Horses lick and nibble each other primarily to strengthen social bonds with preferred companions. This behavior, called allogrooming or mutual grooming, is one of the clearest signs of friendship in a herd. It also serves as a stress-relief mechanism, and in some cases, excessive licking can point to a nutritional deficiency.
Mutual Grooming Is a Friendship Indicator
When two horses stand side by side and scratch, nibble, or lick each other’s coats, they’re engaging in a behavior that researchers consistently link to social preference. Observational studies of both domestic and feral herds have found that mutual grooming occurs exclusively between preferred partners. Horses don’t groom just anyone in the herd. They choose specific individuals they’ve bonded with, and they return to those same partners repeatedly.
This selectivity makes mutual grooming one of the most reliable ways to identify which horses in a group are genuine companions. Researchers studying herd dynamics use it as a marker of affiliative relationships. If two horses regularly groom each other, they’re also likely to spend more time standing near each other, grazing together, and resting in close proximity.
Mutual grooming is always a two-way activity. Both horses participate at the same time, typically standing nose-to-tail or nose-to-shoulder so each can reach the other’s neck, withers, and back. These are areas a horse can’t easily scratch on its own, which is part of the practical appeal. But the social function goes well beyond itch relief.
It Helps Horses Cope With Stress
One of the more interesting findings from recent research is that horses groom each other more often during and after stressful situations. A study of two stable herds of Quarter Horse mares found that grooming frequency and duration both increased in confined environments where other signs of stress were also present. The horses didn’t just groom more in general. They specifically sought out their bonded partners, grooming those preferred individuals at higher rates while largely ignoring other herd members.
Researchers describe this as a “tend and befriend” response, a pattern previously recognized in humans and other social species. When stressed, horses turn toward their closest social allies rather than withdrawing. The behavior appears to be both a stress response and a deliberate social strategy. Domestic horses groom each other more frequently than feral horses do, which suggests that the added pressures of confinement, limited space, and reduced autonomy drive horses to lean harder on their social connections.
This has practical implications for horse owners. If you notice a sudden increase in mutual grooming between two horses, it may signal that something in their environment is causing anxiety, whether that’s a change in turnout routine, a new herd member, or reduced pasture access.
Dominant Horses Often Start It
There’s a common assumption that lower-ranking horses initiate grooming as a way of appeasing dominant ones, but the research points in the opposite direction. Dominant individuals are actually more likely to initiate affiliative interactions, including grooming. This fits with a broader pattern in equine social life where relationships between preferred partners involve a mix of behaviors that don’t always align with simple dominance hierarchies. Bonded horses may have frequent mild conflicts alongside frequent affectionate contact.
Licking and Chewing After Tension
You may also notice a horse licking and chewing on its own, not directed at another horse. This is sometimes called non-nutritive chewing, and it has been widely misinterpreted. Trainers have long described it as a sign of submission or a signal that the horse is “processing” a lesson. Research tells a different story.
When scientists studied this behavior in social contexts, they found that non-nutritive chewing was actually performed more often by the aggressor in a conflict than by the recipient, which rules out the submission theory. Instead, the behavior appears during the transition from a tense state to a relaxed one. Before the chewing, the horse’s body language is tense. Afterward, it relaxes. The likely explanation is physiological: stress triggers a dry mouth through sympathetic nervous system activation, and as the horse calms down, saliva production resumes, prompting licking and chewing. So this behavior is less a social signal and more a physical byproduct of coming down from stress.
When Licking Points to a Nutritional Gap
Excessive licking that seems indiscriminate, directed at other horses, fences, dirt, or objects, can sometimes indicate a sodium or mineral deficiency. A horse low in sodium may lick other horses’ sweat-covered coats to access the salt on their skin. Other signs of sodium deficiency include reduced sweating, poor performance, constipation, decreased appetite, dry or stiff skin, and muscle cramps.
If a horse is licking other horses persistently and especially if it’s also licking non-food surfaces, checking mineral intake is a reasonable first step. Providing a salt block or loose salt and ensuring the diet includes adequate electrolytes will typically resolve deficiency-driven licking within days. This type of licking looks different from mutual grooming: it tends to be one-sided, with the licking horse focused on areas where sweat accumulates while the other horse may not reciprocate or may even move away.
How to Tell the Difference
Not all horse-to-horse licking means the same thing, and context matters. Mutual grooming between bonded pairs is easy to spot: both horses participate, they stand close together in a relaxed posture, and they focus on the neck, withers, and back. It looks calm and reciprocal.
Stress-related increases in grooming look similar but happen more frequently and for longer durations, often alongside other signs of tension like pacing, head-tossing, or increased vigilance. One-sided, persistent licking of another horse’s coat, especially in sweaty areas, is more likely nutritional. And solitary licking and chewing with no other horse involved typically marks the moment a horse is transitioning out of a stressful experience.
Understanding these distinctions helps you read what’s happening in your herd. Most of the time, horses licking each other is a healthy, positive behavior. It means they’ve formed a genuine social bond and are maintaining it the way horses have for thousands of years.