A (mouse) plague o’ both your houses

By Eliza Keck

Everyone loves a good old-fashioned mouse plague, right? Oh yeah, no we don’t. Not at all.

Well, if you’re in Victoria or South Australia grab some steel wool and get the house ready because our experts are expecting a lot of mice this autumn.

Why so many?

There are a few reasons why certain years are better than others for the humble mouse. Our ecologist Steve Henry explained how three key factors can contribute to a plague: climate, food and breeding.

“Their breeding season usually starts in late August or September, but this year we found it started in early August. This is most likely because we’ve had one of the wettest springs on record which led to a terrific harvest, meaning more food for mice,” Mr Henry said.

Because mice aren’t spending all their time hunting for food, they have time to get down to business and procreate. Two or three weeks early doesn’t sound like a big deal, but those extra weeks can have a massive impact.

“By the time I got to my first site, three generations had already been born,” he said.

To put that in perspective, a single breeding pair of mice can produce up to 500 offspring in a breeding season (spring to summer). It takes mice only six weeks to reach maturity and their gestation period is about 19 to 21 days.

“They even get pregnant as soon as they’ve given birth, so they’re gestating a new litter while weaning their current one.

And unless summer brings lots of very hot, dry weather (we’re looking at you, Melbourne), they’ll continue breeding right through. So in autumn, when farmers begin sowing their next crop and the weather is again favourable for breeding, there’ll be a greater ‘base’ population of mice ready to procreate.

Why so serious?

Spreading disease aside, mice do much more than run about leaving droppings everywhere.

In 1993, Australia’s worst ever mouse plague caused an estimated $96 million worth of damage, destroyed thousands of hectares of crops, blighted piggeries and ravaged poultry farms. The whiskered marauders chewed their way through rubber and electrical insulation, damaged farm vehicles, ruined cars and buildings.

Another plague in 2010/11 was almost as bad, affecting 3 million ha of crops in NSW’s central west and the Riverina, as well as parts of Victoria and South Australia.

So what can you do about it?

The good news is that with sufficient warning it is possible to prepare for mouse plagues, and to minimise the damage they cause, through early baiting and removing food supplies and cover. But as well as reducing numbers, our researchers are urging everyone to make use of MouseAlert, a citizen science website where keen-eyed rodent reporters can notify us about mouse sightings, enabling us to better track their numbers and help communities prepare.

So if you see a mouse, don’t stay silent, report it before putting steel wool in all the nooks and crannies of your home!