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Mouse plague on hold thanks to floods, CSIRO thinks

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Mouse plague on hold thanks to floods, CSIRO thinks

Livestock

There may be a silver lining to the destructive flooding that has torn through parts of western New South Wales.

Key points:

  • Flood-ravaged NSW is being monitored for signs of another mouse plague
  • Farmers report low mice numbers, but are concerned about rats and wild pigs
  • Experts are trying to work out why plagues do not always occur during good seasons

The water has washed away farm infrastructure, drowned crops, and killed livestock, but it may have also wiped out any resurgence of a mouse plague. 

It has been just over a year since numbers of the pesky rodent started waning, and the widespread flooding of 2022 appears to have stopped them in their tracks. 

“What we think is happening is adult mice are surviving and getting out of the water, moving to higher country,” CSIRO research officer Steve Henry said. 

“Any babies that are in burrows, when it gets really wet, those burrows fill with water and the babies will drown.”

He said conditions in NSW during spring last year provided an optimistic outlook. 

“Breeding in spring and mouse numbers in spring tend to determine what happens through the rest of the spring, summer, and then the following autumn,” Mr Henry said.

“That’s not saying it won’t happen at all, but we just don’t think that they’ll get to those super high numbers that we saw in previous years.”

He said western and northern Victoria and parts of South Australia, like the York and Eyre peninsulas, could be at risk. 

“Simply because it’s been a great season,” he said.

“There’s a fair amount of grain left behind, they haven’t had significant numbers of mice for a couple of years now, so they are places that we would be expecting mouse numbers to increase pretty dramatically.”

livestock CSIOR researcher Steve Henry weighing a mouse.

Steve Henry says teams will be surveying parts of western NSW to check for mouse activity.(ABC News: Alice Kenney)

Farm feast

While the flooding in NSW may have helped stymie the chances of another plague, the damage to grain crops could work against farmers. 

“A fair bit of grain has been left behind … so that actually provides a scenario that is really good for mice because there’s lots of food, lots of shelter, and there’s a chance that they’ll recommence breeding,” Mr Henry said. 

“I don’t expect to see numbers get really high but it’s certainly something for farmers to be vigilant of as they manage their stubble.

“Using sheep to graze those stubbles, to eat all of that grain that’s been left behind, is a really good way of reducing the amount of food that’s left behind for mice.” 

livestock Mice gathered on the floor of a barn.

Researchers believe the widespread flooding has stymied spring breeding.(Supplied: CSIRO)

Farmers said they were not seeing high numbers of mice, but some were reporting other problem pests.

“I’m hoping they’ve done their dash. Surprisingly, there are a few rats getting around,” Trangie farmer Tony Quigley said. 

“The old hands used to say that the mice plague isn’t over till the rats have arrived.

“I don’t know whether that’s what’s happened here or what the story is. I’m very wary of rats. 

“They’re a bit of concern because of the damage they do to electronic equipment in machinery, particularly headers and tractors and those sort of things.”

He said the other pest problem to be wary of was the “continuation of pigs”. 

“With the amount of grain stored around in silo bags on farms there’s the potential for a fair bit of damage,” he said.

Predicting plagues 

The question experts are trying to answer is why mouse plagues do not always occur when there is a good season. 

Mr Henry said they were able to predict outbreaks about 75 per cent of the time by monitoring in-crop rainfall. 

“We tend to get significant outbreaks after a run of dry seasons and then when it rains again, all the mice start breeding, conditions are good for grain crops, so there’s lots of food, lots of shelter,” he said. 

“What we don’t understand is what actually regulates mouse breeding in seasons that are good when we don’t get a mouse outbreak.”

He said one hypothesis was that mice themselves could be behaving like a biological control, by competing for space and eating offspring in neighbouring burrows.

Posted , updated 

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