The influence of micrometeorological factors on the calling activity of the frog Crinia signifera (Anura: Myobatrachidae)

Abstract

I recorded the calling activity of the males of a population of the common eastern froglet Crinia signifera during 1988 to determine the seasonal and temporal patterns of calling activity and the influence of micrometeorological variables on calling. The patterns of calling were recorded using an automated cassette recorder switched on for 10 seconds approximately every 15 minutes. To assess the effects of micrometeorology on calling I compared the mean hourly calling activity with air temperature, barometric pressure, humidity, rainfall and wind intensity with time of day as a co-variable. This comparison was undertaken for data from three separate two-month periods of the year, as well as with the data from the three periods combined, to determine if there were seasonal differences in the effects of micrometeorology. For the analysis I used a forward stepwise Generalised Linear Model. Chorusing was recorded in every month of the year. Time of day was highly significant as a predictor of hourly calling activity in all of the tested periods, with calling being strongly associated with the hours of darkness. Rainfall over the preceding three days statistically explained a significant proportion of variation in hourly calling when the data from the three periods was combined, but only weakly so. Daily rainfall was the only (weakly) significant predictor within a period and only in January-February. The micrometeorological factor influencing calling activity in this study differs from these reported for other species. This may be because this population of C. signifera lives in a relatively benign, temperate environment where all seasons have at least moderate levels of rainfall.