Horses are herd animals who depend on each other for survival. By studying the behavior of horses who live in feral herds, we can discover information to help us better manage our domestic horses.

Equine evolution has been extensively studied, but the analysis has been done on bones and tells us nothing about how live horses interact with each other and their environments.  When the Spanish brought horses back to North America, some escaped and wild herds soon spread all over North America. Remnants of this population still exist in many remote areas. As late as 1934, Frank Dobie could find no naturalists who had studied the behavior of these wild horses. In the 1970s, research on them finally began.

The equine species is incredibly adaptable and has survived in many varieties of geographic areas. Nature gave them the ability to survive in both cold and hot climates. The variable growth of their winter coats lets them adjust to a wide range of temperatures. Unlike cattle and sheep, horses will dig through the snow to find grass to eat and break through ice to get at the water. In semiarid country, they will dig through damp ground until they find water. In addition to this type of instinctive behavior, wild herds in certain areas have demonstrated some learned behaviors. Only on Assateague Island [a barrier island east of Chincoteague Island, located in the Atlantic Ocean off the coast of Maryland] will they shake grit off dune grass before they eat it. Their clever adaptive behavior preserves their teeth. To protect themselves from insects, these horses will also wade out into the ocean and stand under water.


When scientists began studying the wild herds in various areas of North America, they soon discovered feral horses had emotional relationships within their herds and the ability to communicate with each other. Some individuals or herds also demonstrated cognitive problem solving. When they began comparing behavior in different geographic areas, they discovered a surprising degree of behavioral variation among them. There are three types of such behavioral patterns. If one is common to all of the herds studied, then it is probably instinctive. Behavior that is unique to certain areas may represent some form of social adaptation. When patterns vary among individuals, they could reflect their individual personalities, preferences, or experiences. It may also represent cognitive problem solving.

Scientists have always found two types of herds, harem bands and bachelor bands, in every area they studied. A harem band consists of a stallion, his mares, and their offspring. When young horses reach sexual maturity, they generally leave or are driven away from their birth herd. Fillies will join a new or old harem band while colts will join or form a bachelor band. Such bands consist of stallions who have temporarily banded together. It may include younger stallions who have not yet acquired any mares, as well as older ones who have chosen to avoid family responsibilities. As compared to harem bands, their membership may be relatively fluid.

A wild stallion can choose to stay in a bachelor band or gather his own harem. Regardless of what choice he makes, he will still be with a herd. Domestic stallions are given no choice and all too often kept in solitary confinement. Pasture breeding allows a stallion to be with his mares and court them, as well as play with his foals. In this situation, he will be happier and fertility rates will tend to rise. Unlike stallions, mares only live in harems, but depending on the location and the stallion, they may change harems. Instead of having their young foals torn away from them by humans, they can wean them when they feel they are ready.

Ladendorf-4--montgomery_pass_wild_mustangs3Contrary to popular belief, wild stallions will rarely breed young mares from their own herd. Sometimes, they just wander off, but the stallion or the mares may choose to drive them away. Wild stallions will drive off young males, but there are variations in this behavioral pattern. On Sable Island [a small island in the Atlantic Ocean, 190 miles southeast of Halifax, Nova Scotia], if a young stallion wants to stay and exhibits passive behavior, he may not be driven out. Some stallions even allow one or more bachelors to tag along with their harem band. Most of the harem herds in the Red Desert [located in south central Wyoming] have two stallions. Contrary to popular belief, stallions can live together without trying to kill each other.

A harem stallion must protect his herd from predators and from any stallion who wants to steal his mares. Most males prefer to avoid this responsibility until they are fully mature. In the intervening years, they often practice fighting with other young stallions in their bachelor band. They also may hover around harem bands where they might get a chance to snap up a young mare who is driven away from her birth herd. A harem stallion may choose to ignore them or drive them away. If they dare to challenge him, the combat will continue until one of them submits. Such conflicts rarely continue until one of the contenders is killed. On Sable Island, bands frequently encounter each other and have developed a form of ritual combat that establishes temporary territories.

Domestic horses normally adjust well to life in the wild. Their instincts tell them to find and join a wild herd, but they may have to learn many new behaviors. Domestic mares, stolen or strayed, will soon join a harem band while males usually join a bachelor band. Stallions have been turned loose to improve the quality of the wild herds, but they rarely manage to acquire any mares. Successful stallions generally need to grow up in the wild herds where they can practice fighting and learn from observing the behavior of harem stallions.

In some species of mammals such as dolphins, females and their offspring do not live with mature males, but horses do not follow this behavioral rule. Since wild horses live either in harem and bachelor bands, this split is probably instinctive, but herd members will follow any adaptive behaviors that are common to their herd. Mares who about to foal do exhibit such behaviors. In the Red Desert, mares will stay with their herd to foal. In other areas, mares will leave their herd to foal and bring their new baby back when he or she is a few days old. In some herds, an older mare may go with the one who is about to foal.Ladendorf-3 leaping foal--happy-mccullough-peaks

Unlike some species of equids, horses are not normally territorial. Each band has its home range and may defend its core, but will allow other herds to wander through the rest of it. Wild herds will generally accept the presence of other grazing animals on their ranges. In times of danger, herds may combine and then split again. On Sable Island, bands will even graze together in the deep snow. However, territorial behavior has been exhibited by stallions on some of the eastern barrier islands. This may be a social adaptation to the small size of the islands.

Sable Island is surrounded by the ocean, has no predators, and has enough resources to support the wild horses who live there. Since the island is off the coast of Nova Scotia, their enemy is the harsh winters. On the average, about fifty percent of the foals die every year. In the last fifty years, no humans have been allowed to interfere with the wild herds and the horse population has stayed relatively stable. If it is high, fertility decreases. If the winter die off is high, fertility increases. The less aggressive behavior shown there by the stallions may be a social adaptation to their relatively protected environment.Ladendorf-5--Wild-Mustang-Horses-Picture_12-230x230

Wild herds may shift between summer and winter pastures, but they will normally stay inside their ranges. This may be instinctive behavior. If chased by humans, wild horses will usually travel in a large circle around their range. Mustangers have used this instinctive behavior to trap wild herds. They station horses at relay points and gradually use their fresh horses to drive the wild band to exhaustion and then into captivity. Moyra Williams established that horses, if given no direction by their riders, will try to find their way back to their home.

Animal species who live in groups will normally demonstrate respect for their leaders and establish rank ordering among themselves. In the wild herds, male ranking is usually relatively easy to determine. If wild herds gather at a water hole, which herd drinks first may also be determined by the rank ordering among individual bands. Mares may have ranking, but it can be more difficult to determine. Rank ordering may be instinctive, but leadership and authority do not always go together in the wild herds. In some harems, the stallion is both the leader and the dominant horse. In others, the alpha mare may take over the leadership role. A stallion always drives his herd from the rear, but the lead mare is the one who finds the right path for the herd to follow. If the band has two stallions, the least dominant one will always be between the mares and the dominant stallion.

To survive and thrive, wild horses need to solve problems that are relevant to their continued existence and some of their solutions may have demonstrated the use of cognitive abilities. Out west, wild horses may go into old mines to find water. On Assateague Island, one clever stallion used human structures to protect his herd from raids by other stallions. He would drive them onto the island causeway or into a corral where he could block out any raiders. Another clever stallion used to stand next to one of the water pumps in the park area and beg until somebody gave him a drink of clean water.

Emotion may be the glue that holds wild herds together and allows them to survive. Within herds, groups of friends will generally stay together, groom each other, and play together. Fillies will play chase games, but only colts indulge in mock fights. This genetic difference could be instinctive. Many stallions enjoy playing with their foals and some will even kneel to neck wrestle with them. A few will kill foals, but this behavior is exceptional.

Horses can even be selective about their mates. One dominant stallion in the Pryor Mountains choose to add only mares of a certain color to his harem. Mares can also be selective about who they are willing to accept as a mate. In most harems, one third of the foals are not sired by the harem stallion. If a stallion gets too rough with a mare, the other mares may gang up on him to teach him acceptable mating behavior.

Mares do teach their foals how to behave, but older mares or the stallion will also discipline them. To stop an obstreperous youngster, one harem stallion caught him with a shoulder block that threw him into a pond. Older members of the herd may also show or teach the youngsters survival techniques. The adults share the responsibility of watching for predators and will fight to protect each other and their offspring.

When the life styles of feral horses are compared to the ones lived by domestic horses, research has shown us how different they are. Millions of years of evolution have made the equine species what they are today. Domestic horses have adapted to the life styles imposed on them by humans, but at what cost to their physical and emotional health? If we allow them to share a more natural life style, the happier and healthier they should be.

Feral herds display some behavior that appears to be instinctive, such as digging through the snow to reach the grass. To solve problems relevant to their survival, some wild horses have demonstrated cognitive abilities. Since only domestic horses are subject to castration, the wild herds are always either harems or bachelor bands. This appears to be the only social behavior that is common to all horses in all of the locations studied. This natural behavior may explain why some boarding stables do not turn out mares and geldings together. When they are mixed together, geldings may fight over the mares, especially when they come in heat.
Behavioral variations have been observed that are unique to one location, one herd, or some individuals. This flexibility may explain why horses are able to adapt to the life styles imposed on them by humans. Those who only observe one herd would be well advised not to claim that what they have seen is common to all horses. Horsemen, like Monty Roberts, have made this mistake, as have a few scientists. Research on how feral horses interact with each other and their environment has given us some clues as to how to better manage our domestic horses.

Information Sources:
Berger, Joel. Wild Horses of the Great Basin: Social Behavior and Population Size. University of Chicago Press, 1986.

Dobie, J. Frank. The Mustangs. University of Texas, 1984, pp. IX-X.

Greenwood, Jane, “Pasture Breeding”, Valley Equestrian News, April 2015, p. 17.

Kirkpatrick, Jay F. Into the Wind: Wild Horses of North America. North Word Press, Inc., 1994. pp. 55-58.

Peterson, Dale. The Moral Lives of Animals. NY, Bloomsbury Press, 2011.

Roberts, Monty. The Man Who Listens to Horses. Random House, 1997.

Ryden, Hope. Mustangs: A Return to the Wild. Penguin, 1972.

Smolker, Rachael. To Touch a Wild Dolphin. NY, Doubleday, 2001.

Welsh, Daniel A. “The Life of Sable Island’s Wild Horses,” Nature Canada, April-June, 1973, pp. 7-14.

Williams, Moyra. Horse Psychology. London, Methuen, 1956. pp. 76-82.

This article is based on Chapter 2, “Research on Feral Horses,” in Human Views and Equine Behaviors, by Janice M. Ladendorf. Distributed by Create Space, Kindle Direct Publishing, and Smashwords. Released Dec. 2013.