You must learn a special skill to tame ottuks. The skill is account-wide and the character that earns it doesn't have to be a hunter. Upon reaching Rank 11 Renown with the Iskaara Tuskarr, an NPC will appear and offer you a quest chain beginning with A Lost Tribe and ending with While the Iron Is Hot. The Ottuk Taming skill is taught to you with the completion of the final quest.
Level scaling: Most NPCs will scale with the Hunter's level, within the constraints of their level range. Hunters can tame regular NPCs up to 2 levels higher than them, but can only tame elite NPCs of the hunter's level or below.