I have a stone barn. It is weather tight, and I have a workshop in there, plus coal store, log store, oil tank, other storage etc etc. During the summer, I never see any mice in there. During the winter (this happened last year and now it happening again this year), mice seem to go in there to die. Why? I keep finding healthy (apart from being dead of course) mice in the barn, often in the middle of the floor, just....dead. I found one in there this morning, and three yesterday. There are pently of gaps for them to get in, but why go inside (to get out of the cold weather I assume) and then just...die? There is no poison around and as I said they look healthy before they died. Any ideas?