Lockjaw

You give a creature the ability to use one of its natural attacks to firmly attach itself to an opponent. Choose one of the creature's natural attacks (usually a claw or bite attack). The creature gains the grab ability with that natural attack, including the +4 bonus on combat maneuver checks to start or maintain a grapple. A creature with multiple natural attacks can strike at its grappled opponent with its other natural attacks, but cannot attack any other creature.