# how to find out how mice are getting in attic?



## gobug (Jul 13, 2012)

There are many rodent pathways, not just the attic. First, I suggest you go around the outside perimeter of the house. Use your finger to look for holes, like under the siding. If your finger fits, the mouse has a door. Look for any kind of possible entry. Garages are major rodent entry zones. So is under decks and porches. So are gas/electric/plumbing/phone/internet and cable entries. Close the holes.

Temperature is one way that the mice find the holes. That may not be so easy for you. Once they enter (a wall or garage....) they can move through the walls by following the plumbing or electrical. Since your sink drain has a vent through the roof, that is one pathway to the attic. They can get to that air vent from beneath your sink cabinet. Crawl spaces are often paths into the house. They can get there from many points around the structure. Then rooms have ceiling lights which are wired through the attic. The holes for electric cable are big enough to allow rodent entry in most cases. Plumbing is often in the outside wall. If they can get in from the outside, they could have pathways inside the walls that you won't see.

A question, where is their food source? A typical house mouse can live out it's life in an 8' circle (if food is there). A deer mouse prefers as much as 2 acres for foraging. Stop feeding them, whatever that translates into. Like if you have a pet, do not leave pet food out overnight. Put bulk petfood in a steel container. Processed foods in cardboard boxes are not rodent proof.

Mice are micro-robots. They run the same paths over and over. These paths are mostly right alongside walls. I suggest placing a variety of rodent control devices at about 8 foot spacing. This should quickly reduce the immediate population, but unless you close the doors and stop feeding them, the problems will continue. Glue boards, snap traps, gang traps, etc are all ok. You don't need poison, but poisons take less maintenance if you don't close the rodent doors. The traps are better clues about the source of your problem than poisons.


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## gobug (Jul 13, 2012)

Oh yeah, I forgot. Rodent urine glows in a black light. Mice do not have bladders, they just gradually leak as they run. So their trails glow if you use a black light.


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## user1007 (Sep 23, 2009)

You can lay down some stringline chalk or other indicator that they track to show their paths. A UV light source is a good idea and inexpensive also. 

Remember they have flexible bone structures and it is surprising how small an opening they can fit through. 

In N. California when orchards were ripped out to make room for housing developments many of us were overrun with field mice. Their predators disappeared and the County finally gave us all sacks of poison to bring the populations down. Nasty if a cat got a poisoned mouse, climbed into the crawl space died and bloated to about 20 times it size!

Every exterminator I have worked with says the same thing as mentioned here. You want to be sure to set your traps along runways and parallel to things like walls, etc. A trap set away from a wall in the middle of a space is not going to have the odds of catching anything. 

"Billy the Exterminator" is a fave show of mine now and then. In one episode Billy left Louisiana to help a friend here with a mouse and rat problem. Cockroaches were stealing bait from snap traps. He tricked them by barely screwing in some drywall screws into the baseboard and covering the heads with peanut butter. Rodents stood up to get at the bait and snappo! Seems like a good trick to try with clever mice. 

I mentioned before reading that the LA Police Department has provided homes to ferile cats around precincts (spay/neuter them, provide shots against feline HIV and other things, and give them shelters) and they are really making a difference in mouse populations.

I was lucky that my beasts, even beyond spoiled and well fed, loved to mouse. They would play soccer with rare catches until little hearts stopped beating. 

Of course as also mentioned, limiting food sources is important. The alley rats here really like pet waste which is why ordinances for people picking up after their pets are enforced to some extent.


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## Red Squirrel (Jun 29, 2009)

Interesting about the black light, think I will try this. This works better at night I would imagine right?

I do have an attached garage, and I am suspecting that could be a potential entry point. Will mice normally climb vertical surfaces? The only way I can see is that they are climbing straight up, there's a few places that are covered with wood and I'm not sure what's behind it without taking it apart so it's possible there are holes. All my weep holes in the brick outside have steel wool as well, but I'll have to go around and double check all of them to be extra sure. What about flashing, should I put caulk since I imagine they might be able to slip through it. 

Also can they climb inside ABS pipe? My bathroom fan has a bit of flex that goes to ABS all the way to the basement (straight down) about 8 feet then some flex to the fan itself, and then metal going outside to a dryer type vent. If they can climb ABS then I could see that they'd get in through that and have chewed a hole in the flex pipe. But seems unlikely they could climb that, and it would make more sense if it chewed the flex that's in the basement and go in the basement instead. So far no mice have made it into living space. I put a single peanut in the basement near a wall and it's been there for over a year. Speaking of food sources, I can't think of anything other than any food they are bringing in. Luckly since they're not entering living space my kitchen and my cat's food remains untouched.


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## gobug (Jul 13, 2012)

They can climb vertical surfaces. I watched a mouse climb up my fishing pole.
Does the garage have bulk dry cat food?
Usually attics have insulation. Mouse trails should be visible indents in the insulation. That may give you a clue as to where the trails converge.
If these mice are not eating any of your food or your cat's food, they must be leaving the house to eat.
Wires and tree limbs can be the pathways.


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## dougp23 (Sep 20, 2011)

Mice are excellent vertical climbers, and like others have said, it is very likely they are coming in "low" and going inside a wall to make it to the attic.
Other favorites (other than electrical and plumbing) are chimney chases, they will climb right up the side of the chimney inside your house and get right into the attic.
Look for "grease marks", this is the dirt and urine they leave as they move around. If you see these, that is one point where they are tracking.
Had some problems here when we bought our house, you've definitely got to shut them out of the house, or you will just keep setting traps! They actually like the smell of a dead mouse, so feel free to reuse a trap if you want....


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## Red Squirrel (Jun 29, 2009)

Ha the chimney, I never even thought of that. My house used to have a wood fireplace, but the chimney is capped inside the garage, well, tbh I never put a ladder up there to check, so maybe it's not capped, and maybe there is an entry way through there. It's all cinder block and attached to the firewall. The other side of the firewall is the lower attic. 

It's too late now due to the freezing weather, but what is a good caulk like product to use to block smaller holes? I'm thinking they will be able to chew through caulk, but basically what I want to do is apply a material all around the house where the soffits meet the brick, and any other potential entry points. Think I will just attack this at brute force until I no longer have any. Or will caulk work fine? It's not like I see teeth marks on any outside caulk such as windows.


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## DexterII (Jul 14, 2010)

For small holes, particularly when it's cold enough that I'm not comfortable with caulk, I like duct sealant. It comes in a block, something like maybe 4"x6"x1", sort of like a consumer size block of cheese, and has maybe a bit more consistency than Play Dough. You slice or rip off what you want, roll it in the palms of your hands a little bit, shape it, push it in place, and it remains resilient, but stays in place. I imagine that there are other brands, but one of the most common is Gardner Bender, which the major home improvement big box stores carry, as well as hardware stores, and I assume Canadian Tire. If you're comfortable with it once you have it in place, great, otherwise you can go back in the spring, scrape it out, and apply caulk, foam, or whatever you want at that time.


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## Red Squirrel (Jun 29, 2009)

That sounds like an interesting product, I'll have to look for it.


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## Red Squirrel (Jun 29, 2009)

I finally got around to pulling wire for my mouse trap monitoring project. I've been checking it manually with the ohm meter for now.



Cable comes in from the server rack DIN terminal block, through the floor, up this conduit and to a terminal block. Yeah I know, that's an out of spec bend, but it really wont matter for basic low voltage non-data electrical. 




Will have a cord going up to the attic with a RJ45 end so I can easily disconnect the trap array to bring it down for emptying. The trap array will consist of 6 traps in groups of 2. Undecided yet if I want to do series or parallel. In series I'll know right away if I caught a mouse while in parallel it could take a few mice before one set triggers. 



The mouse trap array, I will be adding 4 more traps and a rj45 jack.

The idea behind this is so I don't have to keep going up in the attic and getting myself full of blown insulation just to check the traps. I'll only have to go up there to empty them. I'll also be able to put everything else back in that closet once things slow down.

I caught like 5 already so far. Will be more fun with this new system since I'll get an email when it happens. I need to figure a way so it also sends a text on my cell lol.


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## dougp23 (Sep 20, 2011)

Red Squirrel said:


> Ha the chimney, I never even thought of that. My house used to have a wood fireplace, but the chimney is capped inside the garage, well, tbh I never put a ladder up there to check, so maybe it's not capped, and maybe there is an entry way through there. It's all cinder block and attached to the firewall. The other side of the firewall is the lower attic.
> 
> It's too late now due to the freezing weather, but what is a good caulk like product to use to block smaller holes? I'm thinking they will be able to chew through caulk, but basically what I want to do is apply a material all around the house where the soffits meet the brick, and any other potential entry points. Think I will just attack this at brute force until I no longer have any. Or will caulk work fine? It's not like I see teeth marks on any outside caulk such as windows.


It's not so much that they might come in from the outside via your chimney, it's that once they get inside, they will go to the chimney in your house and climb up it into the attic. We noticed they were doing that in our house! Turned out they were getting in through a small hole where they house sat on the foundation. Patched it with some steel wool and rodent proof stuff, and so far so good.


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## Too old (Sep 20, 2012)

Another real good hole plugger is steel wool.


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