I can't find anything on how or if grappling interacts with mounted combat. I suppose the first question is, does being mounted affect grappling at all?
If a medium-size creature with Improved Grab successfully attacks a medium size rider on a Large mount, then can it use its Improved Grab ability and automatically pull the rider from saddle, or does the rider get any kind of Ride check to avoid being pulled from his saddle? Does the mounted creature receive any kind of bonus to his grapple check?
Does the answer change if a creature initiates a grapple as normal rather than with Improved Grab? In that case, the attacking creature has to enter the mount's square as well as the rider's square.
If a medium-size creature with Improved Grab successfully attacks a medium size rider on a Large mount, then can it use its Improved Grab ability and automatically pull the rider from saddle, or does the rider get any kind of Ride check to avoid being pulled from his saddle? Does the mounted creature receive any kind of bonus to his grapple check?
Does the answer change if a creature initiates a grapple as normal rather than with Improved Grab? In that case, the attacking creature has to enter the mount's square as well as the rider's square.