Why the Bad Rap? Despite the saying, dogs and cats aren't really natural born enemies. But there are a couple of factors that can make their relationship, well, a little complicated. For example, dogs and cats communicate differently. Take the butt-sniff greeting. Dog meets dog, dogs exchange butt sniffs, dogs are now best buds. Cats, on the other hand, may not respond quite as well to the butt-sniff greeting since it isn't their natural behavior.