Graeme Watson

Within-male variability in call properties and female preference in the grey treefrog

In nearly all female choice experiments with anurans, the values of acoustic properties of experimental stimuli have been fixed. In nature, however, a female usually experiences an array of calls in which acoustic properties, especially dynamic ones, differ between males in variability as well as in mean values. High variability per se does not make a synthetic call more or less attractive to female grey treefrogs, Hyla versicolor, than a non-variable or low-variability call with about the same mean values of pulse number per call, call period, or both. Females did prefer a low-variability alternative with a slightly higher number of sound pulses per unit time than the variable stimulus, suggesting that females can resolve small differences in mean values between the calls of different males despite considerable within-male variability.

Observations on temporary waters in northwestern Australia

The results of preliminary investigations of ephemeral waters of the wet-dry tropics are reported. These poorly known but extensive habitats cover much of the seasonally inundated land of northern Australia. Brief descriptions of the physicochemical characteristics of four contrasting sites are given along with a listing of the non-benthic fauna that utilize them. Ninety-six invertebrate taxa and eighteen species of vertebrates were recorded. Anuran amphibians were particularly abundant in these systems and their patterns of utilization of these temporary waters is described. Because of their seasonal abundance, tadpoles and young frogs are likely to be important prey for a suite of both invertebrate and vertebrate predators.

Significant extension in northern Australia of the known geographic range of the Shield Shrimp Triops australiensis (Crustacea: Notostraca)

The program BIOCLIM predicts the total geographic distribution of species, based upon the biogeoclimatic characteristics common to the localities at which they are known to occur. Field studies in the Northern Territory have located the Shield Shrimp Triops australiensis at localities substantially north of its known and predicted geographic distribution.