You have to pet it.......but THEY WILL ATTACK IF THEY SEE YOU!
The thing about these is that they don't attack anything unless an animal has really low HP and isn't surround by predators. Stick around a ton of Ankys or something like Ankys, and you should be fine. They are found in Scorched Earth, even though tons of people say they are not there. I found four in an Oasis.
Normally you can't tame the pack leader, so just get a pteranodon or argy, pick it up and drop it in a large area (like a separate section of your base). When you take it away from the rest of the pack, it removes its 'pack leader' title, allowing you to tame the highest level hyena of that pack.