“The outbreak had such an impact on people that they really don’t want them to come back, so they’re being really vigilant about them,” he said.
Regional and rural communities across NSW were swarmed last year as mice chewed their way through millions of dollars’ worth of crops, machinery and vehicles.
Estimated financial impacts from the plague were between $50,000 and $150,000 according to a NSW Farmers survey.
While numbers are expected to plateau heading into winter, Henry said a lack of surveillance and baiting could lead to an outbreak next spring.
“Mice are incredibly successful breeders,” he said
“They start breeding when they’re six weeks old, and they can have six to ten babies every 19 to 21 days after they start breeding.”
“But if you get a low level of winter survival, then when they start breeding next spring they start from a much lower population base and the rate of increase is slower.”
Researchers believe an increase in rodent sightings could be due to a number of late summer harvests brought on by wet weather conditions.
“They’ve continued to breed through the autumn where there has been food available for them. So we’re seeing them in high numbers in those late harvest summer crops,” said Henry.
Henry said a recent tweet on his MouseAlert Twitter account helped to identify areas of concern.
“I got responses from Central Queensland, to the west of Murra Murra. There’s a lot of mice out there,” he said.
“I got responses from the Southern Riverina in NSW, and then from the Wimmera in Victoria in the Northern Valley.
“York peninsula in South Australia and of course at the moment there is a lot of mice over in Western Australia for the second year in a row.”
NSW Farmers is joining the push for landowners to remain cautious.
“What we don’t want to see is a repeat of last year’s mouse plague, so please if you see something, say something,” said NSW Farmers Vice president Xavier Martin.
“We need everyone to use their chew cards but also to keep an eye out for mice, and report any rise in numbers.”
Chew cards to monitor rodent activity are available from the Grains Research & Development Corporation website.
CSIRO researchers alongside the Grains Research and Development Corporation (GRDC) conducted a study in 2021 which found that the baiting measures in place were inadequate to control a plague.
During laboratory research, Henry said mice “had eaten what we thought should have been easily a lethal dose and it wasn’t”.
“They were living to tell the story and we thought well what’s going on?”
“All of the mice were half as sensitive as we thought they should have been and what was reported in the literature.
“We were just falling on the results of this work as that mouse outbreak started.”
The Australian Pesticides and Veterinary Medicine Authority then moved to approve an emergency use permit for double strength Zinc Phosphide bait at 50 grams per kilogram, which remains the preferred mice baiting option for farmers across the country.
NSW government rebates providing financial support to those impacted by the plague closed in February this year.