DAILY TELEGRAPH (Sydney, Australia) 10 July 08 Toad cannibalism keeps numbers down (Rosemary Desmond)
Cane toads are not the super species many believe, with less than 1 per cent surviving to adulthood, a researcher says.
Professor Ross Alford, from Queensland's James Cook University's School of Marine and Tropical Biology, says recent research found 99.97 per cent of toads die as spawn or tadpoles.
But if a female toad survived to even one year old, it would have laid around 7000 eggs, he said.
"Nobody knows within coo-ee of how many there are but we have roughly around 200 million cane toads," Prof Alford said.
"What that basically means is that they have been increasing by a factor of about 20 per cent per year.
"Even if one per cent of them survived, in about 50 years, there would have been as many cane toads as there are atoms in the universe, according to the astronomers."
Prof Alford has been studying cane toads for 20 years.
Native to Central and South America, they were introduced to Australia in 1935 and released widely along the Queensland coast in 1936 in a failed attempt to control the sugar cane beetle.
But Prof Alford said the odds were against the toads living past the spawn stage because they were likely to fall victim to insect predators or cane toads themselves.
"Once a population of cane toad is established cane toad tadpoles eat a lot of cane toad eggs, so they actually help to control themselves a bit," he said.
This was one reason toad numbers spiked when they colonised a new area where there was no threat from existing cane toad tadpoles.
If their survival rate decreased by just 0.01 per cent, numbers would start falling, instead of increasing, Prof Alford said.
Prof Alford said a biological control was now needed to control cane toad populations and a toxin or virus would probably be the best bet.
Snakes have a savior