The ongoing mouse plague in Western Australia has been a devastating experience for farmers and communities alike. With up to 8,000 mice per hectare, the scale of the infestation is unprecedented. However, there is a glimmer of hope on the horizon as signs indicate that the plague may soon be over. The reasons for this are multifaceted, and understanding them is crucial for both farmers and the environment.
Firstly, the availability of food plays a significant role. Australia's agricultural landscape is characterized by boom and bust cycles. While favorable conditions lead to bountiful crops, droughts can drastically reduce yields and the growth of native plants. In years like the current one, characterized by reduced rainfall, mice populations can decline significantly due to the scarcity of food. This natural regulation mechanism provides a glimmer of hope for farmers.
Secondly, rainfall patterns are a critical factor in the occurrence of mouse plagues. High rainfall promotes plant growth, including agricultural crops, which serves as a vital food source for female mice. Research indicates that plagues typically emerge about three months after unusually high rainfall. However, it's important to note that mouse plagues do not reoccur for at least two years following a significant event. This cyclical nature of mouse populations offers a strategic advantage for managing the plague.
Lastly, the climate plays a pivotal role in the mouse plague's duration. While mouse plagues can persist from early autumn to winter and even into the summer of the following year under optimal conditions, Western Australia's hot and dry summers pose a unique challenge. These conditions further compact the soil, depleting moisture and making it more difficult for mice to burrow and breed. This natural environmental factor provides a potential solution to the plague.
Despite the relief that may be on the way, concerns arise regarding the impact of double-strength mice bait on native wildlife. The higher-dose bait, containing zinc phosphide, has been approved for use and is expected to provide more effective control. However, there are worries about its potential to poison native birds, particularly those that feed on grain from paddocks. A case in Coorow involved the discovery of numerous dead or dying native birds, including western corellas, little corellas, galahs, Regent parrots, and Australian ringnecks.
The long-term effects of using stronger mice baits on native birds and wildlife remain uncertain. While it is possible to test for exposure to zinc phosphide, these tests are not routinely conducted for screening dead wildlife and can take weeks or even months to complete. As winter approaches and the double-strength baits take effect, it is crucial to closely monitor the impact on local wildlife to ensure the balance between pest control and environmental preservation is maintained.
