Biological control of the cane toad in Australia: a review

Abstract

The marine toad Bufo marinus is native to northern South America, parts of Central America and Southern Texas. It was deliberately introduced into Australia's tropical north-east in 1935 in an unsuccessful attempt to control the cane beetle, a damaging insect pest of sugarcane crops. The toads quickly established in the new environment and began to spread. Today, they inhabit most of the Australian tropics and sub-tropics and have reached Western Australia. Models predict that global warming will enable the toads to extend their range further south. They cause severe environmental impacts, as all life stages of B. marinus contain bufadienolides, alkaloid substances toxic to vertebrates, resulting in death of the predators ingesting it. The continental scale of this biological invasion in combination with the remoteness of the areas affected, poses a specific set of challenges to potential control approaches for cane toads. This review covers different biocontrol strategies pursued over the past 8 years, with particular focus on an immunological approach aiming at the disruption of toad metamorphosis. So far, research efforts have failed to produce a tool for large-scale reduction of toad populations. Considerations of future research priorities and efforts are also discussed.

Excluding access to invasion hubs can contain the spread of an invasive vertebrate

“…The cane toad has recently expanded its range into semi-arid regions of the continent, where it poses a serious threat to carnivorous reptiles [34]. Since the 1980s, considerable effort has been expended on developing biological control techniques to reduce toad numbers and hence impacts, however, efforts to date have had little success [35]. In most years, no rain falls between April and September, and most stream flow occurs during the wet season (December -March) when monsoonal rains bring more than 80 per cent of the annual precipitation.…”

Ecology, Impacts, and Management of Invasive Rodents in the United States

“…The time required for eggs to mature varies with climate, but they typically hatch within 48 hours, and it takes about 30 days for tadpoles to mature. Sexual maturity in cane toads can be reached within one year, depending on the environment (Shanmuganathan et al 2010). They breed year round (Doody et al 2014).…”

“…showed promise for controlling cane toads because all experimental infections caused cane toad death (Speare 1990). However, Shanmuganathan et al (2010) reviewed the biocontrol efforts attempted over an eight-year period in Australia, and concluded that, so far, research efforts have failed to produce a tool for large-scale control of cane toad populations.…”

“…There is no known pathogen that is speci cally lethal to cane toads, which is why a GMO to serve this purpose has been explored (Shanmuganathan et al 2010). Research on a virus (Toddia sp.)…”

“…Their generalist diet, which includes both vertebrates and invertebrates, has almost certainly helped them attain high population densities (over 2000 frogs/ha) in their introduced ranges (Freeland 1986). Finally, eggs, tadpoles, and adults are poisonous to many predators as they contain bufadienolides (alkaloid substances toxic to vertebrates), which make cane toad control via natural predators in the environment challenging (Shanmuganathan et al 2010). …”