Social Behavior of Horses

Horses are social animals that, under feral conditions, live in bands (harems) consisting of six to eight mares, their offspring 3 years old or younger, and one to six adult males. Mares are the core of the group, staying together even if the male(s) leave or die. The group size ranges from 2 to 24.

Multiple-male bands are larger than single-male bands, but their reproduction rate is lower. Groups are not territorial and will travel in search of resources. Fillies leave the group when they become sexually mature.

Hierarchy in horses appears to be linear and not necessarily based on age, weight, height, gender, or time in the group. These are important factors when considering problems in stabled horses, and attentive management is required before introducing horses to each other.

In the absence of conception, mares cycle every 21 days during spring and summer. There are three phases of sexual behavior in horses: courtship, mating, and postmating.

During courtship, the stallion approaches, prances around, sniffs, nuzzles, and grooms the mare. The mare might squeal, kick, or move away to show the stallion she is not ready, or she might stand still, deviate her tail, and urinate, indicating that she is receptive, which encourages the stallion to mount her.

Pasture breeding can achieve 100% success rates, versus 50–60% for “in hand” or controlled breeding. The rate of success with pasture breeding is higher probably because of familiarity between the horses, greater fertility of the mare, and less aggression between horses, as well as more complete copulations.

Mares and foals bond in the first hours after birth. If the mare moves away from the foal, it follows her, but if the foal lies down, the mare stands over the recumbent foal. The closer she is to the foal, the younger it is. Foals spend 15% of their time in lateral recumbency and 5% in sternal recumbency for the first month of life.

The most effective way to begin training a foal to work with humans is to interact with the mare. Feeding and brushing the mare for a few minutes a day in the presence of the newborn foal decreases the foal's fear of manipulation.

Most nursing behavior is initiated by the foal and terminated by the mare, especially in the first month. Foals suckle every 15 minutes. The rate of suckling decreases slowly to once an hour by the time the foal is 1 year old. If the dam is pregnant, the foal will be weaned naturally before the next foal is born—ie, at 11 months, far later than the 4- to 6-month weaning age imposed on many domesticated horses.

During the first month of life, foals show maximal dependence on their dams and have minimal contact with other horses. At first, foals play only with their mother. They gradually begin to venture away from her, exploring the environment and then playing with other foals. At the end of the first month, snapping (teeth clapping) peaks. Foals show this behavior toward adult horses, presumably to decrease aggression. Allogrooming also peaks at this time.

The foal gradually begins to spend more time in adult maintenance behaviors such as grazing and resting while standing. There are sex differences in play: colts mount more and fight more than fillies, which focus on grooming and running. Colts groom only fillies; fillies groom both sexes.

Colts leave the group usually before 2 years of age—sooner if there are no other colts to play with. After leaving their natal band, colts might join a "bachelor band.” The dominant stallion in that band is the most likely to obtain a band of mares, usually by stealing them from a harem group. He is likely to acquire his own mares by 5 years old and lose them by 10 years old.

• Houpt KA. Domestic Animal Behavior for Veterinarians and Animal Scientists. 7th ed. Wiley-Blackwell; 2024.

• Also see pet owner content regarding normal social behavior of horses.