Australia’s Disastrous Mouse Plague
At the moment the mouse plague afflicting Australia feels almost biblical following extensive fires, drought and rain in recent times. Millions of mice are on the move in Western NSW and parts of Queensland, Victoria and South Australia, causing millions in property damage.
The mice arrived with the First Fleet in 1788 and have been a problem ever since with plagues increasing in frequency. The plagues happen approximately every four years with the worst plague in 1993 causing $96 million dollars in damage to crops, livestock, insulation, farm machinery and buildings. The mice consume the grain crops but move on to other food sources when they have exhausted the current one.
A farmer from near Walgett reported that mice wiped out 800 hectares of his sorghum crop and caused $200,000 in damage. He saw the ground around his grain piles writhing and rippling with thousands of mice. Houses are invaded and farmers said that the mice even run over their beds and urinate on them leaving behind a pungent smell. Soon the smell pervades the house and makes it unbearable. Baiting the mice makes it worse as the dying mice go into the ceilings and walls to die.
The farmers are fighting the plague as best they can. They are baiting and slashing the sides of paddocks to make mice movement more visible to predators. Snakes have done well from the abundance of food but if the mice have consumed poison, then it kills them too. In addition native wildlife and pets are eating the mice and getting poisoned as well.
The government has belatedly intervened with a $50 million rescue package with money for new rodent research, free poisons for farmers and mice bait rebates of $1000 for small businesses and $500 for households.
Baiting is the only large scale method of controlling the outbreak, with zinc phosphide currently being the most prevalent poison used. The government has applied for permission from the Pesticide Authority to use bromadiolone, an anticoagulant. The problem is that these poisons don’t break down and go up the food chain. Another problem is that even after using poison, if your neighbour isn’t doing the same then, the mice will just run through the fence. The mice are also expected to return with increased numbers in spring when ripening crops provide new food sources thus perpetuating the cycle.
One of the primary sources of the problem is the extensive monoculture farming. The monocultures degrade soil and reduce biodiversity, so there are fewer predators to control mice populations.
While genetic research could solve the problem a more polyvalent solution would be to improve farming practices.
