In The Wild There are no more truly wild horses left in the world. Even if you see horses running around in the middle of nowhere, without fences, they are bound to be ferals, gone wild from a line of domesticated horses. The only feral horses left in the United States are Mustangs, which only roam in the middle of the US. There is another type of feral horse called the Australian Brumby. They are a strong, tough breed, much like the Quarter Horse. Although there are no more truly wild horses left in the world, every horse is wild at heart.