Though unknown to many (including horse enthusiasts!), there is a difference between wild horses and feral populations. The term “wild horse” is meant to describe horses that have never been domesticated—such as the endangered Przewalski’s Horse. This is the last remaining true wild horse in the world; all others have been driven to extinction.
Therefore, a feral horse is considered to be domesticated, in a sense, because its ancestors have been domesticated. Though some populations of feral horses are managed as wildlife, the term “wild horse” is a misnomer. Feral horses are descended from domestic horses that escaped or were deliberately released into the wild.
As a result of its existence in nature, feral horse behavior has shifted over time; they more closely resemble the behavior of wild horses. They live in groups called bands, herds, harems, or mobs, and are often led by a dominant mare. The rest of the band is composed of additional mares, their foals, and immature horses of both sexes.
Like with most wild herds, band makeup shifts over time as young animals are driven out or welcomed in. Within a closed ecosystem, however, the ability to maintain genetic diversity necessitates a large group size—the minimum size for a sustainable, free-roaming horse population is between 150 to 200 animals.
These domestic feral horses were likely introduced by the Conquistadors in the 15th century AD; some horses escaped and formed the feral herds we now know as mustangs. Australia has the largest population of feral horses in the world—with an excess of 400,000 feral animals, it is not hard to spot one or a group cantering together. Though unusually controversial (livestock producers are often at odds with horse enthusiasts about habitat impact), the domestic feral horse populations will, likely, continue to thrive.