A Mouse in the House

The lowly House Mouse – my goodness but there have been a lot of images placed before us about this little rodent. While some of them may already be going through your mind’s eye, let me offer a few that I can remember.

  • Mighty Mouse – fighting the forces of evil
  • Mickey Mouse – that playful little hero of my childhood
  • The traditional hole in the wall that leads to the happy mouse-home
  • “Quiet as a church mouse”
  • The massive elephant cringing when faced with a mouse
  • The panicked housewife standing on a kitchen chair with a broom, as a mouse runs across the floor

How easily we stereotype things, often leading us to misunderstand the reality. Is it closer to the truth that the House Mouse is a hero, or is it really something to fear? Let’s learn a little bit about it, and allow you to judge for yourself.

Does the House Mouse belong here?

Where did the House Mouse come from? Well, as it turns out, it really does not belong in the United States, or anywhere else in the Western Hemisphere. It is native to the dry grasslands of eastern Asia, but hundreds of years ago it managed to hitchhike with human caravans, traveling to the coasts of Europe where it then hopped aboard ships that transported it to America and all those other countries that it now inhabits. As an introduced species of animal, now living where natural controls and natural predators do not exist, the House Mouse flourished, breeding, multiplying, and expanding its range without anything to stop it, and competing with the existence of native animals in the process.

How can I tell what kind of mouse it is?

There are many kinds of mice in the United States, and it may be easy to confuse those that are natives with those that are introduced. Others you may be aware of around your business or your home are species such as Meadow Mice (also called Voles) or Deer Mice. These usually stay outside the structure, but they too can cause some severe problems, and we are well aware of the recent disease outbreaks spread by Deer Mice – the Hantavirus and Arenavirus, which we have profiled in a separate BugInfo article for you.

Probably most common around homes, of these other mice, will be the Meadow Mouse, and you easily can distinguish between these different kinds by the following characteristics:

  • Meadow Mouse – stocky build, short tail, ears are very furry
  • Deer Mouse – slender build, long hairy tail that is white on the bottom
  • House Mouse – slender, long bare tail, ears are almost bare of hairs, belly light colored

Some important clues about the House Mouse

Some of the habits and the biology of the House Mouse are also important to know, because with knowledge comes the ability to control its presence. Here are some House Mouse characteristics to keep in mind:

  • It does not need to drink water – it can obtain all necessary moisture from its food
  • It can squeeze through openings only ¼” wide to gain access to structures
  • It climbs very well, can jump straight up about 18″, and can swim
  • It likes to stay against vertical surfaces – walls, cabinets, or boxes sitting on them
  • It prefers to eat foods such as nuts, grains, or sweet things – it is NOT particularly fond of cheese
  • It is very curious, and will quickly investigate objects that are placed in its environment
  • If all of its earthly needs are met – food, shelter, sufficient moisture – it may not travel more than 10 feet away from its nest
  • It is nocturnal, meaning it much prefers to be active at night – it avoids open areas
  • It is a creature of habit, and follows known pathways and prefers undisturbed areas

So, the House Mouse has some rather aggravating habits, but does that necessarily mean it poses a problem for us? Well, yes, as a matter of fact it does. This animal is one that we really would prefer not to have to live with. Even its scientific name – Mus musculus – describes it well, for in a general way this name means “little thief”. When living in close association with people the House Mouse makes its living by stealing our food and our possessions, so it isn’t a good tenant.

Why are mice considered a problem?

Let’s look at some of the problems caused by mice, and perhaps offer some solutions for you for helping keep them away.

Gnawing. First, as a member of the group of animals called Rodents, mice will “gnaw”. That is, they constantly are chewing on things, whether it is for food or for pure entertainment. They gnaw holes in walls to gain access to their hiding places. They gnaw holes in boxes and bags to get to food. They gnaw holes in stuffed toys or furniture to gain access to soft nesting materials. And frankly, they gnaw on an awful lot of other things for reasons we can only guess.

Rodents have “incisor” teeth, meaning they have a pair of teeth on the top that butt against the pair of teeth on the bottom. These teeth grow continually, and gnawing may be one way to keep them worn down so that they stay in their mouth. Incisor teeth of rodents are extremely hard, and they easily chew through wood or hard plastic. Rodents also are a major cause of fires that destroy structures, as they chew on electric wires in walls or attics.

Destruction of Food. So, mice and other rodents are destructive. However, beyond that which they physically destroy, they also are responsible for massive destruction of our food, simply by the contamination they cause. Like all animals mice must eliminate their waste materials – urine and feces – and unfortunately they are not particularly discriminating about where they place it. Since they are capable of dropping up to 25,000 fecal pellets each year (let’s see – add the 6, divide by 3, carry the 2 – that’s around 70 times each day!!) they will leave a lot of these little prizes in our cupboards, on the kitchen counter, on our furnishings or floors, or in the bags and boxes of food they have entered.

Rodents are believed to destroy up to half of the food we grow, worldwide, before we even get it to our tables. Australia has periodic outbreaks of mice that absolutely overrun their agricultural areas, causing 100% destruction of the grains and other foods being grown.

Why are mice considered a problem?

Spreading Disease. The third way that mice make themselves unwelcome is by the potential they pose for making us sick. This may be caused in one of two ways – either by germs that are contained in their urine or feces, or by pathogens passed along by their parasites – their fleas, mites, or lice, and they can be carrying a lot of these little critters. As we mentioned earlier, the terrible disease called Hantavirus is vectored (passed onto humans) by mice, although it is Deer Mice that spread the most dangerous form of Hantavirus, and we discuss this in a separate BugInfo article. The House Mouse currently is not incriminated in the spread of any virulent forms of Hantavirus.

However, bacteria, viruses, or other pathogens capable of making people ill are commonly growing on animal waste, and it is never a good idea to allow a buildup of feces of mice, bats, or birds in your walls, attics, or living areas of the home. When these materials dry and become airborne with gusts of wind, they can be inhaled and can cause infection of people. If you believe that you have an accumulation of such animal waste in your home, it is probably a good idea to contact a Licensed Pest Control company in your area, and get their advice or solicit their help in removing it safely, so that no hazard is created. These professionals are trained in the proper procedure for such removal, and will wear the proper safety equipment to avoid exposure.

Okay…so help us get rid of them.

So, what can you do to prevent taking on unwanted guests that can chew holes, contaminate food, and pass along pathogens? Here are some possible steps, taking into consideration some of the habits of mice that we mentioned earlier. As with any kind of pest – bug or rodent – you want to make your home as UNinviting to the invader as you possibly can. Rather than hanging out a great big “Come on in!” sign you’d rather the mice were unable to find anything in the house to support their existence.

The process called Integrated Pest Management – IPM – simply means that we want to change the environment that has welcomed the pest with open arms, and make it uncomfortable for them instead. The use of poisons to kill mice may be a very useful tool, but it is not the first step, and may be one you would prefer to leave in the hands of a Licensed Professional. It is the physical changes that you, as the owner of a property, should do to take that big first step in rodent elimination. Even if you contract with a Licensed Pest Management Professional in your area these physical steps will be very important in ensuring the rodent control is done in the best manner and for long term control.

Let’s look at IPM, and keep in mind some of the habits and biology of the House Mouse that we mentioned earlier.

1. It avoids open areas. The House Mouse is not going to come strolling casually up your driveway, and hang around in the open waiting for a door to open. Nope. This would expose it to predators such as cats, dogs, hawks and owls. Instead, it sneaks up through wood piles, piles of yard debris, in old boxes laying on the ground, or any other piles of material that it can hide in and scurry to quickly as it approaches your home. Removing or properly stacking these types of materials takes away the security the mouse needs.

Large expanses of shrubbery or ground cover, such as ivy, that cover the soil may also provide the ability of the mouse to remain hidden right up to your home, and these need to be trimmed properly or even eliminated.

2. It squeezes through tiny openings. Only one quarter of an inch is all the mouse needs to get into your home. A critical inspection of the outside of the building will discover many such cracks – under doors, around windows, crawl space screens that are torn, holes where pipes or wires enter the home through a wall. These openings MUST be closed to prevent mice from entering easily. You can use steel wool in small holes, concrete patch, new screening, or expanding foam that comes in aerosol cans.

Properly trimming shrubs and trees away from the structure, a good practice for preventing the entry of many kinds of insect pests, also works to keep mice away. As good climbers they easily climb up trunks and along branches, and onto window ledges where branches get too close. I once watched a House Mouse climb straight up a cinder brick wall inside a large store, then turn around and walk straight down again, in both directions walking so easily it might as well have been on the floor.

3. They are creatures of habit. Look for runways that they use repeatedly to know where they are going. These runways will be marked by fecal droppings on them, or possibly greasy “smudge” marks on the surfaces, caused by the oils in their body rubbing on corners as they go by. If you were to place traps or other control devices it would be along their runways that you will intercept the mice.

4. They prefer grains and nuts, or anything made from these foods. Thus, dog food stored in the garage must be in sealed, sturdy containers. Bags of garden seeds also must be made inaccessible, and if the mice have already invaded the kitchen you must place all susceptible foods into sealed containers that the mice cannot easily gnaw into. Remember, if they can’t find food in your house they will not live there.

5. They prefer undisturbed areas, and may not move around much. Once you allow mice to find a nice, comfortable place to live, with food nearby, why oh why would they want to leave? The only reasons a mouse would dare to be seen out and about in the daytime would be because they either have been disturbed from the comfort level they once had, or there are so many danged mice that they are forced to look for other places to live.

If you have a storage area that a lot of boxes and other possessions are left in, without you going there very often to move things, this is ideal for mice. Likely locations around the home might be walk-in attics, basements, and the ever popular garage – known fondly by most men as “The Workshop”. The basement and the garage may also be places where bowls of pet food are left out all the time, so now the mice are being offered all they need to hang around awhile.

By cleaning things up, storing items properly, putting boxes off the floor, moving things around now and then, you disrupt the comfort level mice seek, and if you also take away their food you really put them under stress. Numerous university studies have been conducted, on mice as well as insect pests, and it is pretty conclusive that you put these animals under severe stress when you take away their food, water, and harborage. When they are put under stress their populations immediately begin to drop, for reasons such as cannibalism, early death, lower birth rates, or simply moving out to find a better place.

So, if you have mice in the attic, before you throw a bunch of poison bait up there try to do those repairs and changes that make your house less inviting, and you will have much better mouse control for a longer period of time.

What about bed bugs, since this website is about bed bugs and bed bug exterminators? While bed bugs may feed on mice and other rodents in the absence of a human host, the insects do not typically travel with mice from location to location.