Horse weaving is the common term used to describe when a horse repeatedly swings its head and neck from side to side, for long periods of time. In many cases, the horse will also rock on its front feet. Sometimes the horse will also rock its body from side to side.
This behavior is most commonly seen when a horse is confined (e.g. when the horse is in its box), particularly if a horse is confined for long periods of time. Note that a couple of swings may due to any number of causes (e.g. to shake off biting insects) and be normal behavior, but swinging (weaving) back and forth many times (for minutes or hours) is a definite behavioral problem. From a medical perspective, weaving is unhealthy as it can strain joints and tendons, cause excessive hoof wear or unbalanced hoof wear, in extreme cases abnormal muscle development.
The cause of weaving is not medical, but rather is due to stress, frustration and/or lack of mental stimulation. Depending on the horse, it can respond to these problems in various ways. For example, some horses become box walkers and others become weavers. Just as some people respond to stress by chewing their nails and others respond by pacing. As such, behaviors such as box walking and weaving can be seen as the same problem, just with different symptoms.
One should try to address the problem of weaving as soon as possible, for three reasons. Firstly, it is a sign of a very unhappy horse (bored, stressed). Secondly, it can result in medical issues. Thirdly, if the underlying issues are not solved, the weaving problem can become more severe and habitual, and the underlying mental issues can result in the development of more serious behavioral issues (such as cribbing). For general recommendations on correcting weaving through correcting the underlying issues, see reducing stress and increasing natural mental stimulation. The main specific recommendations are:
- Minimize box time. The more time a horse spends in a box, the more likely it is to become extremely bored and start pacing, an activity which eventually becomes so strong and automatic that it becomes a box walker. The best way to avoid this is to keep box time to a minimum and pasture time to a maximum.
- Good box neighbors. Like people, some horses get along and some don't. Try to put horses which are friendly with each other in adjacent boxes and separate ones that do not get along.
- Companions. Horses are herd animals and social interactions are very important. Consequently, one needs to provide companion animals (preferably horses, although other grazing animals are sometimes accepted as companions). The horse needs to not only see and talk with the other horse (possible if they are in adjacent fields separated by a fence) but also to groom and have physical contact with each other (need to be in the same field) and it may be beneficial if the box walls are low enough that they can easily touch noses and groom each other while boxed in.
- Food. Food provides interest and distraction for a horse. If a horse requires supplemental food (e.g. is not completely pasture fed), providing this food when it is locked in its box is probably the best time (as opposed to providing hay on the pasture). The best foods are one that are low in calories but require a lot of chewing, as this allows feeding to consume the maximum amount of time. For example, hay is much more suitable than musli for this purpose (see feed and behavior for further discussion).