Our Zelda: Ocarina of Time Big Poe Ghost Locations guide will show you where to find all 10 secret Big Poes as Adult Link hidden about Hyrule Field.
These Big Poes, which are spirits that you can capture in an Empty Bottle, are similar to the regular Poe ghosts that appear and attack you as you wander Hyrule Field, however these guys are much larger, are red in color instead of blue, and will ONLY appear when you are riding atop Epona as Adult Link.
The ONLY way for you to beat them is to shoot them twice with your Bow and Arrow from Horseback. Doing so successfully (not easy because they sometimes move quickly away from you so you need to adjust your aim to actually hit them) will kill them, after which you can catch them by walking put to them and talking to them while having an Empty Bottle handy.
The best way to catch them all is to have three Empty Bottles dedicated entirely to this sidequest. To start the sidequest, visit the Ghost Shop which is located at the guard tower in the entrance hallway to Hyrule Castle town before you reach the Market. Talking to him will start the Big Poe Hunt sidequest in which the Ghost Hunter will reward you with “100 Points” on your “Points Card” for each Big Poe that you capture and bring to the Ghost Shop.
Collecting 1,000 Points, i.e. finding ten hidden Big Poes, will earn you your 4th Empty Bottle as a reward.
The Big Poes are deviously hidden throughout Hyrule Field and can be quite difficult to find even if you’ve found them all in a previous playthrough. Thankfully we are here to help!
This video will show you where to find each and every Big Poe: