You are here:

Canine Behavior/Aggressive behavior


My family and I have an 8 year old male mutt. We have had him since he was born, his mother is another dog that we have. He has always been very friendly and loving. He loves to play and is always willing to snuggle. He is a larger dog that still believes he can sit in your lap. My 19 year old sister had him in her room last night and while petting him he bit her. This is abnormal behavior for him. While he does sometimes nip or place his mouth around our hands or arms he never bites down hard enough to hurt. Today while she was home alone he would not go anywhere near her. He is only showing this behavior towards her.  Is there anything that we can do to curb his behavior or should we call in someone who can help us?

I can't see anything from here.  How "bad" was the bite: did the dog leave marks?  Puncture wounds?  Did your sister bleed (if so, she needs to see a Doctor for antibiotics).  NO DOG goes from bite inhibition to actual bite (with injury) for no reason.  It is possible your sister and this dog have a relationship issue you are unaware of and I doubt she will admit to it, even at the relatively mature age of 19.

The fact that the dog is now avoiding her might be the result of what caused the bite or might be the dog's avoidance issue because of her reaction to the bite.

FIRST STOP:  VETERINARIAN.  When any dog suddenly exhibits a behavior that is extremely aberrant, has not been seen before, veterinary examination is absolutely necessary.

Second:  REPORT BACK PLEASE USING FOLLOWUP FEATURE to tell me what the veterinarian found (or did not find).

Third:  Your sister MUST TOTALLY IGNORE THIS DOG and he MUST NOT be left alone with her in her bedroom for any reason whatever.

Fourth: do not "play" any "rough and tumble" games with this dog; if he is having a problem with cognition (which is possible at age 8) he will misconstrue the "games".

Fifth: after veterinary consult REPORT BACK TO ME USING FOLLOWUP FEATURE.  Meanwhile, I strongly suggest a parent (without siblings present) sit down with your sister and ask exactly what happened; they should take notes so I have the "big picture".

Once a dog actually BITES (and leaves physical damage), that dog has lost bite inhibition.  It must be re-taught.  The relationship between dog and your sister must be restored. You may have to find a Certified Applied Animal Behaviorist (NOT a dog trainer), but let's see what the vet says and what info your mother or father can get from your sister.  I can't help you if you don't report back to me.

Canine Behavior

All Answers

Answers by Expert:

Ask Experts


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.

©2016 All rights reserved.