Mice in the house in October: why now, and what actually works.

Why it is happening now

Mice do not hibernate. When overnight temperatures drop, they move toward warmth and stored food, and a house is the best of both. This is why half of South Jersey hears scratching in the attic the same week.

A house mouse fits through a gap about the width of a pencil. Young ones get through less. Any hole that will take your little finger will take a mouse.

Find how they are getting in

This is the part people skip, and it is the only part that matters long term. Look for gaps where something enters the house.

• Where pipes, cables, dryer vents and AC lines pass through exterior walls
• The gap under and around garage doors, especially at the corners
• Where the siding meets the foundation, and around basement window frames
• Soffits, roof-line gaps and anywhere a tree branch touches the roof
• Crawl space vents with torn or missing screens

Seal properly, not with foam alone

Mice chew straight through expanding foam and caulk. The gap needs something they cannot get through — copper mesh or steel wool packed tight into the hole first, then sealed over. Larger openings need hardware cloth or sheet metal.

Do the sealing before or alongside trapping. Trapping alone turns into a standing appointment.

On traps and poison

Snap traps placed against walls, perpendicular, with the trigger facing the wall, work better than traps in the open — mice travel along edges, not across rooms. Bait with something sticky rather than cheese.

Think hard before using poison, especially with pets or children in the house. A poisoned mouse dies somewhere you cannot reach, usually inside a wall, and you will smell it for weeks. Poisoned rodents also kill the owls, hawks and cats that eat them.

When it is worth bringing someone in

If you are hearing activity in the attic or inside walls, if it keeps coming back after sealing, or if you are finding droppings in more than one area of the house, the entry point is probably somewhere you cannot see or safely reach. That is the point where a professional inspection is cheaper than another month of guessing.

Droppings and nesting material also carry real health risks. Wet them down with a disinfectant before cleaning rather than sweeping or vacuuming them dry, which puts particles into the air.