Mouse and rat behaviour
The deer mouse (Peromyscus maniculatus), the house mouse (Mus musculus) and the brown rat (Rattus norvegicus) have long lived in proximity to humans. But that’s no reason to tolerate their presence if they get too close to us!
Rats and mice both belong to the family Muridae, and have spread from Central Asia to nearly every part of the world. They were likely introduced (involuntarily) to North America by European colonists. The house mouse is small, reaching no more than 30 g in weight in Quebec. It is recognizable by its large ears, long tail, brown back and grey belly. The deer mouse, which is more common in rural areas, has brown-white fur with a white underside and feet, and its tail is as long as its body. The brown rat, also known as the sewer rat or Norway rat, has a stocky body and can weigh up to 450 g (1 lb).
In the fall, mice and rats seeking warmth and food are attracted to barns and other farm buildings, warehouses, landfills, houses, etc. These rodents will then be active in those locations all winter long, since they do not hibernate.
Brown rats dig burrows consisting of extensive tunnels. Mice, meanwhile, are content to stay in wall or floor cavities, in cupboards and in boxes.
Both are omnivores. Rats eat meat, fruit and much more, including waste and carrion. Mice are particularly fond of grains and cereals, but will eat just about anything—even glue and soap!
Are mice and rats useful or bothersome?
Useful
Some rats (specially bred strains of brown rats) and mice (albino house mice) are used in laboratories for scientific research.
Both rats and mice are popular as pets, alongside gerbils, chinchillas and other small rodents.
In the wild, both types of rodent are prey for several species of mammals and raptors.
Bothersome
- Rats and mice soil buildings with their saliva, urine and feces. Surfaces contaminated by their droppings are to be avoided. Urine and droppings can also be stirred up into the air as fine droplets (or, if they have dried, as dust). Just breathing in these particles can be enough for a person to become infected.
Both types of rodent actively search for food stored or thrown away by humans, which leads to serious food safety and contamination issues. Avoid all contact with food that appears to have been nibbled at by rodents.
They can chew through wiring, construction materials and (in the case of mice) books, cardboard, plastic and wood.
They can transmit a variety of diseases to humans, including viral, bacterial and parasitic diseases such as typhoid fever and salmonellosis. Deer mice can carry hantavirus, which in humans can cause a rare but very serious pulmonary syndrome.
Rats can attack animals that are larger than them, even people, so be aware of the risk of bites.
Tips for keeping mice and rats away from your home
A mouse can squeeze through an opening as small as a dime, while a rat can fit through a quarter-sized one!
1. Keeping mice and rats out of your house
To keep rats and mice at bay, you need to start by finding their entry points:
Repair pierced sewer lines or add backflow valves (of the normally closed type) to the lines leading from basement plumbing fixtures (these are perfect access points for sewer rats).
Install metal weatherstripping under doors, and make sure windows are well caulked.
Seal any cracks you find in the foundation.
Seal all joints around pipes.
Use fine-mesh metal screens to cover dryer vents, fan intakes and outlets, and roof vents.
Keep your kitchen clean. Store dry foods (including pet food) in metal or glass containers.
2. Keeping mice and rats out of your garden
Cut back tall grass around the house so you don’t provide nesting sites for rodents. For the same reason, remove clutter around the building.
Keep garbage in bins with tight-fitting lids.
If you have wood stacked outside, make sure it is around 30 cm (1 ft) off the ground and away from the house.
Don’t put fatty or oily table scraps, eggs or dairy products in the compost bin, unless it is a sealed model. Line the bottom of the bin with a solid, fine-mesh metal screen.
Eliminate sources of water around the house: leaky taps, flowerpots, etc.
When the weather first turns cold in the fall, keep your doors properly closed: at this time of year, rodents will be actively seeking warm places.
How to get rid of a rat or mouse infestation?
Rats and mice are deemed to be pests, so exterminating them is permitted. Traps can be effective if laid in the right locations. The classic snap trap is best (rather than glue traps, which are less humane because the rodents survive for a time). You can also use food laced with an anticoagulant rodenticide (commonly known as rat poison), which kills rats and mice and causes their carcasses to dry up. Be careful, though: these types of poison are hazardous to children and pets.
If you opt for a baited trap, use strong-smelling foods like peanut butter or bacon drippings, mixed with oat flakes, raisins or gumdrops.
Reset traps two to three weeks after the most recent captures, to catch newly matured young.
Check the traps every day, regardless of which model you use.
Protection is a must
When cleaning areas soiled by rodents, with soap and water, always wear rubber gloves and a HEPA-filter mask.
- If you are dealing with a colony, or need to eliminate one or more brown rats, hire a professional. An authorized exterminator must have a permit from the Quebec Ministry of Sustainable Development, Environment and the Fight Against Climate Change. See our tips on how to choose one wisely.
f you suspect that rats are living beneath your home’s foundation slab, camera inspection of the drains may be necessary. Drain-inspection specialists and some plumbers offer this service.
To learn more about mice and rats
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