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Canine Behavior/2 mix breeds becoming more aggressive with each other


Hi there,
I have male 2 dogs. A, a 1 1/2 yr old terrier mix (looks like a Mini American Eskimo mix of some sort) who is not neutered yet and B, a 3-legged Heeler mix who is about 5months old/is neutered.

We had adopted A when he was 4 months old and more recently adopted B when he was 9 weeks old. They hit it off just fine, nothing out of the ordinary as far as I WAS concerned, behavior-wise. A obviously tries to be the more dominant of the two, but is smaller than B. B has been more mouthy when he plays with both dogs and humans, which is another thing we've been working on. Otherwise, things weren't so bad. Recently however; I left once to get some groceries and came home to find A with some blood spots in his fur around his face.

Today as I was home, I let them out to do their business and heard a fight break out between the two. Again, resulting with A bleeding around his face/neck. At first I thought it was a result of rough playing, until today when I realized it was a fight. Though I didn't see it start, so I have no idea what it was all about. I hollered and they broke off, then I separated them. They are still in separate spaces as I type.

What I'm asking is if there is anything I can do to stop this from happening again. It seems like they won't break out in fights like this indoors and always tends to happen when they are out in the back yard when I'm not around. I would hate to have to separate my dogs from each other all the time or even permanently (which is what the husband is saying we may have to do) before trying everything I can to help. Though I do not want to risk the well-being of my dogs and children. Thank you for your time, look forward to a response.

Sorry it has taken more than 24 hours to answer your question.  My cable was out all afternoon and evening yesterday for no apparent reason, very frustrating.

OK:  It appears that A MIGHT be instigating something he can't finish without injury, or B (and at five months old this would be highly unlikely) is demonstrating rank opportunism.  B's "mouthiness" might be the cause but....HUGE BUT....YOUR PRESENCE is absolutely REQUIRED when these two dogs are "turned out" together.  YOU CANNOT ALLOW A REPEAT PERFORMANCE of anything that has begun out of your sight and resulted in real injury to one or both dogs.

GO OUT WITH YOUR DOGS.  If this is not convenient, re-home one of them. This could get very bad, very quickly.  You cannot keep them separated indoors: separation will only make it worse.  You cannot consistently maintain such.  The dogs cannot be allowed "alone together" when you are not at home.  They must each be confined in a safe place, behind a closed door, with a cushy bed and a bowl of water.

Also: there are children in the mix here.  If A is instigating B, or reacting to B's "rough play" when you are not present, a child might easily get into this mix innocently and be hurt (or worse, one bite to an artery on the leg is all it takes).

If it were me: I would find a Certified Applied Animal Behaviorist ASAP:

Were I (or other such professional as can be found in above links) to come to your home, I would evaluate each dog independently of the other, and then observe them together in various situations (different rooms, outdoors in the back yard, walking in tandem on leash off your property).  I would then evaluate both dogs in their relationships with your children by interviewing YOUR CHILDREN without YOU (you'd be surprised what children have told me when parents aren't in the room!)  I have rehabilitated dog to dog aggression between MALES in homes after determining what is really going on.  I can't see anything from here.

Until then: keep both dogs on house tab (lightweight leash with handles cut off) when you are at home; separate them comfortably while you are out; if a "fight" or rough play begins, pick up tab of B and remove him from the room, put him behind a closed door for ten seconds, say nothing, do nothing.  Open the door, let him out, and observe.  Since B is far younger, it is unlikely (IF HE REALLY IS ONLY FIVE MONTHS OLD) that he is deliberately attempting to pull "rank" on A.  If A is the instigator (not realizing he is smaller), both A and B will learn that A is higher up in social hierarchy.  This is a short term solution.

Get your children together, both parents present and singing the same song.  Tell the children NEVER INTERFERE if the dogs are playing or actually fighting, NEVER.  They are to walk away, come find Mom or Dad.  

Canine Behavior

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Jill Connor, Ph.D.


I have spent my entire professional life rehabilitating the behavior of the domestic dog and I can answer any question regarding any behavior problem in any breed dog. I have answered more than 5,000 QUESTIONS on this site in the past (almost) eight years. If you are a caring, committed owner and need advice, I'm here for you. I am personally acquainted with my colleagues (Turid Rugaas, Ian Dunbar, etc.) who were members of an elite group in EGroups that I founded: K9Shrinks. THERE ARE NO QUICK FIXES for serious behavioral issues; not only is it unprofessional to offer same, it is also unethical. IF I ASK YOU SUBSEQUENT QUESTIONS, I NEED YOU TO INTERACT WITH ME. More information equals more credible answers and a more successful outcome. If you want ANSWERS THAT WORK, participate in any way I request. I'm quite committed to working on this site for YOUR benefit and the benefit of YOUR DOG. Help me in any way you can.


30 years of solving serious behavior problems in domestic dogs; expert in dog to human aggression; Internet columnist for for 5 years; former radio talk show host, WHPC.FM, Garden City, NY "Bite Back" (1995 through 2000). List owner, international animal behavior experts, Seminar leader: "Operant Conditioning and Learning"; "Aggression in The Domestic Dog"; "Solving Problem Behaviors" -- conducted for various training facilities on Long Island from 1993 through 2000. Former clinical director of "Behavioral Abnormalities" in conjunction with Mark Beckerman, DVM, Hempstead, New York.

Member, APDT (UK); Psychologists in Ethical Treatment with Animals

Harcourt Brace Learning Direct: "The Business of Dog Training" "The Fail Safe Dog: Brain Training, not Pain Training"

Ph.D., UC Berkeley

Past/Present Clients
Board of Directors: Northeast Dog Rescue Connection; The Dog Project; Sav-A-Dog Foundation; etc. Pro Bono counselor: Little Shelter Humane Society My practice is presently limited to forensics. I diagnose cause of dog bite, based upon testimony before the Court, for attorneys and insurance companies litigating dog bites, including fatal injuries. I also do pro bono work for bona fide rescue organizations, humane societies, et al, regarding such analysis in an effort to obtain release for dogs being held for death in municipal shelters in the US.

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