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Juvenile Murray cod Maccullochella peelii exhibited a type II functional response while preying on blackworms Lumbriculus variegatus, and the parameters of the type II model did not differ significantly between clear (0 NTU) and turbid (150 NTU) treatments. Further experiments showed that vision may not be necessary for prey detection and capture by juvenile M. peelii; consumption of inanimate prey was not significantly different between light and dark (<1 × 10(-4) µE m(-2) s(-1)) trials. These results imply that the sensory physiology of M. peelii is well adapted to a turbid visual environment. In addition, habitat complexity increased the food consumption rate of juvenile M. peelii, perhaps by relaxing innate predator avoidance behaviours that depress foraging in more open environments.

The acoustic niche hypothesis proposes that to avoid interference with breeding signals, vocal species should evolve to partition acoustic space, minimising similarity with co-occurring signals. Tests of the acoustic niche hypothesis are typically conducted using a single assemblage, with mixed outcomes, but if the process is evolutionarily important, a pattern of reduced acoustic competition should emerge, on average, over many communities. Using a continental-scale dataset derived from audio recordings collected by citizen scientists, we show that frogs do partition acoustic space. Differences in calls were predominately caused by differences in spectral, rather than temporal, features. Specifically, the 90% frequency bandwidths of observed frog assemblages overlapped less than expected, and there was greater distance between dominant frequencies than expected. To our knowledge, this study is the first to use null models to test for acoustic niche partitioning over a large geographic scale.