call properties within and among males of Agalychnis moreletii at a breeding population in Belize. As a first step toward understanding female preference for specific male advertisement calls, I examined the variation of call traits from 575 calls of 30 individuals. I described and quantified call properties both within and among males and examined the relationship between mating success and body size. All of the call traits that I examined exhibited significantly higher among-male variation than within-male variation. Static call properties such as dominant frequency and call amplitude had the lowest variation within and among males. Dominant frequency was negatively correlated with body size, supporting a body-size constraint for this call trait. Call properties such as call rates, mean pulses per call, and call durations displayed greater variability among males. Such variability in these dynamic call traits suggests energy constraints because calling longer and calling more frequently are energetically costly. As a result, dynamic properties may be indicators of male quality and play a greater role in mate choice. Indeed, males found in amplexus produced a greater number of calls and those calls were of longer durations and tended to have a shorter intercall interval. Here, I characterize call trait variation and document call properties as indicators of  mating success in the process of sexual selection in anuran communication.

Patterns of advertisement call evolution in toads and chorus frogs

Reginald B. Cocroft and Michael J. Ryan

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Abstract: Patterns of evolution in the acoustic signals of two groups of anuran amphibians were examined. Call character matrices for clades ofBufo(Bufonidae) andPseudacris(Hylidae) were derived from analysis of tape-recorded calls, and these call characters were mapped onto phylogenetic trees based on morphological and biochemical data. It was found that the characters that make up a call evolve at different rates. In hylids, characters allied with the morphological aspects of sound production were more conservative than those based on the physiological or behavioural aspects of calling, while in bufonids divergence rates of these character types did not differ. Observed patterns of character change within sets of close relatives suggest a focus for process-oriented research by identifying the origin and direction of important changes in calling behaviour.