biting

Question
hi..a couple of years ago, we found a stray dog, or i should say he found us. he is a cocker spaniel and most of the time pretty good. he has been abused by his previous owner. we suspected that and the vet comfirmed it. however, there are times he bites us or tries to bite for no reason. yesterday he was laying on his back, acting like he wanted me to rub his stomach, so i started to do that. next thing i knew his teeth were sinking into the palm of my hand, and there is a good amount of damage to it. my question  is..what would make any dog behave this way? he has been out of the abusive situation now for pushing three years, and he knows we dont treat him that way. thank you!!

Answer
It's hard to say why the dog is doing this, but a good bet would be that he is not happy about body handling.  There are ways to change this, but it does require some knowledge, and probably the help of a good positive trainer, or behaviorist, who can demonstrate some desensitization and counter-conditioning techniques for you.  Dogs always bite for a reason, but humans may not always know what it is.  Some of them have pain in their joints, others don't like to be touched in certain areas, some are suffering from occasional neurological issues, some have hypothyroidism which can lead to aggressive behavior.  The reason, however, is less important than what you do about it.  If a dog is upset when you do certain things, then the answer is to gradually change his mind about liking those things.  In other words, changing his emotional response.  If you are interested in this approach, there is a great video by Dr. Sophia Yin (YouTube) on changing a Jack Russell Terrier who doesn't like air blown on his face, and who responds aggressively.  After she works with him for a while, you can see the change in his demeanor.  If you are interested in finding a trainer, you can look on the Pet Professional Guild web site, and if you need a behaviorist, check the DACVB site.