Abstract
Cane Toads (Rhinella marina) are invasive pests in many parts of the world, including the Japanese island of Ishigaki. Extensive research in Australia has identified promising new methods for control, but also has shown that toads exhibit geographic variation in many traits (suggesting that methods developed in one location may not work in another). Can the approaches developed in Australia play a useful role for controlling this invasive species in Japan? Our experimental trials on Ishigaki Island suggest that these new methods can be successfully applied to Japan. First, Cane Toad embryos exposed to chemical cues of conspecific tadpoles exhibited a reduction in viability (subsequent growth and development). This response appears to be species-specific, with native frog embryos not being affected by exposure to cues from toad tadpoles, and Cane Toad embryos not being affected by exposure to cues from native frog tadpoles. Second, Cane Toad tadpoles were attracted to traps containing water from conspecific eggs, and toxin from adult conspecifics. Third, adult Cane Toads were attracted to acoustic cues of calling males, with sex differences in rates of attraction to specific versions of a synthetic call (males were attracted to choruses whereas females were attracted to low-frequency calls). Our results suggest that the methods developed by Australian researchers are applicable to controlling invasive Cane Toads in Japan.
Highlights
Invasive species can have major ecological impacts on native taxa, and such impacts can be especially severe on islands that are refuges for endemic fauna [1,2]
After 10 days, survival of Cane Toad tadpoles in the Control treatment was 91 +/- 5% SE, while survival of tadpoles exposed as embryos to the four groups of conspecific older tadpoles ranged from 80% to 100% (Lucrin Group 1: 80 +/- 12% SE, Lucrin Group 2: +/- 8% SE, Wild Group 1: +/- 11% SE, Wild Group 2: 100 +/- 0% SE)
Our experiments generated an encouraging result: the intraspecific growth, developmental and behavioural responses recently identified for potential control of Cane Toads in Australia were observed on Ishigaki Island in southern Japan
Summary
Invasive species can have major ecological impacts on native taxa, and such impacts can be especially severe on islands that are refuges for endemic fauna [1,2]. Managers need effective methods with which to reduce the abundance of pest species. Eradication is often difficult or impossible, but pro-active management can reduce local densities of the invasive species to levels that mitigate their environmental impacts [3]. One of the most-intensively-studied invaders worldwide is the Cane Toad (Rhinella marina), a large anuran that was introduced to more than 40 countries worldwide in illadvised attempts at biocontrol of pests [4].
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