Colorado horses form groups that are called harems. A harem is composed of one adult male, several females, their foals, and younger horses of both sexes, and one to five stallions. Each group is led by a dominant mare. Harems are usually small, containing between 3 and 35 animals; this number changes as young animals are driven out of their natal band and join other bands, or as stallions challenge each other for dominance.
A band or harem should not be confused with a herd. In herds, there is usually a single stallion, though occasionally a few less-dominant males may remain on the fringes of the group.
It is no secret that horses have evolved to live in herds. As with many animals that live in large groups, establishment of a stable hierarchical system is important to reduce aggression and increase group cohesion. Dominance can depend on a variety of factors, including an individual horse’s need for a particular resource at a given time. Some horses may be dominant over all resources and others may be submissive for all resources.
The herd stallion is not the king of a harem of females. The horse that tends to lead a wild or feral herd is often a dominant mare. The mare will lead the herd to food and other resources as well as control the groups routine and movement. This mare will ensure the general health of the group of horses under her.
However, there was a recent theory published that says there is no single horse that leads the group. In this 2014 study, it was observed that some herd movements may have been stared by any individual horse, although higher-ranked members are followed more often by other herd members. For more information on horses and their behaviors, contact Colorado Horse Property.