Why Ann Arbor Homes Are Especially Prone to Mouse Infestations in Winter

If you live in Ann Arbor and have ever heard scratching sounds behind your walls on a cold January night, you are not alone. Every fall and winter, thousands of Ann Arbor homeowners deal with the same unwelcome guests — mice looking for warmth, food, and shelter. But why does this city seem to get hit harder than others? The answer lies in a combination of Michigan’s brutal winters, Ann Arbor’s unique housing stock, and the biology of mice themselves.

Michigan Winters Push Mice Indoors

Ann Arbor winters are no joke. Temperatures regularly drop below 20°F between November and February, and wind chills can make it feel even colder. For a mouse, surviving outdoors in those conditions is nearly impossible. Their small bodies lose heat rapidly, and their food sources — seeds, insects, plant matter — are buried under snow or simply gone.

So what do they do? They migrate toward warmth. Your home, with its heated rooms, insulated walls, and accessible food in the kitchen, becomes the perfect winter habitat. A mouse can squeeze through a gap as small as a dime — about 6–7mm — meaning even a well-maintained home can be vulnerable if there are any small cracks around pipes, foundations, or door frames.

Ann Arbor’s Older Housing Stock Is a Major Factor

Ann Arbor has a rich history of architectural diversity. Neighborhoods like Old West Side, Germantown, and the areas surrounding downtown are filled with homes built in the early to mid-1900s. While these homes have tremendous character, they also come with aging foundations, deteriorating weatherstripping, gaps around utility lines, and basement walls that have settled and cracked over decades.

These structural imperfections are essentially open invitations for mice. Unlike newer construction, older homes were not built with modern pest-exclusion techniques. Over time, wood framing shrinks and shifts, creating gaps that a mouse can exploit with ease.

If your home was built before 1980, your risk of a winter mouse infestation in Ann Arbor is significantly higher than someone living in a newer subdivision near US-23 or in Pittsfield Township.

The Biology of Mice Works Against You in Winter

House mice (Mus musculus) are not hibernators. Unlike some other wildlife in Michigan, mice stay active all year long — which means they are actively searching for food and nesting sites even in the coldest months. Once a mouse finds a warm entry point into your home, it does not leave on its own.

Here is what makes the situation escalate quickly:

• 1
  A female mouse can give birth to 5–10 litters per year, with each litter containing 6–8 pups.
• 2
  Mice reach reproductive maturity in just 6 weeks.
• 3
  A small infestation of 2 mice can turn into over 60 mice within a few months if left unchecked.
• 4
  Mice are nocturnal, so most homeowners do not realize they have an infestation until it is well established.

This rapid reproduction cycle means that waiting until spring to deal with the problem is not a safe strategy. By the time Ann Arbor temperatures warm up in April or May, a winter infestation can already be deeply embedded in your walls, attic, or basement.

Common Entry Points in Ann Arbor Homes

Knowing where mice get in is the first step toward stopping them. In Ann Arbor homes, the most frequent entry points include:

Even if you cannot see an obvious gap, mice are expert at finding them. If there is a draft, there is likely a gap large enough for a mouse.

Warning Signs of a Mouse Infestation

Mice are secretive, but they always leave evidence. Watch for these signs, especially as temperatures drop in October and November:

Why DIY Solutions Often Fall Short in Winter

Hardware store snap traps and bait stations can help, but they rarely eliminate a full infestation — especially during peak winter months in Ann Arbor when mice are entering homes in greater numbers. Common DIY mistakes include:

• Placing traps in the wrong locations (too far from walls and runways)
• Not using enough traps for the scale of the reproductive cycle
• Failing to seal entry points, which allows new mice to replace trapped ones
• Using bait improperly, which can pose risks to pets and children

A professional rodent control service understands the specific behaviors of mice in Michigan’s climate, knows the construction patterns of Ann Arbor’s older homes, and can create a comprehensive exclusion and elimination plan that solves the root cause rather than just treating symptoms.

When to Call a Professional Rodent Control Service

The best time to call is before you have a full infestation. If you are seeing early warning signs in October or November, that is your window to act. A professional inspection can identify entry points, assess risk areas, and put preventive measures in place before mice have settled in for the winter.

If you are already dealing with an active infestation, do not wait. The longer mice are in your home, the more damage they cause — chewing wires (a fire hazard), contaminating food, and spreading diseases like Hantavirus and Salmonella through their droppings.