Australia's Mouse Plague: What You Need to Know

By Joanna Prendergast

ABC Midwest and Wheatbelt

Agricultural Pest Control

Wednesday, 20 May 2026, at 7:00 am

Farmers and community members are fighting to clean up dead mice daily.

Mice are hiding in beds, biting fingers, chewing machinery, and destroying crops.

Some regions are experiencing a mouse plague not seen since 2021.

Millions of rodents have been causing trouble for months.

There is no easy solution in sight.

Here's what you need to know about the mouse plague.

Why is there a mouse plague?

Mice started breeding after the summer grain harvest in Western Australia.

Agronomists and farmers raised the alarm in February, surprised by the number of rodents.

Mice can multiply quickly, breeding at six weeks old and giving birth to up to 10 offspring every 20 days.

Some people are catching hundreds of mice daily.

Conditions were perfect for breeding, with plenty of food and fewer sheep to clean up grain.

Summer rain provided mice with water and milder temperatures.

Where are the mice?

Mice usually live near humans but are not always seen.

When they reach plague levels, they are everywhere.

Mice breed quickly, multiplying their numbers.

Some towns in Western Australia have mice in public buildings and homes.

Community leaders worry about disease outbreaks, and the Department of Health has issued a public health alert.

A map shows mouse distribution in Australia.

Farmers in South Australia, Western Australia, and northern NSW are seeing high mouse numbers.

Citizen science website FeralScan reports mice in every grain-growing state.

A grocery store owner is fed up with the mouse problem.

Why is the standard bait not working?

The standard bait contains 25 grams per kilogram of zinc phosphide.

A mouse must eat two or three grains of poisoned wheat to die.

In some paddocks, mice may only eat one poisoned grain and survive.

Eating one grain makes the mouse sick, but it won't die, and it may learn not to eat another poisoned grain.

There are so many mice that while bait may remove half of the population, the remaining rodents quickly breed and rebuild.

Mouse bait is wheat treated with poison.

The Australian Pesticides and Veterinary Medicines Authority issued an emergency permit for a double-strength bait.

The stronger bait should bring mouse numbers down quickly.

What's the environmental risk of the stronger farm bait?

CSIRO mouse expert Steve Henry has been studying this.

Zinc phosphide doesn't bioaccumulate, and most of the toxin is used up killing the mouse.

The pest chemical regulator approved permits for farmers to use double-strength bait.

The chances of an animal eating poisoned mice and getting sick are low.

There is a risk that birds may eat poisoned grains and get poisoned.

So far, CSIRO research does not show bird deaths as a concern.

The APVMA imposed strict conditions on the emergency permit to protect non-target species.

What damage are the mice doing?

Grain farmers are planting, but mice are eating the seeds.

Crops that grow are vulnerable to mice chewing them off.

Mouse holes are along lines of seeded crops, and mice ate the seed before it could grow.

Some producers will have to re-seed their paddocks, a significant cost.

Mice are damaging cars and farm machinery, eating wiring and hoses.

Mice ate a radiator hose, causing a vehicle to lose its coolant.

Mice have spread to towns, where food-based businesses are inundated.

They are taking a significant mental toll on people who have been trapping and baiting them for months.

Some communities rely on income from wildflower tourism in winter.

How long will this plague last?

Mouse plagues typically end due to food shortages, disease, and cold weather.

Once farmers spread the more effective baits, they should see a reduction in numbers within hours.

The bait can only be used on farms, not in urban areas, and it's not a silver bullet.

Mice may stop moving en masse out of paddocks into houses, but they'll still need to be removed.

Residents will need to keep trapping and baiting the vermin.

ABC Midwest and Wheatbelt - local news in your inbox

Wednesday, 20 May 2026, at 7:00 am

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