I have two adult (5-year-old) male cats, who live indoors. They are very curious about the outdoors, and I worry about them getting out, especially in summer months when we might accidentally leave a door open. I tried putting collars on them, and at first they didn't seem to object at all (no scratching, etc.). But after a few days I noticed cat pee in the bathtub, and then on the bathroom doorsill. Then, progressively, cat poop in the bathtub and in front of the litter box. This went on for about two weeks. I talked to the cats' previous owner, and she told me that they pooped around the house when she tried to put collars on them. So I took the collars off, and sure enough, the behaviour stopped. Yes, they are microchipped, so I haven't tried the collars again, but I'm wondering if there is a way around this behavior? Thanks.