Queensland farmers attempting to recover from years of drought are now keeping a wary eye on mouse numbers.
Trap monitoring carried out by the Department of Primary Industries' Queensland Biosecurity has found mice in plague proportions on properties around Clifton, south-west of Brisbane, and burgeoning populations elsewhere in the state's peak grain-growing areas.
Queensland Biosecurity zoologist Peter Cremasco said while it was too early to declare a regional plague of the rodents, damage bills were already mounting.
"At this time of year we expect mice numbers to be increasing exponentially, but this year they've started off from a higher base than normal," Mr Cremasco said.
"We've seen numbers in some areas go basically through the roof to the extent that the particular growers in the areas affected would be calling it a plague.
"To those people it's a major problem."
Mr Cremasco said mice were in worrying numbers on the Darling Downs, particularly in the Clifton-Pilton area, around Pittsworth and on parts of the Central Downs.
While Biloela, south-west of Gladstone, shows no abnormal numbers, 50km away between Banana and Theodore there is a worrying increase.
He said further monitoring in July would determine whether mouse numbers were likely to continue rising.
This will determine the likelihood of a full-blown mouse plague, more likely next year.
"I'm expecting next year to be the problem year," he said.
Apart from crops in the field and in silos, farm machinery were another costly target.
"One farmer is up for $3,500 repairs to his four-wheel-drive after mice gnawed through the fanbelt, which took out the cam belt, causing the valves to drop into the pistons," Mr Cremasco said.
"Electrical wiring in tractors and headers gets taken out, filters in air conditioners, wiring in sheds and homes."
Females can produce a litter of up to six each month during the breeding season, gestation lasting from 19-20 days, and the newborns can breed from five weeks.
The region's last major mouse plague in 1995, which affected a region from Dalby to Goondiwindi, was estimated to have cost up to $30 million.
A comprehensive aerial baiting campaign using strychnine over an area of 250,000 hectares was required.
Since that event the state government has authorised the use of a new rodenticide, MouseOff.
