I have had Sebastian since infancy and he has never been a problem. Over the last few weeks he has taken to nipping during play time. I think it is meant in play and not offensive but it hurts. Last night he crawled down my arm and bit the top of my hand. I "tssk"ed him but he just scampered off without caring. What is up?? He is 9 months old so I think we might be hitting the "terrible twos" stage. Suggestions?

I had to no bite train Raja when we first got him, so I know how to do that but this is not defensive or offensive like a new glider bite. It seems like overly rough play.

Yes, sounds like the teenage stage...or maybe he likes your hair product?

Have you been giving treats during tent time or when ever you have contact with him and now stopped it?
Did you move his cage from another spot recently, like from high traffic area to a quietier area or vice versa?
Is he nipping and looking directly at you after as to being like he is asking for something?

It may also be he wants to be boss so to speak.
Can you pick him up or slide your hand under him and bring him to your chest?
When you tssked him did you pet him right after as to make contact with him?
Have you tried moving away but behind him to pet on him just before he nips as to get him to avoid or go around that walk up nip step? Make contact with him before he has a chance to nip you.
Art
P.S. Where did you see or read about terrible twos?

He could be grooming you.

Could be grooming or a communication nip for a treat or drink.
Art