THE VOCAL BEHAVIOUR OF MALE EUROPEAN TREEFROGS (HYLA ARBOREA): IMPLICATIONS FOR INTER- AND INTRASEXUAL SELECTION

Abstract

[Calls and calling behaviour were studied over two years in a population of individually marked European treefrogs ( Hyla arborea ), a hylid frog with a prolonged breeding season and a lek mating system. A mean daily air temperature of 4.5°C and a nightly water temperature of 9°C were found to represent lower thresholds for nightly calling activity. Large choruses started calling earlier and showed a longer nightly duration of calling activity than small choruses. Temporal properties of advertisement calls were determined mainly by water temperature, which explained up to 88% of the observed variation. Dominant frequency was determined mainly by male body weight, which explained 20% of the observed variance. Within-bout call rate, call duration, pulse period, number of pulses per call and dominant frequency showed little within-male variability, but overall call activity and the number of calls per call bout varied considerably between different recordings of the same individual males. Statistically significant differences between different males were found for withinbout call rate, call duration, number of calls per call bout, number of pulses per call, and dominant frequency. Observed patterns of variability in call properties are discussed in the context of possible implications for female mate choice and male-male recognition., Calls and calling behaviour were studied over two years in a population of individually marked European treefrogs ( Hyla arborea ), a hylid frog with a prolonged breeding season and a lek mating system. A mean daily air temperature of 4.5°C and a nightly water temperature of 9°C were found to represent lower thresholds for nightly calling activity. Large choruses started calling earlier and showed a longer nightly duration of calling activity than small choruses. Temporal properties of advertisement calls were determined mainly by water temperature, which explained up to 88% of the observed variation. Dominant frequency was determined mainly by male body weight, which explained 20% of the observed variance. Within-bout call rate, call duration, pulse period, number of pulses per call and dominant frequency showed little within-male variability, but overall call activity and the number of calls per call bout varied considerably between different recordings of the same individual males. Statistically significant differences between different males were found for withinbout call rate, call duration, number of calls per call bout, number of pulses per call, and dominant frequency. Observed patterns of variability in call properties are discussed in the context of possible implications for female mate choice and male-male recognition.]