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Rodent Rampage

Relatively sheltered from the ravages of Covid-19, Australia has been experiencing a series of natural disasters over the past years that have stunned locals with their ferocity and intensified the debate about the effects of climate change on the Red Continent. From an intense drought that has plagued the eastern half of the country since 2017 and catastrophic bush fires in late 2019 and early 2020 to flash floods and freak weather in early 2021, Australians and Australian farmers in particular have experienced nature at its most ferocious. Now an epic plague of mice has descended on rural Australia, gorging on stores of hay intended for farm animals and invading homes, leaving a trail of chewed up cables, furniture, appliances and cars.

Australia's agonising drought was temporarily relieved by rains during the southern spring and summer, producing bumper crops of grain and hay unseen in years of dusty dryness. Long suffering farmers thought they had turned a curve and survived the worst. Then the mice arrived - in their hundreds of thousands. Munching their way through bales of hay and leaving their noxious urine and droppings to spoil anything they left behind, the rodents have caused massive damage to farmers only just starting to recover from years of hardship.

Farmers have tried to come up with inventive ways of combating the plague, fashioning water traps out of buckets and planks and luring mice into cages scattered with grain. But the mice breed so quickly and have already multiplied exponentially that trapping, drowning and killing mice in myriad ways is merely slowing their relentless march across the country's grain belt. In many cases the only way to retard the vermin is to burn hay bales and grain stores in huge pyres, sending tens of thousands of dollars of feed up in smoke.

One of the reasons for the explosion in the mouse population is thought to be a change in farming practices. The fields, bone-dry after years of little or no rain, have been reduced to dust. To retain some of the moisture in the ground, farmers have been sowing crops directly onto the stalks of the last crop. This gives mice more food and places to hide and breed. The mouse's prodigious capacity to breed leads to exponential populations growth. They typically start reproducing at around 6 weeks old and after three weeks of pregnancy usually give birth to a litter of around 10. Female mice continue this cycle of reproducing throughout their life of 12 to 18 months without a break between pregnancies. This means that a single pair of breeding mice can produce a brood of some 500 in the space of a single breeding season of 8 months.

In New South Wales, one of the worst affected states, the government has procured 5,000 litres of the highly toxic pesticide bromadiolone, an anticoagulant that prevents the blood from clotting. While highly effective in controlling outbreaks, environmental campaigners are worried that native species of birds, snakes and reptiles could also die from the poison intended for mice. In Queensland, health authorities are raising the alarm over a steep increase in cases of leptospirosis, a flu-like illness that can lead to meningitis, kidney failure and respiratory problems in humans. The rise is thought to be caused by mouse to human transmission of the virus common in rodents. Mouse plagues are not unusual in Australia. Many farmers remember horrendous plagues in the 1970s when the ground beneath their feet was moving with swarms of rodents. Back then, the end of the infestations usually came when the mouse population grew so big that it couldn't sustain itself. When faced with starvation, mice turn on each other, thus bringing a natural end to the crisis. With temperatures at historic highs in Australia over the past decade, however, some farmers worry that the mice could survive the winter and return in even larger numbers in the spring. Some scientists worry that rising temperatures and decreasing rainfall could lead to mouse plagues becoming a chronic problem in Australia.

For now, Australia's farmers are hoping that the infestation will leave them just enough feed to tide them over the winter. Matthews Abbott visited some of the worst affected farming communities in New South Wales.

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