Mouse plague map: are the mice terrorising regional NSW about to invade Sydney?
City slickers might be panicking, but what does the data on the latest sightings show about the rodents’ movements?
Over the past six months, millions and millions of mice have terrorised the people of regional New South Wales.
They have found them in their homes, ceilings, fields, bins, in children’s classrooms as they sit Naplan exams, in the stuffing of armchairs, and even biting them in hospital beds.
The mouse plague has so far cost millions of dollars in damaged property and crops, prompting the NSW government to create a $50m rescue package and fast-track the approval of the world’s deadliest mouse poison.
On Thursday night, an alarmingly arresting map, prepared by Channel 10 News Sydney, implied that the mice would soon “march” on Sydney.
The map appeared to show the mice forming four military columns and organising in a highly sophisticated pincer movement.
According to the Channel 10 report, the mice could “invade Sydney by August”. It quoted Dieter Mafra, a “mouse technician” from Kevin Joyce Pest Management, who said the mice could enter cities “as they hitch rides on trucks and food pallets”.
What does the data show?
The most recent mouse monitoring report from the CSIRO and Grains Research and Development Corporation measures mouse activity based on monitoring sites around Australia. This report in March showed “moderate to high mouse activity in many regions of southern Queensland; northern, central and southern NSW; north-western Victoria; and parts of South Australia”.
The associated MouseAlert website and app, run by the NSW government and the CSIRO, provides a platform for grain producers and farmers to report mouse sightings with the aim of making it easier to monitor mouse activity in almost real time.
The map shows very few sightings with “high” activity in agricultural areas approaching the east coast, suggesting a coordinated assault on Sydney or other large cities is unlikely.
So will there be a mouse attack on Sydney?
The CSIRO researcher and mouse expert Steve Henry told Guardian Australia it was unlikely that the mice were marching on Sydney because they usually do not move far from their nests.
“Mice are not migratory animals,” he said. “Mice can move 100 metres from their nest or burrow to forage, but they will return at the end of the night.”
Henry said it was more likely that new mouse sightings in urban areas were due to local populations growing.
“Mice live everywhere humans do, and most of the time go undetected,” he said. “Recent reports of increased mouse activity in urban areas are due to a localised build-up in the system.”
That could be due to more food scraps and shelter, or because “cooler weather encourages mice to find shelter inside homes, making them more likely to be seen”.
However, he did add that the large number of mice due to a bumper breeding season could force “juvenile mice to disperse to find other places to live”, leading to their entry into new areas.
So is this latest mouse panic just driven by city slickers?
It seems partly.
Guardian Australia has been reporting on the mouse plague in the regions for months. In March, we reported that three people had been bitten by mice while in hospital receiving treatment for separate, non-mice-related reasons.
We have written about farmers who got approval to fly poison-laden drones to airstrike the mice, about the residents who “can’t escape the smell”, and the disputed idea that new poisons would be able to “napalm” the mice.
Last week, we wrote a feature about six months of the plague – and how whole towns have accepted their presence like “an injury where you’re just in constant pain”.
What has caused the mouse plague and how can we stop it?
Henry said mouse plagues of this magnitude happen every 10 years, but “farming practices have also changed over the years”.
“Water conservation and environmentally sustainable methods, such as minimum or zero tillage have resulted in significant increase in both available shelter and alternative food sources for mice in fields.”
Henry said farmers should use zinc phosphide-coated wheat bait in crops to keep the rodents at bay.
The Australian Pesticides and Veterinary Medicines Authority (APVMA) granted an emergency use permit on 7 May to allow farmers to cover these baits in double-strength zinc phosphide.
People in urban areas have been urged to patch up holes in their home with steel wool, put seals on doors, and keep food scraps away.
The state government has lodged an emergency request to approve another poison, bromadiolone, which is currently outlawed for use in fields. The NSW agriculture minister, Adam Marshall, described it as “the equivalent of napalming mice”.
But leading rodent experts have said they “aren’t convinced” and it could instead kill native and domestic animals.