Mice 101

Mice have been around for many many years. When someone finally discovers that they have mice in their home, I doubt that they want them there. The information that I will present are facts that you should know about if you have mice. I will endeavor to cover all aspects regarding mice so that you will have a broad knowledge of this pest. Topics will include:

  • Why you have mice in your home
  • What Pest Control companies offer and how to choose the right one
  • House mouse identification, habits and the diseases they can transmit

If you take the time to read the information I have given you, you will have a tremendous amount of knowledge to combat the issue without paying tons of money and not getting the results you desire.

First of all, my name is Jim Middleton and I have been the owner and operator of my business…Reliance Pest Management here in Winnipeg, Manitoba for 8 years. I have studied insects, birds and animals my whole life so for me, the habits of pests that come into the home, comes to me easily. I became interested in pest extermination because I saw the need to help people who were paying tons of money to get rid of pests but not always getting successful results. Reliance Pest Management also does not need to use chemicals or poisons to successfully exterminate pests in the home.

When you think of the words…”pest control”…it really doesn’t give anyone the impression that someone is going to exterminate the pest issue but just merely “control” the issue. The way I look at it is, in the case of mouse issues, if the reasons why mice have come into your home, why they breed in the home and what sustains them are not addressed…then the mouse issue will never be exterminated. This will be dealt with a bit later.

Why do I have mice?

There are various species of mice in Manitoba ranging from House mice, Field mice, Deer mice, Voles etc. but I am only going to concentrate on the most common and most destructive of the species…the house mouse.

The house mouse normally eats insects, plants and seeds they find outdoors in the non-winter months. Many people believe that mice came into their house in the fall because it is getting colder outside and they are looking for a warm place. In reality, the foods that the house mouse was finding in the warmer months are dying out and disappearing come the fall. House mice then have to secure another food source and that is usually found in your home. A house mouse, even full grown, can fit through a “dime” size opening which you will never discover every one to be able to say you sealed up every opening. This fact is hard to accept when some Pest Control companies even guarantee that they can do this. Mice have been known to even scale your outside walls to your roof where they find an opening to access your home. They are just looking for food. More information will be given in the section dealing with house mouse habits.

Species and Mouse Identification


Perhaps the most common mouse species that invades homes and buildings. This mouse has a pointed snout, large, rounded ears and a long and hairy tail.

House mice have an adult body length (nose to base of tail) of 3″-4″ with the tail length being 2″-4″ long. They vary in colour from light to dark brown. The ears and tail have little hair. The voice is a high-pitched squeak.

The best way to distinguish the difference between male and female is the presence of five pairs of glands and nipples on the female’s underbelly.

The house mouse is the species that have been domesticated as pets and for uses in a laboratory.


Most mice species begin to mate at 6 weeks old while they only reach sexual maturity in 20-30 days of age. House mice have a polygamous mating system meaning that each male mates with multiple females. The breeding season of house mice lasts throughout the year and females are able to produce an average of 7 young with 5-10 litters each year under favorable conditions. The pregnancy would last typically 19-21 days which makes it possible for the mouse population to reproduce at such stunning and alarming rates. Adult mice live 1-2 years.

I am going to give you a possible scenario of what to expect in a year when mice get into your home, find a food source, start breeding and become an infestation. Suppose (3) house mice find their way into a home. Say there is 2 females and one male. After about 6 weeks, there could be a total of 17 mice. After about 3 months, the total can be about 73 mice. If the mouse infestation has not been addressed and they are still finding a food source and ofcourse still breeding, after 6 months there could be upwards of 3825 mice in and around your home. With every female potentially having about (5) litters every 6 months and the conditions are optimal…there could potentially be 19,125 mice in your house. When conditions get as bad as this, there is no doubt that the infestion can spread to nearby homes and businesses.

Behavior and Habits

As far as the various species of mice that present themselves as definite pests, the house mouse is the most common. One should not state that they don’t have a mouse problem because they haven’t seen any mice. Mice are normally nocturnal coming out at night to find food. I have frequently heard many people say…”I haven’t seen any mouse droppings or mice running around so therefore I have no mice”.

In the wild, mice live in single male-dominated colonies. A typical colony consistsof a dominant male, several females and their young. Occasionally males may share territories but like most animals, dominant males may fight with each other. In the case of mice living in the home, one may hear fighting and squeaks in the walls as they cross paths. The abundance of food plays a big part in this.

It is important to understand the behavior and habits of this mouse species to be able to control them. I am a firm believer that the secret of controlling any pest is to understand the pest, know what they require to survive and take it away from them so they have to come to you.

Mice construct nests and will usually locate these close to where they find food. If they have found a food source in the kitchen…food in the cupboards, counters or in a garbage can…they may adopt to nest right under your feet. This may be under the bottom cupboards, under the fridge or stove or in the walls. The nesting material may be obtained by raiding what they find in the garbage (paper towel, newspaper or kleenix), insulation found in the walls, stove and fridge or even scraping the material from cardboard boxes and even chewing clothing. When the infestation gets larger, they may even adopt to nesting amongst clothing in a closet or inside couches.

A mouse has the ability to squeeze through a very small opening. An adult mouse can squeeze through about 1/4″ hole…if their head fits through, the rest of their body will squeeze through. I have chased a mouse into a kitchen where it was heading for a small hole…too small, I thought, for the mouse to fit through. It literally went through it like butter! If they find an entry point that they would rather use all the time, they will gnaw at it to make it bigger. Obviously, then, a young mouse does not need that big of a hole to gain entry anywhere.

Mice have great sense of smell and hearing but their eyesight is not very good. Vision is relatively unimportant as mice are mainly nocturnal and rely more heavily on other senses to travel. Mice use their whiskers to help navigate by sensing air movements and surfaces. Because of their poor eyesight and sensitive to bright lights, mice tend to forage for food when you are asleep. You may surprise them if you come into a room at night and quickly turn the light on. Even though mice couldn’t care less about you and would rather not confront you, it can scare most people to have a mouse run across the floor at night while you are watching television. Once an infestation gets to major status, seeing mice running around may happen often and even in the daytime. Do not underestimate what a mouse can do. They are able to jump as high as 18″ and can climb 13″ up smooth vertical walls. If they want to get on top of your fridge, inside your cupboards or on your counters, they will find a way. The only thing they can’t do is fly. Mice can run 12 feet per second and can swim as far as 1/2 a mile.
Mice chew constantly. One reason is that their teeth never stop growing and they need to gnaw to wear down their teeth.

When this mouse lives outside, it normally feeds on seeds, plants and insects. Once autumn comes and plants and insects die off, they will be in search of food. Many people think that they get mouse issues in their home in the fall because winter is coming or it is forecast that a cold, long winter is coming. Really, it does not have anything to do with weather. They are in search of food. They have been accustomed to living inside a home or building more than living outside. They will follow the outside of buildings looking for food or openings that may lead them to food. If they find an opening (say around a house), they will usually find their way inside to the basement. Once there, they will completely search the basement for some kind of food. If they don’t find any, they will utilize the walls, floors and ceilings eventually ending up in the kitchen. One main entry point in the kitchen is under the sink cupboard where they can gain entry because there is usually a space around water pipes that either go through the wall or floor. Many people keep their garbage can inside this cupboard. The mouse now finds food if they are able to access the garbage can and will set up it’s nest usually in close proximity to their food source. Once a mouse finds a food source in a home…they don’t leave. They will begin to nest usually very close to their food source. If that is in the kitchen, then that is where they will stay.

The food that mice will eat in the home is widely varied. Cereals, cookies, crackers, rice, seeds, chocolate, candy, the garbage…anything they can get into. If food is scarce, they may gnaw on potatoes, chew into a box of Kraft Dinner or even a bag of flour. Leftover food on the counters or stove and unwashed dishes still give mice an access to food.

Mice are typically nibblers and will eat numerous times in a day. They don’t need water to drink as they get this in their food. Mice don’t have bladder control and therefore when they have to go to the bathroom…they just go…wherever they may be. Their droppings and how many are seen are not a good indicator of how many mice could be living in the home. Their droppings are about 1/4″ long and pointed at the ends. A single mouse may produce 50-75 droppings a day. When they urinate, it will be somewhat translucent and may not be seen.

Mice are at the bottom of the food chain. They know that almost everything will try to prey on them which is why they breed so much. When they move around outside, they try not to in the open but rather close to objects, bushes, long grass, places where they can escape if attacked. In the home, they will generally run along the walls and dip under the stove or fridge if surprised. Mice like to follow their previous paths and with many mice using them, they produce grease marks on the walls or around holes from the oil on their bodies.

Mice are always looking for food. They will follow along buildings and if there is long grass or weeds flanking the building, this will guard against predators from seeing them. An adult mouse can squeeze through an opening as small as 1/4″. Entry points in a home where mice can enter can be cracks in the foundation, openings around the dryer vent or air conditioning units and where Hydro wires enter your home. Of course there is always openings under outside doors because of missing or damaged door sweeps and cracks around windows. Sometimes mice have the advantage of gaining access to the home by entering the garage if it is attached to the home. Regardless, it should be noted that no one can 100% “mouse-proof” a home since you cannot find every hole around your home. There has even been instances where mice have gone down a crack in the soil or gravel along the foundation of a home to find a crack in the wall that allowed them to get in. It is true though, that regular inspections of the possible entry points listed above can lower the chances of mice gaining access.

If a mouse were to completely search your entire home and not find food, they would leave. They don’t begin breeding unless they find a food source. Once in the kitchen and being down a floor level, the food sources they find are usually a garbage can they can get into, food on the floor or under the stove, pet food down on the floor or accessing the bottom cupboards. If these food sources are not available or someone moves them away they will find a way up to the counters, on top of the fridge or stove. There they can possibly find leftover food from the previous night, foods like cereal, buns, bread, baked goods, chips, candy etc. left on the counter. If these foods are not present, they may find access to the upper cupboards or pantries where the majority of food is stored. Do not underestimate mice! They will find a way to the top of your fridge by climbing up the back and they can get to your counters by climbing up cords, other objects and up the back of a dishwasher to the top where now they are inches from the counters.

If mice are able to find your food on the counters or in the cupboards such as boxed food (cereal, crackers, cookies etc.), if the box has been left open, they will just jump in and eat. If they can’t get into it but they can smell food, they generally will chew a hole in the bottom corner just big enough to enter. Many people may not notice this until they use the product or see food remnants in the cupboard. Canned foods or foods kept in plastic containers, spices, are usually safe from mice. If food is stored in the basement, mice can get into it and flourish before you notice the problem. Other notable foods that are sometimes bought in large quantities and stored in the basement are rice, beans, and dog food which have to be contained so that mice don’t have a major food source.

Another area where a mouse infestation can start is the garage. If bags of grass seed are stored there or any other edible food source, it can allow a mouse infestation to grow out of hand and it won’t take long before the population comes sniffing around your home.


Diseases and Preventative Measures

It is important to realize that when you have a mouse infestation in your home, you risk having diseases transmitted by coming in contact with the mouse, their droppings and their urine. When mice have to go…they go wherever they are, like birds. That can be on your dishes, cutlery, counters, floors or on your food. Considering where mice could have walked or got into, you can only imagine the bacteria, germs and diseases that can be transmitted. If a family seems to be always sick or having issues with nausea or food poisoning, I would definitely find out if that home has any kind of mouse problem. Take the mouse issue away and see if the health issues decrease.

One of the major reasons why mice in the home present health risks is the possible diseases they can transmit. Listed below are some of them:

Salmonella (transmitted by all mice)

Mice are frequent carriers of this disease. It spreads to humans by contact with mouse droppings, especially through consumption of contaminated food. You could eat foods such as cereals, rice and other small foods that have had mice accessing them. This disease cause serious, sometimes fatal gastroenteritis. Household pets are often subjected to this disease and die as a result. A mouse may appear quite healthy and act normal even when carrying Salmonella.

Prevention: Keep all foods closed and contained as much as possible. Follow the guide-lines below for cleaning up droppings and urine from mice. If mice got into any foods…throw it out! Always wash your hands.

Leptospirosis (transmitted by all mice)

The disease is transmitted when infected urine or semen comes in contact with the eyes, mucous membranes, or broken skin. This can be from direct contact or present in contaminated foods. Leptospirosis begins with flu-like symptoms ( vomiting, fever, myalgia, intense headache). The patient seems to recover, then a more serious phase sets in which can lead to meningitis, liver damage, kidney failure and death. This bacteria can remain in water or soil for months.

Rat-Bite fever (transmitted by mice and rats)

This disease is fatal in 10% of untreated cases. Usually contracted from rats but the infection can also occur from mice. The bacterium causing this disease enters the body through bites, as it’s name suggests, or from urine contaminating either food or pre-existing skin wounds. The symptoms include fever, body aches, vomiting and a red rash with small bumps.

Tapeworms (transmitted by all mice)

Mice host small tapeworms that can spread to humans who eat foods contaminated with mouse droppings ( or when hands are merely dirtied by droppings and not washed before meals). These parasites hatch out in the gut where they grow and reproduce.

Understanding that the presence of mice in your home can present a major health risk if it is not exterminated. Mice can also harbour ticks, mites and fleas. If a mouse in your home gets caught in a snap trap that you set, these parasites may climb off the now dead host and get on your dog or cat…or even you.

Now that it is known the implications of handling or coming in contact with mice urine and droppings, here is some suggestions when dealing with them.

  • When mouse droppings dry they become brittle but still retain their form. Most people, when confronted with cleaning up droppings on the floors or inside the cupboards, sweep or vacuum them up. This can break the droppings up into small particles that float around in the air where they can be inhaled. A better way of disposing of mouse droppings is to wear gloves and preferably a painters mask. In a spray bottle of water, add one part bleach to nine parts water and spray the droppings thoroughly. Wait a few minutes until the droppings have become soft. With a cloth, wipe up the droppings and disinfect the area. There is almost zero chance of inhaling small particles of droppings as when they were dry.
  • Mouse urine can be almost translucent and may not be completely dry right away. You can see mouse urine on surfaces with an ultra-violet light which will show up yellow in the dark. Mice could have been anywhere in your kitchen…cutlery drawer, on your plates, counters, dining table or floors. You now get a pretty good idea of the health risks that can be present when you eat from these items or when a child is crawling on the floor and puts their hands in their mouth.

Once a mouse issue has been exterminated completely, it is imperative that all surfaces be disinfected. It doesn’t matter what you use but products that will kill 99% of bacteria or steaming surfaces are the best. If using a steamer, it is an easy way to disinfect rugs, floors and furniture. Getting rid of all urine containing bacteria is very important especially with children, pets and people with respiratory issues in the home.

One other way to disinfect the entire home is with the use of UVC lights. This method of sterilization has been used in hospitals and research buildings for years. It really only involves the use of a UVC light with or without ozone. With ozone, the whole room where the light is placed will completely disinfect everywhere within an hour. You will have to ventilate the room for half an hour but the procedure is safe. People, pets and plants must be out of the rooms during this sterilization.

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