Variation In Dominant Frequency Research Articles

Interpopulational Variation in Vocalizations of Bufo woodhousii

Variation in dominant frequency, pulse rate, and duration of advertisement and release calls was investigated in populations of Bufo woodhousii australis and B. w. woodhousii. Temperature had a significant influence on all three advertisement call variables in both populations. The positive relationship between pulse rate and temperature was similar in both populations, as was the negative relationship between call duration and temperature. Although temperature-adjusted call durations were equal, adjusted pulse rates were slightly but significantly different between the two populations. When adjusted for body temperature, dominant frequency was the only call variable significantly (negatively) correlated with snout-vent length in either population. The two populations differed in adjusted dominant frequency but not in the negative relationship between frequency and snout-vent length. Analysis of temperature related variation in release calls was not possible, and the two populations differed signifi- cantly only in mean pulse rate. It is suggested that sympatric congeners may have influenced divergence in advertisement call frequency among subspecies of B. woodhousii.

Fighting, assessment, and frequency alteration in Blanchard's cricket frog

This study examines the use of dominant frequency for assessment of fighting ability in Blanchard's cricket frog Acris crepitans blanchardi. Like most anurans, the dominant frequency of the call is negatively correlated with size. However, unlike many anurans, dominant frequency varies within individual males, providing a less reliable signal of size. Wrestling contests between male cricket frogs were differentially won by larger males. I thus tested the hypothesis that males use dominant frequency for assessment of an opponent's fighting ability. Males retreated from, or became satellites of, broadcasts of synthetic low frequency calls, simulating the calls of a large male. In contrast, males attacked broadcasts of synthetic high frequency calls, simulating the calls of a small male. The dominant frequency of the call therefore appears to contain information about size which males use to assess the fighting ability of opponents, despite the lower degree of reliability resulting from individual variation in the signal. Individual variation in dominant frequency arises partially as a consequence of active alteration of the signal in response to social competition. Males differentially lowered their dominant frequencies in response to lower frequency broadcasts, thus in response to larger opponents. Furthermore, the higher a male's dominant frequency relative to that of an opponent, the greater was the decrease in dominant frequency. These results suggest that smaller males may conditionally lower their dominant frequencies in order to sound larger to larger opponents, thereby inflating their apparent fighting ability. Two alternative hypotheses are discussed.

Variations in Vocalizations Produced by the Giant South American Toad, Bufo blombergi

The vocalizations of two male Bufo blombergi Myers and Funkhouser, which were recorded in the laboratory, show greater diversity than the mating calls of any of the species of Bufo which have been previously recorded. The calls of B. blombergi were of three distinct types: untrilled; slow-trilled; and fast-trilled. The two trilled types show no ove'lap in trill rates, with the mean of the fast-trill type being rnore than three times faster than the mean of the slow-trilled type. Slow-trilled calls show considerable variation in dominant frequency, duration and the proportion trilled, whereas untrilled and fast-trilled types exhibit less variation. Various combination and intermediate calls were also produced by the two animals. The behavioral significance of the different call types is not understood.