Managing Mice

Key points:

• 'Trial' result - an owl will deliver 1 mouse every 15 minutes to a nest.
• If you walk 100m down a single furrow and count the mouse holes in a 1m strip - x100 to work out the number of burrows/ha. Potential for 6-10 pups/burrow.
• Pups will start breeding themselves once they reach 6 weeks old.
• New litter of pups every 21 days. Mice gestate the next generation whilst weaning the current generation. Can get preggers 3 days after giving birth.
• Breeding starts in spring and continues through to autumn.
• 1 pair can produce 500 offspring between spring & autumn.
• Mice need food, shelter and water to survive/thrive.
• Mice need 3g of food per day. 22 cereal grains = 1g. 1 mouse needs 66 grains per day.
• 1T/ha of barley (say after a weather event and prior to harvest) = 2,200 grains/sqm = 33 feed days/sqm = 330,000 feed days/ha.
• Typical harvest losses ~ 300kg/ha = 10 feed days/sqm = 100,000 feed days/ha.
• Headers will likely be going fairly quick given the year. Worth using drop trays to measure losses to estimate level of food competition?
• Baiting principles:
• - aim to use 50g ai bait. 1 grain is a lethal dose. Mice become averse to bait after taking sub-lethal dose.
• - Baiting at seeding:
• - spread bait at 1kg/ha = 3 grains/sqm. Hence reduce food competition:
• -- seed destructors.
• -- straw removal. Current fertilizer prices a big discouragement for this.
• -- burn stubbles.
• -- spread bait behind the seeder. Alternative food buried.
• --- mount a baiter behind the seeder. Use a ute - wasted staff member - but good job for a teenager.
• - prioritize paddocks where there was a weather event prior to harvest - increased food availability.
• - keep monitoring through winter. Less activity - food stored in burrows? Breeding pause.
• - Spring baiting:
• - will see holes in canola after seeding, but damage less visible in spring. Pods on the ground are a sign.
• - peg 10 chew cards 10m apart along a 100m line. Start 30m from the paddock edge. Soak the cards with canola oil - use an aerosol can for convenience.
• - retrieve the cards the following morning. Monitor medium activity paddocks and bait high activity paddocks.
• - spread baits again in spring as breeding starts up again and before population explodes.
• - spread baits by plane or with a spreader mounted on a boomspray (bait gap should be <12m wide).
• - aim to spread bait while weather is good. Avoid going before a rain event.
• Don't use ZP (zinc phosphide) in domestic setting as it releases phosphine gas which is extremely dangerous.

Lake Grace 2022 Observations:

• Much less mouse activity in paddocks that carried sheep/livestock over the summer. Continual croppers to consider agistment?
• 2021 canola paddocks had worse mouse activity:
• - surely not related to availability of food as barley paddocks would be worse in that regard
• - canola stubble deters owls/birds of prey over the summer from controlling mouse numbers
• -- anecdotes of canola paddocks that were speedtilled having less mouse activity this season
• -- if this is true dragging a chain over canola stubbles this summer should be a good opportunity to control numbers.
• - cutting cereals lower also a potential strategy