Here's why:
* Feral horses come in various sizes. They are descendants of domesticated horses that have gone wild, and their size depends on the original breed and the environment they live in.
* "Mustang" is often used for feral horses in the American West. However, a mustang can be any size, and the term is more about their wild status than their size.
Instead of a specific name, you could describe the horse:
* "Small feral horse"
* "Small wild horse"
* "Small mustang" (even though it's not always accurate)
It's important to note that "feral" and "wild" are not the same. Feral horses are domesticated horses that have returned to a wild state, while wild horses are horses that have never been domesticated.