Social Dominance in Foals and Young Horses

In every horse herd, the various horses quickly sort out which one is the boss and where each horse ranks in the social hierarchy. This dominance pattern is sometimes achieved only after some chasing, biting, and kicking, but once the horses understand where they rank, there are usually few serious battles among the members of the group.

In wild horses, a dominant ranking is believed to give horses better access to forage and a higher likelihood of reproductive success. The advantage of dominance in domestic herds may not be as pronounced, but the social hierarchy is still present any time two or more horses are pastured together.

In a study reported in Journal of Animal Science, scientists in the Czech Republic analyzed the factors that influence dominance within a group of foals, with particular attention paid to the rank of the dams and whether their positions were related to that of their foals.

The researchers watched eight groups of mares and their nursing foals. At a later date, they also studied four groups of the same foals after they had reached three years of age. They found that older foals, which would be physically larger than later-born foals in the same group, reached higher dominance positions. This was true regardless of dam rankings.

Maternal care patterns by the dam did not seem to influence a foal’s rank, although foals born to the same mare in two successive years tended to have similar herd rankings as foals and as three-year-olds. This suggests that there might be some unidentified effect of the mare on the social success of her foal.

Earlier-born, larger foals that had been in the herd longest had the highest ranking. These foals were also weaned first and therefore were the first to be placed in a weanling group, maintaining their social rank. In this study, age/size and length of time in the group were the most important factors in establishing a dominance ranking.