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Emma Gray was among the first to notice signs of the impending plague.
A biological researcher, Gray went to northwest Queensland in Australia in June to study one mammal but unexpectedly ended up focusing on another. During her field work, she caught more than 1,000 long-haired rats. As Gray looked around, she saw evidence of far more.
“You could just see tunnels everywhere in the grass,” Gray, a postdoctoral researcher at Queensland University of Technology in Brisbane, told The Washington Post.
Gray said she immediately knew what was happening: an explosion in the number of long-haired rats. Native to Australia, long-haired rats normally eke out an existence in relatively low numbers, only to skyrocket into legions when the right conditions present themselves.
Gray was right. Hordes of the rats have since spread north as government officials warn of a “Rat Plague.” The rats have most recently hit the country’s coastal towns, including Karumba, where they have chewed through electrical wires, devoured food reserves, attacked pets and, in at least one case, destroyed a car.
“They’re causing havoc with everything,” a Karumba resident told 4BC radio, adding: “They’re eating anything and everything they can get their hands on.”
Known as Rattus villosissimus to scientists and majaru or mayaroo to Indigenous Australians, the long-haired rat typically lives in arid and semiarid habitats. They normally hide inside cracks in clay soil, which provide shelter both from the heat and from predators such as barn owls, letter-winged kites and feral cats, Gray said.
Long-haired rats eat wild plants, specifically their leaves and seeds, Gray added, because unlike the brown rats familiar to city dwellers around the world, they are not commensal, or reliant on humans for food and shelter. Every three to five years, though sometimes more often, La Niña weather brings increased rainfall to Australia, including every year since 2020, when an unusual “triple-dip” La Niña unleashed record-breaking rains across the country, causing flooding and forcing evacuations, the BBC reported.
For the long-haired rat, more rain means more vegetation growth, and more food means more rats — lots more. With a strong food supply, long-haired rats can give birth every three weeks, producing litters with as many as 12 babies, Gray said.
“It’s a very natural phenomenon that’s been happening basically as far back as our records go, to early explorers,” she said, adding that, despite the lack of historical records, she suspects the boom-and-bust cycle has been going on for thousands, if not tens of thousands, of years.
Explosions in the long-haired rat population happen every three to 17 years, the last one occurring in 2011 after two years of above-average rainfall, Gray said. Luke Wharton, a resident of a nearby community that was also hit by rats, told the Australian Broadcasting Corporation that this year’s plague “might top it.”
More rats mean more problems, at least for people.
“They’re quite destructive when they get into such large numbers,” Gray said.
Karumba is only the latest town to suffer under the onslaught. After Gray’s discovery in June near the inland town of Julia Creek, the rats marched steadily northward, hitting other inland communities as they pressed toward the sea, according to the ABC. Along the way, they contaminated water sources and destroyed crops.
Long-haired rats have quickly worn out their welcome in Karumba. Jemma Probert, who owns a fishing charter, told the ABC that she’s had to flick them off her boat, while commercial fisherman Brett Fallon told the news organization that every night, at least 100 invade his vessel. Derek Lord, who runs a car rental business, told the AFP that they destroyed a vehicle by stripping the wiring out of the engine bay. He said they also drove his pet ducks “mad” by breaking into their cages and stealing their eggs.
“There’s rats everywhere,” Lord said, adding: “They’re just like, bold as hell.”
The rats swim out to sandbanks during low tide, only to drown when the water rises, Probert told the ABC. Fallon said that he caught sight of their corpses floating on the water surface.
“When the moon came over the town last night, the river was well and truly alive with the bodies of rats,” he said.
The rats’ bodies — thousands and thousands of them — then wash ashore. While government officials clean up many of them, others rot.
“The stench is quite bad,” Carpentaria Shire Council Mayor Jack Bawden, who represents Karumba, told NPR.
But spikes in the long-haired rat population end quickly. Although scientists aren’t exactly sure why, a number of factors are thought to contribute, including inbreeding, an increase in the number of predators and a declining food supply.
Although the triple-dip La Niña ended earlier this year, Australia is moving into the wet season, when the rats’ food supply should be ample, University of Sydney environmental sciences professor Peter Banks told the ABC. Bawden told the news agency that he and other local government officials are preparing to cope with wave after wave of tiny, four-legged invaders.
“We’re not getting any relief anytime soon,” he said, adding: “We may just have to wait it out.”