Why are my dogs aggressive and possessive after new puppy?
I'm sorry to hear that you're having this issues! It sounds like there are a few different things going on here with both dogs, which definitely makes the situation more complicated. From your description, I can't quite tell if your male dog's crate aggression issues are directed at the puppy only, or if this is more of a general problem and he also snarls and runs from the puppy at other times as well. This is important information to help determine what may be going on so that we can make suggestions.
I'm not sure how old your new puppy is, but if she is younger than six months, aggression at this age is quite uncommon and very concerning. Possessive aggression (also called resource guarding) over owners is a relatively common problem that can often be successfully treated, but you would really need an expert who can help you in person. Particularly in a young puppy, a veterinary behaviorist would be your best bet to evaluate the pup and put together a detailed plan to start working on this problem ASAP.
If you want to keep both dogs, this will definitely require some professional assistance and quite a bit of time and effort for training. I would recommend asking your veterinarian to refer you to a board-certified veterinary behaviorist for some hands-on guidance.
Updated on September 23rd, 2025