Horse Hierarchy

You know your horse-feeding routine backward and forward and which horse will meet you at his bucket first or last. Jack always eats before Jenny, who eats before Andy, who eats before Sam. So you’ve got the dominance and the social design of your herd all worked out. Right?

Now try watching them at pasture all day. And think again.

Swiss researchers have learned that the “bucket test,” used to determine horse dominance, has its place, but it can give significantly different results than an all-day field test of horses at pasture. That’s especially true, they said, for the lower-ranking horses.

“We noted a rate of difference of 58% between a field observation test and a food dominance test in the hierarchy of our group of 12 study mares, with the greatest variations seen in the most dominated horses,” said Marie Roig-Pons, MSc candidate studying in association with Anja Zollinger, BSc, scientific collaborator the Agroscope national research center at the Swiss National Stud, in Avenches. Roig-Pons presented her group’s work at last year’s Swiss Equine Research Day.

“This leads us to question the reliability of the food dominance test method, especially for horses in the lowest ranks,” she said.

Horse Hierarchy

Roig-Pons and Zollinger tested 12 mares from the Swiss National Stud that already had an established social hierarchy and group stability. They first tested them by presenting a bucket of feed to two horses at a time until they’d tested all pairs, which gave the researchers a ranking order. They then observed the mares at pasture for 11 hours, taking note of all positive and negative interactions. They also recorded “nearest neighbors”—which horse stood closest to which—every 10 minutes of the 11-hour observation.

They found clear hierarchical structure in the pasture test, but it didn’t always agree with the ranking they found in the bucket test phase, Roig-Pons said.

They also recognized that many of the social interactions and actions weren’t necessarily related to hierarchy, she added.

“Our observations in the pasture revealed that the other behavioral parameters we observed, especially with regard to the level of aggression between individuals, their number of friendly interactions, and their nearest neighbor, cannot be explained by hierarchy status alone (regardless of the kind of test and calculation used),” Roig-Pons said. “Hierarchy is not the only way to describe social relationships within a group.”

Knowing a group’s hierarchy, and paying attention to it, can help owners and breeders create and/or maintain more harmonious groups, the researchers said.

This could not only reduce injury risk but also improve each individual horse’s welfare, they said.