Original story at The West Australian
Even crocodiles are sick to death of cane toads.
Dwarf, pygmy or stone country crocs are a recognised form of the freshwater croc – Crocodylus johnsoni. While there are some genetic differences distinguishing these populations they aren’t significant enough to warrant the classification of a separate subspecies. Photo: Grahame Webb
Dwarf crocodiles have met their match in the poisonous invader, as new research shows it has wiped out entire populations of the reptile in northern Australia.
Charles Darwin University’s Research Institute for the Environment and Livelihoods has studied the effects of the toad on the smallest crocodile species found in northern Australia’s upstream escarpments.
Evidence of the destructive effect of the cane toad invasion on one of northern Australia’s top predators, the freshwater crocodile, was first found in 2008. Jake O’Shaughnessy
The growth of the dwarf freshwater crocs is stunted by a lack of food, making them half the size of a typical crocodile.
Cane toads came along and provided the dwarf crocs with a plentiful but deadly dinner, says Senior Research Associate Dr Adam Britton.
“We already know that cane toads kill freshwater crocodiles, but we were concerned that cane toads might have a major impact on dwarf populations because of their small size and lack of alternative food sources,” he said in a statement.
Like many other native species, dwarf crocodiles are poisoned when they ingest the bufotoxins in cane toads, which presents a major conservation issue for the entire upstream escarpment ecosystem.
The researchers found there were significant declines in the number of dwarf crocodiles at two of three survey sites following the arrival of cane toads.
“We found dead crocodiles and cane toad carcasses with crocodile bite marks,” Dr Britton said.
There’s still a long way to go towards understanding how native species cope with destructive invasive species like the cane toad.
But Dr Britton said his study offered an insight into why some populations were entirely wiped out while others were mostly unaffected.
The research team found possible evidence that dwarf crocodiles could adapt their behaviour in the future by only eating the back legs of toads to avoid being poisoned.
The team is conducting further research into the genetics of dwarf freshwater crocodiles to better understand the long-term impacts of cane toads on their populations.
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