Puppies that nibble do so to investigate their surroundings, and adult dogs that nibble never learned to break the habit as puppies, or do it out of a desire to play. Dogs may nibble out of aggression, due to fear or anxiety, and this type of nibbling may turn into aggressive biting or be accompanied by growling or an aggressive body stance.
Teaching a puppy not to nibble is important, because adult dog nibbles are more painful and stronger than puppy nibbles. Dog owners can teach a puppy not to nibble, by substituting toys or treats to redirect the behavior. Dogs that struggle to break the nipping or biting habit may need the help of a professionally trained animal therapist.