Why mice move in in November
As soon as nights drop below freezing, mice and wood mice leave the meadows, hedges and forest edges to look for a warm shelter. In the mountains this happens early: often late October at the bottom of the valley, sometimes as early as September around Argentière and Vallorcine.
Homes and chalets in the valley offer everything they need: warmth, food and plenty of hiding places. Timber wall linings, false ceilings, service ducts and insulation form a real network of passages, invisible from the living areas.
The telltale signs
- Droppings: black, 3 to 6 mm, rice-grain shaped, along walls, in drawers, under the sink or behind appliances.
- Scratching at night in walls, false ceilings or the loft, especially early in the night and at dawn.
- Gnawed packaging: cereal, pasta, biscuits, pet food, bags of seed.
- Nests: balls of shredded paper, fabric or insulation in a cupboard, a drawer or behind furniture.
- A smell of urine, strong and lingering, in a closed cupboard.
- Greasy marks along skirting boards, on regular runs.
Mouse, wood mouse or dormouse?
The house mouse is grey, with large ears and a long tail. The wood mouse, reddish-brown with a white belly and big eyes, comes in from the fields, mainly in autumn. The treatment is the same for both.
The edible dormouse, however, is bigger, has a bushy tail and hibernates in winter. If you hear a lot of noise in the loft in spring or summer, it is probably a dormouse: it is dealt with differently, so have it identified. More in closing your chalet without mice or dormice.
Why you shouldn’t wait
- They breed very fast: a few mice in November can become several dozen by spring.
- They gnaw electric cables, a real risk of short circuits and fire.
- They soil food and surfaces with urine and droppings.
- They damage loft and wall insulation, which is expensive to replace.
Mistakes to avoid
- Putting poison down loose: dangerous for children, dogs and cats, and a poisoned mouse can die inside a wall and cause a strong smell.
- Setting traps at random: you catch a few mice, but the colony and its ways in remain.
- Blocking holes before treating: the mice stay trapped inside and look for other routes.
- Relying on ultrasonic devices: they have not been shown to work, and mice quickly get used to them.
How I get rid of them
I start with a diagnosis: finding the runs, the nests and above all the entry points. I then set locked professional bait stations that only a technician can open, so children and pets cannot reach the bait. Once activity has stopped, I proof the entry points (steel wool, sealant, mesh) so the mice don’t come back.
It usually takes two to three weeks to eliminate a colony. Rodent control costs €149 to €209 depending on the area, travel within the valley included. An extra visit with Racumin foam, if needed, costs €79.
Good habits for the winter
- Keep dry food, pet food and seed in sealed glass or metal containers.
- Fill the gaps around pipes and cables that go through walls.
- Fit door sweeps on outside doors and the garage door.
- Keep firewood away from the chalet walls.
- Check the loft and cellar once a month during the winter.
Scratching or droppings at home? I come out within 24 to 48 hours anywhere in the Chamonix valley. See rodent control and prices.