| Domestic horses are social animals. In feral situations, they live in a harem group or band with one to several stallions, multiple mares, and those mares’ offspring. |
| One stallion (the highest-ranking or “dominant” animal) is primarily responsible for most of the breeding. In many species, rank is associated with age or some ability to survive and thrive in challenged environments. Old age can be a gauge of the latter. High-ranking males are the first to secure access to a receptive female and the first to displace a female from another band. In the absence of conception, horses cycle every 21 days, except when seasonally anovulatory (fall and
winter). Within a harem group, the highest-ranking individual is usually, but not always, a stallion. This high-ranking stallion will force foals to leave the group once they are ~2 yr old, as they begin to become sexually and socially mature. |
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Snapping (tooth clapping or champing) is a facial expression given by young horses to adults, particularly stallions. It peaks in frequency at 2 mo of age, after which it decreases; it may function to decrease aggression from adults, but is also compatible with displaced nursing behavior. This is not the same behavior
as smacking, which is an aggressive threat in which the ears are laid back and the mouth is open with lips smacking, but the lips are not retracted. |
| Social maturity is not attained until 5 yr of age. Most fillies and all colts leave the natal herd at about this age. Fillies that remain in their natal group may have decreased reproductive success. Young stallions form bachelor herds, and the highest-ranking stallion within this group is usually the next one to acquire a mate. Fillies can join a bachelor herd but are often incorporated into other bands. Stallions are rarely solitary; when this occurs, the stallions appear to be
old or infirm. |
| While hierarchical rank in males is evaluated primarily on the basis of access to females, hierarchical rank in females is determined by effect on group behavior and activity (ie, seeking out resources such as water holes). Horse groups are largely structured by females, and females make the decision about whether to leave or to stay within a harem. Such decisions are usually based not on specific stallions or their characteristics, but on the female’s assessment of food resources.
High-ranking females can successfully interfere with the nursing of foals by lower-ranking females. Mares have preferred associates, are preferentially groomed, and will groom certain individuals. This pattern is typical of many social animals in that rank is conferred largely by the deference of other animals—not by the results of outright combat. |
| Hierarchical relationships within groups also depend on the age and sex distribution of the group. The more members of the herd, and the more within each age and sex group, the less likely it is for a linear dominance hierarchy to exist. Relationships within most horse bands are triangular and complex. Hierarchical rank depends on multiple factors and probably their interaction, eg, age or length of residence in the social group, sex (although probably less important than age),
size, and inheritance (rank of the mother). These factors are important to consider when addressing problems that may arise in stabled horses. |
| Hierarchical social effects also exist between herds. Multi-stallion herds are dominant over single-stallion bands, possibly because lower-ranking stallions within a herd conduct most of the fighting that occurs between groups. Herds that are currently occupying an area or using a resource (eg, a water hole) tend to retain it. Groups, as well as individuals within them, follow specific patterns of fecal marking. |
| Many behavioral problems are associated with confinement. Under free-ranging circumstances, horses will wander and spend >60% of their day foraging. The remainder of their time is spent standing, lying down, or engaging in another activity. This same pattern is the preferred one under barn conditions; even with free choice of grain, horses will choose to eat many small meals a day. |
| Horses also use free-ranging locomotion as part of their play development. Until ~3 mo of age, most play is solitary. Interactive play peaks at 3-4 mo of age. There are sex differences in play; colts play more than fillies and play different games than do fillies. Colt games focus more on fighting and mounting, while filly games focus more on running and mutual grooming. Fillies will groom both colts and fillies; colts tend to groom only fillies, which has been interpreted as
practice for later courtship behavior. |
| Recent data on the role of play in carnivores suggests such behaviors may be best interpreted as learning how to make and recover from social mistakes. The ability to make a mistake successfully may be more important than previously appreciated. The social experience of play is important for normal social interaction in adult life. |
