When the Nights Turn Cold: Getting Ahead of Fall Mice

Seal the house and garage in late summer, before the first cold nights. NMSU Extension says rodents may move indoors in fall or winter looking for food and shelter, and a garage full of boxes is an easy first stop. A few weekends of work in August or September beats a winter of traps.

Albuquerque's dry, high-desert climate swings hard from day to night, especially on the east side and up in the mountains. When nights start dropping, the mice living in the brush along the foothills and the mesa look for somewhere warmer. Here's where to look and what to fix.

Walk slowly around the house and look low. The state rodent guide says no hole bigger than a quarter inch should stay open. NMSU compares that to the size of a dime. Check:

• Garage door seal and both bottom corners
• Where stucco stops above the foundation
• Gas, water, AC and cable entries
• Dryer, bath and attic vents and their screens
• Door sweeps on every exterior door
• Swamp cooler ducts and the roof curb

NMSU recommends quarter-inch hardware cloth over openings and says steel wool, latex, plastic, rubber and wood don't hold up. The state guide lists cement, concrete, galvanized sheet metal and hardware cloth as gnaw-resistant. Foam by itself isn't enough. If the job's bigger than a few gaps, a provider can do the whole house. See rodent exclusion.

The state guide suggests firewood and lumber on racks about 18 inches off the ground, plants trimmed back 3 to 4 feet from the walls and a clean, weed-free strip about 3 feet wide along the foundation. Clear out the garden once it's done, pick up fallen fruit, clean up under bird feeders and bring pet food in at night.

Get stored boxes off the floor and into plastic bins with lids. Put birdseed, grass seed and dog food in metal cans. Check shelves and corners for droppings now, so you know what's new later. If you have a car or camper that sits all winter, check it every few weeks. Mice in RVs and campers covers stored vehicles.

A couple of snap traps along the garage wall in early fall tell you whether mice are getting in. NMSU recommends setting them along travel routes, at right angles to the wall, and checking them daily. A catch means there's a gap somewhere, and it's worth finding before the weather turns. If mice are already in the house, house mouse control and mice in walls and ceilings are the next step.

Cabins in the East Mountains need the same prep before they're closed up for the season. See cabin and shed rodent control.

Spread the work over a few weekends in late summer:

• Week one: walk the outside, list every gap and buy hardware cloth, sweeps and a garage door seal
• Week two: replace the garage door seal, add door sweeps and screen vents
• Week three: seal utility entries with mesh and mortar or sealant
• Week four: clean up the yard, rack the firewood and move feed into metal cans
• Then: set two snap traps in the garage and check them every few days through fall

Homes that back onto open land in the foothills, Four Hills or the mesa around Westgate see more fall pressure than homes in the middle of town. For those, a professional sealing job in late summer is often worth the cost, since one missed gap is enough. See prevention and monitoring.

It usually starts in the garage: a few droppings on a shelf, a chewed bag of birdseed. Then the kitchen: droppings in a drawer or under the sink. Scratching in a wall at night often follows. If you catch it at the garage stage, trapping and sealing the garage may be all it takes. By the time mice are in the walls, it's a bigger job. See one mouse in the house.

If you're closing a cabin in Cedar Crest or a weekend place in Edgewood for the season, do the fall prep before you leave. Remove all food, store bedding in sealed bins, set snap traps along walls and check the door sweeps. When you come back, air it out for at least 30 minutes before you start cleaning. Cabin and shed rodent control covers the rest.

A monitoring visit partway through the winter can catch a problem before your next trip up the mountain.

• Rodents After the Monsoon: What Wet Summers Change
• Mice in Adobe and Stucco Homes: Finding and Closing the Gaps
• Saw One Mouse? Here's How to Tell If It's Alone
• Deer Mice in Garages and Sheds: Cleanup and Keeping Them Out

Services: Sealing and Exclusion / House Mouse Control / Prevention and Monitoring

1. NMSU Extension Guide L-209: Rodent Control and Protection from Hantavirus
2. New Mexico Department of Health: Domestic Rats and Mice