Bestiary entry from the Clan Primer:
This creature always drops a trophy when it is defeated. This trophy is used in the Hunt Club side quest which involves trading in the trophies for items, armor and accessories.
|Common - (55%)||(Nothing)|
|Uncommon - (10%)||(Nothing)|
|Rare - (3%)||Hi-Ether|
* The Bull Chocobo has a 40% chance of appearing in the southern-most tip of the South Tank Approach in the Ogir-Yensa Sandsea. Just exit and re-enter the area if the Bull Chocobo does not appear. You must have started the Hunt Club side quest in order for it to appear.