Monday, October 26, 2009

Mice ate my car !! Support group needed...

One reader referred me to a blog with  382 posts, mostly about mice destroying their cars. After slogging through hundreds of posts, I found:
  • Insurance will often pay for the damage
  • The problem is most common with Hondas, especially Honda Pilots.  Honda even has a service bulletin on rodent damage.
  • The repair bill for an Audi TT was $18,250--mice chewed nearly every wire and hose in the car.
  • Beyond the smells and bills, there are issues of fire (from nests on the engine), and the possibility that mice may have disabled your airbags.
This is indeed a terrible problem that causes much anguish and monetary damage.  Not to mention having a mouse run across the dashboard while you are driving.

Lee has the best advice, based on much trial and error, so I'll reprint it here:

"There is no magic bullet, only ongoing control.

1. Don’t store anything in or near your car that mice like – i.e. granola bars, grass seed, bird seed.

2. Get someone to screen off any entry points that your particular vehicle might have that can be screened off. Every vehicle is different – some have obvious ones, some not.

3. Leave your heater/air conditioner system on recirc (or Max A/C) when you park for the night. It’s bad enough to have mice in the fan, worse to have them run up your leg.

4. Set traps (snap traps, sticky traps, Hav-A-Hart traps) on the ground at the front of your car every day and empty them every day. Bird seed works better than cheese or peanut butter. NO POISON! It’s bad enough having mice in your car, far worse to have dead, decaying mice in unreachable places.

5. Skip the mothballs, fabric softeners, peppermint oil, sonic noise chasers, etc. They might work for a while, but then the critters get used to them. Mice are a chronic problem – there’s no cure, only control. Don’t attract them, and kill or trap them when they arrive. I trap three to five mice per week, every week. They don’t live long enough to start nesting in my car."

He says this may seem like a lot of work, but it's better than cleaning up after a mouse attack.  I'll go on to elaborate on some of Lee's points.


Remember... mice need access, food, and shelter.  Deny them!!

Access: If your car is in a garage, plug any holes  larger than a dime that mice can use to get in. Use balls of aluminum foil or steel wool.  Also follow Lee's advice about plugging entry points to your car, especially if you have a Honda.

Food: If you leave food in your car or in your garage (like catfood, birdseed, grass seed), you are asking for trouble.  If you have to store these, put them in a rodent-proof container.  Don't forget the garbage.

Shelter: Mice are probably moving into your car because they are safe there from cats and predators. But they also thrive where there's clutter and cover.  So tidy up the area around your car.

Inspection is part of prevention

Before mice move into your car, they are probably thriving someplace nearby.  A population explosion drives them to look for a new home.  So be a mouse detective--look for mouse turds.  They look like black grains of rice.  If you see one turd, you've got mice!  (Or, another small rodent like chipmunks.)  Immediately set traps, and keep it up till the turds disappear.  Thereafter, keep one trap set all the time. 

Denying food, shelter, and access, combined with inspection, will probably work in most cases.  But if you park in a woodsy area where you can't do those things (or your neighbors are sloppy), then you have to up the ante.  That's when I'd do things like putting screens on the places in your car where they get in (Lee's advice), set lots of traps by the car's wheels and in the car, and even inspect for nests on the engine if you haven't driven for a few days.

Part of being a "mouse detective" is knowing what kind of animal you are dealing with.  The size and kind of droppings will be a good sign.  Mice can be a problem almost anywhere.  Rats in big cities.  Rabbits in Wyoming.  Pack rats in Arizona.  In New Zealand, parrots eat tires. 

Time of year

I live in Wisconsin, and fall is the time that mice come indoors.  They don't fancy our cold winters any more than the people do.  The garage is the easiest place to enter.  So that's where you set a lot of traps in the fall.

In California, Robert notices a problem during the rainy season.  He thinks that the rain collapses (or floods) the mouse tunnels, so they go looking for a car to trash. 

So, depending of when the rodents come knocking, be ready for them. 

Are rodent attacks becoming more common?

Some bloggers wondered whether damage to cars was becomming more common.  One blogger said he didn't remember this problem when he was younger.  Some readers suggested that rodent damage to cars seemed to be increasing because of:
  • Climate change
  • Insulation on wires in some cars (especially Hondas) are now made with a soy-based chemical, tasty to rodents.  They suggest a "taste test for rodents" before the cars go to market.  So far, no one has been able to verify this.
  • the internet makes us more aware of problems that really aren't more common.
The real reason why rodents like your car
Mr. Rat says that pack rats are looking for a place that's safe from predators.  I suspect this is true for mice and other rodents as well.  It's dark and sheltered under the hood, with plenty of places to hide.  Hard for cats to enter, and if they do, they will make plenty of scratching noise to warn the mice.  So much the better if you had food in your car, or if maple seeds accumulated below your windshield. In Wisconsin, they might enjoy a warm engine as well.

So if that's the reason they covet your car, why are rodent attacks increasing?:
  • More autos every year.  More beaters every year, as Wall Street drives the rest of us into poverty
  • The internet makes the attacks more visible
  • Cars are more complicated, and the parts are smaller and more easily damaged
  • As cars get more compact and tightly packed, there are more nooks and crannies that make rodents feel safe from predators
  • The mice are always going to be ahead of the predators.  First the mice move in.  Eventually some predators may catch on--that's why people are now finding dead cats in their cars!
Rodents in RVs

Yes, I had mice in my trailer!  Trailers are more at risk than cars because
  • Many  rodents at campgrounds know the drill, and are used to getting handouts or raiding trailers
  • Trailers are chock full of food, and have lots of roomy passageways.
  • They have more access points--convenients steps and electric wires they can run up.
The solution is the same, to deny access and food.  Keep your rice or nuts in plastic containers with lids.  Deny access by putting a little aluminum collar your can make yourself over the a/c cord leading into your trailer.  Watch for droppings, and if you find them, immediately set traps inside the trailer.

How to trap mice

Rats are hard to trap, but mice are pushovers. Mice are constantly investigating the area around your car, and will quickly find the trap and get caught.  Place traps on the floor close to walls, on top of air conditioner ducks, and other places where mice will run.  You know where they are, because you see the droppings.  I use cheese squished onto the trigger, or peanut butter.

I favor the old-fashioned Victor wooden snap traps.  They are very cheap and effective.  You can just throw them away when you catch a mouse.  Death is instant, so they don't suffer.  The only problem is that some people find them scary to set-- or gruesome to dispose of the foolish mouse.

Some people think it's cruel to trap a mouse.  It's a lot more cruel to have someone die in your car because the airbag didn't work (because a mouse chewed the wires).  It's a lot more cruel to have a mouse fry on your engine than to die instantly in a trap. 

People who catch and release are just as cruel.  They force the mouse to undergo a long journey to try to find home, crossing highways (squish).  Or, fighting macho gang mice to the death in the new place where the mouse is released.  Or, if the mouse survives, you just gave someone else your problem.

I have tried the plastic snap traps that you pinch to set.  These have not proved reliable.  No, you can't invent a better mouse trap than the Victor.

Here's a website with some good advice for trapping mice.

Old grandpa tales, old wives tales...

Many bloggers recommend things like mothballs, bounce sheets, peppermint oil, cayenne powder, ultrasonic devices, or fox urine.  Come on... give me a break!  If someone offered you free food, and free shelter, would a little peppermint smell cause you to move out?  What happened to common sense?

And what about fox, bobcat, or coyote urine?   So...  how do you know it's really fox urine?  Do you think there are fox farms where they milk the foxes?  Some scammer probably just pissed in a bottle.

The reason these old grandpa tales persist, is.... you find the problem, you disturb the mice, and you stuff a million bounce sheets all around your engine.  The mice move out.  Of course!  They don't like all that attention, all that opening of the hood every day to stuff in more bounce.

These bad ideas are started by people who are promoting a product they have to sell--they pose as ordinary posters to blogs.  The rest of us don't recognize these posts as the deceptive advertising they really are.

Even if some of these things do work a little, the mice get used to them.  Free food and shelter trump fox urine every time. 

More on urine.

If nothing else works...
"...get a backhoe and build a deep moat around your garage or parking space. Fill the moat with water or maybe red fox urine. Failing that, get a crane with a strong magnet attached to the end of the cable and lift your car one foot off the ground when it’s parked. Be careful not to scratch the paint on the roof. Then find a way to keep the mice from climbing the crane boom and scaling down the cable. If all else fails, ask the auto manufacturer why they can’t put a simple screen over the drainways where the mice crawl up. How hard would that be?”  Thanks to Lee, post 99.


  1. Awesome blog! You did a great job of summarizing bits from the unbelievable stream of comments (I expected to get maybe 4 or 5 comments from my original post) and combining it with lots of useful info and suggestions.

    Playing the Denial of Service game with the mice is definitely the way to go. I started by removing the bag of bird seed (which was by then topped with mouse turds) from the garage. Then I nailed a piece of wood over the notch in the crawlspace door that a previous owner had cut out in order to run an extension cord. At the front of the house, I wove steel wool around the hole in a wire grid where the water pipe enters the crawl space. When we replaced our wood garage door, I made the guy install a custom-cut strip of wood along the bottom of the door so that it comes within a few millimeters of touching the uneven garage floor across the entire length of the door.

    I also repeatedly reset and baited traps along the walls of the crawlspace and the walls of my garage, as well as on the floor just inside of the Audi's tires after I parked. I use the most basic of snap-traps. I haven't seen signs of nor trapped a mouse now for a few years.

    Of course, our rainy season in the SF Bay area is just starting, so it's once again time for vigilance.

  2. Robert, the reason your mice come in at the start of the rainy season is probably that this is the time they begin to breed. They are looking for places to nest. The rainy season is the fertile time for them, when plants grow, and it's fat city. Lots of resources. All that's needed to complete the pucture of comfort is a nice cozy car interior.

  3. Dubious argument - killing is better than live trapping?

    Seriously, if you let a mouse or squirrel go out in the wilderness somewhere, it's true that it may be a tough journey. If it's eaten by predators, at least it will be part of the food chain instead of in your trash can! On the other hand, it might just get lucky and be able to start a new life.

  4. More on killing VS trap and release:

    If you release the animal anywhere near humans, you have just passed your problem on to other people--is that ethical?

    Then there's the concept of "carrying capacity." According to this idea, habitats are already fully occupied. So if you release a raccoon into the wild, there's no room for it, and that raccoon, or some other one, will probably die from lack of resources.

    I think it depends on the animal and the situation--but any blanket assumption that trap-and-release is more "humane" is probably incorrect.

    Surely the most humane thing is to avoid any feeding of wild animals (or access to your house and food) in the first place. That way, you aren't bringing more young animals into the insecure world of depending on humans.

  5. This is a great article. I need to find a how-to on installing the screening.

    Don't know how accurate this is, but I just saw on a tv show that mice had been live-trapped, marked, and released up to a mile away, and had found their way back within a day or two, so it is not the way to go.

    I actually like mice but not in my car or house!

  6. I don't know this particular research--about mice homing, but it sounds right. Animals havae an amazing ability to home. They found with the threatened box turtle that when moved, they will try to home.

    In the 1960's, I did research on penguin navigation and homing. One researcher took Adelie penguins from their nest and flew them to the other side of the continent. The next year, they were back on their nests in the original place. And penguins don't fly!

    I was part of some experiments where we took penguins several hundred miles inland, and then released them on a completely flat, featureless icecap. By an amazing chance, one pengin was found 5 days after release on the coast--200 miles away. He had averaged 40 miles a day, walking in the snow, without food or water.


Comments are welcome.