This video taken today shows how puppies play at this age - when they are 9.5 weeks old. They are starting to learn about social structure and pack ranking. Their wrestling, mounting and biting may look very rough to us but this is a part of normal process. It allows puppies to learn about bite inhibition. To quote from Dr. Joël Dehasse:
Play-fighting and learning to control biting:
Play-fighting, which begins at 3 weeks, can sometimes be painful when a puppy begins cutting teeth, especially when its ears are bitten. A bitten puppy whimpers or squeals. In a one-on-one or one-on-two fight the bitten puppy is able to turn the tide of the 'battle' and bite its adversary(ies). And this is precisely one of the "rules of the game": to change roles, with the biter becoming the bitten and vice versa.
- The puppy learns to make an empathetic link between the opponent's squeal and the pain invoked.
- Reciprocal biting negatively reinforces its intensity.
- Biting is thus stopped, inhibited and controlled.
These play-fights also lead to a certain hierarchization of relations.