Rear (horse)

Rearing occurs when a horse or other equine "stands up" on its hind legs with the forelegs off the ground. Rearing may be linked to fright, aggression, excitement, disobedience, or pain. It is not uncommon to see stallions rearing in the wild when they fight, while striking at their opponent with their front legs. Mares are generally more likely to kick when acting in aggression, but may rear if they need to strike at a threat in front of them.

When a horse rears around people, in most cases, it is considered a dangerous habit for riding horses, as not only can a rider fall off from a substantial height, but also because it is possible for the animal to fall over backwards, which could cause injuries or death to both horse and rider. It is therefore strongly discouraged. A horse that has a habit of rearing generally requires extensive retraining by an experienced horse trainer, and if the habit cannot be corrected, may be deemed too dangerous to ride.

A horse that rears when being handled by a human who is on the ground also presents a hazard, as it is able to strike out with its front feet and can also fall even without the weight of a rider to unbalance the animal. A rearing horse can also break away and escape from a human handler.

However, rearing also has survival value in the wild. It is a tactic that can be used to dislodge a predator that has landed on the animal's back, it is used when equids fight one another, and a horse can rear slightly to add force when striking out with its front feet. For these reasons, horses, particularly young ones, are sometimes seen rearing when loose in a pasture, particularly when playing or mock-fighting with pasturemates.

There are also a few times when rearing is considered acceptable by humans. Rearing may be taught as a trick for circus horses and the like. There are also two movements in classical dressage, the Levade and the Pesade, in which the rider asks the horse to set well back on its hindquarters and raise its front legs off of the ground to varying degrees. However, horses properly trained to do any of these movements are taught to respond to very specific commands and only raise their forequarters when given the command.

A horse generally must stop before it can rear. Generally a rider can feel if a horse is about to rear, as the horse shifts its weight strongly to its hindquarters and begins to feel "light in the front end." When this occurs, rearing can still be prevented by a number of methods, the simplest of which is to either encourage the horse to move, either forward or to turn the horse in tight circles so that it cannot engage its hindquarters enough to rear. If the horse is allowed to stop or back up while behaving in a disobedient manner, it can more easily rear.

...
Wikipedia