The mustang horse is a living symbol of America's history. When Columbus discovered the New World in 1492, there were no horses on the continent, so the conquistadores that arrived in the early sixteenth century brought their own from Europe. These first horses were mainly of Iberian ancestry, though with time many more types and breeds would follow. As the journey across the Atlantic was long and difficult, and conditions remained tough in the new land, only the most hardened horses survived. They were used as riding and packing animals, and fundamental in America's history. Over time, some were released, abandoned or escaped from their owners, and these animals banded together in herds, roaming the plains in Mexico and North America.

When more horses were imported from overseas, several of these joined the mustang herds, adding their own characteristics to the gene pool and creating a wide and diverse population.

Fighting drought, starvation, a harsh climate, predation and hunting, life for the early mustangs in the New World was hard, but they managed, resulting in healthy and resilient horses, capable of living on a slim diet, with only limited weak traits due to natural selection. The local tribes quickly learned how to catch, handle, train and breed the animals, and used them for all kinds of purposes. Some, like the Chickasaw and Nez Perce people, created the foundation for new breeds, like the appaloosa horse.

But the horses were sometimes also recaptured by explorers moving to the West. They needed riding and packing animals capable of coursing through the unknown terrain, and the early mustangs were perfect as life had already conditioned them for that purpose. Others were seen as pests, competing with other livestock for food, and therefore hunted for meat or sport. This became a real problem in the twentieth century when entire herds were rounded up and numbers dwindled nationwide as humans strived to drive them from their lands in sometimes horrible ways. In 1959, a first free-roaming horse protection law was created, followed by another in 1971, which placed several established herds in the care of the Bureau of Land Management (BLM). Using an adoption programme, the BLM keeps population growth under control, though controversies over the herds and their future remain.

Mustang horses are often called wild animals, but despite them being born in the wild, they are actually 'feral' animals: animals of domesticated ancestry that adapted to a life in the wild.

Colour genetics

As mustang horses have a very diverse ancestry, many colour genes are present in the population. Some isolated strains, like the kiger mustangs, show less diversity, but overall the representation is varied. Present are the base colours, including several varieties of agouti, cream, dun and grey. Pangaré is sometimes seen in herds that have clearly been influenced by draft horses. The silver and champagne dilution are very rare, but appear occasionally. Pearl is hypothesised to be present due to the large Iberian influence.

White patterns are also very diverse. Frame, tobiano and roan are seen often, though their numbers alter between herds. Sabino, rabicano and appaloosa traits also exist, but more rarely.

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