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Why is my senior dog suddenly aggressive with our new puppy?

Updated on September 23rd, 2025

Pet's info: Dog | Mixed Breed Large (61lb +) | Male | neutered | 11 years old

My beagle angrily chase after our new puppy today after the puppy came near him. He is usually okay with the puppy around but why did he do this? We have been keeping thier kennels separate but walking them together and letting the puppy downstiers on a leash. we can’t keep them separate forever. Please help!

1 Answer

Most Helpful Answer

Answered By Megan, DVM, CVA

Veterinarian

Published on January 7th, 2019

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!

2Pet Parents found this answer helpful

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