The relationship between environmental conditions and activity of the giant barred frog (Mixophyes iteratus) on the Coomera River, south-east Queensland

Abstract

Determining the population density of ectotherms is often confounded by individual activity levels, which are highly dependent on ambient climatic conditions. In this study we used radio-telemetry and streamside surveys to examine the influence of local climatic conditions on individual activity levels (detectability) and streamside density of a population of endangered giant barred frog (Mixophyes iteratus) along the Coomera river in south-east Queensland. Temperature was the most important climatic variable influencing the behaviour and hence detectability of M. iteratus. The results indicated that males bury under the leaf litter during cold conditions (<18°C) so fewer were detected during surveys. Although females were also found to bury under the leaf litter in cold weather, no significant relationship between exposure and streamside density was detected. This is likely to be due to the lower number of females detected during surveys. The streamside density of juveniles was significantly related to temperature and rainfall, but little of the variance in the data was explained by climatic conditions, despite greater numbers of juveniles being found than adults. These results indicate that, for increased efficiency, surveys of Mixophyes iteratus should be undertaken when temperatures exceed 18°C.