Can we use the tadpoles of Australian frogs to reduce recruitment of invasive cane toads?
Native to the Americas, cane toads Bufo marinus are an invasive species causing substantial ecological impacts in Australia. We need ways to control invasive species such as cane toads without collateral damage to native fauna. We explored the feasibility of suppressing survival and growth of cane toad tadpoles via competition with the tadpoles of native frogs. Compared to the invasive toads, many native frogs breed earlier in the season and their tadpoles grow larger and have longer larval periods. Hence, adding spawn or tadpoles of native frogs to toad-breeding sites might increase tadpole competition, and thereby reduce toad recruitment. Our laboratory trials using tadpoles of eight native frog species gave significant results: the presence of six of these species (Cyclorana australis, C. longipes, Litoria caerulea, L. dahlii, L. rothii and L. splendida) reduced toad tadpole survival and/or size at metamorphosis. Litoria caerulea also increased the duration of the larval period of cane toad tadpoles. Tadpoles of the other two frog species (Litoria rubella and Litoria tornieri) did not affect survival or growth of larval cane toads any more than did an equivalent number of additional toad tadpoles. Native frog species with larger tadpoles exerted greater negative effects on toad tadpoles than did native species with smaller tadpoles. Synthesis and applications. Encouraging the general public to construct and restore waterbodies in peri-urban areas to build up populations of native frogs - especially the much-loved green tree frog Litoria caerulea - could help to reduce recruitment rates of invasive cane toads in Australia.