#21-A case of aggression between familiar dogs

NMVMA listserve Behavior Tip #21
A case of aggression between familiar dogs

Jeff Nichol, DVM
Veterinary Behavior Medicine
Veterinary Emergency and Specialty Centers
Albuquerque and Santa Fe

A case of aggression between familiar dogs

Dear colleagues-

The following is a question from a colleague that may be valuable to others because it involves a medical history that may be an important influence on the aggression problem. I’ve omitted the doctor’s name.


Hi Jeff,

I am also writing to ask for your advice on a case I have.  A client of mine has three dogs, a 13-year-old spayed female Husky Mix and two pit bulls, a 1.5-year-old spayed female and a 2-year-old neutered male.

The older female, Mandy, has Addison’s disease that is controlled with monthly injections of Percorten (DOCP) and 2.5 mg of prednisone every 48 hours.  She takes omega fatty acid supplements and 5.4 mg apoquel every 48 hours for atopy and has moderate to severe osteoarthritis which we manage with Duralactan joint supplement and Adequan injections (once monthly).  We have discussed other medications (NSAIDs, tramadol, gabapentin) to help control pain if needed, but the owner feels Adequan and joint supplements are working well.

Mandy came to the clinic Monday for her monthly Percorten injection.  She looked great on exam but did snarl a little when we gave the injection, which is abnormal for her.  We did give the injection with the owner in the room, which we typically do not do with Mandy, so I don’t know if this was the cause of her behavior Monday.

Monday night, a fight broke out between all three dogs.  The owner said Mandy may have growled at the female pit bull, but she is unsure.  The female pit bull attacked Mandy and then the male pit bull joined in.  The owners were able to stop the fight, however, one of the owner’s was bit accidentally and went to urgent care for her injuries.

They have been separating Mandy from the pit bulls using a baby gate but say that Mandy growls at the other dogs if they walk by, sniff through the gait, etc.  I recommended separation of the dogs at this time to protect the dogs as well as the owner.  The owner does not want to separate the dogs long term.

What are your suggestions?  We spoke about introducing the dogs separately but I asked them to keep them separated until I could talk with you.

Hi Doc-

The aggression among your client’s dogs may be a bit of a puzzle. You certainly did the right thing by advising her to keep them separated until a solution can be found. The baby gate was a good idea because it gave the dogs the opportunity to safely interact. Mandy’s growling indicates that she wants distance from the other dogs. To reduce the risk of an escalation in hostility from threatening body signals across the baby gate I would urge the owner to separate the dogs so they can’t even see each other.

Mandy’s painful joints and her prednisone may be factors. Lots of dogs have pain-related aggression. Even the anticipation of pain (worry that a person or another dog might plow into her) can trigger defensive behavior. Tramadol may help Mandy by reducing her pain and because it is serotonergic. This can reduce anxiety and the potential for aggression. Depending on Mandy’s response there may be a better long term approach but a 2-3 week tramadol trial could be diagnostically valuable. Remember not to combine tramadol with other serotonergic drugs like clomipramine (Clomicalm) or SSRIs.

I have to agree that Mandy’s current prednisone dosage is reasonable but corticosteroids are a possible cause for aggression in some dogs. I suggest a tramadol trial first. You can try stopping the pred for a while later if you would like, just to see if it makes a difference.

Essential to all behavior cases is the necessity to rule-out physical influences first. I recommend keeping Mandy completely isolated from the pit bulls while you conduct the above trial(s). If the baby gate test goes badly again I would suggest referring the case to me for a behavioral evaluation and treatment plan.


Thank you so much Jeff!

The owner started on tramadol and actually further isolated Mandy last night.  The younger female pitbull is actually intact (I said she was spayed in my original email), so I assume this may be playing a role in the aggression between the two?

I will keep you posted on the progress between the dogs.


Hi again Doc-

It is true that estrus status can be a factor in aggression between female dogs. Interestingly, about 55% of aggression cases between familiar dogs occurs between females.

Early separation of familiar dogs who are prone to fight is important. Even if and when the inciting cause (physical or behavioral) is resolved the hostility-based association between them can be long lasting. Your clients would be wise to leave leashes (drag lines) on their dogs at all times when they are indoors. Just in case Mandy gets together with the other dogs, they can be separated using the drag lines. Reaching into a dog fight puts a panicked dog owner at risk of serious injury from redirected aggression.

Please stay in touch on this case.