My Louis (Lab) passed last year but he was fine with them. Running to the back door, tail wagging. Once he was out he was chasing them around the garden, well trying too anyway. The cats we have however, were initially startled but were fine. Got into a debate with a new puppy owner on face book. She was fuming over them, saying how her pup was terrified. I told her, take it for a walk and when one goes off, reassure it, give it a treat and a good boy/girl speech. it was a labrador. Gun dog. She wouldn't accept any help, just telling everyone how bad they are and inconsiderate.