My dog and cat had never seen them until 8 years ago......they are still working out what to do with them. Mostly the cat just watches them but every now and then she will catch them and drop them near the dog or sometimes in the water bowl where she puts everything she finds and steals. The dog does kill them most of the time if he can find them, he doesn't seem to know what his nose is for. Granted, he is a sight hound who's sight is failing with old age so the nose was never used as much as it could have been.
I just find it so frustrating to have to get my daughter to come and rescue the dog and cat. She is much faster at finding the mice and catching them with her hands than both of the dogs and the cat all put together, lol.