Finding a mouse in the house means you need to eliminate and exclude them from getting into the home. Zack Ciras, quality manager with Colonial Pest Control, discusses how to safely rid your home from mice and keep them away for good. Listen or read more to find out about how to get rid of mice.

John Maher: Hi, I’m John Maher. I’m here today with Zach Ciras, quality manager with Colonial Pest Control. Today our topic is how to get rid of mice. Welcome, Zach.

Zack Ciras: Oh, thank you so much.

John: So, Zach, what are some signs that you might have mice in your home?

Zack:  You know, this is actually — it sounds like a really normal common thing to people everybody would know. But one of the most common things that we hear from customers is “I never knew. I never knew I had mice. I never knew I had this many mice.” So, obviously, if you see a mouse running through your kitchen, you have a pretty good idea you have mice. If the cat brings you one to the bedroom, you know you have mice.

A lot of times, people hear some scratching in the walls and they’re not sure “is that a tree, is that the wind or is that something else?” And a lot of times that’s scratching the wall or even in the ceiling, that could be mice. So, there’s audio clues with the mice. Sometimes that cat might not get the mouse, but might be staring at a wall. And just incessantly staring at that wall. There might be something in there, like a mouse.

The droppings are another sign of mice. A lot of people might just sweep them up, not notice the droppings. They might be behind the refrigerator or the stove. They’re small and they almost look like chocolate sprinkles. If you remember the chocolate sprinkles, they look a little bit like that but don’t eat them. Trust me, don’t eat them. So, the droppings might be a sign. Some nesting material. I actually, in my personal vehicle, I don’t drive very often in the back hatchback there’s the spare tire. I opened that up not too long ago and found a little mouse nest. It just looked like this big ball of soft material that they had taken from around the area, around the truck and just kind of made a nice little nest for them [crosstalk] .

John: Almost like a little ball of lint or something like that. Little ground up pieces of paper or fabric or like things like that.

Zack:  Exactly. Yeah. Yeah.

Anything soft from dental floss to fabric that they can rip up to paper, like you said. Labels on some containers. I just met a lady the other day who it was her Pepsi and peanut butter labels that the mice were chewing up to make nesting material.

John: And you could tell from the nest what it was.

Zack:  I could, but I could see how a lot of people would just see that, sweep it off and forget about it.

Signs of Mice: What to Look For

John: Right. Any other signs of mice and where would you find those droppings typically? I know that you know maybe in your kitchen cabinets or things like that.

Zack:  Yeah, the droppings can be wherever the mice are. Because mice are running around and they don’t have a very good control of that function of their biology. So, wherever they’re running there’s going to be droppings. Typically, they’re going to be sticking into corners and tight spaces. They really like the small areas. They feel safer in those small confined areas. A very common place for the mice to actually be is just down in the basement up on the basement sill. They’ll run along there.

That leads me to the other sign that most people have no idea what it is. If you see dark brown reddish, sometimes even purple or black staining, it almost looks like somebody took a paint brush or a spray can and just kind of make small lines all over the place on the items down in the basement or up on the sills, especially if they have to crawl up the corner or loop around to get around a floor joist or some wiring, those are called rub marks or sebum staining. And mice, just like all animals, even us, we have oil and grease around our skin and our coat. They have a lot extra oil. It helps them slip into some small tight areas. That mixed with all the other bodily fluids that you might think of with mice running around in the wild. They’ll leave evidence behind them. I kind of say that they’re bad criminals. They’ll leave the rub marks, they’ll leave the droppings, they’ll leave the nesting and they chew as they go. They’ll chew to get into small openings. A lot of times you’ll even see some food debris, whether it’s acorns, bird seed or any kind of food they love. They love kisses, little chocolate kisses, they love chocolate. So, if you see a pile of those wrappers with some droppings around it, you know where the mice have been hanging out.

John: I know another thing that I’ve seen before. You go into your pantry and like you said, if you have a bag of chocolate chips or something like that that you might have in your pantry and you see the corner of that bag kind of whipped open, it’s chewed open and they’ve gotten into there.

Zack:  Yup. And just a small little teeth marks. Yup.

Mice Carry Diseases

John: So, are mice in the home dangerous to have or are they just kind of a nuisance and something for my cats to play with?

Zack:  That’s another thing I hear all the time. Especially husbands say, “Oh I don’t mind them. The wife gets scared, but they’re really not doing any harm.” Or a lot of us are animal lovers. And if you can justify “It’s just a wild animal and he needs some place to stay too.” You can make yourself believe that they’re not dangerous.

But the truth is they, they carry a lot of different diseases. Hantavirus for field mice, lymphocytic choriomeningitis virus, LCMV is a common disease carried by house mice, things like that that can actually really harm yourself, LCMV in particular harms pregnant women and the baby inside can be very, very detrimentally impacted by LCMV.

Not just the health issues though, because you remember they’re pooping and peeing everywhere and they’re getting into your food. They’re commensal rodents. Commensal or semi-commensal for field mice rather than house mice. Commensal basically means to share one’s table. So, if it’s a commensal rodent, it’s a rodent that wants to eat the same cereal and kisses and chocolate chips that you’re eating.

In addition to the health aspects, they’re actually rodents. Rodent is translated from the Latin “to gnaw”, to actually chew on things with their incisors. That’s what a rodent means. Something that gnaws like that with that style of teeth. So, mice chew on everything. They can cause some damage to the structure. But more importantly when they get into the attic, when they get along the basement sills, they’ll start chewing on wires. And that’s something we’re really mindful about. Any kind of wires that might be compromised from the rodent chewing on them, we really want to address that before it causes a big problem. It could be a fire hazard.

John: Right, because if they’re chewing through the outside of the wires and leaving the bare wires, then all it takes is for a couple of those bare wires to touch each other or something and a spark to happen and then you’ve got a fire.

Zack:  Exactly. Exactly. Or the next mouse to come in. There’s a little joke in the industry. The early bird may get the worm, but the second mouse gets the cheese. If the second mouse gets to the wire that the first mouse has already chewed on, then he could become that circuit that ties it all together and really makes a bigger issue out of it.

Lethal and Non-lethal Ways to Get Rid of Mice

John: Right, right. So, okay, I’ve got mice. I want to get rid of them. What are some lethal ways to get rid of mice and maybe nonlethal ways to get rid of mice? Maybe I am an animal lover and I don’t like the idea of just poisoning them or something like that.

Zack:  Right, right. Yeah, so the primary thing that folks do in the industry standard is to do some kind of poison. Usually it’s an anticoagulant poison. For a couple decades now we’ve really been relying on second generation anticoagulant poisons. So those are much quicker, more effective. And the first-generation anticoagulants, the blood thinners, like Warfarin, Coumadin, that style, they actually have been finding mice and rats for long time that’ve been building resistance. So, they went to a second generation, which is quicker, is more reliable, not so much resistance has been documented with them building that up. So those are the primary things the professional brands that you’ll find. They’re mostly second-generation anticoagulants. There are some other toxicants out there, but it’s usually the blood thinner in the bait, which is not a great way to go.

Another lethal way to do it would be snap traps, glue boards, we call those mechanical devices. There are also other devices, multiple catch traps, Havahart traps, things like that that might be designed to catch them and keeping them alive, but a lot of times are actually designed to catch them and make them expire inside the traps as well. So mechanical traps as well as anticoagulants or other types of rodenticide bait. Those are the lethal ways.

The quickest would probably be the snap trap. We’re not big fans of glue boards these days, the glue traps. It’s just not very humane, so we try to stay away from those. There are times where that tool is very useful for a clean-out, but we really try to do something that’s a little bit more humane than those. So, the snap traps [are] a great way to go for a quick control. But the industry standard for being able to get as many mice as possible, for being able to do it quickly, to affect as many mice as possible in the shortest period of time, that’s where the anticoagulant baits come in. In their camper system base stations placed out in the safe way, safe area, secure it down if they need to be. That’s the most common lethal way to take care of the mice.

As far as non-lethal, it’s really tough to do it reliably unless you have a full exclusion done in the exterior of the home to prevent new ones from coming in. But the non-lethal ways would be using those similar multiple catch traps. The Tin Cats is a common brand, Havahart’s another common brand, but it’s not very reliable to catch all the mice and bring them outside of the house and then assure yourself that they’re not going to come in. I think for folks like us who are animal lovers at heart, the best thing we can do is to understand that there’s life inside the house we love. There’s life outside of the house we love. But we need that no-go zone in-between.

So that’s where the exclusion comes in. The actual closing of the entry points around the exterior of the home to prevent them from coming in. The fewer mice we let inside the house, the fewer mice we have to deal with, whether it’s in the lethal or non-lethal way.

John: Yeah, that’s a good point. And, obviously if you are, like you said, catching the mice in a non-lethal way and then you’re just putting them right outside of your house —

Zack: It’s just a weird trip.

John: Yeah. They came in somewhere so they’re most likely to just turn right around and just come right back in that same way.

Keeping Mice Out of the House

Zack:  Exactly. And my mice have very good cultural memory, I’ll say. They’ll follow the same pheromone trails and other signs that mice have been using generation after generation after generation.

So, you’ll get a lot of the same families of mice following the tracks. Maybe if you did an exclusion 10 years ago and you had mice coming in, you stopped them, you took care of what was inside the house, you prevented new ones from coming in. But maybe the materials that you used weren’t quite strong enough. I see a lot of people using that spray foam insulation and that might hold them off for a little bit, but then you can . . . 10 years later if the pheromones are still on the surface of the house, still underneath the deck, however they were getting in, another family of mice will come in since that and just start chewing to see if they can get through. And that foam alone is not very strong. It’s very easy to chew through. You can just take your finger and start picking at it and get through that.

So, when we do a whole house exclusion to really try to permanently, or at least for a long period of time, keep mice out of the house, we use stronger materials than just the foam. We’ll use the foam in certain areas in conjunction with other things like copper mesh, galvanized steel, different metals and harder materials to really seal up the house.

Keeping Pets Safe from Mouse Exclusion Methods

John: That’s really interesting. What about pets? If I have pets in my house and you are going to use like those poison baits for the mice, do I need to be concerned that my pets are going to maybe catch and eat the mice that have been poisoned and then they’re going to get poisoned too?

Zack:  Yeah. The highest toxicity risk is from primary poisoning, that would be if your cat or your dog or your pet would actually eat the bait firsthand and get exposed to it that way.

That’s the highest way that they’re going to be affected negatively by the bait. And they do a lot of studies, I’ll tell you the millions and millions of dollars that go into pesticide, rodenticides labeling, it’s insane. But when they do the testing, the safety material sheet has a lot of data with their testing. Even if it’s a medium sized dog, he would have to eat a good amount of bait that we probably don’t even put into the house to really affect him to the point where he might not be able to come back.

But with secondary poisoning, that definitely is a risk. Secondary poisoning would be the mouse eats the bait, the cat eats the mouse. A lot of that is stored into liver of the mouse because it’s a toxicant. And all toxicants get your filter through the liver and gets stored there. So that is the highest risk. If the cat eats the liver of the mouse. So, if the cat eats the top of the mouse and leaves you the body as a gift or a prize, then it’s less risk for the cat. But even with that, there is some of the material that could be stored into the musculature of the mouse. So, there may be some transfer over. But by that time, especially when we do a good enough job to really quickly eliminate the population that’s inside the house, prevent new ones from coming in, that doesn’t give a lot of time for that material to build up inside the mouse. It takes a few days after they eat it for it to get them. So there might be more than one lethal dose feeding on that, but by the time that poison goes through the mouse and then gets consumed by the cat and whatever percentage is left, in most cases it’s negligible. It really shouldn’t be an issue.

But I understand that there’s always a risk. There’s always a risk with anything, and many medicines are a poison, it just depends on the dosage. So, with the anticoagulants, there is an antidote, which is a really great thing to have. And just about every veterinary clinic, every hospital has a syringe basically ready to go filled with vitamin K or vitamin K1. A lot of pet food actually has vitamin K as a nutrient inside of the pet food. So that’s another thing to consider. If the mouse is eating the pet food, he might be getting the antidote to the poison that we’re trying to use to control them.

But with a secondary poisoning from a pet, from a cat or dog eating the mouse, if there is any real concern, and I don’t think there’s a huge risk to it, it would be a rare situation for secondary poisoning in a normal situation to negatively affect the animal to the point where it needs to be brought to the vet. But if that is the case, then the vet will know because we are legally obligated and we comply with that to label all of our written side applications. We give you a copy of everything that we use. So, the veterinary clinic will know, okay, they used an anticoagulant. It was this trade name, this active ingredient. We know vitamin K is going to solve the problem, so they might just preemptively give them a little shot of vitamin K. So, there is a risk with everything, but I think it’s a pretty minor risk.

Another more environmental risk around homes for secondary poisoning. We’re seeing a lot of birds of prey these days, a lot of eagles. We’ve even seen a good amount of bald eagles out there in the wild. The hawks are really exploding in population and we’d love to see that. They’re a lot more susceptible to the anticoagulants.

So, if we’re in an area where it’s up against an animal preserve, up against a vast wilderness where we know that there’s hawks and eagles in that area, we have some other alternatives such as the mechanical devices that don’t have the poisons inside of them. Or we actually have a bait that’s basically, is vitamin D3 which is the calcium mobilizer and birds have hollow bones. So, if a bird eats the mouse that’s eaten the D3 poison, then there’s virtually no ill effects to that bird. But the only thing with that is it’s always a trade-off. There’s a treatment if a non-bird eats the mouse that’s eaten poison and get secondary poisoning. There’s a treatment, but there’s not a real curative antidote.

So, we go into every situation really with our eyes open and see what might the risks be, what are we dealing with, what’s the environment like and how do we get the best results while first of all, keeping everybody that we love inside the house safe.

Most Effective Mouse Removal Methods

John: Right. Yeah, that’s really good. All of these different ways that you’ve talked about getting rid of mice, what do you find, assuming that maybe I don’t have pets or I’m not up against a nature preserve or some of these other things that you’ve mentioned, what do you find is the most effective way of getting rid of mice?

Zack:  The most effective way in most situations is going to be using the anticoagulant baits. Those baits that we use, we use those on over 90% of the jobs that we do for mice, the anticoagulants, a second generations. Those are gonna give us really good results relatively quickly. We usually ask for about 14 days patience because the mouse has to find it, be comfortable, then eat it. And after that it takes, three, four or five days after they eat it for them to expire.

And I think that that’s the most effective way because we’re not chasing them down into areas that they’re not frequenting, trying to put snap traps and other mechanical devices in areas that might be tough to get to. They accidentally set it off. Now they’re trap shy and they don’t go to the trap. I think the baits, using their behavior to fight against them, using their own behavior against them, that’s going to give us the best results in the quickest way and more comprehensive way because one mouse to one trap.

But if you have bait stations and say it’s 0.75 ounces to a full ounce per bait, you can have multiple mice feeding on that. They’ll eat about a 10th of an ounce per feeding site per night, multiple feeding sites. They’re like little nervous nibblers. So theoretically you could eliminate seven and a half mice with one bait station rather than the snap trap with just one mouse. I love snap traps. If there’s a situation where we know we can put them in their best areas, I love using the snap traps because they’re quick, they’re effective, you know where they’re going to be. But overall I would say the anticoagulant baits is the way to go in most situations.

Keep Out Mice — For Good

John: Okay. And then finally, like we talked about how do I keep the mice from coming back? I don’t want to just be constantly killing them all the time and or trapping them and releasing them and then they’re just coming right back into the house again.

Zack:  Exactly. Yeah. The long-term control — that’s really where the industry has turned. We turned this way almost a decade ago, really trying to focus on excluding new pests from coming in. I’ll often say we have three ‘E’s to pest control, especially for rodent control. Elimination, that’s taking care of what’s in there. Education, part of that is what we’re doing here. Part of that is talking to the homeowner. How is the environment set up around the house? Within the house? Are there hoarding sites? What’s the behavior we should expect? The education portion of that. But then the third E is I think the most important long-term, that’s the exclusion.

So, we have a couple of different programs. What a lot of folks go with is the less expensive option and that’s a minor exclusion. That says to looking around the more common spots around the foundation where they’re coming in or on the doors, the lower windows, around the chimney, the lower sections where the mice are typically running on the ground and getting into a smaller hole. We’ll close up the holes. About an inch in diameter or smaller is the typical size hole for a mouse for a minor exclusion. And then anything beyond that, we’ll bring it to the attention, kind of work with the homeowner to make a plan going forward. And that’s good in a lot of situations.

The best way to keep them out though is to do that smaller minor exclusion and then go a step further. So, we know we’ve closed up all the holes that they’re actively using that they have been using for however many years. But what’s the next spot? What’s the next weakest spot? Is there some water damage? Is there a gap along the sill of the house? A lot of homes were poured where the foundations weren’t laser designed like they are these days and you’ll have shims to kind of prop up the wooden sill to make the house straight on top of the crooked foundation. In between those areas, a lot of mice get into those areas.

So, we’ll go around basically every inch of the house. Foundation, all the way around, around the chimneys and doors and all the areas that we do for minor exclusion. But we’ll use harder materials right off the bat and be a lot more extensive with the program. So, it’s not just closing the holes that are there. We’re really shoring up the entire house to prevent the next hole from opening up. A mouse needs about a quarter of an inch, three eighth technically, if you can put your pinky finger in the hole, it’s about size of a dime or so. That’s easy pickings for a mouse. But if you have a hole that’s an 8th of an inch or 16th of an inch with a little bevel to it and you have some water damage starting to form around there, there’s going to be a quarter of an inch with just a few scratches and nods by the rodent.

And additionally, we don’t want to just focus down low where the mice are most likely to come in. If the house has any climbable access to the roof, that’s an exposed chimney, maybe you can some power lines, some overhanging vegetation, some trees, any place that the mice can crawl onto that the roof of the House that might open up the entire roof of the house.

So, we really want to spend some time looking at what the ridge vent looks like. Does that need to be shored up? Do we need to do some extra wrapping, some extra exclusion around the gable vents, around the gable junctures where the roofs come together. So, this is a lot more expensive, but it gives you a much longer term . . . I think the state of the world is entropy and we’re all falling apart at some point and homes are made of the wood for the most part. So that’s going to have some sort of entropy, some kind of falling apart along the way. So, nothing’s permanent. But with this full exclusion program that we do, we are so detail oriented with it. If it’s not forever, it’s for a really long time.

John: All right, well that’s really extensive and really awesome information, Zach. I really appreciate you speaking to me today about mice.

Zack:  Oh, my pleasure. My pleasure. Thanks a lot John.

John: And for more information, you can visit the Colonial Pest Control website at colonialpest.com or call 1-800-525-8084. That’s 1-800-525-8084.