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Part II – The mouse war continues!

May 27, 2010 by · 9 Comments 


The Professor’s Science Lesson on Mice. – or –  Everything You Probably Never Wanted to Know About Mice.

From time-to-time I like to write about the aspects of owning a camper that, if ignored, can spoil a great destination experience.  The previous articles on water leaks, batteries 099 and the current one on preventing rodent infestations are examples of proactive procedures that can help avoid unpleasant surprises.

Being a retired professor,  I can’t just say, “do this”.  It is in my genetic make-up to explain why we do it a specific way.  That is the teaching part of me still hanging on.


In the military, a commander will quickly tell you that if you want to win a war, you must know your enemy.  Where they sleep, what they eat, how they think, what they value and what weapons they have at their disposal.

After a rather lengthy and grueling ordeal trying to get rid of mice that had invaded our camper, I decided that I needed to apply this plan for my continuing war on mice.

So, I began to study them.  I wanted to learn as much as I could about how these little creatures behaved.  Consider the following as a primmer for mouse dummies (like me — before I researched the subject.)

Mice have a short lifespan. They are lucky to live for as long as four months – unless they are in captivity.

Female mice can produce a litter of 6 to 12 “pups” every 40 to 45 days. The pups reach maturity and can produce their own offspring in about the same amount of time.

A male mouse will mate with multiple females, even their own offspring, at an alarming rate. Thus, one male mouse with four females can quickly multiply into hundreds during their expected lifespan of 3-4 months in the wild.

They are extremely adaptive creatures and can live in most any environment provided they have a source of food and water. Their diets include most every imaginable grain, nut, vegetable and fruit – except grass.  The mouse is the second most successful mammal living on earth today, after humans.

Their adeptness at climbing, chewing, burrowing and their uncanny ability to compress their skeletal system to squeeze through an opening one quarter of their size makes them skilled invaders. They can squeeze through openings smaller than a dime or cracks down to 1/4″ wide.  If the opening is too small, they can easily gnaw it to a larger size.

If humans had the physical abilities of mice, they could easily jump over tall buildings in a single bound, out run a speeding bullet, hear a whisper or smell food a mile away, and carve a large totem pole with our front teeth in a normal 8 hour work day. In fact, mice must constantly gnaw on items to keep their fast growing front teeth worn down.  If they do not gnaw the teeth will grow over their mouth.  This may explain their taste for electrical wires and plastic plumbing pipe.

Mice are mostly nocturnal. They are more active at night than in daylight.

They have poor eyesight but make up for this shortcoming with excellent smell and hearing.

Their sense of smell is so good that they can sniff out food sealed tightly in plastic zip lock bags and containers. With their sharp incisors they can easily gnaw through even the toughest plastic to get to the food source.

Their natural enemies include humans, cats, foxes, snakes, owls, hawks, and sometimes dogs.

So, in summary, mice are indeed blind (like the Three Blind Mice?), but have exceptionally keen hearing and sense of smell.  Thus, smell and hearing are their main defense against being eaten by predators.

Playing on the keen sense of smell mice possess, strong objectionable odors that either mask those of predators or smell like their predators may work as a repellant.  The following represent a rather unscientific, but apparently accurate, list of methods used to deter mice from living in a camper by using “smelly” repellants.  I can’t say that these are methods that I would advocate using.

At the top of this list you will find “moth balls”.  Moth balls contain naphthalene and paradichlorobenzene.  Both sublimate, meaning they transition from a solid state to a gas.  Thus, they do not last very long in an open environment.  The odor they leave behind is as objectionable as mouse urine.  Not a very good choice.

Next on the list is oil of peppermint.  Once again, it sublimates quickly and needs frequent replacement.  The lingering smell is not as objectionable or toxic to humans and pets as moth balls.  Peppermint oil can be difficult to find.

Some campers believe that fabric softener sheets like you place in the dryer work to keep mice away.  But, their perfume like smell is short lived and weekly replacement would be required.   I have not observed any better results with keeping mice out of a camper by using them.

Bobcat and fox urine are at #4.  Once again hard to find locally and must be ordered from an on-line supplier. The urine is available as a liquid or in pellet form.  It may be expensive and as with other smell based repellants, it needs frequent replenishing.  Being urine, I am not so sure its smell will not be objectionable as well.

Used cat litter earns 5th place.  It is easy to acquire if you have a house cat.  But, who wants used cat litter sprinkled around their camper?

Apparently smell based repellants are not the best way to keep mice away.

Since mice depend upon their exceptional ability to hear and feel vibrations that signal movement of predators perhaps noise that will interfere with these senses will work?

As it turns out mice will avoid environments where there is enough ambient noise to keep them from hearing the slither of a snake or footsteps of a cat.  If the ambient noise contains some low frequency bass that causes vibration of surrounding objects it is even better.  This may be the basis of the so called “ultrasonic” pest repellants which, incidentally rarely work as advertised.

My current and highly successful approach is to keep a “boom box” playing as loudly as possible inside the camper (the more bass the better) without disturbing any neighbors (we have none).  Boom boxes with now outdated cassette tape recorders/players are abundant in donation focused resale stores like Goodwill for a fraction of their retail cost.   If you have country mice, it is best to play rap music.  They hate it (as I do).  For a large RV, use two or more radios.

Being nocturnal, mice do not prefer living accommodations with a lot of light.  Keeping the lights on in a camper may help in deterring mice from taking up residence.  Placing lights in confined areas seems to work well.  It is best to use small fluorescent lights to avoid the heat and chance of fire from hot incandescent lights.

Some simple proactive steps to protect your camper help considerably.  Close all cabinets tightly.  Open drawers so the inside is not a cozy and inviting nesting area.  Store pillows, toilet tissue rolls, paper towels, bath and hand towels in plastic Space Bags.

Rather than purchasing commercial poisons, a mixture of plain white flour and Plaster of Paris placed on a paper plate is considered a smorgasbord by mice.  When they ingest the mixture the plaster hardens from the moisture in their digestive system and literally clogs them up.  They will die in about two days and cannot horde the flour and plaster mixture like pellets.  Moisture in the air will eventually cause the mixture to harden so it does need occasional replacement.

Mice apparently like paraffin as a food.  You can buy this at most grocery stores in the home canning section.  Adding a little peanut butter to paraffin shavings makes it more appealing.  The paraffin (wax) will also clog up their system causing them to die.

A rather novel and simple trap can be made by using a piece of wood as a ramp on the outside of a 5 gallon or deeper plastic bucket.  Bait such as peanut butter is placed in the bottom of the bucket.  Unless the mice are exceptional jumpers they will not be able to escape the bucket.  You can release the mice live if so inclined or place a lid on the bucket and pour in enough water to drown the vermin – then flush them down the toilet or bury them in a hole dug in the backyard.

Of course, make a conscious effort to seal up any openings in your camper that mice can squeeze through.  The most prominent areas to check are around the drains for holding tanks and where water lines, gas lines and wires enter the inside of the camper.  Unfortunately, these openings are usually in almost inaccessible places near the furnace, refrigerator and under cabinets.  Great Stuff expandable foam sealant works well as does Duct Seal non-hardening putty (if you can get to the holes).

Perhaps the most important step is to check a stored camper frequently for signs of invasion by mice.  The sooner you can eliminate the tribe and close their access the less damage you will endure.

Remember, your first defense is to make the inside of your camper as uninviting to mice as possible. “Think like a mouse” as you add, change or remove items from the environment.

Lastly, understand that not all mice will read these expectations and follow them.  There are always rebellious mice that ignore the rules and show up for dinner without an invitation.


9 Responses to “Part II – The mouse war continues!”
  1. Peanut says:

    Awesome! I have been overrun by mice every fall. Now I know how to fight back. The flour and Plaster of Paris mix will be safer than rat poison around my dogs and cats. Thanks for doing the research and giving us the info.

  2. Deangelo says:

    That sounds like a great idea but my wife doesn’t want to see the mouse ever again, especially in our camper. I actually found this trap online that is sure to make my wife happy.

  3. Tina D says:

    I too absolutely hate mice and for years i’ve tried everything out there and nothing has worked for any length of time. I protected my RV with a product called Mouse Free that is actually working for me. Its a coating that goes on the undercarriage of your trailer or motorhome that keeps mice out. The site where I found it was I used the do it youself kit but there are also RV dealers who can do it for you. The videos on the site are really good for showing how it works.

  4. Nancy & Eddie says:

    We got some mice in our motorhome and tried all kinds of things that didn’t work until I found this article. We removed the food they could eat in our cabinets and made up the mixture of flour and plaster of paris, We placed the plates around inside and outside and underneath and then left for a few days. We came back to see it had been joyfully eaten by the mice. We shook the plates to level them out, cleaned everything out, sprayed it with a lemon cleaning spray and left again for a couple days. Returning to undisturbed plates and no signs of mice at all. We have never seen anything work so well that I have made up the mixture for many people who have also used it with great success. Thank you for the tip!!!

  5. Steve says:

    @Professor, my big fear is that the mice will die somewhere behind the walls after eating the flour/plaster or any other poison. Any thoughts on this?

  6. Lyle Gingell says:

    Your ramp to 5 gal pail can work another way. Put 6" water in the pail. This is hard to describe without a diagram. Cut a piece of card board wider than the pail like a lid. Cut a "diving board" at one half of the lid. Place your bait securely at the end of the diving board. If you build this right the mouse's weight will tip the him in to the water and the card board will fall back into place for the next mouse. I caught 11 mice one night with this.

  7. Great Idea Lyle I will try this

  8. Tony Roemer says:

    fantastic idea below for "diving board bucket" thanks so much!

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