First introduced into Queensland in the 1930s, cane toads are now found as far south as Sydney and as far west as Kununurra. Despite originating from the rainforests of South America, the toads have managed to conquer some of the hottest and driest parts of the Australian continent.
To understand why cane toads continue to venture into new and potentially hostile environments, the scientists put cane toads from a recently established population in the Northern Territory through a mix of behavioural tests.
They found that some toads were bold and daring, while others were shy and cautious, they report in the journal PLoS One .
It is this mix of bold and shy personalities that has given the cane toads a foothold in Australia, says study co-author Professor Rick Shine of the University of Sydney.
"It is a pretty amazing situation that most frogs are stay-at-home creatures and don't really move too far from where they live, yet here we have got cane toads romping across the landscape," Shine says.
"But if cane toads were all timid then presumably they would still be sitting in Queensland."
To examine how personality traits varied within a cane toad population, the researchers set up feeding stations in the field using artificial lights to attract both insects as food and wild cane toads.
At some of the feeding stations the researchers placed a single cane toad in a mesh enclosure while the other feeding stations were left empty, allowing the wild toads to choose between an empty foraging site or one with another toad present.
A total of 95 cane toads approached the feeding stations within a two-hour period, with an almost even mix between those happy to eat on their own and those that preferred another toad to be present.
Shine says the presence of another toad in the area provided some of the toads with valuable social cues about the suitability of the area for foraging. But for those toads that fed alone, the social cues weren't needed.
To further test their personalities, the researchers placed each toad into a makeshift shelter in the laboratory and timed how long it took for the toad to leave the shelter and begin exploring its new environment.
They found the cane toads that happily ate on their own left their shelters much quicker than the more social cane toads, which tended to be more timid.
Bold v timid toads
"The bolder toads were happy to waltz out and walk around and the other guys stayed hiding," says Shine.
"It shows that some toads are prepared to leap out there into the unknown while some are scaredy-cats."
Shine believes it is the bold cane toads that venture forth and invade new areas. The shy toads follow on later, using social cues from the bolder toads to guide them. The result is a rapid swell in cane toad numbers in the first few years following the invasion into a new area.
"To boldly go where no toad has gone before is probably the sort of thing that a bolder individual is going to do better than a shy individual."
Read more at Discovery News
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