The Ecological Impact of Invasive Cane Toads ( Bufo Marinus ) in Australia

School of Biological Sciences A08, University of Sydney, NSW 2006, Australia.
The Quarterly Review of Biology (Impact Factor: 4.89). 09/2010; 85(3):253-91. DOI: 10.1086/655116
Source: PubMed


Although invasive species are viewed as major threats to ecosystems worldwide, few such species have been studied in enough detail to identify the pathways, magnitudes, and timescales of their impact on native fauna. One of the most intensively studied invasive taxa in this respect is the cane toad (Bufo marinus), which was introduced to Australia in 1935. A review of these studies suggests that a single pathway-lethal toxic ingestion of toads by frog-eating predators-is the major mechanism of impact, but that the magnitude of impact varies dramatically among predator taxa, as well as through space and time. Populations of large predators (e.g., varanid and scincid lizards, elapid snakes, freshwater crocodiles, and dasyurid marsupials) may be imperilled by toad invasion, but impacts vary spatially even within the same predator species. Some of the taxa severely impacted by toad invasion recover within a few decades, via aversion learning and longer-term adaptive changes. No native species have gone extinct as a result of toad invasion, and many native taxa widely imagined to be at risk are not affected, largely as a result of their physiological ability to tolerate toad toxins (e.g., as found in many birds and rodents), as well as the reluctance of many native anuran-eating predators to consume toads, either innately or as a learned response. Indirect effects of cane toads as mediated through trophic webs are likely as important as direct effects, but they are more difficult to study. Overall, some Australian native species (mostly large predators) have declined due to cane toads; others, especially species formerly consumed by those predators, have benefited. For yet others, effects have been minor or have been mediated indirectly rather than through direct interactions with the invasive toads. Factors that increase a predator's vulnerability to toad invasion include habitat overlap with toads, anurophagy, large body size, inability to develop rapid behavioral aversion to toads as prey items, and physiological vulnerability to bufotoxins as a result of a lack of coevolutionary history of exposure to other bufonid taxa.

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    • "In the case of anuran amphibians, the two most widespread taxa (the American Bullfrog Lithobates catesbeiana [5 Rana catesbeiana] and the Cane Toad Rhinella marina [5 Bufo marinus]) both possess potent chemical defenses (Kats et al. 1988; Crossland et al. 2008; Adams et al. 2011; Szuroczki and Richardson 2011). Indeed, the distinctive bufadienalide toxins (cardioactive steroids; Hayes et al. 2009) of Cane Toads have been the primary mechanism for their devastating impact on native predators in Australia (Shine 2010). The success of the Cane Toad invasion has been widely attributed to the inability of native predators to tolerate these toxins, rendering the toads invulnerable (e.g., Covacevich and Archer 1975; Burnett 1997; Letnic et al. 2008). "

    Herpetological Monographs 12/2015; 29(1):28-39. DOI:10.1655/HERPMONOGRAPHS-D-13-00007 · 1.73 Impact Factor
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    • "Toads arrived in our study area in 2005 (Brown et al. 2006). Cane toads possess highly toxic defensive compounds, and many native predators (including fishes, frogs, lizards, snakes, crocodiles and marsupials) have been fatally poisoned when they have attempted to eat the invasive toads (Shine 2010). In our study area, cane toads remain active year-round but tend to be restricted to sites with permanent water during the dry season. "
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    • "Ensuring the barrier's effectiveness will require restricting water access across a 100km-wide strip of suitable coastal habitat (Tingley et al. 2013a). The barrier needs to be this wide because cane toads at the invasion front have evolved to disperse faster than their counterparts in eastern Queensland (Phillips & Shine 2006; Phillips et al. 2010). The invasion front now moves more that 50kms in a season, whereas their long-established conspecifics typically travel less than a fifth of this distance (Phillips et al. 2008; Alford et al. 2009). "
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