Any horse will kick or bite at their belly to chase away an irritating fly. But in the case of automutilation, it goes beyond that. The horse bites or kicks, or shows other behaviours resulting in damage or injury to itself. 

Automutilation is a form of stereotypical behaviour. Mutilation means ‘to inflict damage’, so automutilation is literally ‘to damage yourself’. Often automutilation is confused with other conditions, such as colic, epilepsy, or hormonal imbalance, because they have similar symptoms. When your horse starts to self-injure, it is wise to first look at a possible physical cause. 

It is most common in domestic stallions. They can develop this behaviour through (a combination of) sexual frustration or insufficient free movement because, for example, they are kept in their stable continuously. When they cannot express their sexual behaviour on mares in cycle, some stallions will become frustrated and express this behaviour towards people, mares that are not in cycle or young horses. When there are no other horses around, the stallion may resort to expressing it on himself. You will mainly see behaviour that is shown in the wild towards each other, such as biting at the neck and legs. The behaviour can become more violent in the breeding season than in the rest of the year, because the stallion has more sexual needs. It may also occur in geldings, mares and foals, but this rarely happens. It is difficult to determine how many horses suffer from automutilation, but fortunately it is not a common problem. 

In addition to self-centered male aggression, automutilation can manifest itself as a calm, often rhythmic, repetitive movement. For example, biting different parts of the body in a fixed pattern, stomping or kicking an object rhythmically. You can also see this rhythmic and repetitive behaviour in other stereotypies, such as weaving or box walking. In extreme cases of automutilation, the horse can throw its head or body against a wall or throw itself completely to the ground. 

Since it is a form of stereotypical behaviour, it has the same consequences. When performing the behaviour, the horse produces substances called endorphins, which make him feel happier. In addition, it has an analgesic effect. A horse can become addicted to endorphins and so will continue to perform the behaviour to recreate the happy feeling. This makes it very difficult, or impossible, to unlearn the stereotypical behaviour. When limiting or preventing automutilation, it is important to look at stable management. Prevent chronic stress by taking into account (as much as possible) the natural needs of the horse. Ensure sufficient (free) movement, social contact and a good diet. Social interaction is important for stallions as well. A Swedish study showed that it is possible to place a herd of stallions together without serious injuries. You can read more about this research in an article by Equus Magazine. If physical contact is not possible, make sure that they can see and hear other horses. If a stallion that shows a lot of sexual and aggressive behaviour, has no purpose for breeding and/or sport, you may consider gelding it. This ensures that the sexual and aggressive behaviour can decrease and it is easier to place the horse in a herd, which is better for its wellbeing. For some stallions, automutilation stops after gelding, but this is not the case for all stallions.

Below you see two video’s. The first one shows the behaviour of rhythmic, repetitive automutilation. The second shows from minute 1.20 on a stallion that exercises automutilation.