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Canine Behavior/Aggression between two female littermates


We have five mastiff dogs.  The oldest are the male and female parents of the other three.  The "puppies" are a year old and we have one male and two females.  

The female litter mates always got along fine up until they were about 5 months old.  We gave away all the other puppies to family and also gave away one of the females #that we currently have#.  Unfortunately the living situation didn't work out for her and the family member that took her in, so we took her back.  She was with the family member for about a month.

From the moment that she was "re-introduced" back to the other two male and female puppies we had, the females started being possessive with toys and having what I thought was little "tiffs" of growling over toys or being in the same area as each other.  I #stupidly# thought they were re-establishing the hierarchy since one of the females left for a month.  But it only escalated.  One day they just jumped each other and had a vicious fight.  Since then we have tried on several occasions to let them around each other.  Even slowly introducing each other.  Only once were we able to successfully allow them to roam our fenced yard together with no problems.  However, they both stayed a distance away from each other.  The next day we tried the same thing and they immediately fought upon sight of each other, under the same circumstances.  Neither I, nor my husband wants to find a new home for either of them since separately they both get along with the rest of the group and are very sweet dogs toward humans.  But this is so frustrating and we are now at the point that they have to be kept in separate pens and rotated every day so that they both get to spend time with the rest of the dogs.  

How can we work with them on this when they fight immediately upon sight of each other now??

Thanks for your help.

Fight on sight between two bitches is the death knell for rehabilitation.

When the one female was removed, the social hierarchy shifted; you don't truly know (because people will not tell you the truth) why this bitch was returned to you.  Once re-introduced, being so close in temperament (because they are litter mates), especially since the introduction was most likely done casually (since you are not expected to recognize the serious problems that might occur), they do NOT "recognize" one another as "sisters" but rather they are aware of one another as close in social hierarchy.  Body language between/among dogs takes seconds, so fast the average person (because not educated to see it, understandably) cannot interpret and avoid that first confrontation.

Have the male neutered; do not spay the female(s) at this point except for the one you MUST select for re-homing.  You have no choice in the matter.  These two will fight to the death and, unfortunately, one of you may be seriously injured (or worse) trying to prevent this.  I can almost guaranty it.

I suggest you Google the AKC website for the Mastiff breed that you own (which includes MANY varieties, I have no idea which you have there).  Go to the "Rescue" link and try to make contact with the AKC rescue associated with the breed club.  Your bitch needs an experienced home, this is NOT a casual companion breed (despite the variety).  Aggression toward other dogs is high, aggression toward "strangers" is high.  This variety requires a very experienced owner with an understanding of dog psychology and a true understanding of the breed they have chosen.  Socialization of these dogs as young puppies must be done regularly, systematically, off property and on property, and puppy kindergarten with followup in basic obedience training (POSITIVE reinforcement ONLY) must be done or you will end up with potentially dangerous dogs.

If you wish to attempt to manage the situation as it exists (which is close to impossible from my perspective), you can obtain the help of a Certified Applied Animal Behaviorist (CAAB) who has been informed fully, during telephone interview, of the seriousness of this situation.  Not all CAABs can (or will try to) effectuate a reconciliation between dogs of certain breeds, especially two bitches:

These two CANNOT, under any circumstance, be "turned out" together nor allowed to interact with one another and you must be aware that the extreme anxiety caused by the disintegration of their pack order is affecting your entire pack.

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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

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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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