Plagues of "bold as hell" rats have overrun tropical fishing towns in northern Australia, where residents are clearing piles of "smelly" dead rodents off the beach every morning.

The native long-haired rats have been steadily marching towards the coast after a bumper wet season in inland Australia, spreading hundreds of kilometres in their hunt for new crops to nibble on.

Now they have reached the gulf towns of Karumba and Normanton in the state of Queensland, harassing pets, clambering over boats and stripping cars of their wiring.

"Mate, there's rats everywhere," said Normanton local Derek Lord, 49, who runs a vehicle hire business.

"They're that bold they're coming out during the day," he told AFP.

"We have hire vehicles and they literally destroyed a car overnight, taking all of the wiring out of the engine bay."

Lord said his pet ducks had been "going mad" as rats broke into their cages and stole their eggs.

"Last night, the ducks were going mad and I went downstairs to see what was going on thinking maybe there's a cat in there or something.

"And there's bloody lots of rats running through the cages, through the pens chasing ducks.

"They're just like, bold as hell."

Rats have also infested the nearby town of Karumba, better known as the barramundi "fishing mecca" of Australia.

Fishing charter owner Jemma Probert told AFP piles of drowned rodents had been washing up on the shore front every morning.

"It's pretty bad here. The last week we've had them all over the beaches, some alive, some dead," she said.

"It's not very nice down there, it's a bit smelly.

"The council has been cleaning up the beaches every morning, just to try and keep that at bay."

Boom-and-bust weather cycles dominate much of inland Australia, where heavy rains can fuel rapid crop growth after years of crippling drought.

These patterns are often accompanied by booming populations of pests such as locusts, rats, and mice.

With more wet weather likely for Queensland, Probert said she had been told the worst was yet to come.

"We've heard there are still more that are coming," she said.

"It's not a good thing to leave Karumba remembering."

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