Field trials of chemical suppression of embryonic cane toads (Rhinella marina) by older conspecifics

1. Laboratory experiments have shown that the viability of embryos of the invasive cane toad (Rhinella marina) can be reduced by exposure to chemical cues from older conspecific larvae. These effects (very strong in laboratory trials) may offer an exciting new approach to controlling this problematic invasive species in Australia. However, the degree to which the method works in natural environments has yet to be assessed.

2. Our experiments in the laboratory and in semi-natural outdoor waterbodies show that chemical cues from tadpoles do indeed suppress the growth, development and survival of conspecific larvae that are exposed as embryos and do so in a dose-dependent manner; higher tadpole densities cause greater suppression of embryos.

3. In semi-natural outdoor waterbodies, suppressor-exposed tadpoles were less than half as likely to survive to metamorphosis as were controls, and were much smaller when they did so and hence, less likely to survive the metamorph stage. Addition...