Older dog suddenly aggressive with other dogs after new puppy?

A few thoughts here: first, esteemed PhD level animal biologist Ray Coppinger debunked the "alpha" concept when it comes to dogs several decades ago, but the idea seems to persist for some reason. Second: you should always introduce a new dog to existing members of your canine household on neutral ground. Bringing a "stranger" into your home invites territorial behavior. You don't say how long you've had the newest dog. If it is a short time, they may be working out dominance issues and, as long as no one is getting hurt, this can be okay. Sometimes, there is more noise and posturing than anything really serious going on. Not being there, I can't know for sure. If you are really concerned, or if blood has been drawn, I would ask your vet for a recommendation to a canine behaviorist (NOT the same as a dog trainer!) for help. Good luck with this!

Hi There. It sounds like Bobby is trying to establish his dominance over the new puppy. This is quite normal and provided there are no fights, may resolve with time. There are some great resources on Dr. Sophia Yins website (draophiatin.com) that discuss dominance aggression. You may also want to consider working with a certified trainer or a veterinary behaviorist. You can find one in your area on www.acvb.org.

If your dog does not get along with other dogs it was probably a very bad idea (and a very stressful one) to bring a new puppy into the house. A new puppy can also be hard around a newborn as they aren't yet sure how to interact with each other. You can try to continue to get the two to get along by starting with limited introductions that are supervised, however if a fight breaks out the interaction should be stopped immediately and started again later. Never leave the two unsupervised together as even a good play sessions can cause accidental injury. You can also use baby gates as a way for the two to "meet" each other without being able to physically be together. If fights are continually breaking out, talking to a trainer or behaviorist that can observe within the home is best.

This behavior is likely so-called dominance behavior. You will need to find out who is the boss and the dominant dog (boss) should always get fed first, be petted first and addressed first. If you start preferring the Number 2 dog over the dominant dog, then the dominant dog will try to punish the Number 2 dog. You need to let the two dogs work it out themselves, and not feel sorry for the underdog. Once the ranking is clear the biting and aggression should stop.

Puppies can sometimes be A LOT for senior dogs and it can take some time for them to get use to one another. If there were any food, treats, toys or special people near by Buddy could have just been acting protective over these. Also, with Buddy being older, if they puppy is always playing, jumping on him, or nipping at him, he may have been just trying to tell the puppy to leave him alone or trying to set some boundaries. Also, if he is arthritic and he knows the puppy jumping on him hurts, he could have reacted to prevent this. I would continue to keep them separate until you know they can be left alone together. I would definitely feed them separately as well. I would be sure you are still spending plenty of alone time with Buddy as he may be feeling frustrated that his home life has changed with the new addition. I would continue to have short but frequent times of them being together. You could also start Buddy on an anti-anxiety chew like composure or composure pro and get him a calming collar like sentry or adaptil. If these don't help, talk to your vet about anti-anxiety medicine like fluoxetine or trazadone. I hope this helps!

There are some articles here that may be worth reading. http://www.veterinarypartner.com/Content.plx?P=SRC&S=1&SourceID=47 Every new dog is a new pack member with thier owne personality. A new dog is challenging your other dogs place and potentially taking resources (food, toys, attention). You need to slowly make introductions and not leave the dogs alone unsupervised until they have reached a stable peace. http://www.veterinarypartner.com/Content.plx?P=A&A=2465&S=1&SourceID=47

You will likely need to separate the new dog from the 2 "older" dogs for a period of time. Spend time with each separately, but make sure that they cannot see the new dog, i.e. keep him in a separate part of the house behind a closed door for at least one to two weeks. Then you can allow them to see each other, but not have contact. Move slowly, from this phase on to allowing them to see and smell each other across a barrier such as a baby gate. Finally, allow them to spend supervised time together. Reward good behavior with high value food treats (i.e. bits of cooked chicken) and go slow.