The hyenax had a hierarchical method of succession and lived in packs. If the pack leader was killed by another creature, that creature automatically became their pack leader. This trait was not limited to members of their species, as evidenced by a hyenax pack following Darth Vader, a Human, after the latter successfully killed their pack leader.
In 0 BBY the Sith Lord Darth Vader crash-landed on Vaal after the Battle of Yavin. There, he was attacked by a pack of hyenax. Vader killed several of them, including the pack leader. With this, the hyenax withdrew. Later the same evening, Vader found himself surrounded by the canines, who had brought him the body of their former leader, whose position Vader had unknowingly assumed by killing it.
The next day, the pack attacked an unidentified creature, who killed several of them. In anger, Vader killed the beast with his bare hands.
- Empire 14: The Savage Heart (First appearance)