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A state of origin match is being played out in Sydney's drains, but unlike the real thing it is the Queenslanders being massacred.

It has been discovered that a colony of cane toads who hitched a ride from the sunshine state are being eaten by the local rodents.

Cane toads were discovered some time ago in an industrial area of Taren Point, in Sydney's south.

Since then the local council, State Government and scientists have been working to eradicate them.

University of Sydney biologist Rick Shine, a passionate toad buster, says toads have been fitted with radio transmitters to monitor their behaviour.

Professor Shine says one of the "entertaining" things to emerge from the monitoring is how rats are munching away on the toads and living to tell the tale.

"The toads quite frequently use drains as cover and the drains contain rats, which we don't normally think of as our best friends," Professor Shine said.

"But rats evolved in the northern hemisphere, in the same place that toads did, and they're capable of dealing with the toad's poison.

"So one of our telemetered toads got massacred and eaten by a rat.

"Unlike a native predator, which a toad would be a fatal meal for, for a rat a toad's just a pretty nice breakfast.

"So we may have some of the old invaders helping get rid of some of the new invaders.

Professor Shine says they have also discovered a Sydney breeding ground for the pests, a pond of tadpoles.

He says it is the "Achilles heel" of the breeding cycle.

"It's a big step in controlling the breeding of the toad as one female can produce as many as 30,000 eggs," Professor Shine.

The tadpoles are euthanised.

He says there are hundreds of the toads in the Shire and hundreds more arrive every year by hopping on trucks carrying things like building materials and mulch from Queensland.

Professor Shine says because the toads are such effective stowaways they will keep on coming.

A toad was found in Launceston in Tasmania's north last week after apparently hitching a ride in a container at Christmas time.

There are several records of toad sightings in other areas in Sydney, but Taren Point seems to be their favourite home.

Source http://www.abc.net.au/news/stories/2011/04/20/3196478.htm?site=sydney