MouseAlert app map shows how mice plague has spread to four Australian states

As the CSIRO warns how long the mice infestation will last, see the maps that show how quickly the plague spread from northern NSW to four states.

Australia’s mice infestation may not yet have peaked, and it could last two years, the CSIRO has warned.

The first reports of mice in plague proportions came from northern NSW and now stretch the length of the state.

The rodent pests are as far north as Biloela in Queensland, in various locations around Melbourne and Geelong, and in isolated spots in South Australia and Western Australia.

Analysis of the MouseAlert app showed five areas of highest level of observed infestation in January. That figure has now jumped to more than 100.

MouseAlert map showing the extent of the mice plague in January, 2021. Red represents high numbers, orange shows medium numbers, yellow shows low numbers and grey represents none. Picture: MouseAlert

MouseAlert map showing the extent of the mice plague in May, 2021. Red represents high numbers, orange shows medium numbers, yellow shows low numbers and grey represents none. Picture: MouseAlert

CSIRO project officer Steve Henry said while there was no Richter scale equivalent to measure the severity of a pest plague, the current infestation “is comparable to the biggest mouse outbreaks that we’ve had”.

CSIRO researcher Steve Henry says this year’s plague is comparable to the worst Australia has ever seen. Picture: Supplied

But the alarming idea of mice marching on our major cities was a furphy, he said.

“It’s important to remember that mice weigh about 15 grams, and they’ve got really little legs,” he said. “The concept of mice moving kilometres across a landscape is really flawed. Mice live everywhere that humans are on the planet … and when conditions are favourable, these localised populations build up to higher numbers and they become more obvious.”

They would become more noticeable as conditions get cooler and they seek shelter indoors, he said.

Mr Henry said mouse plagues in Australia occur about once per decade and typically follow one of two trajectories: one-year outbreaks involving a surge in numbers followed by a quick crash; and a two-year outbreak of a population boom, then a plateau, and a second burst the following spring.

It was too early to say what trajectory the current outbreak would follow, Mr Henry said, but the CSIRO were urging farmers to be vigilant.

“If mouse numbers plateau through this winter, it’s no good becoming complacent at that point; (farmers) need to keep monitoring and be ready to bait in the spring,” he said.

The stuff of nightmares. A screen grab taken from Ben Storer's iPhone footage of the mice plague at his family farm located outside of Warren in NSW. Thousands of mice can be seen scattering across the road near his hay shed. Supplied: Ben Storer

The good news is that when conditions turn and baiting treatments like zinc phosphene start to take effect, mice numbers should crash quickly.

“When populations are very high that facilitates the spread of disease,” Mr Henry said. “Food starts to run out, and once you start to get sick and weak animals in the population they turn on each other and start to eat each other. And then the population drops dramatically.”

GrainGrowers chair Brett Hosking said some farmers were expecting a drop in yields of 20 per cent because of damage from mice, and the plagues were having an emotional impact too.

“There’s a human cost, with mice in houses and that sort of thing. They’re very difficult to control in those situations,” he said.

Mr Henry said one farmer near Gilgandra trapped and removed 400 mice from his home in an eight-hour stretch between 6pm and 2am one night.

While farmers were used to dealing with pests as a standard part of their job, the current outbreak was frustrating for some, Mr Hosking said.

“We’re at a time of the year when there’s a bit of moisture around, (farmers) want to get crops in the ground, and it should be an optimistic time of the year, yet they’re having to face this continuing challenge of having to manage mice populations, without a clear end in sight,” he said.