Good ways to keep mice from getting in?
August 15, 2020 7:10 AM   Subscribe

We have mice coming into our home, through the downstairs,

which is four feet below ground. We don't want to let exterminators in right now because of COVID. What can we do to encourage them to stay away? So...what are good (preferably humane) ways to trap them? And/Or would peppermint oil help keep them from coming through?

We've sealed up everything that can be sealed except there is a trap door to the plumbing in the hallway, and they may be getting up from down there. We can't seal that. We could pour bleach down in there, though (we did that once to eliminate sewer flies).

We also have two cats, who are very interested in that area (that was our first tip-off that the little creatures are around. Since then I've seen 3 mice in the hallway there, chased them away).
posted by DMelanogaster to Home & Garden (12 answers total) 2 users marked this as a favorite
Make sure your cats have access to the all the places the mice are getting in. Let the cats chase the mice away. Let the cats catch and kill one if the can as an example to the others (🎶 “Circle of life...🎶). Do everything you can to encourage the cats to make the mice tell their friends that there are deadly predators in that house, and to pick a safer one.

Mice wanna get it in, they’re gonna get in. It’s what they do. But “bodega cats” are a thing for a reason, and that reason is the smell of cat hair, and yeah, the odd discrete drop of cat urine here and there, lets the rodents know that it’s their life on the line if they wana fuck around and find out.

If your cat ever shows up with a dead mouse which it drops at your feet, dispose of the corpse and say “Good hunter” to your cat.

These mice are wild animals. The most humane thing you can do is make the mice know mortal fear your cats, and then fuck off on their own.
posted by Pirate-Bartender-Zombie-Monkey at 7:26 AM on August 15, 2020 [14 favorites]

If you need to trap them, good old fashioned cheap spring traps are the best method. Yeah you’ll need to deal with the corpses. But they kill instantly and humanely. Whatever you do, avoid glue traps. They are exceedingly inhumane.
posted by spitbull at 8:36 AM on August 15, 2020 [5 favorites]

We've sealed up everything that can be sealed

I remember thinking this too, then I found a hole behind our oven that a cable came through. The hole was literally dime sized. I thought there was no way they could be getting in thru that, though there was a LOT of evidence of mousiness under the oven. I sealed it up and the problem dramatically reduced. I bet there is some tiny hole somewhere. Those little fuckers are like water, they get in everywhere.
posted by selfmedicating at 8:37 AM on August 15, 2020 [3 favorites]

Yes, mice can get through holes around plumbing lines, electrical lines, basically any type of penetration into your house. Here's a charming video showing someone having fun with this.

Best way to seal up holes is with steel wool and expanding foam like Great Stuff. Great Stuff alone won't work because they will happily chew through it.
posted by little king trashmouth at 9:18 AM on August 15, 2020 [4 favorites]

Best answer: They can enter through tiny spaces. Inspect every inch of the outside. Once they learn there's food, they are relentless. Poison means they may die in a wall and smell. Traps are sometimes cruel, glue pads are always cruel. Cats are not kind, but are part of nature. You can trap mice with a 5 gal. bucket, a ramp, and a dab of peanut butter in the bucket. A little oil or furniture wax on the inside of the bucket is insurance against them climbing out. Take them to the yard of the home of your nemesis.
posted by theora55 at 9:50 AM on August 15, 2020

Great Stuff (and Tomcat) do make rodent-proof expanding foam, which I recommend around anything with any gap.

My issue is rats, and I use ratzappers - rats are much smarter than mice and will be suspicious of it for a while, mice will likely go in pretty quickly if you bait it with something good-smelling. If you live in a dry climate I recommend baiting it with something watery - a cut-open cherry tomato, or I use a little wedge of orange since I have a tree. They're thirsty, this time of year, and I've got oranges on the ground every morning with proof they're eating them.

You want to be humane, I do to, but a lot of "quick" endings aren't, poison is awful and bad for other wildlife, catching them live is so terrifying they may die of fright before you get them relocated, and relocation almost certainly means being killed by something in the territory it's invading. The electric box is quick, and you take the whole unit to your outside garbage and tip the corpse in without having to look much. (You do then, however, likely need to clean the inside with some wet paper towels and then dry it before re-assembling and re-arming it. It's not a horror show in there, but...something did die in there.)
posted by Lyn Never at 9:58 AM on August 15, 2020 [5 favorites]

There's some good advice above but I'll add, in regards to expanding insulation foam like Great stuff, there is a type of expanding foam that has bittering agent in it that is specifically designed for pests. Get that stuff. They still may nibble but I've found that they get discouraged more easily with it due to the strong taste. I've also had some luck with those buzzing plug-in things meant to annoy mice but I've found that mice just get used to the noise so unplugging regularly helps with that.
posted by Ashwagandha at 10:23 AM on August 15, 2020

Be absolutely obsessive about filling cracks and holes. They can fit through a whole the diameter of a ballpoint pen so you really need to find any and all holes.

If you have any air bricks or vents on the outside walls, put a wire mesh over them.

Use spring traps and secure your food to minimise attractive smells and access.
posted by knapah at 3:09 PM on August 15, 2020

Stuff holes with wire wool and seal in place with expanding foam. Wire wool really does seem to be the only thing they won't chew through, which I guess makes sense given how unpleasant it is to handle. As has been indicated, a hole means any gap you can fit a standard thickness pencil into. I had a smallish two bedroom flat and it took me over 12 hours to find and seal every hole, so if you're in a house and haven't exhausted yourself looking for holes, you've probably missed some.
posted by howfar at 4:40 PM on August 15, 2020 [1 favorite]

We had mice in our small home and used these humane traps to get rid of them. The traps worked really well, the mice didn't seem disturbed by being inside, and they could fully turn around, which was important to me. We trapped about 6 mice over a few days with 4 traps set each night. Every day we diligently vacuumed and cleaned to make sure there were no crumbs to entice them. So far we are still mouse free.
posted by stripesandplaid at 5:55 PM on August 15, 2020 [1 favorite]

Mouse Cubes have worked very well for us.
posted by ZenMasterThis at 7:49 PM on August 15, 2020 [1 favorite]

If your cats are indoor cats who have potential contact with mice they will need to be treated for worms and inspected for fleas. It never ceases to amaze me that cat fleas are often carried by mice, but they are.
posted by Jane the Brown at 4:00 AM on August 17, 2020

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