maintain rodents from trashing your car this winter

This story was originally published in December 2018.

It’s not uncommon for many country folk to have seasonal vehicles—cars for summer roads and older, more rugged four-wheel drives for the winter months. It’s also not uncommon for mice and other rodents to take up residence in vehicles during the off-season – especially during the winter when they need a place to hide.

Unfortunately, these tiny, furry critters can wreak havoc on mechanical components and interior upholstery.

Because of this, car owners must be constantly vigilant to ensure mice and other rodents don’t nest in the myriad of small spaces and cavities within a vehicle.

“They certainly tend to get in a car to seek shelter from the snow and rain,” said Griffin Dill, a pest control expert at the University of Maine at Cooperative Extension. “They like to nest in the winter, and cars and other vehicles provide ideal shelters for mice and small mammals because they have small spaces that provide shelter from wind and predators.”

These spaces become even more desirable to rodents when a vehicle has been driven recently and these spaces around the engine are toasty warm.

“Mice can actually find that very inviting,” Dill said.

What do mice do with a car?

Once inside a vehicle, mice and other small mammals can be more than a simple nuisance, they can create dangerous situations.

“They can get inside the engine and chew up wires,” said mechanic Kassey Michaud, owner of Madawaska Auto Parts-NAPA in Madawaska. “Plus, they love getting in and clogging air filters.”

Mice and other rodents build nests or store food in spaces like air filters, Michaud said, and often pack materials so tightly that they disrupt or block airflow through the car’s filter and cause problems with vehicle performance.

“I saw them get into a car’s heater and blower units,” Michaud said. “Then when you turn on your heater, small dusty bits of the nest or its lining fly straight at you through the vents.”

And while Michaud never saw it, online sites dedicated to rodent control, such as JP Pest Services in New Hampshire, are warning of the danger of mice or other vermin chewing through a vehicle’s hoses that carry vital fluids like brake fluid, Carry transmission fluid or coolant and cause leaks. These leaks can mean loss of braking, steering, or a vehicle overheating.

Do mice make a mess?

At the very least, mice or other rodents living in a vehicle can wreak havoc, according to Michaud.

“It will smell,” he said. “I had mice nesting in my plow truck and when I first turned on the heat this winter the smell was so bad it made me choke.”

This unpleasant odor is the result of the animals’ excrement collecting in the engine, air vents and even the upholstery as they chew on it to build nests in the seats or carpets.

Odors are also generated by rodents’ food stores of seeds, nuts and other edibles, which they collect and store in the cracks of a car.

How to prevent mice from getting into a car?

According to Dill, the best defense against a rodent carjack is a good offense.

“Parking your cars in a secure, mouse-proof garage is ideal,” Dill said. “But a lot of us don’t park our cars there, and if it’s a vehicle we don’t use all the time, sometimes it’s parked next to a garage or to the side of a building in tall grass.”

That, Dill said, just puts a vehicle right in the middle of the mouse’s habitat.

“Those areas really make your car vulnerable,” he said. “Once you place it in or near its natural habitat, it becomes very inviting.”

Mice can squeeze through openings as small as the diameter of a pencil, Dill said, and they’ll exploit any entry point into a parked car.

“Areas around air vents, the steering column and the pedals allow access to the interior of the car,” he said. “And most areas of the engine block are accessible too.”

Once the presence of mice is detected, dill traps or poisonous baits can be used to control or eradicate them.

To keep even more mice from moving in, Michaud swears by Bounce dryer tissue sheets.

“I stick these between the seats of a vehicle or cracks in a seat [stored] boat,” he said. “They don’t seem to like the smell and since I started using it I haven’t had any problems with mice.”

However, Michaud said it’s a good idea to regularly check a vehicle’s air filters to make sure no rodent has sneaked in, despite traps, poison or dryer sheets.

Dill said that in addition to cars, boats, lawnmowers, snowmobiles, and ATVs can also be damaged by mice and should be checked regularly.

And while he’s personally never had a mouse-vehicle problem, he said he’s familiar with what they can do.

“With our old one [Extension] We had this chipmunk in the office that loved to climb into parked cars,” he said. “But he hasn’t moved to our new office, so I can only assume he’s someone else’s problem now.”

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