Dog & cat aggression

Question
We adopted an 8-yr-old male English Springer Spaniel two months ago.  He is very submissive with people and other animals, very sweet.  We have also had a 5-yr-old female tortoise-shell cat for 4 yrs.  She's always been feisty, common to the breed.  She hisses and sometimes strikes out at the dog when he gets close, and he has always backed out and avoided her.  The past two weeks, though, he's barked and showed his teeth at least three times when she's done this.  She has safe places to go, so that's not the issue.  She really is the aggressor with the dog. Neither has gotten hurt yet, and I don't know if it would get to this point. I don't know if the dog is finally feeling comfortable standing up for himself, or just sick of her taunting him. Any advise on getting them past this?  Thank you.

Answer
This is a tricky situation, since the dog will perceive any device you use on the cat to modify her aggression and will take that as a rank promotion. Both animals also seem to have noticed that this behavior is GETTING YOUR ATTENTION. Your cat is behaving normally and the fact that she's willing to be in the same room with the dog is remarkable.  I'm uncertain that the cat is the true aggressor since you seem to describe her reacting to the dog approaching her, which is very normal for an adult cat that has never lived with a dog.  Your dog, when 'showing teeth', might very well be showing a fear grimace rather than a dominance aggression statement.  Barking would accompany a fear response as well as a dominance statement and it's impossible to tell which one it is without seeing it.  The fear grimace is more of a wide grin while the dominance snarl shows front upper and lower teeth.  It's unlikely that the dog will attempt to attack the cat at this point but of course you don't want to take that chance; he's simply giving her signals he thinks she should understand.  Reinforce your cat's position in your household by spending quality time with her away from the dog and teach your dog a solid response to a verbal command.  Use positive reinforcement and re-teach him a "sit" command (not using that word).  By working with the dog you will be spending quality time with him and giving him a new skill, and by spending time with the cat away from the dog you will be minimizing the cat's need to get your attention by beating up the dog.  Restrain the dog on long house leash even when he has this command with 100% response, as the cat's presence will cause a breakdown in his new skill.  When the cat enters the room, ask the dog to 'sit' and reinforce any actual performance with a huge reward.  If he learns that sitting is more rewarding than showing interest in the cat, the cat will learn that she does not need to be aggressive toward the dog and, in time, there should be some sort of truce between these two (although it's unlikely they will be best of friends.)  If the dog absolutely refuses to "work" with the cat present,  go to the end of the long house leash (in the other direction from the cat) so that the dog cannot go toward the cat and turn YOUR BACK to both of them.  This is an effective withdrawal of your attention to both animals and is, in fact, a "punisher".  It might take a few days of persistence on your part for both cat and dog to get the point that you will NOT be participating in this "game", but they will eventually get it.  Any further questions, please re-post.