Mice inexplicably dying in basement for unknown reason


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Old 11-04-18, 01:56 PM
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Mice inexplicably dying in basement for unknown reason

We have a house in WI out in the country and late fall right around this time every year mice start finding their way into our unfinished basement. Typically I just put some traps out and that helps keep them in check. This year something very odd is going on which has never happened before... I have already found at least 5 mice laying dead in the middle of the floor with no sign of what killed them. And twice I have found a mouse just sitting there - still alive - and when I tap it, you can see it moving but it doesn't run away. I pick it up by the tail and it moves and squirms while I take it outside and toss it in the woods. The two I have caught like this I am very confused by their behavior (not running away like all mice do). And the fact that I have found 5 or so just laying dead in the middle of the floor with no trauma is very odd to me.

My first thought is they are getting into some kind of substance which is poisoning them (I have never set out any poison).
Another thought is I have carbon monoxide in my basement and that is killing them - but I have 3 different CO detectors down there and none have ever gone off.
I dont have any pets that would be getting them either.

Has anyone ever had this? Any thoughts at what might be killing them? Or turning the ones I find in a "zombie" state?
 
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Old 11-04-18, 02:10 PM
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I have no idea what could be killing that many. My experience with CO detectors is that they are very sensitive and would surely be going off.

I wonder if they are chewing into insulation or related substance. That would do it.
 
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Old 11-04-18, 09:51 PM
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Being an annual event you need to find and seal those entrance points.
Next zombie you catch, put it in a a container with some holes in the lid and take it to a state of university department for advice.

As for the CO detectors they actually aren't as sensitive as we would like. But when they make them more sensitive they give too many false alarms. But any thought about CO needs to be taken seriously and we can review your combustion appliances and ventilation to see if there is any risk.

Bud
 
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Old 11-05-18, 04:58 AM
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It's common for mice to come inside look for a warm place as winter approaches. Do you have any neighbors that may have put out mouse or rat poison? Maybe they were poisoned elsewhere and the slow acting poison didn't kill them until they were in your basement.
 
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Old 11-05-18, 05:37 AM
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Very good thought... however we have no close neighbors, so that isn't a possibility

And just to be clear, we have never had any indication of carbon monoxide. It was just a crazy thought I had with no evidence whatsoever to back it up. Part of our basement is finished and we often have guests stay down there without incident as well.

I like the idea of capturing the next one and taking it in, but I wouldn't even know where to start with that. And if they would even give me the time of day if I were to somehow find the right person or department at the university (which is nearly an hour away)
 
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Old 11-05-18, 07:54 AM
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Eh, it sounds a bit like distemper, there have been outbreaks across the upper us, mostly with raccoons, (google zombie raccoon)
but appears that some strains also infect mice.
 
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Old 11-05-18, 08:18 AM
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Not to belabor the point about CO, but smaller creatures are more susceptible. It's why kids and pets get sick first. Though I can't find anything indicating a permissible exposure level or a fatal level in mice.

As Bud mentioned, CO detectors do have selectively tuned sensitivity. I actually have two detectors that have digital readouts, and while I can press the "peak level" button and see what it's gotten up to in the past (usually no more than 10-15 ppm), I never see a reading on the display. Per the manufacturer, that's normal. People were seeing very low readings, but still calling for help. So, while the detector monitors the level constantly, the display doesn't come "alive" until something like 30 ppm. They're also programmed to alarm quicker with higher levels of CO. Kidde, for example, says it will take 10 hours at 40ppm to go into alarm, but only 4-15 minutes at 400ppm. Just some trivia to keep in the back of your head.

Maybe the mice were unfortunate enough to spend time in a very high CO area (next to/inside the furnace maybe)? What about food and water source? Could they possibly be starving to death, having come inside to be warm but not able to get to food?
 
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Old 11-05-18, 08:29 AM
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Thanks for the info... the ones I have found are right near the furnace. It is a newer, high efficiency furnace and I confirmed there are no blockages outside. And two of my CO detectors are within 5 feet of the furnace (low to the ground)

I am no mice vet but the ones I have found all look normal... not like skin and bones or anything like you might expect from starvation. They seem to have the proper "plumpness" (did I mention I am not a mouse vet despite my technical terms). And my water drain is right there for my AC and water softener so I am guessing they could get water from there if need be.
 
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Old 11-05-18, 08:57 AM
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I'm not very familiar with water softeners. What kind of water drains out of it? Is it purging contaminants, salt, etc, out of that drain, that could have poisoned the mice? I know I surely wouldn't drink the water out of my AC condensate pan.
 
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Old 11-05-18, 09:38 AM
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Consider that they may be chewing something to make nesting material that is killing them either through toxicity or ruining their digestive and internal organs. Fiberglass insulation would do that among other things.
 
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Old 11-18-18, 06:17 PM
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My wife just informed me that the mice had gotten into a bag of some Nestle chocolate chips, so perhaps that is what did them in. I know chocolate can make dogs real sick so maybe they got one final sweet, delicious meal before they met their maker.
 
 

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