The horse here is named Chrome. He can be found on the island with the fast travel boat, on the side closest to the enclosures.
This horse is named Pearl. She can be found by facing away from the front of the helicopter, walking forward, past the fence, and to the right.
The horse here is named Zoro. Original Location Unknown.
This map has two horses available, however neither are named at this time. They can be found just up the hill from the helicopter, by a little house.