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Why is my spayed female dog aggressive towards my other dog?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed | Female | spayed | 3 years old

Ever since I got my dogs spayed hazel has been really aggressive towards daisy, they both got fix in June and she's still aggressive, it's to the point where they have to be separated, it breaks my heart not seeing them together at more..hazel always starts the fight and ends up getting hurt. What can i do? Or why is she acting like that? Hazel only fights with daisy and no other dog and I'm not sure what to do any more.

1 Answer

Most Helpful Answer

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Answered By Alysia Van Scoy, DVM

Veterinarian

Published on October 19th, 2017

Dog to dog aggression is usually a hard problem to fix. It sounds like they might both want to be alpha of your pack.... Hazel might want to be leader, but Daisy keeps re-establishing her leadership with the fights. I highly recommend getting an evaluation by a good dog trainer. There are lots of trainers out there, so I would get a recommendation from your veterinarian to make sure that you get a good. one. A good trainer can evaluate your situation and see if there are subtle signs that will tell them what is going on in your dog's head. In my opinion, Same sex (female to female in your case) dog aggression such as this is extremely hard to solve. I don't believe that it was caused by the spaying, but this is the maturity level that they will start to get worse. If they are littermate- the problem is even larger. Littermate syndrome is real problem in dogs. I am sorry that you are going through this. I would get the evaluation by the trainer and get a behavior plan started. Sometimes behavior plans work, and sometimes the dogs just have to be separated for their own safety. Thank you for reaching out to Petco Pet Education Center, formerly Petcoach!

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