Needs review
Source: Monster Manual II

Description: You can grapple more easily with your claws or bite.

Prerequisites: Access to a form with either claws or bite as natural weapons

Required for: Rend

if you hit with a claw or bite attack, you automatically attempt to start a grapple as a free action without provoking an attack of opportunity. If you get a hold with a claw on a creature four or more size categories smaller than yourself, you squeeze each round for automatic claw damage. If you get a hold with your bite on a creature three or more size categories smaller than yourself, you automatically deal bite damage each round, or if you do not move and take no other action in combat, you deal double bite damage to the snatched creature. As a free action, you can drop a creature you have snatched, or you can use a standard action to fling it aside. A flung creature travels 10 feet (and takes 1d6 points of damage) for each size category greater than Small that you are. If you fling a creature while you are flying, it suffers cither flinging or falling damage, whichever is greater.