Mice Are Moving In This Week: The First Signs Most People Miss

The first freezes have come through the New River Valley, and the mice outside have noticed. A field mouse that spent the summer in the tall grass behind the fence is now looking for the same thing every other animal wants in late October: somewhere warm, dry and close to food. Your house is all three. This is the week the calls start, and most of the people calling have had mice in the house for a while before they knew it.

How they get in

A mouse needs an opening just over a quarter of an inch. That is the gap around a water line where it comes through the wall, the corner of a garage door where the weather seal has worn, the hole the cable installer drilled and never sealed, a dryer vent with a torn screen, or the space under a door with no sweep. Mice follow the edges of the house at night, and when they find warm air leaking out of a gap, they go in. They do not need a door. They need a crack.

Once inside they stay close to the entry point and to food. A mouse rarely travels far from its nest, so the pantry, the cabinet under the sink, the drawer with the dog treats and the wall behind the stove are where things start.

The signs people miss

Everybody knows to look for droppings. By the time there are droppings on the counter, the mice have been inside for a while. These are the earlier signs, the ones that usually get explained away.

Sounds after dark. Mice are active at night, and the first week the heat runs is when people start hearing a faint scratching or scurrying in the ceiling, inside a wall, or behind the kitchen cabinets after the house goes quiet. The common explanation is "the house settling." Houses do not settle in short bursts that stop when you turn on a light.

The dog or cat staring at the wall. Pets hear and smell what you cannot. A cat that sits in front of the stove, a dog that paws at the bottom of a cabinet or will not leave the corner of the laundry room alone is telling you something lives there.

One dropping, somewhere odd. A single dark pellet the size of a grain of rice in a drawer, on a shelf in the garage, in the silverware tray, or on top of the water heater. One is never one. A house mouse can leave fifty or more a day, so a single dropping means the rest are somewhere you have not looked yet.

Chewed cardboard and paper. A torn corner on a cereal box, shredded paper towel in the back of a cabinet, a chewed bag of birdseed or dog food in the garage. Mice gnaw to get at food and to build nests, and they use whatever is soft and nearby: insulation, paper, the stuffing out of a cushion in the shed.

A smell you cannot place. A musty, ammonia-like odor in a closet, a cabinet or the crawl space hatch is mouse urine. It builds up along the routes they use, and a lot of people live with it for weeks, blaming the damp.

Rub marks and tracks. Mice travel the same paths along walls and pipes every night, and their fur leaves a faint greasy smudge along baseboards and around the holes they use. In a dusty attic or basement you can sometimes see the tiny tracks and the tail drag.

Why a few mice in October is a lot of mice in January

Outside, cold weather and predators keep mouse numbers in check. Inside a heated house there is no winter. A female house mouse can have a litter of five or six about every three weeks, and the young are ready to breed in a couple of months. Two mice that came in through the garage in October are a population by the time the holidays are over, and by then they have found the pantry, the insulation in the attic, and in some houses the wiring, which is the part that should worry you most. A mouse chews constantly to keep its teeth worn down, and wire insulation is a favorite.

The other thing mice bring is what lives on them. A house that picks up fleas in late fall with no pet to blame has usually picked up a tenant under the floor or in the walls, which is a pattern we wrote about last week in our post on fleas in October.

What we do about it

Traps and bait on their own are a temporary fix, and we have been saying that since our rodent control guide years ago. Our first job is finding how they got in, which means walking the outside of the house at ground level, checking the pipe penetrations, vents, door sweeps and garage seals, and looking at the crawl space and the attic for the routes they are using. Then we seal what we find, so the mice already inside are the only mice you ever have to deal with.

Inside the house we use snap traps, placed where the mice are travelling, not where it is convenient to check them. We do not put bait inside a home, because a mouse that eats bait in the attic dies in the wall, and a dead mouse in a wall is a problem you can smell for a month. Bait belongs outside, in tamper-resistant stations around the foundation, where it stops the next ones before they ever reach the gap you sealed.

For homes that have had mice more than once, the quarterly service keeps those outside stations maintained and gets a set of eyes on the foundation four times a year, which is how new entry points get caught before the next cold snap.

If you heard something last night

Do not wait for the droppings. If you are in Blacksburg, Christiansburg, Radford or anywhere else in the New River Valley and the ceiling has started scratching after dark, give New River Pest Control LLC a call or text at (540) 818-9375. We will find out how they are getting in, close it, and clear out the ones that already made the move. The mice have picked their winter spot. It does not have to be your kitchen.