Predator-free short-hydroperiod wetlands enhance metamorph output in a threatened amphibian: insights into frog breeding behaviour evolution and conservation management

Context. Knowledge on the drivers of breeding behaviour is vital to understand amphibian ecology and conservation. Proposed drivers of amphibian reproductive behaviour include selection of optimum water quality, and avoidance of tadpole predators and competition. These hypotheses are underpinned by the logic that amphibians will choose breeding habitat that will result in enhanced metamorph output. Aims. We aimed to infer key drivers that influence metamorph output in the threatened green and golden bell frog (Litoria aurea). We hypothesised that (1) metamorph output would be higher in recently refilled wetlands than in wetlands with a longer hydroperiod, (2) metamorph output would be negatively correlated with tadpole predator abundance, and (3) waterbodies with long hydroperiods would have higher abundances of aquatic predators and lower abundances of L. aurea tadpoles. Methods. We tested these hypotheses by monitoring breeding, tadpole and predator abundances in a wild population of L. aurea. We coupled this with metamorph counts that were adjusted to represent per capita numbers via genetic means. We also ruled out the influence of detection probability in explaining the results with a manipulative experiment. Key results. We found support for all three hypotheses and hence provide evidence that the adaptive behaviour of L. aurea to preference recently refilled wetlands is governed by the abundance of tadpole predators. We found metamorph counts per clutch to be 8.2-fold greater in short-hydroperiod wetlands (26 +/- 15-44 95% CI) than in long-hydroperiod wetlands (3 +/- 2-5 95% CI). Four predator taxa were associated with low metamorph output and two of these occurred in higher abundances in longer-hydroperiod wetlands. Conclusions and implications. These results have provided evidence that the behavioural adaptation of L. aurea to select recently refilled wetlands has evolved in response to tadpole predation pressure. We recommend practitioners to conduct tadpole releases in newly refilled wetlands to enhance survival to metamorphosis in future reintroductions.

Automated summary

The study found that L. aurea's preference for recently refilled wetlands is driven by the abundance of tadpole predators. Metamorph counts per clutch were 8.2 times higher in short-hydroperiod wetlands compared to long-hydroperiod wetlands. Four predator taxa were associated with low metamorph output, with two occurring in higher abundances in longer-hydroperiod wetlands.