So a tip to taming these guys is pretty simple.

1. Craft a bow/crossbow

2. Craft some narcotics and tranq arrows

3. Find one and gather about 100 berries

4. Climb a VERY tall rock

5. Shoot it. Try to get your shots on its back

6. When it is knocked out, put the berries and narcotics in it's inventory

7. Keep an eye an the torpor and only feed it narcotics if the torpor is low.

8. Equip a saddle and enjoy your new trike