Understanding Herd Dynamics

What are your horses’ pasture behaviors telling you and what can you do to help groups live together harmoniously?
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Understanding Herd Dynamics
The strongest positive social sign that horses give is rather anticlimatic: standing peacefully near each other. | Photo: iStock

What are your horses’ pasture behaviors telling you and what can you do to help groups live together harmoniously?

On some days my two horses walk the perimeter of their field along the fenceline. Patrolling, I guess. Or getting exercise. The 4-year-old gelding, Solstice, is always in front. His mother, Sabrina, is behind.

My teenage daughter tells me, “Look, Solstice is the leader!” But watching Sabrina’s head down and nose out close to Solstice’s tail makes me think that Sabrina’s “pushing” Solstice, making her the more dominant one.

That’s the funny thing about horse herd dynamics. Even in a small domestic group, horses can show behaviors that we humans don’t always understand. Like, if Horse A is finished drinking, why does he still refuse to let Horse B approach the water? Or, how come the sorrel loves sidling up to the other sorrel but chases the gray away?

As more owners recognize the importance of giving horses outdoor social time, there’s a growing need to better recognize and understand herd dynamics. While most horses will work out their differences without human intervention, it’s still important to be aware of what’s going on. And having an enlightened view of our horses’ social interactions helps us appreciate them more, understand them better, and communicate with them more effectively.

Social Behaviors: the Good and the Bad

Horses use a wide variety of subtle communication methods. Says Sue M. McDonnell, PhD, certified applied animal behaviorist and founding head of the equine behavior program at the University of Pennsylvania’s School of Veterinary Medicine, even a flick of the ear or tail is sufficient for a horse to “speak” to its entire herd.  

That’s especially true when a herd’s roles are clearly defined, she says. “The greater the separation and clarity in order of dominance, the more subtle the directives and seemingly peaceful the herd interaction.”

Horses can also convey information through vocal sounds, such as whinnies, nickers, snorts, and blows, as well as hoof noises, like pawing and stomping. And odors certainly come into play when conveying information as well, she adds. They frequently smell droppings as well as each other’s breath.

With all that communication happening, how can handlers decipher if their horses are actually getting along well? Researchers suggest that the strongest positive social signs that horses give are probably rather anticlimactic. Standing close to each other likely tops the list, says Line Peerstrup Ahrendt, PhD, researcher in the department of animal science at Aarhus University, in Denmark. A close second is mutual grooming, where horses nibble at each other’s withers, neck, or back.

By contrast, negative interactions include squeals, bite threats, kick threats, pinned ears, and rolling eyes. In extreme cases the threats can lead to actual kicks and bites.  

But handlers should understand that these negative behaviors don’t necessarily mean the horses aren’t getting along, Ahrendt says. Such communication serves the purpose of setting up and maintaining social hierarchies, which is a perfectly normal phenomenon among herds. Unless horses become particularly violent and dangerous toward other horses, which we’ll talk about later, humans are better off letting them work out their hierarchies and establish order on their own, according to their natural instincts.  

When they do, what you’ll usually see is just that subtle kind of communication, says McDonnell. “This is especially the case with a truly confident, dominant animal directing truly submissive, respectful, deferential herdmates,” she says. In such cases, “no overt aggression is necessary.”

Understanding Herd Dynamics - Mutual Grooming
A common positive interaction between horses is mutual grooming, where horses nibble at each others withers, neck, or back. | Photo: iStock

Dominance, Leadership, and Hierarchy

It’s just part of equine nature, stemming from wild herd days, that domestic groups of horses create social hierarchies. These rankings work to safeguard the herd, maintain family groups, and determine priority access to resources (food, water, and shelter).

“We like to think of our horses as being nice and generous, but the thing is that what they’re really looking out for is themselves,” says Elke Hartmann, PhD, of the Department of Animal Environment and Health at the Swedish University of Agricultural Sciences, in Uppsala.  

As such, horses will set up an order of who eats first, drinks first, and accesses shelter first. “It’s all about resources when it comes to social order in domestic horses,” Hartmann says.  

In fact, some horses can be so dominant that they actually “stand guard” over the resources, even if they don’t necessarily need them right away, just so the other horses can’t get to them for a while. “You’ll see them hovering in entryways into shelters without actually going in, or keeping their heads over a shared water source,” Hartmann says.  

Even so, motivation plays an important role, Hartmann adds. “If the highest-ranking horse is not hungry, it will certainly allow the other horses to feed first,” she says.

Horse hierarchies are often rather complex. There’s not some clean line of pecking order from top horse to bottom horse. “It’s never linear,” Ahrendt says. “Some horses will be at equal levels, and sometimes you can have triangles where one horse is dominant over another, and that horse is dominant over the third, which is dominant over the first.”

Two things are clear, though: There’s always a leader, and there’s always a top dominant horse over the herd. But interestingly, that’s not always the same horse. In fact, Hartmann adds, there isn’t necessarily one horse that’s the constant leader. “It has been proposed that a combination of different factors, including social status, affect the decision to follow an initiator of movement,” she says.

Understanding Herd Dynamics
Horses can gather information from sniffing other horses' manure. | Photo: The Horse Staff

Getting the Whole Picture

Researchers often identify herd hierarchies through extensive field observations—up to 15 hours a day, says Ahrendt. Fortunately, she and her fellow researchers developed a faster method: their “limited resource” test.

By placing three bins of food in a herd’s pasture, they studied the interactions among 25 geldings for as few as 80 minutes over a four-day period. “The results suggested that the less-time-consuming limited resource test can provide the same information regarding hierarchy based on aggressive encounters as when determined by field observations,” she says.  

For nonresearchers though, herd dynamics can be determined through regular observations over time. Intermittent checks on your horses once or twice a day won’t give you an accurate picture, says Hartmann. You’ll need to sit and observe frequently.  

Plus, relationships can develop and change over weeks, months, and years. “A horse is not born dominant and will not have a dominant position all its life,” Hartmann says.  

Making Groups, Making Friends

Within a herd, horses will usually break up into what researchers call “subgroups”—smaller groups of horses that tend to stay clustered together without straying too far from the whole herd, says Hartmann. It’s in these subgroups that horses actually have their closest “friends,” if we can call them that.

“It’s a bit anthropomorphic to speak of ‘friends’ among horses,” says Ahrendt. “What we do know is that they form close relationships with the horses in their subgroups, something similar to what we see in human friendships.”

Why does a horse like one horse in the field and not another? Hartmann and Ahrendt both admit that they don’t really know. Color could have something to do with it: “Horses of a similar color often seem to pair up,” says Hartmann. “It might remind them of their mothers, or their friends when they were young.”

Ahrendt has heard of white or light gray horses often being less liked by other horses. “But so far there’s no scientific evidence of that,” she says.

Past experience will also influence horses’ choices, causing them to prefer equine companions that are similar to others they liked in the past, Hartmann says.

Personality and temperament likely also play a key role, Hartmann adds. “It’s like humans,” she says. “It’s very individual.”

Managing Your Herd

Unfortunately, there’s not much you can do to encourage horses to like each other, the researchers say. They’re either going to make peace or they’re not.

But one thing you can do is give them the opportunity to keep space between themselves. “They really need a big enough area to be able to get away from each other if they have to,” Ahrendt says.  

How big? Well, again, science hasn’t gotten this far in studying herd dynamics. Use common sense when putting two or more horses together in a field, say the researchers. Make sure each one has room to allow subordinate horses to express subordinate behavior—essentially fleeing the other horses’ pursuit. Also watch them closely in their early days together to see if any horses appear “trapped” or unable to escape the threats of other horses.  

The Small Herd

Two horses still qualify as a herd, but their relationship could be somewhat unnatural because the horses have no choice in their companionship, says Hartmann. Each is stuck with the partner that we’ve chosen, and he will have to make do with that horse to meet his social needs.

The fact that the horse has a companion at all is good for his well-being, our sources add. But it does mean keeping a closer eye on the horses to make sure they’re tolerating each other. “You can’t expect them to be friends necessarily,” says Hartmann. “But sometimes giving them some time with physical contact without being able to hurt each other (through stall bars, for example) can be helpful.”

When to Intervene

Given enough pasture space, most horses will work out their differences on their own. Even breeding stallions can create a safe and harmonious hierarchy in a large field without human intervention (and without mares!), as Swiss researcher Sabrina Briefer-Freymond, PhD, observed in up to eight of her country’s National Stud stallions living peacefully together for two years (for the full study see TheHorse.com/31929).

But while we strive to respect horses’ natural rhythms and behaviors, we do still have a “responsibility” to step in when things go wrong, Hartmann says.  

“If you see that one horse is losing weight and isn’t getting enough to eat because he’s a slow eater and is subordinate to an aggressive horse that takes his food, then you need to manage that problem,” Ahrendt says. Tie the horses up during mealtimes, or separate the slow eater until he’s finished.  

Be patient and observe interactions closely before intervening, however, Hartmann adds. “You have to watch how things develop,” she says. “But if you see that the aggression level is unnecessarily high, and if the other horse isn’t walking away to protect itself, then you may need to intervene and perhaps change out the members of the group.” Still, time might fix the problem, as horses learn from their experiences, Hartmann adds.  

The best thing you can do to ensure good socialization among horses is get them started with a good social education, Ahrendt and Hartmann say. Place horses in group settings starting when they’re young—ideally from birth onward, but especially in the first four formative years.  

And place them with horses of all ages, sizes, breeds, sexes, and colors during those years. “We now know that the old tradition of keeping all the weanlings, yearlings, 2-year-olds together, and all the 3-year-olds together is not what’s best for their social education,” Hartmann says.  

Take-Home Message

Horses are social animals and seek companionship with other horses, and they communicate to establish solid social orders. By recognizing our herds’ social order—and managing the horses based on both their choices and needs—we can help ensure their well-being in a domestic environment.

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Passionate about horses and science from the time she was riding her first Shetland Pony in Texas, Christa Lesté-Lasserre writes about scientific research that contributes to a better understanding of all equids. After undergrad studies in science, journalism, and literature, she received a master’s degree in creative writing. Now based in France, she aims to present the most fascinating aspect of equine science: the story it creates. Follow Lesté-Lasserre on Twitter @christalestelas.

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