House Mouse

Unlike some of their country cousins, the house mouse in Australia is most commonly found in urban areas. They're widely distributed across the whole country and prefer to live in close proximity to human habitations where food and shelter are easy to find. Even if you've never seen a house mouse there's a chance you're living closer to one or several of these small rodents than you might feel comfortable with.

House mouse characteristics

• Scientific name: Mus musculus
• Colour: They can be grey, or light brown ranging through to black
• Weight: From 40 g to 55 g
• Size: Body from 75 mm to 100 mm, tail from 50 mm to 100 mm
• Diet: Omnivorous. Mice mainly eat grains, vegetables and fruit but can eat meat.
• Bite: Rarely bite people, but can transmit diseases if they do.
• Danger: Contaminate food, damage your home and spread multiple diseases.

How to identify a house mouse

The Australian house mouse has short fur, with the colour varying through grey, brown and black. Unlike the field mouse which tends to have greyish-white fur on the belly and darker hairs on the rest of the body, house mice are generally uniform in colour.

The tail, which is used for balance, is around the same length as the body and is almost hairless. House mice have a pointed nose and large ears, which, like the tail, are almost hairless.
As far as house mouse identification goes, the house mouse’s size could lead you to mistake it for a young rat. They can be easily differentiated however, the house mouse's tail is longer in proportion to the body than a rat's tail, their feet are smaller and their ears are larger.

There are, of course, numerous other mouse species in Australia but most are far less common than house mice, field mice and rats. If rodents move into your home, they're most likely to be house mice or rats.

The first clue that you have an unwanted mouse invader in your house often comes when you spot faeces or damage to food packaging. Finding mouse poop in your house is also a sure sign that you have the vermin themselves.

House mouse droppings are typically pointed and around 6 mm long, they can be soft and moist or dry and hard. House mouse poop changes in colour as it ages, fresh droppings are dark and somewhat shiny, over time they dry out, becoming paler and chalky.

The lifespan of a house mouse

How long does a house mouse live? This depends very much on the environment. Shelter from the elements, protection from predators and access to food all play a part in determining how long a house mouse will survive.

In laboratory conditions, the common house mouse has a lifespan of up to three years. When living outdoors, exposed to harsh weather, a range of natural predators and competing with other creatures for limited food, the lifespan of a house mouse is very much reduced. In fact, they're unlikely to survive for more than a year.

A mouse living in a house, however, is protected from common predators, has shelter from extremes of weather and once it gains access to your food stores it has everything it needs for a healthy house mouse diet. In these conditions, house mouse lifespan could be the same as that of mice kept in laboratory conditions, up to three years or so.

Check also: Rat Life Cycle: Lifespan and Habitat

The house mouse’s habitat

House mice are superbly adaptable. The preferred house mouse habitat is indoors near human habitations but they'll also venture outdoors in favourable conditions. In Australia, this is generally at the end of the growing season when they feed on loose grain in the fields. In this situation, the number of outdoor house mice can reach epidemic proportions in a short space of time. The house mouse dislikes damp conditions but is tolerant of cold. Nevertheless, even if individuals move outdoors when food is plentiful they'll move back inside as the colder months approach.

Mice in houses prefer to live in secluded parts of the building. A mouse in the house might be found living in attics, wall voids or crawl spaces. Since they like to live near food sources they favour locations in larders, under food cabinets or, classically behind skirting boards. Once settled in a home, the house mouse doesn't need a lot of space to cause a vast amount of damage and it can squeeze through spaces the width of a pencil.

Breeding habits

Female mice reach breeding age somewhere between 8 and 12 weeks after birth. The gestation period is just three weeks and it's not uncommon for a house mouse to give birth to up to 12 pups, litters of 14 or 16 are not unknown.

Females are fertile almost as soon as they give birth so the second litter could arrive just 25 days after the first. Typically a female house mouse will have 7 or 8 litters a year.

A house mouse baby is born hairless, blind and defenceless. The mother nurses the pups for the first 21 days, during this time they develop rapidly. Hair begins to grow at around day 6, by day 10 they have a full covering of fur. By the time the pups' eyes open, at around day 14 they're almost fully developed. Baby mice are weaned at 21 days and while they might continue to live close to their mother, they will survive totally independently of her.

Where does a mouse nest in a house?

House mice rarely travel more than 10 metres from their shelter to their food source. This distance can include going up and down as well as across since mice are good climbers. If you're looking for mice or signs of infestation, start near where you store your food.

Places, where you might find a mouse nest in the house, include:

• The back of less used kitchen cabinets
• In gaps under the floors
• Around rubbish bins, especially those used for food waste
• In attics or basements
• Wall voids and crawl spaces
• In sewers (mice don't like damp or wet conditions but they can swim very well)

The first sign of a house mouse nest is often the discovery of chewed fabric or paper. House mice make nests that are roughly ball-shaped, between 10 and 15 centimetres in size. Materials used include cloth, paper, stuffing from mattresses, pillows or cushions, and anything else the mouse finds that is soft and insulative.

Check also: What Food Attracts Rodents to Your Home

Important facts about the house mouse

• House mouse diseases that can be spread to humans include salmonellosis, hantavirus, typhus, bubonic plague and many more.
• House mice mostly spread disease through their urine and droppings, a single mouse produces between 40 and 100 droppings a day.
• The house mouse diet doesn't have to include water, so long as the food they eat has a moisture level of around 15%.
• It's rare for house mice to bite people but there is at least one account of someone developing meningitis after a house mouse bite.
• Mice will gnaw wood, fabrics and plastic and can cause structural damage to a property. There is also a fire risk if they chew the insulation on wiring.

If you suspect that you have rodents in your home it's best to consult a professional pest control company. Any time you spend trying to eradicate mice yourself is time when the population could be increasing; a single female mouse could give rise to an infestation of hundreds within a year. Call the specialists in and you can be confident that you'll get a thorough assessment of the situation and safe treatment that guarantees reliable results.