Cats catching weasels? Eeeek! I didn't think they would dare. But there hasn't been a cat here since 2013, and he was indoors-only and lived on my lap.Cats have been documented to prey on several species of weasel, it's not that unusual AFAIK - FWIW, you can find videos of cats preying on weasels (or the aftermath) on Youtube. I've even seen one from someone in the US whose cat brought in a live stoat that he managed to release later. Rarer than catching mice or lizards, but then again there's a huge number of unattended cats wandering about. Dogs catch all manner of critters that are more agile than themselves; it's not like they have to be particularly dexterous given the size discrepancy, at least as long as the dog isn't worrying much about getting bit by its prey. Irrespective of the actual success rate of either species, the disturbance is still there.
In any case, weasels can fit through very small spaces indeed, and probably have spaces of their own. I first saw my current little guest on the afternoon of Christmas Eve. I was going outdoors when I saw a pretty little white face at the small opening in the outer door where the extension cord goes through! I can't imagine how that head could fit through the tiny crack. We looked at each other a bit, then the rest of him came through, crossed the entry, hid, then poked his head out and looked at me some more. If you want to build a safety shelter for them, I can only say that this one - big as weasels go - had no trouble coming through an opening of much less than an inch!