Horses eat tree bark for a handful of reasons, but the most common are boredom, insufficient forage, and unmet nutritional needs. In some cases, bark chewing is simply normal exploratory behavior, especially in younger horses. The good news is that once you identify the trigger, it’s usually straightforward to reduce or stop.
Bark Chewing Is Not the Same as Cribbing
Before diagnosing a problem, it helps to know what you’re actually looking at. Bark chewing (sometimes called wood chewing) and cribbing are two completely different behaviors that people often confuse. A cribbing horse grabs a fixed surface with its front teeth, arches its neck, and sucks in a gulp of air. A bark-chewing horse simply gnaws and strips material off the tree without that signature arched-neck pose or air intake. The posture changes depending on what part of the tree the horse is working on.
This distinction matters because the causes and solutions differ. Cribbing collars, for instance, will not stop a horse from chewing bark or wood. If your horse is stripping bark off trees but not gulping air, you’re dealing with wood chewing specifically.
Not Enough Forage to Chew On
The single most common reason horses turn to bark is that they don’t have enough long-stem forage in front of them. Horses are built to spend the majority of their day chewing. When hay or pasture runs out, they look for the next best thing, and tree bark fits the bill. A typical adult horse needs to eat 1.0 to 2.0 percent of its body weight in forage every day. For a 1,000-pound horse, that’s 10 to 20 pounds of hay or grass.
If your horse finishes its hay hours before the next feeding, those empty hours create a gap the horse tries to fill. Slow-feed hay nets, more frequent feedings, or increasing total hay volume can make a dramatic difference. The goal is to keep forage available for as much of the day as possible so the horse’s natural chewing drive stays satisfied.
Boredom and Frustrated Foraging
Horses that spend long hours in stalls or small dry lots with little to do are far more likely to chew bark. The behavior often stems from frustrated foraging motivation: the horse wants to browse and graze, but there’s nothing appropriate available. A 2025 observational study found that 17 out of 31 mares and 28 out of 31 foals in fenced paddocks engaged in wood chewing, with foals doing significantly more of it than their mothers. The researchers concluded that for young horses in particular, much of the chewing was developmental exploration rather than a sign of dietary problems.
Colts chewed more than fillies, likely due to differences in exploratory tendencies between the sexes. For adult horses, though, the amount of browsing access in their environment influenced the behavior. Horses with more things to interact with, such as varied vegetation, had different chewing patterns than those in bare paddocks. Turnout on pasture, companion animals, and even simple enrichment like hanging treat balls or providing safe browse material can reduce the drive to strip bark off your trees.
Mineral Deficiencies and Pica
Sometimes bark eating signals that something is missing from the diet. Horses deficient in phosphorus, salt, or other minerals can develop pica, a compulsion to eat unusual materials. Phosphorus deficiency occurs in regions where the soil is naturally low in the mineral and can cause a range of symptoms beyond bark chewing, including stiff joints, muscle weakness, poor growth in young horses, and impaired weight gain in adults.
If your horse’s forage comes from phosphorus-poor soil, or if the diet is heavily grain-based without a balanced mineral supplement, a deficiency is worth investigating. A simple blood panel and forage analysis through your vet can confirm or rule this out. Providing a free-choice mineral block or a balanced mineral supplement often resolves bark chewing when a nutritional gap is the root cause.
Trees That Are Dangerous to Chew
While bark chewing itself is mostly a management nuisance, it becomes a genuine safety concern if your horse has access to toxic trees. Several common species pose real risks:
- Red maple: Wilted leaves are highly toxic and can cause severe red blood cell destruction. Hybrids of red maple, including crosses with sugar and silver maple, may also be dangerous.
- Wild cherry and chokecherry: The seeds, leaves, bark, and shoots all contain cyanide compounds. Wilted leaves from fallen branches after a storm are especially hazardous because cyanide concentrations increase as the leaves dry.
- Black walnut: Shavings from this wood cause laminitis when horses stand on them, and there is evidence that pollen and leaves can trigger mild respiratory issues.
Walk your pastures and paddocks and identify every tree your horse can reach. If any of these species are present, fence them off or remove them entirely. Even a horse that doesn’t normally chew bark might strip a branch after a storm knocks it within reach.
How to Protect Your Trees
Once you’ve addressed the underlying cause (more forage, enrichment, mineral supplementation), you may still need to physically protect trees while the habit fades. Several approaches work well.
The most reliable option is fencing trees off so the horse simply can’t reach them. A strand of electric fence set a few feet out from the trunk keeps horses at a safe distance without removing shade from the pasture. For stall and fence boards, metal panels or angle iron caps over wood edges eliminate the chewable surface entirely.
Chemical deterrents can also help. Capsaicin, the compound that makes chili peppers hot, can be applied to wood surfaces as a taste and nasal irritant. It works as a repellent for many horses, though some persistent chewers learn to tolerate it. Commercial chew-stop sprays are available and typically need reapplication after rain. Whatever product you use, confirm it’s labeled as non-toxic to horses before applying it to any surface they can mouth.
Combining deterrents with management changes gives you the best results. A deterrent alone treats the symptom. Fixing the forage, enrichment, or mineral gap fixes the reason the horse wanted to chew in the first place.
Young Horses Are Different
If your bark chewer is a foal or a young horse under two, the behavior may be completely normal. Research suggests that wood chewing in foals is more closely associated with developmental exploration than with any nutritional problem or frustration. Young horses mouth and chew their environment the way puppies do: it’s how they learn about the world. Teething discomfort can also drive foals to seek hard surfaces to gnaw on.
This doesn’t mean you should ignore it, especially if toxic trees are nearby. But it does mean that a foal stripping bark doesn’t necessarily signal a dietary problem. Most foals naturally reduce the behavior as they mature, particularly if they have adequate turnout and social interaction with other horses.