Sorry guys, I know this has been done a few times, but I couldn't find anything so specific as relating to an older dog. Charlie is our 10yr old cesky terrier, he's been with us for 18 months, and prior to that was with my g/f's mum for 6 years. He's been no trouble apart from incessant whining, and has always always got on well with other dogs, always happy to go up and have a sniff and a play and thats it. about 2 months ago, he had a little scrap with a young (2yrs I think the owner said) labradoodle!, the owner of the dog went to split them up and ended up with a cut (from Charlie) on his hand. he dismissed it as an accident (which it was) and all was okay. But I was never happy at why or what caused charlie to go for this other dog. fast forward to yesterday morning, I took charlie out to play ball - I usually have his complete undivided attention. But yesterday a very very young (only a few months) chocolate lab came around the corner with it's owners (owners kids I suspect). Anyway, Charlie ignored getting the ball and ran over to them, fine I thought, he'll have a sniff then go and fetch the ball... Nope I saw the lab didn't move or do anything to upset charlie, and Chas just jumped on his back and bit the puppy on the neck. The lab rolled to the floor and started squealing like it was being murdered, I sprinted over, shouting at charlie to get off, and he paid no attention to me. I got there, pushed charlie to one side, and apologised profusely to the owners who said it was 'okay' but I'm sure were just being polite. It was honestly completely unprovoked, I was so disappointed, it put me in a bad mood all day. I really can't have this behavior increasing, we live on a house which fronts onto the field where we walk him... I'm wondering if this 'new' dog was invading his territory? Any thoughts would be gratefully recieved.