Just to clarify, this isn't a nibble. It's a single, very deliberate pinch!
He's a Staffordshire Bull Terrier, and he's getting quite 'long in the tooth' now. I mind him quite regularly when my sister goes away and this habit/defence thing/whatever, is very annoying.
He just came up to me for some attention, so I picked him up (again, he's old), sat him next to me, gave him some smooths which he seemed to enjoy(he sneakily clambered his front end onto my lap), my forearm went close to his mouth, and he quickly, but carefully got his canine teeth pressed against the skin and pinched quite painfully.
I emphasized "carefully", because he makes adjustments to ensure his canines are in a pinching position against the skin before making any kind of bite motion. He makes the adjustments quickly but very deliberately. It leaves a small, circle bruise with broken skin at the centre. It can be small but on occasions, he's given me a larger, deeper bruise, bleeding slightly at the centre.
- He also jumps up to nip at your face if you look at his face while fussing him. In the past(his younger days), he has bitten my lip, making it swollen and bleeding slightly. He seems to really love the fuss, and also seems to know he shouldn't nip faces like that, as the fusses always end with a row. But it's like he can't help doing it; it's out of excitement.
- He also pinches your arm if you try to stop him doing something where your arm is near his mouth (e.g. moving him away from something). If he only did it in this type of situation, I'd understand it's to get you to move your arm away.
- Sometimes, if you touch his collar he will pinch you.
- When he pinched me during that smooth, I started pinching his face (not hard at all) and he started play-biting me normally but quite gently, like he was afraid to bite down any harder, but did a little when I continued to play-fight.
- He doesn't always do it - I was just fussing him on the floor, smoothing quite firmly and touching my arm against his mouth and got no response, just a happy-looking dog.
He's a really loving dog who sleeps on my sister's bed with her when he's at home, but I really want to know why he pinches like this; is it hostile, defensive, a nervous reaction or just a fun habit for him? Maybe if I know why he does it, I can try to respond accordingly.