We know that the horse has a very strong and long neck. This allows the animal to signal its emotions via its neck and head.
The head shake has its origins in the irritation caused by flies which buzz around a horse’s eyes, nose and face. They move their head to disturb the flies, albeit for a brief period of time. The headshake merges with the upward head toss and the up-and-back movement of the head jerk. It’s believed that the major role of these three types of neck and head movement are concerned with self-comforting which as you can see is an evolution from removing the frustration of flies.
Dr Morris says that it is the equine equivalent of a person scratching the back of their head even though it is not itching. It’s an irritation reaction. Experts have described this as “headshaking syndrome”. As it is a self-comforting behaviour, the horse must be in mental discomfort and the cause needs to be discovered. The discomfort might be caused by physical or emotional pain.
In the video below the woman puts a net over the horse’s mouth and nose which stops the headshaking. Comments on the video say that there are very many reasons for headshaking including pollen, inner ear infections and toothache. The nose net is said to be effective because it stops insects landing on that sensitive area, irritating the horse.
Or perhaps when there are no insects, the net comforts the horse as a reassurance. This supports the argument at the beginning of the paragraph about the head shake originating in a horse getting rid of flies.
Head bobbing is a different movement and equine action. The head is ducked down and back repeatedly. It’s a way for a horse to better understanding what he/she is seeing by increasing their range of vision. You see a similar action in domestic cats when making a tricky jump. They are getting a clear visual map of the landing zone by using their binocular vision.
When the tip of a horse’s nose is twisted from side to side while the top of its head is more or less static, it is called a “head wobble”. The message that the horse is giving is that it is ready for action. In humans we can see it in the form of a cocky head sway, Dr Morris says, which has a similar meaning.
Head thrusting and lunging
Head thrusting, lunging and nose nudging are self-assertive actions. The thrust and lunge are related to biting while the nose nudge is less aggressive and is a form of body language which says, “Hey, what about me?”
The horse is demanding attention. The horse might be trying to get attention when in discomfort and as a consequence it should not be ignored and the cause should be investigated. The human equivalent is perhaps touching somebody on the arm in conversation to make sure that they listen. I do this. Maybe I shouldn’t ?.
When a horse sways its head away from something that it finds unpleasant it’s a signal that it wishes to avoid that unpleasantness.
When a horse wobbles its head from side to side on an outstretched neck, called head snaking, it indicates that a dominant stallion is having difficulty rounding up females. The snaking action is a vestigial behaviour from bite threats which have evolved-out. Mares understand the action and what the stallion demands of them.
When a horse moves its whole neck in a twisting action it can mean that the horse wants to go in different directions at once or it can signal that the horse wants to get out of a place.
Weaving and circling – stereotyped actions
Sometimes horses make stereotyped actions which have been well documented. These are done to relieve boredom and are coping mechanisms when horses are in isolation in small stalls. They might include repeated weaving actions and head circling. People should respond to these actions as an indication that the environment in which the horse lives is unsatisfactory and too sterile. The animal’s husbandry needs to be improved as quickly as possible.
You see various forms of coping mechanisms in zoo animals such as those described above one of which is pacing. It is distressing for the viewing public to see.