Researchers have recorded between 100 and 200 mice per hectare at some monitoring sites on South Australia's Adelaide Plains, with numbers reaching 400 to 600 per hectare where traps are at saturation point. A mouse plague is officially defined as 800 mice per hectare. Mice dig along seed furrows during seeding, consuming grain before it can germinate and causing visible damage described as UFO rings or circular patches of bare earth. Growers near Geraldton and Ravensthorpe in Western Australia have shared footage of mice moving through paddocks and stubbles, while residents in Morawa, about 360km northeast of Perth, have described coming home to mice overrunning their pantries.
The mouse threat is the latest in a series of blows for growers, who have already cut paddock movements to conserve fuel. Grain producers are dealing with increasing uncertainty about fuel and fertiliser access due to escalating global conflict affecting trade routes. Farmers are under compounding pressures, contending with fuel shortages and spiralling fertiliser prices from disruption to global trade due to the US-Israeli war on Iran. Roughly 20 to 30 percent of global fertiliser supply comes from the Middle East, and the effective closure of the Strait of Hormuz has halted exports of urea, ammonia, and phosphate from Saudi Arabia, the UAE, and Qatar. Australia imported 3.85 million tonnes of urea in 2024.
Scientists and agronomists say the industry is better prepared this time, with improved understanding of zinc phosphide bait and earlier warning systems. The last major mouse plague in 2021 caused an estimated $1 billion in damage across several states, with rural New South Wales alone suffering losses of around $660 million. Elevated mouse numbers have been seen across a broad stretch of the country, with CSIRO flagging concerning populations from Geraldton to Esperance in Western Australia and into southern Queensland. Western Australia's Kwinana West region has been assessed as high risk. High-value crops such as canola are at particular risk given seed shortages this year.
Mouse populations can escalate rapidly, with small numbers turning into large infestations within weeks. Pest controller Peter Cekanauskas put out 7.5kg of bait and it was consumed in less than three days. The severity of the current mouse threat compared to the 2021 plague in terms of geographic spread and economic impact projections remains unclear, as does what specific measures are being taken by farmers or authorities to control populations before they reach plague levels. The timeline for seeding season and how it aligns with peak mouse activity periods, along with any government or industry support programs to help farmers mitigate mouse damage and other compounding pressures, have not been detailed.