Eating through grain plastic, household appliances and more. Now they are turning on one another. Australia is suffering the worst mice plague in decades.
"If you leave them long enough they start eating each other, quite easy. They take the weakest one out then they work their way to the strongest one."
Farmer Norman Moeris has had his grain stocks depleted- he puts the figure at around 100,000 US dollars in losses and over 2000 sheep have died.
His farm - located in the northwest of the state of New South Wales is one of many that has seen a plague last for several months.
The state offered farmers free bait to deal with the problem, but the size of the outbreak has led to more calls on the government to step up and allow the use of a toxic poison currently banned in the country.
Despite laying bait around paddocks and traps around the house, the mice just keep coming.
And it is taking a toll on his family too.
"It's just hard. After the drought, that's the biggest trouble. We've been on our knees, we got up a bit, now we're back on our knees with the mice."
Mice - believed to have arrived in Australia along with the first European settlers - are well suited to the country's often harsh climate. They can survive long periods of dry weather and thrive as food and water becomes available.