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Cane toads are among the world's most successful invasive species. Photo: Tim Dempster
Invasive, toxic and a major threat to Australia's native predators, the cane toad (Rhinella marina) has been a relentless coloniser of Australia's wet-dry tropics and is now conquering Australia's northern deserts.
Just how this normally tropical amphibian can survive the long, hot dry seasons in arid Australia has puzzled scientists. But research led by the University of Technology, Sydney (UTS) has finally revealed this ugly amphibian's secret: the toad may be changing a key behaviour to survive harsh conditions, and so improving its chances of survival.
Researchers led by University of Technology, Sydney ecologist Dr Jonathan Webb have, for the first time, documented the normally nocturnal adult cane toad entering man-made dams to cool down and rehydrate during the day. This dramatic change in activity patterns allows toads to avoid the hostile daytime conditions.
By putting acoustic fish tags on 20 adult cane toads and placing data loggers in dams near the Tanami desert – Australia's northernmost desert – the researchers were able to record the toads’ activity patterns. The 16mm long acoustic tags transmit through water, but not air, so the loggers record the presence of a toad only when it is in water.
“No one has ever put fish tags on amphibians before to study their activity and what we found shows amazing behavioural flexibility on the part of these toads,” says Dr Webb.
“We found that cane toads visit the water during the day time, with peaks of activity in the morning. This is very different to what toads do in their native geographic range and the rest of Australia. Usually, adult toads are strictly nocturnal. This daytime hydrating and cooling down allows them to survive an environment where ground temperatures often exceed 40 degrees for several hours each day,” he says.
The team, which includes conservation scientists from the University of NSW and the University of Melbourne, believes such behavioural flexibility, or “plasticity”, may explain why cane toads are one of the world's most successful invasive species. That is more bad news for already environmentally stressed populations of native predators such as quolls and goannas.
“Plasticity, or evolution in behavioural responses, is a key attribute of successful animal invasions,” says Dr Webb. “The behavioural phase shift that this research has revealed has rarely been reported in invasive species and could facilitate ongoing invasion success for the cane toad.”
The research was published in February in the Royal Society journal Biology Letters and was funded by the Hermon Slade Foundation and the Australian Research Council.
This story written and produced by the University of Technology, Sydney, for Brink, a publication distributed monthly in The Sydney Morning Herald.