Physical Characteristics - General Equine
Horses are prey animals with a well-developed
fight-or-flight instinct. Their first response to threat is to startle
and usually flee, although they are known to stand their ground and
defend themselves or their offspring in cases where flight is not
possible, or when their young are threatened. They also tend to be
curious; when startled, they will often hesitate an instant to
ascertain the cause of their fright, and may not always flee from
something that they perceive as non-threatening. Through selective
breeding, some breeds of horses are quite docile, particularly certain
large draft horses. However, most light horse riding breeds were
developed for speed, agility, alertness and endurance; natural
qualities that extend from their wild ancestors.
Horses are herd animals, with a clear hierarchy of rank, led by a
dominant animal (usually a mare). Horses are also social creatures who
are able to form companionship attachments to their own species and to
other animals, including humans. They communicate in various ways,
including vocalizations such as nickering or whinnying, mutual
grooming, and body language. Many horses will become difficult to
manage if they are isolated. When this behavior occurs while being
handled by human, the horse is called "herd-bound". However, through
proper training, it is possible to teach any horse to accept a human
as a type of companion, and thus be comfortable away from other
horses. When confined with insufficient companionship, exercise or
stimulation, horses may develop stable vices, an assortment of bad
habits, mostly psychological in origin, that include wood chewing,
wall kicking, "weaving" (rocking back and forth) and other problems.
Age Depending on breed, management and environment,
the domestic horse today have a life expectancy of 25 to 30 years. It
is uncommon, but a few horses live into their 40s, and, occasionally,
Regardless of a horse's actual birthdate, for most competition
purposes, horses are considered a year older on January 1 of each year
in the northern hemisphere and August 1 in the southern hemisphere.
The exception is endurance riding, where the minimum age to compete is
based on the horse's actual calendar age.
The following terminology is used to describe
horses of various ages:
Foal: a horse of either sex less than one year old. A nursing
foal is sometimes called a suckling and a foal that has been weaned
is called a weanling. Most domesticated foals are weaned at 4-6
months of age. Yearling: a horse of either sex that is between one and two
years old. Colt: a male horse under the age of four. Filly: a female horse under the age of four. Mare: a female horse four years old and older. Stallion: a non-castrated male horse four years old and older.
Some people, particularly in the UK, refer to a stallion as a
"horse." A Ridgling or "Rig" is a stallion which has an undescended
testicle. If both testicles are not descended, the horse may appear
to be a gelding, but will still behave like a stallion. Gelding: A castrated male horse of any age, though for
convenience sake, many people also refer to a young gelding under
the age of four as a "colt."
In horse racing the definitions of colt, filly, mare, and stallion
or horse may differ from those given above. In the United Kingdom,
Thoroughbred horse racing defines a colt as a male horse less than
five years old and a filly as a female horse less than five years
old. In the USA, both Thoroughbred racing and harness racing defines
colts and fillies as four years old and younger. A very rough
estimate of a horse's age can be made from looking at its teeth.
Sleep Patterns Horses are able to sleep both standing up and
lying down. They are able to doze and enter light sleep while
standing, an adaptation from life as a prey animal in the wild.
Lying down makes an animal more vulnerable to predators. Horses are
able to sleep standing up because a "stay apparatus" in their legs
allows them to relax their muscles and doze without collapsing.
Unlike humans, horses do not sleep in a solid, unbroken period of
time. They obtain sleep by means of many short periods of rest.
Horses may spend anywhere from four to fifteen hours a day in
standing rest, and from a few minutes to several hours lying down.
Total sleep time in a day may range from several minutes to a couple
of hours. Horses require approximately two and a half hours of
sleep, on average, in a 24-hour period. Most of this sleep occurs in
many short intervals of about 15 minutes each.
Horses must lie down to reach REM sleep. They only have to lie down
for an hour or two every few days to meet their minimum REM sleep
requirements. However, if a horse is never allowed to lie down,
after several days it will become sleep-deprived, and in rare cases
may suddenly collapse as it involuntarily slips into REM sleep while
still standing. This condition differs from narcolepsy, though
horses may also suffer from that disorder.
Horses sleep better when in groups because some animals will sleep
while others stand guard to watch for predators. A horse kept
entirely alone will not sleep well because its instincts are to keep
a constant eye out for danger.
Size The English-speaking world measures the height of
horses in hands, abbreviated "h" or "hh," and is measured at the
highest point of an animal's withers. One hand is 4 Imperial inches,
or, as defined in British law, 101.6 mm. Intermediate heights are
defined by hands and inches, rounding to the lower measurement in
hands, followed by a decimal point and the number of additional
inches between 1 and 3. Thus a horse described as 15.2 hh tall,
means it is 15 hands, 2 inches, or 62 inches/1.57 m in height.
The size of horses varies by breed, but can also be influenced by
nutrition. The general rule for cutoff in height between what is
considered a horse and a pony at maturity is 14.2 hands high.
(abbreviated "h" or "hh") (147 cm, 58 inches) as measured at the
withers. An animal 14.2h or over is usually considered a horse and
one less than 14.2h is a pony.
However, there are exceptions to the general rule. Some smaller
horse breeds who typically produce individual horses both under and
over 14.2h are considered "horses" regardless of height. Likewise,
some pony breeds, such as the Pony of the Americas or the Welsh
pony, share some features of horses and individual animals may
occasionally mature at over 14.2h, but are still considered ponies.
The difference between a horse and pony is not simply a height
difference, but also a difference in phenotype or appearance. There
are noticeable differences in conformation and temperament. Ponies
often exhibit thicker manes, tails and overall coat. They also have
proportionally shorter legs, wider barrels, heavier bone, shorter
and thicker necks, and short heads with broad foreheads. They often
have calmer temperaments than horses and also a high level of equine
intelligence that may or may not be used to cooperate with human
Light riding horses such as Arabians, Morgans, or Quarter Horses
usually range in height from 14.0 (142 cm) to 16.0 hands (163 cm)
and can weigh from 386 kilograms to about 540 kg (850 to 1200 lb).
Larger riding horses such as Thoroughbreds, American Saddlebreds or
Warmbloods usually start at about 15.2 hands (157 cm) and often are
as tall as 17 hands (172 cm), weighing from 500 kg to 680 kg (1100
lb to 1500 lb). Heavy or draft horses such as the Clydesdale,
Belgian, Percheron, and Shire are usually at least 16.0 (163 cm) to
18.0 hands (183 cm) high and can weigh from about 680 kg up to about
900 kg (1500 lb to 2000 lb). Ponies cannot be taller than 14.2h (147
cm), but can be much smaller, down to the Shetland pony at around 10
hands (102 cm), and the Falabella which can be the size of a
medium-sized dog. However, while many miniature horse breeds are
small as or smaller than a shetland pony, because they are bred to
have a horse phenotype (appearance), their breeders and registries
classify them as very small horses rather than ponies. The largest
horse in history was a Shire horse named Sampson, later renamed
Mammoth, foaled in 1846 in Bedfordshire, England. He stood 21.2
hands high (i.e. 7 ft 2 in or 2.20 m ), and his peak weight was
estimated at over 3,300 lb (approx 1.5 tonnes). The current record
holder for the world's smallest horse is Thumbelina, a fully mature
miniature horse affected by dwarfism. She is 17 inches tall and
weighs 60 pounds.
Reproduction and Development Pregnancy lasts for approximately 335-340 days
and usually results in one foal (male: colt, female: filly). Twins
are rare. Colts are usually carried 2-7 days longer than fillies.
Females 4 years and over are called mares and males are stallions. A
castrated male is a gelding. Horses, particularly colts, may
sometimes be physically capable of reproduction at approximately 18
months but in practice are rarely allowed to breed until a minimum
age of 3 years, especially females. Horses four years old are
considered mature, though the skeleton usually finishes developing
at the age of six, and the precise time of completion of development
also depends on the horse's size (therefore a connection to breed
exists), gender, and the quality of care provided by its owner.
Also, if the horse is larger, its bones are larger; therefore, not
only do the bones take longer to actually form bone tissue (bones
are made of cartilage in earlier stages of bone formation), but the
epiphyseal plates (plates that fuse a bone into one piece by
connecting the bone shaft to the bone ends) are also larger and take
longer to convert from cartilage to bone as well. These plates
convert after the other parts of the bones do but are crucial to
Depending on maturity, breed and the tasks expected, young horses
are usually put under saddle and trained to be ridden between the
ages of two and four. Although Thoroughbred and American Quarter
Horse race horses are put on the track at as young as two years old
in some countries (notably the United States), horses specifically
bred for sports such as show jumping and dressage are generally not
entered into top-level competition until a minimum age of four years
old, because their bones and muscles are not solidly developed, nor
is their advanced training complete. For endurance riding
competition, horses may not compete until they are a full 60
calendar months (5 years) old.
Skeletal System Horses have, on average, a skeleton of 205 bones.
A significant difference in the bones contained in the horse
skeleton, as compared to that of a human, is the lack of a
collarbone--their front limb system is attached to the spinal column
by a powerful set of muscles, tendons and ligaments that attach the
shoulder blade to the torso. The horse's legs and hooves are also
unique, interesting structures. Their leg bones are proportioned
differently from those of a human. For example, the body part that
is called a horse's "knee" is actually the carpal bones that
correspond to the human wrist. Similarly, the hock, contains the
bones equivalent to those in the human ankle and heel. The lower leg
bones of a horse correspond to the bones of the human hand or foot,
and the fetlock (incorrectly called the "ankle") is actually the
proximal sesamoid bones between the cannon bones (a single
equivalent to the human metacarpal or metatarsal bones) and the
proximal phalanges, located where one finds the "knuckles" of a
human. A horse also has no muscles in its legs below the knees and
hocks, only skin and hair, bone, tendons, ligaments, cartilage, and
the assorted specialized tissues that make up the hoof (see section
Digestion A horse is a herbivore with a digestive system
adapted to a forage diet of grasses and other plant material,
consumed regularly throughout the day, and so they have a relatively
small stomach but very long intestines to facilitate a steady flow
of nutrients. A 1000 pound horse will eat between 15 and 25 pounds
(approximately 7-11 kg) of food per day and, under normal use, drink
10 to 12 gallons (about 38-45 litres) of water. Horses are not
ruminants, so they have only one stomach, like humans, but unlike
humans, they can also digest cellulose from grasses due to the
presence of a "hind gut" called the cecum, or "water gut," that food
goes through before reaching the large intestine. Unlike humans,
horses cannot vomit, so digestion problems can quickly spell
trouble, with colic a leading cause of death.
Teeth Horses are adapted to grazing. In an adult horse,
there are 12 incisors (six upper and six lower), adapted to biting
off the grass or other vegetation, at the front of the mouth. There
are 24 teeth adapted for chewing, the premolars and molars, at the
back of the mouth. Stallions and geldings have four additional teeth
just behind the incisors, a type of canine teeth that are called
"tushes." Some horses, both male and female, will also develop one
to four very small vestigial teeth in front of the molars, known as
"wolf" teeth, which are generally removed because they can interfere
with the bit.
There is an empty interdental space between the incisors and the
molars where the bit rests directly on the bars (gums) of the
horse's mouth when the horse is bridled.
The incisors show a distinct wear and growth pattern as the horse
ages, as well as change in the angle at which the chewing surfaces
meet. The teeth continue to erupt throughout life as they are worn
down by grazing, and while the diet and veterinary care of the horse
can affect the rate of tooth wear, a very rough estimate of the age
of a horse can be made by looking at its teeth.
Hooves The critical importance of the feet and legs is
summed up by the traditional adage, "no foot, no horse." The horse
hoof begins with the distal phalanges, the equivalent of the human
fingertip or tip of the toe, surrounded by cartilage and other
specialized, blood-rich soft tissues such as the laminae, with the
exterior hoof wall and horn of the sole made essentially of the same
material as a human fingernail. The end result is that a horse,
weighing on average 1,000 pounds, travels on the same bones as a
human on tiptoe. For the protection of the hoof under certain
conditions, some horses have horseshoes placed on their feet by a
professional farrier. The hoof continually grows, just like a large
fingernail, and needs to be trimmed (and horseshoes reset, if used)
every six to eight weeks.
Senses The senses of a horse are generally superior to
those of a human. As prey animals, they must be aware of their
surroundings at all times. They have very large eyes (among land
animals only the ostrich has a larger eye), with excellent day and
night vision, though they may have a limited range of color vision.
The side positioning of the eyes gives the horse a wide field of
vision of about 350°. While not color-blind, studies indicate that
they have difficulty distinguishing greens, browns and grays. Their
hearing is good, and the pinna of their ears can rotate a full 360
degrees in order to pick up sound from any direction. Their sense of
smell, while much better than that of humans, is not their strongest
asset; they rely to a greater extent on vision.
A horse's sense of balance is outstanding; the cerebellum of their
brain is highly developed and they are very aware of terrain and
placement of their feet. Horses' sense of touch is better developed
than many people think; they immediately notice when a fly or
mosquito lands on them, even before the insect attempts to bite.
Their sense of taste is well-developed in order to determine the
nature of the plants they are eating, and their prehensile lips can
easily sort even the smallest grains. Horses will seldom eat most
poisonous plants or spoiled food unless they have no other choices,
although a few toxic plants have a chemical structure that appeals
to animals, and thus poses a greater risk of being ingested.
Gaits All horses move naturally with four basic
gaits: the walk, trot or jog, canter or lope, and gallop. Besides
these basic gaits, some horses pace, instead of trot. In addition,
there are many "ambling" gaits such as the slow gait, rack, fox trot
running walk, and tölt. These special gaits are often found in
specific breeds, often referred to as "gaited" horses because they
naturally possess additional gaits that are approximately the same
speed as the trot but smoother to ride. Technically speaking,
"gaited horses" replace the standard trot (which is a 2 beat gait)
with one of the four beat gaits.
Horse breeds with additional gaits that often occur naturally
include: the Tennessee Walking Horse which naturally performs a
running walk; the American Saddlebred which can be trained to
exhibit a slow gait and the rack; Paso Fino, which has two ambling
gaits, the paso corto and paso largo; the Peruvian Paso, which
exhibits the paso llano, and sobreandando; and Icelandic horses
which are known for the tölt. The fox trot is found in several
breeds, most notably the Missouri Foxtrotter. Standardbreds,
depending on bloodlines and training, may either pace or trot.
Horse Care Horses are animals that were evolved to graze.
They eat grass or hay, sometimes supplemented with grain. They
require a plentiful supply of clean water, a minimum of 10 to 12
gallons per day. Although horses are adapted to live outside, they
require shelter from the wind and precipitation, which can range
from a simple shed or shelter to an elaborate stable.
Horses require annual vaccinations to protect against various
diseases, need routine hoof care by a farrier, and regular dental
examinations from a veterinarian or a specialized equine dentist. If
horses are kept inside in a barn, they require regular daily
exercise for their physical health and mental well-being. When
turned outside, they require well-maintained, sturdy fences to be
safely contained. Regular grooming is also helpful to help the horse
maintain good health of the hair coat and underlying skin.
Equine Benefits Horses are trained to be ridden or driven in
many different sporting events and competitions. Examples include
horse shows, gymkhana and O-Mok-See, rodeos, endurance riding, fox
hunting, and Olympic-level events such as three-day eventing,
combined driving, dressage, and show jumping. Although scoring
varies by event, most emphasize the horse's speed, maneuverability,
obedience and/or precision. Sometimes the equitation, the style and
ability of the rider, is also considered.
Sports such as polo and horseball do not judge the horse itself, but
rather use the horse as a partner for human competitors as a
necessary part of the game. Although the horse assists this process
and requires specialized training to do so, the details of its
performance are not judged, only the result of the rider's actions
-- be it getting a ball through a goal or some other achievement.
Examples of these sports of partnership between human and animal
also include jousting (reenacting the skills used by medieval
knights), where the main goal is for one rider to dismount the
other, and buzkashi, a team game played throughout Central Asia, the
aim being to capture a goat carcass while on horseback.
The most widely known use of horses for sport is horse racing, seen
in almost every nation in the world. There are three types: "flat"
racing; steeplechasing, i.e. racing over jumps; and harness racing,
where horses trot or pace while pulling a driver in a small, light
cart known as a sulky. Most race horses in the developed world are
Thoroughbreds, a breed which can reach speeds up to 40 mph/70 km/h.
In the case of a specialized sprinting breed, the American Quarter
Horse, speeds over 50 mph have been clocked. In harness racing,
performed by Standardbred horses, speeds over 30 mph have been
measured. A major part of the economic importance of horse racing,
as for many sports, lies in the gambling associated with it.
There are certain jobs that horses do very well, and no amount of
technology appears able to supersede. Mounted police horses are
still effective for crowd control. Cattle ranches still require
riders on horseback to round up cattle that are scattered across
remote, rugged terrain. Search and rescue organizations in some
countries depend upon mounted teams to locate people, particularly
hikers and hunters, who are lost in remote areas.
Some land management practices such as cultivating and logging can
be efficiently performed with horses. In agriculture less use of
fossil fuels, reduced soil compaction and degrading of soil
structure can be seen over time with the use of draft animals such
as horses. In forestry, logging can be done with horses and can
result in reduced damage to soil structure and less damage to trees
due to more selective logging.
Horses can also be used in other areas where it is necessary to
avoid vehicular disruption to delicate soil. Examples include areas
such as a nature reserve. They may also be the only form of
transport allowed in wilderness areas. They are also quieter than
motorized vehicles. Peace officers such as rangers or game wardens
may use horses for patrols, and horses may also be used for clearing
trails or other work in areas of rough terrain where vehicles are
In less affluent countries such as Romania, Kyrgyzstan, and many
parts of the Third World, horses, donkeys and mules are routinely
used for transport and agriculture. In areas where roads are poor or
non-existent and fossil fuels are scarce or the terrain rugged,
riding horseback is still the most efficient way to get from place
People with disabilities obtain beneficial results from association
with horses. The movement of a horse strengthens muscles throughout
a rider's body and promotes better overall health. In many cases,
riding has also led to increased mobility for the rider. Horses also
provide psychological benefits to people whether they actually ride
or not. The benefits of equestrian activity for people with
disabilities has also been recognized with the addition of
equestrian events to the Paralympic Games and recognition of
para-equestrian events by the FEI.
Hippotherapy and therapeutic horseback riding are names for
different physical, occupational and speech therapy treatment
strategies that utilize equine movement. In the hippotherapy
environment, a therapist uses the horse's movement to provide
carefully graded sensory input, whereas therapeutic horseback riding
uses specific riding skills.
"Equine-assisted" or "equine-facilitated" psychotherapy uses horses
as companion animals to assist people with psychological problems.
Actual practices vary widely due to the newness of the field; some
programs include Therapeutic Horseback Riding and hippotherapy.
Non-riding therapies simply encourage a person to touch, speak to
and otherwise interact with the horse. People appear to benefit from
being able to be around a horse; horses are very sensitive to
non-verbal communication and are an ideal resource for working with
individuals who have "tuned out" human therapists.
Equine Assisted Learning (EAL), Equine guided education, or equine
assisted professional development, is another relatively new field
of experiential learning for corporate, professional and personal
development. There also have been experimental programs using horses
in prison settings. Exposure to horses appears to improve the
behavior of inmates in a prison setting and help reduce recidivism
when they leave. A correctional facility in Nevada has a successful
program where inmates learn to train young mustangs captured off the
range in order to make it more likely that these horses will find
adoptive homes. Both adult and juvenile prisons in New York,
Florida, and Kentucky work in cooperation with the Thoroughbred
Retirement Foundation to re-train former racehorses as pleasure
mounts and find them new homes. Horses are also used in camps and
programs for young people with emotional difficulties.