The mouse plague in Western Australia has been a devastating event for farmers and rural communities, with houses, sheds, and fields inundated with mice. The scale of the plague is unprecedented, with up to 8,000 mice per hectare recorded, far exceeding the threshold for declaring a plague. This article delves into the reasons behind the plague, the impact on local wildlife, and the potential relief on the horizon.
The Perfect Storm: Why So Many Mice?
The mouse plague in WA's northern wheatbelt region began in April, following a cyclone that brought increased rainfall and soil moisture, ideal conditions for mice to thrive. Scientists had predicted a potential plague as early as March, based on modeling and field monitoring. Large-scale mouse plagues are primarily observed in Australia and China, but the reasons for this geographical concentration remain a mystery.
The Three Factors Behind the Plague's End
The good news is that the mouse plague is likely to end soon, thanks to three key factors:
Less Food: Australia's agricultural boom-and-bust nature means that in drier years, such as the current one, mice populations can drop dramatically due to reduced crop yields and less available food. This natural cycle provides a built-in check on mouse populations.
Less Rain: Rainfall is the strongest predictor of mouse plagues. High rainfall boosts plant growth, providing food for female mice to breed rapidly. However, research shows that plagues generally occur about three months after unusually high rainfall, and they do not reoccur for at least two years after a significant event.
More Heat: WA's hot, dry summers make it challenging for mice to burrow and breed. This environmental factor naturally limits the duration of the plague, as mice struggle to survive in such conditions.
Concerns for Local Wildlife
The mouse plague has caused significant disruption in rural communities, coinciding with the critical crop sowing period. Farmers have had to lobby for double-strength mice bait, containing zinc phosphide, to be made available. This higher-dose bait is more effective at killing mice quickly. However, concerns have been raised about its impact on native birds, particularly those that eat grain from paddocks.
Scientists worry that the double-strength bait could directly poison native birds, as it has previously been used during mouse plagues without causing secondary poisoning. A local wildlife carer reported finding 106 dead or dying birds in Coorow, including western corellas, little corellas, galahs, Regent parrots, and Australian ringnecks. While testing for exposure to zinc phosphide is possible, it is not a routine practice, and the long-term effects on wildlife remain unknown.
A Glimmer of Hope
As winter sets in and the double-strength baits take effect, there is hope that the mouse plague will soon be a distant memory. The combination of natural factors and human intervention provides a glimmer of relief for farmers and communities, offering a chance to recover and rebuild.
In conclusion, the mouse plague in Western Australia has been a challenging and unprecedented event. However, the potential for relief offers a positive outlook for those affected, as nature and human ingenuity work together to restore balance to the region.
