Evaluating equine dominance in draft mares

The social hierarchy of a herd of 12 draft mares was assessed using agonism in the field, paired-feeding tests and a group-feeding test. Results from the paired-feeding test correlated significantly, but imperfectly, with those from the field. Differential motivation among subjects for the feed and disruption of ambiguous relationships among mares reduced the reliability of the paired-feeding test as a measure of social dominance. Results from the group-feeding test did not correlate significantly with the field hierarchy and only a few mares ever ate from the bucket. Height, weight and age each correlated significantly with rank; a mare's tendency to remain alone did not. Total aggressive scores during the paired-feeding test correlated with rank. However, a high-ranking mare was no more aggressive to each of her subordinates than was a low-ranking mare. Rather, all mares aggressed more against individuals close in rank to themselves and with preferred field associates. In the field, mares associated most with other mares of similar rank.