Common mice can be recognized by their ocher-brown coat and dark grey or chamois underbelly. They are one of three species (in addition to Norway rats and roof rats) that live in a close relationship with humans. Unlike young rats, mice have a rather pointy nose, smaller feet and well-developed ears. The white (albino) form is the most frequently used laboratory animal. Other small rodents with which they can be confused are indigenous species (native to our regions) often seen in the wild. For example, the damage sometimes observed at the base of young trees is usually caused by voles that are incorrectly referred to as “field mice”. Deer mice are also found in country homes or outdoors; they are hard to differentiate from white-footed mice (with white underbellies), jumping mice (with long tails) and shrews (with very pointed noses and tiny eyes).
Common mice will dig nest holes in the ground if they have no access to other shelters. Their nest resembles a 10 to 15 cm diameter ball made of fine shreds of paper or cloth. Mice can have 5 to 10 litters in any given year, each with about 6 young (laboratory mice have produced up to 100 offspring in one year). However, those that live in cities must compete for food and shelter in addition to avoiding predators (rats and cats). The young are born hairless, with their eyes closed and they mature between the sixth and tenth week. Mating can occur throughout the year, but is most common in spring and late summer.
Common mice are less dependant on water supplies than rats. They also consume lesser amounts of food and nibble here and there (3 g per day). They love seeds and grain, but sometimes prefer food rich in sugar, proteins or fats such as bacon, chocolate or butter. They also feed on vegetables, fruits, fungi, roots, meat, insects, etc. Mice cannot distinguish colors but have excellent senses of smell, taste and touch. They are primarily nocturnal animals. Their daily activities take place within a radius of 3 to 9 meters. They are able to climb and can jump over 30 cm.
Places where they can be found in the home
Mice infest stored food as well as pet food. They can gnaw structures in addition to wires, and damage wall insulation materials, and can shred clothing and documents when looking for nest building materials. Common mice nest in boxes, closets, attics, basements or garages. If you see more mice in the area around your house, you should suspect an indoor problem, since they tend to occupy hard to reach places such as inside walls and spaces under floors. Common mice are found in homes and stores more often than rats. They also infest museums and garages. If food is accessible, these mice can also live on farms or in fields where they will dig their burrow in the ground or make a nest under a rock. The access hole to their burrow is 2.5 cm in diameter.
Signs of infestation include: the noises they make; finding excrements that are sharp at one or both ends (0.6 cm or less in length) on the floor or in cupboards or closets (they produce from 40 to 100 per day); tracks left by their feet (1 to 1.9 cm) or tails (2 mm wide); greasy traces left by their coat in passing; damage they cause by gnawing (1 to 2 mm wide marks); or entrance holes (4 cm or less in diameter). The urine of this mouse fluoresces when illuminated by ultraviolet light. Also, because it deposits hundreds of droplets of urine along its path, you can smell its specific odour. You can spot mice during the night using a flashlight.
Keep food in sturdy containers, sweep often, and practice good waste management to reduce sources of food for mice. It is also best not to leave boxes or other rubbish, which could serve as shelter, lying around. These measures alone are not enough to solve a mouse problem but they will help a lot; the mice will have fewer alternatives to the toxic bait offered to them, it will be easier to detect signs of their presence, and the population will not become too numerous.
Since mice can enter houses through small openings, it is best to inspect the exterior of the house and plug up any openings greater than 0.6 cm (which is not easy) with resistant materials such as mortar, cement or galvanized sheet metal. Such measures should also be applied to the holes around pipes that enter the house. Some authors suggest that mice can get through a slot the thickness of a dime, hence the importance of plugging such openings. Installing screens on windows and air vents; metal panels under wooden doors are also recommended.
If these prevention methods are not adopted, there will be nothing to stop new mice from getting into your home.
Mice are said to eat only about one-tenth of the food they spoil by urinating and defecating, or leaving their hair behind. They can also transmit the virus that causes meningitis (69% are infected) as well as tapeworms, and pass on various pathogens by biting, or via flees or mites they carry. Since they can contribute to starting fires when they damage electrical wires, their presence should not be tolerated.
You should learn to distinguish common mice, that are not just temporary invaders, from other indigenous species that can get into the house in the fall. To control common mice you will also need to monitor their food source and trap individuals that live somewhere in the house.
The options for combating mice are more or less the same as for rats. However, even though mice are less afraid of new objects and are less dependent of a water supply than rats, they only require a little space and manage to survive on very small amounts of food that they nibble on here and there. This is why a strategy is required to get them to absorb the necessary dose of anticoagulant or poison. Always read the label carefully before using a rodent killing chemical.
It is often better to use mousetraps and attach them to solid objects to prevent bad smells from undiscovered dead animals. You can glue two mousetraps together, side by side, and enlarge the trigger by attaching a piece of metal to it. The bait must be placed near the wall, along the mouse’s path. Let the mouse get used to the bait for several days at first before setting the traps. Small pieces of bread, chocolate, bacon, cake, dried fruit, cheese, seeds or peanut butter can be used as bait. The traps should be set close to one another since mice do not wander far from their sources of shelter and food. You can also capture mice (regardless of their size) with sticky traps by placing bait (peanut butter, jam or cake crumbs) in the middle. Live-capture traps are also available.
You should allow mice time to get used to the bait if you want to add anticoagulants (that cause hemorrhages) or poisons, otherwise they may avoid the bait – with or without a rodent killing chemical – for weeks or even months. In some places in Canada, 75% of the mice have apparently acquired a resistance to the first anticoagulant (Warfarin). Shelters containing bait can also be used for a few days so that the mice feel safe there. Slower-acting products are more often used to overcome the wariness of mice, since these chemicals do not allow them to make the link between their conditions and consumption of the bait. Some formulas (e.g., pellets) are also easier for the mice to handle.
Powders containing a toxic substance (tracking powder) that the mice walk over are also used, but they are not recommended in houses because the rodent killing product is highly concentrated.
Some claim that mice evolved from rats that lived in conditions where it was better to be able to escape into small holes than to be big and ferocious.
A hybrid of a rat and laboratory mouse has been produced using artificial insemination.
Some individuals in a mouse population are trap-shy by nature, and will not venture near traps, while others, more adventurous, will risk it more spontaneously.
One author claims that common mice are the most numerous mammal in cities after human beings.
You might think you have no mice (or rat) problem because of your pets, but the two can live in close harmony in an urban or suburban setting. Pet food often provides mice with a ready source of nourishment, and the mice can even live under doghouses, taking advantage of your pet’s absence to feed. Getting cats will not solve a mouse problem alone, but cats can prevent a new infestation.