So last week my wife and I discovered some evidence of mice fooling around in our kitchen at night (e.g. shuffled cleaning supplies under the sink, hoarded dog food, and of course their droppings). After a little research, I decided to get the classic spring-style mouse traps. I set them with some peanut butter and after a night or two, I woke up to a dead mouse. After that, I cleaned up and set traps again. Things were quiet for a few days but then we got another hit. A second dead mouse captured. We were happy up until this point because we figured it was just one mouse but since we got the second one, I had to ask myself "when do I stop setting traps?" and "did the mouse come in because it smelled the peanut butter set trap?". It's sort of a catch 22 now. I am afraid that the mouse got in "because" I had peanut butter out (as part of the set trap). I'm afraid that if I keep setting traps that I may just be inviting these little guys in. Suggestions?
Setting traps will kill what you have, but you still have the problem of the mice getting in. you need to figure out how they are getting into the house. Mice can get through incredibly tiny holes, so it might be a chore to find them all. But as you find holes, seal them up. Steel wool is useful for this as they don't like chewing through it.
I personally go with 'forever'. I've got a good-size house, on a little bit land, and a garage door that I leave open for fair amounts of time each day in good weather. I'm ALWAYS going to have mice getting in, even though I've patched every hole I can find. It's just sort of inevitable at this point. So I keep the snap-traps under the sink and in the basement. I check them every couple of weeks, change the bait (I like cheese) now and then, and I get a few mice every year.
But no major infestations, and they don't seem to get past my initial trap points, so I don't get them in the pantry or anything.
According to the CDC's website, keep putting out the mouse traps and after five straight days of no mice, you should be in the clear. I did that in our attic and it seemed to do the trick --- and yes, there is always more than one... we caught 5 in 5 days. Three traps were left with peanut butter and no catches. After 30 days, I put out two traps again just to make sure and after five days there were no more catches. I recommend the 5 day rule.
Oh, and my recommendation with the snap traps. You don't have to touch the trap/mice if you put the trap in a small box (shoe size or smaller) before putting it in your basement/attic.
For what it's worth, I decided to contract with a pest control company for ongoing service. Periodically they refill the bait containers in the basement, and this has been sufficient to keep any mice from nesting in the attic. I don't like bait a lot -- among other things I worry about a poisoned-but-not-dead-yet mouse being found by a cat -- but it has been effective.
Reportedly, old style snap-the-neck traps are actually the least painful killing trap, but of course those have to be more actively maintained. Nonkilling traps are a nice idea but you have to empty them somewhere before the mice starve; I think what I really want is a nonkilling trap that sends email when it has caught something.
Warning: Mice often carry ticks, and in some areas ticks can carry things like Lyme disease. Be careful when disposing of carcasses. I've been tempted to put out Daminix as well, though it isn't cheap.