Boxer is showing aggression towards our other dog

Question
My female boxer is becoming very territorial with our other dog a puggle. They are together 24/7, and they are constantly snuggling together in their cage, BUT just recently when I give them a treat within their cage the boxer began shaking the puggle rigorously to the point she pooped herself. I stopped giving treats within the cage, and now she is beginning to become more and more territorial with the puggle. If I seperate them, then the boxer cries until i put the puggle back in the cage with her. I know my boxer loves our other dog, but she is scaring me that one day she will shake her too hard and kill her. The boxer wants to grab the puggle by the neck and shake her vigorously when she is in territorial tirate. What do I do?
Sincerely,
Betsy

Answer
Wow, that is scary!

How much time do they spend in the cage together? By cage do you mean a kennel run in the back yard or a crate that they both share?

I am guessing that your other dog is also female? Maybe they are both coming into an age that they would compete for status?

Either way, 24/7 may not be best at this time. Remember that expression "familiarity breeds contempt?" That may apply here. I think they need some time away from each other doing some constructive things (like training) or fun things (like hiking) so they don't have the chance to freak about the other dog not being there.

With the Boxer I would focus on self control exercises like good solid sits, down and an off command. Once she is good away from the cage, start to incorporate control around and then in the cage. Not with the Puggle present until she is much more reliable.

It does not sound so much like a territorial problem as an arousal issue. Or resource guarding as it was around treats.

I would suggest that you get someone qualified out to meet with you in your home to help get things control before it escalates and someone does get hurt. That will be much harder to undo.

Try here: www.ccpdt.org

Make sure they are familiar with aggression and have a successful track record working with dogs and these very complex issues.