All land mammals require deep sleep for proper physical, mental and emotional functioning.
Yet equine sleep is rarely considered as a significant contributor to the well-being of the horse. Perhaps this arises from the flawed presumption that horses can “sleep standing up.”
Unfortunately this misunderstanding can have serious implications to the well-being and welfare of the horse.
Mature horses frequently rest and doze in an upright position. In this position they distribute their weight between three limbs instead of four and appear to be leaning on one hip while the other hind limb is cocked at the hock with the toe resting upon the ground. All large land prey animals, including horses, have a unique “locking” system of sinews and muscles that allows them to rest in a standing position with minimal energy expenditure. All the while they are able to flee quickly if approached by a predator.
This is not a sleeping state for the horse. In order for the horse to meet its physiological need for and enter into the state of deep sleep known as REM (rapid eye movement) the horse must either lay flat on its side in lateral recumbency or lay chest down in sternal recumbency, with its head propped up or supported upon the ground.
Only then can the horse achieve loss of muscle tone and complete relaxation. This places a flight animal into its most vulnerable position. Therefore a horse must feel a sense of ease, safety and security within its surroundings in order to lay down. This level of sleep is considered to be of particular importance to the health of an animal’s nervous and immune systems.
The scientific data regarding the sleeping behaviours of horses is fairly limited yet some general observations can be made. First, the sleeping pattern of a horse changes with its age. Foals sleep laying down frequently, often napping and/or “sun bathing” for up to half of their day. As the foal approaches three months of age, the amount of time spent laying down to sleep gradually diminishes until the young horse matures.
The sleeping habits of the adult horse vary somewhat amongst individuals and their environment, however, it appears that the requirement for REM sleep by horses can be fulfilled during 2-1/2 to three hours of recumbency over a 24-hour period. Certain horses may sleep only during nightfall while others may lay down for a period during daylight as well.
In herd situations with a stable social structure it is not uncommon for several horses to lay down and sun bath in the late morning while one or two herd members remain standing, taking on the duty of sentinel. Horses prefer to sleep within visual contact of one another. This is a natural behaviour for the safety of the herd. When horses have suitable environmental conditions, sufficient space and healthy social relationships their sleeping habits develop into a regular and rhythmic nature.
Horses that have access to soft grass or bedded areas lay down more than horses without access to such areas. In a group setting of horses, prime bedding areas are often highly valued and claimed by the higher-ranking horses. As a result, individual horses may experience a secondary fatigue due to social tensions, particularly if bedding areas and space are limited.
Healthy social bonds between the members of the herd require both sufficient time and physical space and room to develop. As the social bonds evolve they nurture the horse’s sense of companionship, social security and safety that is necessary to achieve deep states of sleep.
Researchers who study equine sleep (yes these people do exist) have identified that the irritable behaviour and ill health effects of sleep deprivation is not uncommon in horses and yet unfortunately it is poorly recognized.
Even though vigilance against predation may no longer be required by the domesticated horse it appears that the modern-day environment does present stressors of a different flavour to the horse. These modern-day stressors are of equal concern to the horse’s feeling of safety and comfortability and thus its willingness to lay down and achieve proper sleep.
These environmental, physical and social insecurities include but are not limited to: the lack of available physical space or the social isolation and distress that can occur in box stalls or confined paddocks, poor diet, lack of movement, noise, artificial or interrupted light settings, lack of exposure to sunshine, traffic noise, high-voltage power lines, and the changing environments and time schedules inherent with show agendas, including the phenomena of jet lag experienced by international athletes.
Horses that experience painful conditions whether secondary to an injury, or as a result of a chronic condition such as arthritis, often become sleep deprived because their abilities to lay down and rise with ease are compromised. Overweight horses may also find it difficult to lay down and rise with ease. In addition to addressing the health condition of these horses, they have an even greater need for the physical comforts of ample room and bedding and environmental and social security to entice them to lay down.
The ability of the horse to receive sufficient deep sleep can easily be overlooked in the management of its health and welfare. Nonetheless, it is through these deep states of sleep that the horse is able to access its body’s own source of innate and highly intelligent healing.