Aggressive sometimes

Question
We got our dog from a kennal 1 week ago .  We think he is about 2yrs, and a Patterdale terrier cross.  He has been lovely and no barking, until yesterday.  I got him a BIG bone to chew on.  He is always going to the door to go outside to it. When he does he runs like mad and goes to his bone.  My children know not to go near him when he is at his bone.  But on a few occassion before yesterday he has snapped and snarled at my sons (12yrs) friends.  Today he grabbed a trouser and ripped it.  But then he is all sad looking and lays down to be stroked.  We are very wariy of him. The majority of the time he is lovely.  What should we do.  I am getting him neutered next week.  Obviously we know nothing about his past.

Answer
It sounds like you definitely may have a resource guarding issue. There's a great book by Jean Donaldson called "Mine" which is all about resource guarding. As to the rest of it. There's no information about what else was going on when he reacted to your son's friends, and for most owners describing exactly what may have happened, the dog's exact behavior, what lead up to it, etc. is pretty difficult. ANYTIME human aggression is involved my first recommendation is that you get with a really good trainer or behaviorist who can observe your dog in person and guide you the direction you need to go. It's far too important to make guesses over the internet. And until you can get help, he needs to be put up (securely) any time children come to play. Otherwise you could end up facing a lawsuit if he bites. Sandy Case MEd CPDT www.positivelycanine.com