Why is there a mouse plague in Australia and can it be stopped?
Millions of mice are terrorising Australian farmers, and there's no end in sight. The mouse plague, which started 10 months ago, has ruined the drought recovery as the pests devour new crops and destroy machinery. The problem is so severe that mice are biting people in their beds, sending some residents to the hospital in a critical condition. Here's what you need to know about Australia's mouse plague. The mouse plague has been caused by a "perfect storm" of optimal weather conditions for breeding and the end of the 2017 to 2019 drought. The mice first appeared in the spring of 2020 when farmers were harvesting a bumper crop. There was plenty of grain in the paddocks and in storage for the mice to eat, as well as fewer predators, which died during the drought. That year regional New South Wales had a particularly mild, moist summer that allowed the mice to keep breeding throughout summer and into autumn. Winter crops and well-established burrows keep the population well-fed and protected from the colder weather as farmers struggle to eradicate their ever-growing numbers. The mouse plague has stretched across NSW to southern Queensland, northern Victoria and into South Australia. Experts say there are millions of mice. However, it's impossible to know their true number because of how quickly they breed and their ability to hide. The problem first began in the grain belt across western NSW, including Dubbo, Coonamble, Warren, Nyngan and Narrabri. Mouse populations then spread to southern Queensland, forming the "epicentre" on the plague before also spreading to southern NSW. The prevalence of mice in South Australia across the Adelaide Plains, York Peninsula and Eyre Peninsula has surprised experts given the regions' dry summer. The mouse plague has stretched across NSW to southern Queensland, northern Victoria and into South Australia. The red spots show where the mice are concentrated most. The mice have caused hundreds of thousands of dollars of damage to farmers' crops and fodder. Many farmers have lost most, if not all, of their first big crop since 2017, sending the drought recovery backwards. Regional homes and businesses, particularly food-related businesses like grocery stores and cafes, have also been impacted. The mice even cause extensive damage to cars and machinery. It is also expensive to kill the mice, with the cost of bait rising as demand surges. The financial destruction, and the disturbing experience of being inundated by mice, is also impacting peoples' sleep and stress levels. Starvation or disease are typically the reason mouse plagues die out. And while bating is critical to control mouse populations, it's typically not what will end a mouse plague. Experts say it's crucial farmers and other impacted residents are vigilant with baiting through winter, otherwise there will be a huge number of mice breeding in spring and the problem could get worse. Farmers are currently using a chemical called zinc phosphide to poison mice in paddocks. The inorganic compound is coated on wheat to turn the grain into the bait. That poisoned grain is then scattered around pastures, with a single grain providing a lethal dose to an adult mouse. Many regional residents have become innovative with bucket traps, with reports they are catching as many as one thousand mice a night. Farmers are using a range of methods to kill the mice ( Supplied:  The NSW Government has urgently applied to the independent Australian Pesticides and Veterinary Medicines Authority for the chemical bromadiolone to be registered for agricultural use. NSW Agriculture Minister Adam Marshall has described bromadiolone as "napalm for mice". As an anticoagulant, bromadiolone stops the mice's blood from clotting until they bleed to death internally. It can be lethal in one day, which is quicker than other chemicals currently in use. Bromadiolone has been de-registered since 2017, and there are concerns about what impact the chemical will have on native animals. Mice are not migratory animals and will only move about 100 metres from their nest or burrow to forage. While there may be increased reports of mouse activity in urban areas, it would be due to localised breeding rather than the plague travelling from the country to the city. Mice always live where humans do, although they are often undetected. Existing populations increase when they have access to food and shelter. They may be sighted more frequently during the cooler, wet months as they seek warmth inside homes.