Understanding the Scale of a Mouse Plague
A mouse plague is currently affecting farms and homes in southern and Western Australia. For those not directly involved, it can be challenging to grasp the full impact of such an event. However, for communities in parts of Western Australia and South Australia, the reality is far more intense.
Mice are known for their rapid breeding cycles, especially under favorable conditions. This has led to an explosive increase in their numbers, causing significant damage to crops, sheds, and grain silos. In some areas, the situation has become so severe that people have abandoned their homes.
The CSIRO defines a mouse plague as having more than 800 mice per hectare. To put this into perspective, a hectare is a square measuring 100 meters by 100 meters—approximately 2.5 acres. Visualizing 800 mice in this space might seem overwhelming, but in the worst-hit areas of Western Australia, the numbers are even more staggering.
The Reality of 8,000 Mice Per Hectare
In some regions, the mouse population has reached up to 8,000 per hectare. Scientists estimate these numbers by counting mouse burrows. They’ve found areas with 40 burrows per 100 square meters, which translates to 4,000 burrows per hectare. With at least two mice per burrow, this gives an estimate of 8,000 mice per hectare.
For those unfamiliar with the size of a hectare, considering other spaces can help. A rugby or soccer field, roughly two-thirds of a hectare, could hold around 5,440 mice. A tennis court would have about 156 mice, while a typical suburban block of 400 square meters could see 320 mice. Even a small bedroom of 3m x 4m might share its space with around 10 mice.
Psychological and Practical Impacts
Steve Henry, the CSIRO’s mouse plague expert, highlights the psychological toll of such an infestation. “It’s the psychological impact. You simply can’t get away from them,” he says. Residents in affected areas, like Morawa, describe the mice as inescapable. Karen Chappel, the shire president, mentions that mice are present in homes, cars, sheds, paddocks, schools, and everywhere else.
Reports include incidents where mice have bitten toes and nested in beds after people returned from holidays. The plague zones span the west coast around Geraldton, further south at Merredin and Esperance in Western Australia, as well as the Adelaide Plains and Yorke Peninsula in South Australia.
Economic and Social Consequences
Mice are also spreading into towns, causing businesses to lose thousands of dollars in stock. Mr. Henry notes that the current plague in Western Australia is similar to the one seen in New South Wales and Queensland in 2021, which caused millions in damage and mental distress.
Historically, mice have been a problem on Australian grain farms since the 1880s, with plagues occurring every four to five years following periods of heavy rainfall. The worst recorded plague was in 1993, causing an estimated $96 million in damage.
While Western Australia has not faced the same level of mouse issues as the eastern states, recent years have seen an increase in high mouse numbers. Mr. Henry explains that the area around Geraldton has had four good cropping years in the last five, leading to an abundance of food for the mice.
Fighting Back Against the Plague
Farmers are now taking action to reduce mouse populations. An emergency permit for double-strength mouse bait has been issued for grain paddocks. Once consumed, the bait takes about eight hours to kill the mice. Mr. Henry estimates that if the bait works effectively, it could lead to an 80% or greater reduction in mouse numbers.
However, he warns that the effectiveness of the bait depends on the availability of other food sources. “It depends on how fast the mice discover those grains that have the bait in amongst all of the other grains that are there.”
Conclusion
The mouse plague in Western Australia is a complex issue with far-reaching consequences. From the physical damage to homes and crops to the psychological stress on residents, the situation demands both immediate and long-term solutions. As farmers and scientists work together, the hope is to mitigate the impact and restore normalcy to affected communities.
