A feral horse is a free-roaming horse of domesticated ancestry. As such, a feral horse is not a wild animal in the sense of an animal without domesticated ancestors. However, some populations of feral horses are managed as wildlife, and these horses often are popularly called "wild" horses. Feral horses are descended from domestic horses that strayed, escaped, or were deliberately released into the wild and remained to survive and reproduce there. Away from humans, over time, these animals' patterns of behavior revert to behavior more closely resembling that of wild horses.
Feral horses live in groups called a band, herd, harem, or mob. Feral horse herds, like those of wild horses, are usually made up of small bands led by a dominant mare, containing additional mares, their foals, and immature horses of both sexes. There is usually one herd stallion, though occasionally a few less-dominant males may remain with the group. Horse "herds" in the wild are best described as groups of several small bands who share a common territory. Bands are usually on the small side, as few as three to five animals, but sometimes over a dozen. The makeup of bands shifts over time as young animals are driven out of the band they were born into and join other bands, or as young stallions challenge older males for dominance. However, in a given closed ecosystem such as the isolated refuges in which most feral horses live today, to maintain genetic diversity the minimum size for a sustainable free-roaming horse or burro population is 150-200 animals.
Feral horse populations
Horses which live in an untamed state but have ancestors who have been domesticated are not true "wild" horses; they are feral horses. The best known examples of feral horses are the "wild" horses of the American west. When Europeans reintroduced the horse to the Americas, beginning with the arrival of the Conquistadors in the 15th century, some horses escaped and formed feral herds known today as Mustangs. The Australian equivalent to the Mustang is the Brumby, feral descendants of horses brought to Australia by English settlers. With an estimated 300,000 individuals, Australia has the largest population of feral horses in the world.
In Portugal, the free-ranging feral horse is known as Sorraia. There are also isolated populations of feral horses in a number of other places, including Sable Island off the coast of Nova Scotia, Assateague Island off the coast of Virginia and Maryland, and Vieques island off the coast of Puerto Rico. Some of these horses are said to be the descendants of horses who managed to swim to land when they were shipwrecked. Others may have been deliberately brought to various islands by settlers and either left to reproduce freely, or abandoned when assorted human settlements failed.
A modern feral horse population (Janghali ghura) is found in the Dibru-Saikhowa National Park and Biosphere reserve of Assam, in northern India, a herd of approximately 79 Feral horses descended from animals that escaped army camps during World War II.
Modern feral horses
Modern types of feral horses that have a significant percentage of their number living in a feral state, even though there may be some domesticated representatives, include the following types, landraces, and breeds:
- Banker horse, on the Outer Banks of North Carolina
- Brumby, the feral horse of Australia
- Camargue horse, in marshes of the Rhone delta, southern France
- Cumberland Island Horse, on Cumberland Island off the coast of southern Georgia
- Danube Delta horse, in and around Letea Forest, between the Sulina and Chilia branches of Danube
- Dartmoor pony, England; predominantly domesticated, also lives in feral herds
- ?Elegesi Qiyus Wild Horse (Cayuse), Canada; lives in the Nemaiah Valley, British Columbia
- Exmoor pony, England; predominantly domesticated, also lives in feral herds
- Kaimanawa horse, New Zealand
- Kondudo horse, in the Kondudo region, Africa; threatened with extinction
- Misaki, Japan; endangered
- Mustang, the legally protected free-roaming horse of the western United States
- Namib desert horse of Namibia
- New Forest pony, predominantly domesticated, also lives in feral herds in the area of Hampshire, England
- Sorraia, a feral horse native to Portugal and Spain
- Sable Island Pony found in Nova Scotia
- Welsh Pony, mostly domesticated, but a feral population of about 180 animals  roams the Carneddau hills of North Wales. Other populations roam the eastern parts of the Brecon Beacons National Park.
Feral populations are often controversial, with livestock producers often at odds with horse aficionados and other animal welfare advocates. Different habitats are impacted in different ways by feral horses. Where feral horses had wild ancestors indigenous to a region, a controlled population may have minimal environmental impact, particularly when their primary territory is one where they do not compete with domesticated livestock to any significant degree. However, in areas where they are an introduced species, such as Australia, or if population is allowed to exceed available range, there can be significant impacts on soil, vegetation and animals that are native species. If a feral population lives close to civilization, their behavior can lead them to damage human-built livestock fencing and related structures.  In some cases, where feral horses compete with domestic livestock, particularly on public lands where multiple uses are permitted, such as in the Western United States, there is considerable controversy over which species is responsible for degradation of rangeland, with commercial interests often advocating for the removal of feral horse population to allow more grazing for cattle or sheep, and advocates for feral horses recommending reduction in the numbers of domestic livestock allowed to graze on public lands.
Certain populations that have considerable historic or sentimental value, such as the Chincoteague pony that lives on Assateague Island, a national seashore with a delicate coastal ecosystem, or the Misaki pony of Japan that lives on a small refuge within the municipal boundaries Kushima. These populations manage to thrive with careful management that includes using the animals to promote tourism to support the local economy. Most sustained feral populations are managed by various forms of culling, which, depending on the nation and other local conditions, may include capturing excess animals for adoption or sale, or the often-controversial practice of simply shooting them. Fertility control is also sometimes used, though it is expensive and has to be repeated on a regular basis.
- ↑ Wild Horse Genetic Diversity and Viability: Management Toward Extinction
- ↑ Nimmo, D. G., & Miller, K. K. (2007) Ecological and human dimensions of management of feral horses in Australia: A review. Wildlife Research 34: 408–417.
- ↑ Dobbie, W.R. Berman, D. & Braysher, M.L. 1993, Managing Vertebrate Pests: Feral horses. Australian Government Publishing Service, Canberra.
- ↑ Dibru-Saikhowa National Park and Biosphere reserve
- ↑ http://www.fonv.ca/activities/articles/wildhorses/
- ↑ http://www.dailypost.co.uk/farming-north-wales/farming-news/2007/11/22/our-little-ponies-facing-extinction-55578-20142744/
- ↑ Nimmo, D. G., & Miller, K. K. (2007) Ecological and human dimensions of management of feral horses in Australia: A review. Wildlife Research, 34, 408-417.
- ↑ Dobbie, W. R., Berman, D. M., & Braysher, M. L. (1993) Managing vertebrate pests: Feral horses. Canberra: Australia Government Publishing Service.
- ↑ Nimmo, D. G., Miller, K., & Adams, R. (2007). Managing feral horses in Victoria: A study of community attitudes and perceptions. Ecological Management & Restoration 8 (3) , 237–243
- ↑ Bomford, M., & O'Brien, P. (1993). Potential use of contraception for managing wildlife pests in Australia. USDA National Wildlife Research Center Symposia. Retrieved on May 12, 2008 from http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1004&context=nwrccontraception