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The horse (''Equus ferus caballus'') is a
domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that sec ...
one-toed hoofed mammal. It belongs to the taxonomic family
Equidae Equidae (sometimes known as the horse family) is the of s and related animals, including the extant horses, s, and s, and many other known only from s. All species are in the ', which originated in North America. Equidae belongs to the order ...
and is one of two
extant Extant is the opposite of the word extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the endling, last individual o ...
subspecies In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactio ...
of
''Equus ferus''
''Equus ferus''
. The horse
evolved Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...
over the past 45 to 55 million years from ''
Eohippus ''Eohippus'' is an extinct genus of small equid ungulates. The only species is ''E. angustidens'', which was long considered a species of ''Hyracotherium''. Its remains have been identified in North America and date to the Early Eocene (Ypresian ...

Eohippus
'', a small multi-toed creature, into the large, single-toed animal of today. Humans began domesticating horses around 4000 BC, and their
domestication Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that sec ...
is believed to have been widespread by 3000 BC. Specifically, horses in the subspecies ''caballus'' are domesticated, although some domesticated populations live in the wild as
feral horse A feral horse is a free-roaming horse The horse (''Equus ferus caballus'') is a domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over t ...
s. However, these feral populations are not true
wild horse The wild horse (''Equus ferus'') is a species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular ...

wild horse
s, as this term is used to describe horses that have never been domesticated. There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from
anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, ...
to life stages, size,
colors Color (American English), or colour (English in the Commonwealth of Nations, Commonwealth English), is the characteristic of color vision, visual perception described through color ''categories'', with names such as red, orange (colour), ora ...
,
markings Marking may refer to: Symbols Marking may refer to human-made symbols and annotations in several contexts: On vehicles * Aircraft marking * Emergency vehicle equipment markings ** Battenburg markings, emergency vehicle patterns * Vehicle markin ...
,
breeds A breed is a specific group of domestic animals having homogeneous Homogeneity and heterogeneity are concepts often used in the Science, sciences and statistics relating to the Uniformity (chemistry), uniformity of a Chemical substance, substa ...
,
locomotion Locomotion means the act or ability of an entity or person to transport or move oneself from place to place. Locomotion or Loco-Motion may refer to: Motion * Motion (physics) *Specific types of motion ** Animal locomotion *** Terrestrial locomoti ...
, and behavior. Horses are adapted to run, as this trait allows them to quickly escape predators. They also possess an excellent
sense of balance The sense of balance or equilibrioception is the perception of balance and spatial orientation. It helps prevent human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposa ...
and a strong
fight-or-flight response The fight-or-flight-or-freeze or the fight-flight response (also called hyperarousal or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack Attack may refer to: Warfare and comba ...
. Horses developed an unusual trait that is related to their need to be able to quickly flee from predators: they are able to sleep both standing up and lying down, with younger horses tending to sleep significantly more than adults. Female horses, called
mare A mare is an adult female Female (symbol: ♀) is the sex of an organism that produces the large non-mobile ovum, ova (egg cells), the type of gamete (sex cell) that fuses with the Sperm, male gamete during sexual reproduction. A female ...

mare
s, carry their young for approximately 11 months, and a young horse, called a
foal A foal is an equine up to one year old; this term is used mainly for horses. More specific terms are colt (horse), colt for a male foal and filly for a female foal, and are used until the horse is three or four. When the foal is nursing from its ...

foal
, can stand and run shortly following birth. Most domesticated horses begin training under a
saddle The saddle is a supportive structure for a rider of an animal, fastened to by a . The most common type is the equestrian saddle designed for a . However, specialized saddles have been created for en, s and other animals. It is not known p ...

saddle
or in a harness between the ages of two and four. They reach full adult development by age five, and they have an average lifespan between 25 and 30 years. Horse breeds are loosely divided into three categories based on general temperament There are spirited "hot bloods,” which are known for their speed and endurance. "Cold bloods,” such as
draft horse A draft horse (US), draught horse (UK) or dray horse (from the Old English ''dragan'' meaning "to draw or haul"; compare Dutch language, Dutch ''dragen'' and German language, German ''tragen'' meaning "to carry" and Danish language, Danish ''d ...

draft horse
s and some
ponies A pony is a small horse The horse (''Equus ferus caballus'') is a domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction ...

ponies
, are more tempered and suitable for slow, heavy work. “
Warmblood Warmbloods are a group of middle-weight horse types and breeds primarily originating in Europe and registered with organizations that are characterized by open studbook policy, studbook selectionStudbook selection is a process used in certain ...
s" developed from crosses between hot bloods and cold bloods, often focusing on creating breeds for specific riding purposes, particularly in Europe. There are more than 300 breeds of horse in the world today, developed for many different uses. Horses and humans interact in a wide variety of sport competitions and non-competitive recreational pursuits, as well as in working activities such as police work,
agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary behaviors su ...
, entertainment, and
therapy A therapy or medical treatment (often abbreviated tx, Tx, or Tx) is the attempted remediation of a health Health, according to the , is "a state of complete physical, and social and not merely the absence of and ".. (2006)''Constitution ...
. Horses were historically used in warfare, from which a wide variety of
riding
riding
and
driving Driving is the controlled operation and movement of a vehicle, including cars, motorcycles, trucks, buses, and bicycles. Permission to drive on public highways is granted based on a set of conditions being met and drivers are required to follow ...
techniques developed, using many different styles of
equipmentEquipment most commonly refers to a set of tool A tool is an object that can extend an individual's ability to modify features of the surrounding environment. Although many animals use simple tools, only human beings, whose use of stone tool ...
and methods of control. Many products are derived from horses, including meat, milk, hide, hair, bone, and pharmaceuticals extracted from the urine of pregnant mares. Humans provide domesticated horses with food, water, and shelter, as well as attention from specialists such as
veterinarian A veterinarian (vet), also known as a veterinary surgeon or veterinary physician, is a medical professional who practices veterinary medicine by treating diseases, disorders, managing reproductive health and injuries in non-human animal ...
s and
farrier : ''The Farrier'' Image:Panamanian_farrier_at_work.jpg, Rasping the Horse hoof, hoof A farrier is a specialist in equine hoof care, including the trimming and balancing of horse, horses' horse hoof, hooves and the placing of horseshoe, s ...

farrier
s.


Biology

Specific terms and specialized language are used to describe
equine anatomy Equine anatomy refers to the gross and microscopic The microscopic scale (from , ''mikrós'', "small" and σκοπέω, ''skopéō'' "look") is the scale of objects and events smaller than those that can easily be seen by the naked eye, requiri ...
, different life stages, and colors and breeds.


Lifespan and life stages

Depending on breed,
management Management (or managing) is the administration of an organization An organization, or organisation (English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-ise, -ize (-isation, -iz ...
, and environment, the modern domestic horse has a life expectancy between 25 to 30 years. Uncommonly, a few animals live into their 40s and, occasionally, beyond. The oldest verifiable record was " Old Billy," a 19th-century horse that lived to the age of 62. In modern times, Sugar Puff, who had been listed in ''
Guinness World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book A reference work is a work such ...
'' as the world's oldest living pony, died in 2007 at age 56. Regardless of a horse or pony's actual birth date, for most competition purposes, a year is added to its age on January 1 of each year in the Northern Hemisphere and each August 1 in the Southern Hemisphere. The exception is in
endurance riding Endurance riding is an equestrianism, equestrian sport based on controlled long-distance races. It is one of the international competitions recognized by the International Federation for Equestrian Sports, FEI. There are endurance rides worldw ...

endurance riding
, where the minimum age to compete is based on the animal's actual calendar age. The following terminology is used to describe horses of various ages: ;
Foal A foal is an equine up to one year old; this term is used mainly for horses. More specific terms are colt (horse), colt for a male foal and filly for a female foal, and are used until the horse is three or four. When the foal is nursing from its ...

Foal
: A horse of either sex that is less than one year old. A nursing foal is sometimes called a ''suckling'', and a foal that has been weaned is called a ''weanling''. Ensminger, p. 418 Most domesticated foals are weaned at five to seven months of age, although foals can be weaned at four months with no adverse physical effects. ; Yearling : A horse of either sex that is between one and two years old. ; Colt : A male horse under the age of four. A common terminology error is to call any young horse a "colt," when the term actually only refers to young male horses. ;
Filly A filly is a female horse that is too young to be called a mare A mare is an adult female Female (symbol: ♀) is the sex of an organism, or a part of an organism, that produces non-mobile ovum, ova (egg cells). Barring rare medical condit ...

Filly
: A female horse under the age of four. ;
Mare A mare is an adult female Female (symbol: ♀) is the sex of an organism that produces the large non-mobile ovum, ova (egg cells), the type of gamete (sex cell) that fuses with the Sperm, male gamete during sexual reproduction. A female ...

Mare
: A female horse four years old and older. ;
Stallion A stallion is a male that has not been (). Stallions follow the and of their , but within that standard, the presence of s such as may give stallions a thicker, "cresty" neck, as well as a somewhat more muscular physique as compared to fema ...

Stallion
: A non-castrated male horse four years old and older. The term "horse" is sometimes used colloquially to refer specifically to a stallion. Ensminger, p. 420 ;
Gelding A gelding is a castration, castrated male horse or other equine, such as a pony, donkey or a mule. Castration, as well as the elimination of hormonally driven horse behavior, behavior associated with a stallion, allows a male equine to be calmer an ...
: A
castrated Castration (also known as orchiectomy or orchidectomy) is any action, surgical Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical or dental specialty t ...
male horse of any age. In
horse racing Horse racing is an equestrianism, equestrian performance sport, typically involving two or more horses ridden by jockeys (or sometimes driven without riders) over a set distance, for competition. It is one of the most ancient of all sports, ...

horse racing
, these definitions may differ: For example, in the British Isles,
Thoroughbred The Thoroughbred is a list of horse breeds, horse breed best known for its use in Thoroughbred horse race, horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only t ...

Thoroughbred
horse racing defines colts and fillies as less than five years old. However, Australian Thoroughbred racing defines colts and fillies as less than four years old.


Size and measurement

The height of horses is measured at the highest point of the
withers The withers is the ridge between the shoulder blades of an animal, typically a quadruped. In many species, it is the tallest point of the body. In horses and dogs, it is the standard place to measure the animal's height. In contrast, cattle are o ...

withers
, where the neck meets the
back The human back, also called the dorsum, is the large Posterior (anatomy), posterior area of the human body, rising from the top of the buttocks to the back of the neck. It is the surface anatomy, surface of the body opposite from the chest and th ...
. Whitaker, p. 77 This point is used because it is a stable point of the anatomy, unlike the head or neck, which move up and down in relation to the body of the horse. In English-speaking countries, the height of horses is often stated in units of
hands A hand is a prehensile, multi- fingered appendage located at the end of the forearm The forearm is the region of the upper limb between the Elbow-joint, elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, ...
and inches: one hand is equal to . The height is expressed as the number of full hands, followed by a
point Point or points may refer to: Places * Point, LewisImage:Point Western Isles NASA World Wind.png, Satellite image of Point Point ( gd, An Rubha), also known as the Eye Peninsula, is a peninsula some 11 km long in the Outer Hebrides (or Western I ...
, then the number of additional inches, and ending with the abbreviation "h" or "hh" (for "hands high"). Thus, a horse described as "15.2 h" is 15 hands plus 2 inches, for a total of in height. Ensminger, p. 51 The size of horses varies by breed, but also is influenced by
nutrition Nutrition is the biochemical Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: st ...
. Light riding horses usually range in height from and can weigh from . Larger riding horses usually start at about and often are as tall as , weighing from . Heavy or
draft horse A draft horse (US), draught horse (UK) or dray horse (from the Old English ''dragan'' meaning "to draw or haul"; compare Dutch language, Dutch ''dragen'' and German language, German ''tragen'' meaning "to carry" and Danish language, Danish ''d ...

draft horse
s are usually at least high and can be as tall as high. They can weigh from about . The largest horse in recorded history was probably a
Shire horse The Shire is a British breed of draught horse A draft horse (US), draught horse (UK) or dray horse (from the Old English ''dragan'' meaning "to draw or haul"; compare Dutch language, Dutch ''dragen'' and German language, German ''tragen' ...

Shire horse
named
Mammoth A mammoth is any species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organ ...
, who was born in 1848. He stood high and his peak weight was estimated at . Whitaker, p. 60 The record holder for the smallest horse ever is
Thumbelina Thumbelina ( da, Tommelise) is a literary fairy tale A fairy tale, fairytale, wonder tale, magic tale, fairy story or ''Märchen'' is an instance of a folklore genre that takes the form of a short story A short story is a piece of prose fi ...
, a fully mature
miniature horse Miniature horses are horses defined by their small height. They can be found in many nations, particularly in Europe and the Americas, and are the result of centuries of selective breeding File:Big and little dog 1.jpg, This Chihuahua (dog), Ch ...

miniature horse
affected by
dwarfism Dwarfism occurs when an organism is exceptionally small. In humans, it is sometimes defined as Short stature, an adult height of less than , regardless of sex; the average adult height among people with dwarfism is , although some individuals ...
. She was tall and weighed .


Ponies

Ponies A pony is a small horse The horse (''Equus ferus caballus'') is a domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction ...

Ponies
are taxonomically the same animals as horses. The distinction between a horse and pony is commonly drawn on the basis of height, especially for competition purposes. However, height alone is not dispositive; the difference between horses and ponies may also include aspects of
phenotype In genetics Genetics is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular inter ...

phenotype
, including conformation and temperament. The traditional standard for height of a horse or a pony at maturity is . An animal 14.2 h or over is usually considered to be a horse and one less than 14.2 h a pony, but there are many exceptions to the traditional standard. In Australia, ponies are considered to be those under . For competition in the
Western Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that ide ...

Western
division of the
United States Equestrian Federation The United States Equestrian Federation (USEF or US Equestrian) is the national governing body for most equestrian sports in the United States The United States of America (USA), commonly known as the United States (U.S. or US), or Amer ...
, the cutoff is . The
International Federation for Equestrian Sports The International Federation for Equestrian Sports (, FEI) is the international sport governing body, governing body of equestrianism, equestrian sports. The FEI headquarters are in Lausanne, Switzerland. An FEI code of conduct protects the wel ...
, the world governing body for horse sport, uses
metric METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) is a computer model Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of or th ...

metric
measurements and defines a pony as being any horse measuring less than at the withers without shoes, which is just over 14.2 h, and , or just over 14.2 h, with shoes. Height is not the sole criterion for distinguishing horses from ponies. Breed registries for horses that typically produce individuals both under and over 14.2 h consider all animals of that breed to be horses regardless of their height. Conversely, some pony breeds may have features in common with horses, and individual animals may occasionally mature at over 14.2 h, but are still considered to be ponies. 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 may have calmer temperaments than horses and also a high level of intelligence that may or may not be used to cooperate with human handlers. Small size, by itself, is not an exclusive determinant. For example, the
Shetland pony The Shetland pony is a Scottish breed A breed is a specific group of domestic animals having homogeneous appearance (phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. ...

Shetland pony
which averages , is considered a pony. Conversely, breeds such as the and other
miniature horse Miniature horses are horses defined by their small height. They can be found in many nations, particularly in Europe and the Americas, and are the result of centuries of selective breeding File:Big and little dog 1.jpg, This Chihuahua (dog), Ch ...

miniature horse
s, which can be no taller than , are classified by their registries as very small horses, not ponies.


Genetics

Horses have 64
chromosome A chromosome is a long DNA molecule with part or all of the genome, genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by Chaperone (protein), chaperone proteins, bind to and ...

chromosome
s. The horse genome was
sequenced In genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Mendel, Moravia, Moravian scientist ...

sequenced
in 2007. It contains 2.7 billion DNA
base pair A base pair (bp) is a fundamental unit of double-stranded nucleic acids Nucleic acids are biopolymer Biopolymers are natural polymers produced by the cells of Organism, living organisms. Biopolymers consist of monomeric units that are Covalent_ ...
s, which is larger than the dog genome, but smaller than the
human genome The human genome is a complete set of nucleic acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule found within individual Mitochondrial DNA, mitochondria. These are usually treated se ...

human genome
or the
bovine genome The genome In the fields of molecular biology and genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for ...
. The map is available to researchers.


Colors and markings

Horses exhibit a diverse array of coat colors and distinctive
markings Marking may refer to: Symbols Marking may refer to human-made symbols and annotations in several contexts: On vehicles * Aircraft marking * Emergency vehicle equipment markings ** Battenburg markings, emergency vehicle patterns * Vehicle markin ...
, described by a specialized vocabulary. Often, a horse is classified first by its coat color, before breed or sex. Horses of the same color may be distinguished from one another by white
markings Marking may refer to: Symbols Marking may refer to human-made symbols and annotations in several contexts: On vehicles * Aircraft marking * Emergency vehicle equipment markings ** Battenburg markings, emergency vehicle patterns * Vehicle markin ...
, which, along with various spotting patterns, are inherited separately from coat color. Many
genes In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
that create horse coat colors and patterns have been identified. Current genetic tests can identify at least 13 different
allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is one of two, or more, forms of a given gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance ...
s influencing coat color, and research continues to discover new genes linked to specific traits. The basic coat colors of
chestnut The chestnuts are the deciduous trees and shrubs in the genus ''Castanea'', in the beech family Fagaceae. They are native to temperate climate, temperate regions of the Northern Hemisphere. The name also refers to the edible nut (fruit), nut ...
and
black Black is a color which results from the absence or complete absorption Absorption may refer to: Chemistry and biology *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a rout ...

black
are determined by the
gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...

gene
controlled by the
Melanocortin 1 receptor The melanocortin 1 receptor (MC1R), also known as melanocyte-stimulating hormone receptor (MSHR), melanin-activating peptide receptor, or melanotropin receptor, is a G protein–coupled receptor that binds to a class of pituitary peptide hormones ...
, also known as the "extension gene" or "red factor," as its recessive form is "red" (chestnut) and its dominant form is black. Additional
gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...

gene
s control suppression of black color to
point coloration with a seal point coloration. Point coloration refers to Coat (animal), animal coat coloration with a pale body and relatively darker extremities, i.e. the face, ears, feet, tail, and (in males) scrotum. It is most recognized as the coloration of Si ...

point coloration
that results in a
bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface ...
, spotting patterns such as
pinto Pinto is a Portuguese Portuguese may refer to: * anything of, from, or related to the country and nation of Portugal Portugal (), officially the Portuguese Republic ( pt, República Portuguesa, links=no ), is a country located on the Iberia ...
or
leopard The leopard (''Panthera pardus'') is one of the five extant in the ', a member of the cat , . It occurs in a wide range in , in some parts of and , , and on the to and . It is listed as on the because leopard populations are threatened ...
,
dilution gene A dilution gene is any one of a number of gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecul ...
s such as
palomino Palomino is a genetic color in horse The horse (''Equus ferus caballus'') is a domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the ...

palomino
or
dun 250px, Ruined dun in Lewis ">Isle_of_Lewis.html" ;"title="Loch Steinacleit on Isle of Lewis">Lewis A dun is an ancient or medieval fort. In Ireland and Britain it is mainly a kind of hillfort and also a kind of Atlantic roundhouse. Etymolo ...
, as well as graying, and all the other factors that create the many possible coat colors found in horses. Horses that have a white coat color are often mislabeled; a horse that looks "white" is usually a middle-aged or older
gray Grey or gray (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American En ...
. Grays are born a darker shade, get lighter as they age, but usually keep black skin underneath their white hair coat (with the exception of pink skin under white
markings Marking may refer to: Symbols Marking may refer to human-made symbols and annotations in several contexts: On vehicles * Aircraft marking * Emergency vehicle equipment markings ** Battenburg markings, emergency vehicle patterns * Vehicle markin ...
). The only horses properly called
white White is the lightest color and is achromatic (having no hue). It is the color of snow, chalk, and milk, and is the opposite of black. White objects fully diffuse reflection, reflect and scattering, scatter all the visible spectrum, visible wa ...

white
are born with a predominantly white hair coat and pink skin, a fairly rare occurrence. Different and unrelated factors can produce white coat colors in horses, including several different alleles of
dominant white Dominant white (W) is a group of genetically Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Men ...
and the sabino-1 gene. However, there are no "
albino Albinism is the congenital absence of any pigmentation or colouration in a person, animal or plant, resulting in white hair, feathers, scales and skin and pink eyes in mammals, birds, reptiles, amphibians and fish and invertebrates as well. V ...
" horses, defined as having both pink skin and red eyes.


Reproduction and development

GestationGestation is the period of development during the carrying of an embryo An embryo is the early stage of development of a multicellular organism. In general, in organism In biology, an organism (from Ancient Greek, Greek: ὀργανι ...
lasts approximately 340 days, with an average range 320–370 days, Ensminger, p. 156 and usually results in one
foal A foal is an equine up to one year old; this term is used mainly for horses. More specific terms are colt (horse), colt for a male foal and filly for a female foal, and are used until the horse is three or four. When the foal is nursing from its ...

foal
; twins are rare. Horses are a precocial species, and foals are capable of standing and running within a short time following birth. Foals are usually born in the spring. The
estrous cycle The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the ...

estrous cycle
of a mare occurs roughly every 19–22 days and occurs from early spring into autumn. Most mares enter an ''anestrus'' period during the winter and thus do not cycle in this period. Ensminger, p. 150 Foals are generally
weaned Weaning is the process of gradually introducing an infant 222x222px, Eight-month-old sororal twin sisters An infant (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is the more formal or specialised synonym ...
from their mothers between four and six months of age. Horses, particularly colts, sometimes are physically capable of reproduction at about 18 months, but domesticated horses are rarely allowed to breed before the age of three, especially females. Horses four years old are considered mature, although the skeleton normally continues to develop until the age of six; maturation also depends on the horse's size, breed, sex, and quality of care. Larger horses have larger bones; therefore, not only do the bones take longer to form
bone tissue A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubit ...

bone tissue
, but the
epiphyseal plate The epiphyseal plate (or epiphysial plate, physis, or growth plate) is a hyaline cartilage Hyaline cartilage is the glass-like (hyaline) but translucent cartilage found on many joint surfaces. It is also most commonly found in the ribs, nose, la ...
s are larger and take longer to convert from
cartilage Cartilage (cartilaginous tissue) is a resilient and smooth elastic tissue Elastic is a word often used to describe or identify certain types of elastomer An elastomer is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-m ...

cartilage
to bone. These plates convert after the other parts of the bones, and are crucial to development. Depending on maturity, breed, and work expected, horses are usually put under saddle and
trained Image:Christer Fuglesang underwater EVA simulation for STS-116.jpg, An astronaut in training for an extravehicular activity mission using an underwater simulation environment on Earth. Training is teaching, or developing in oneself or others, any ...
to be ridden between the ages of two and four. Although
Thoroughbred The Thoroughbred is a list of horse breeds, horse breed best known for its use in Thoroughbred horse race, horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only t ...

Thoroughbred
race horses Horse racing is an equestrianism, equestrian performance sport, typically involving two or more horses ridden by jockeys (or sometimes driven without riders) over a set distance, for competition. It is one of the most ancient of all sports, ...

race horses
are put on the track as young as the age of two in some countries, horses specifically bred for sports such as
dressage Dressage ( or ; a French term, most commonly translated to mean "training") is a form of horse riding performed in exhibition and competition, as well as an art sometimes pursued solely for the sake of mastery. As an equestrian The word equestr ...
are generally not put under saddle until they are three or four years old, because their bones and muscles are not solidly developed. For
endurance riding Endurance riding is an equestrianism, equestrian sport based on controlled long-distance races. It is one of the international competitions recognized by the International Federation for Equestrian Sports, FEI. There are endurance rides worldw ...

endurance riding
competition, horses are not deemed mature enough to compete until they are a full 60 calendar months (five years) old.


Anatomy


Skeletal system

The horse skeleton averages 205 bones. A significant difference between the horse skeleton and that of a human is the lack of a
collarbone The clavicle, or collarbone, is a slender, S-shaped bone approximately 6 inches (15 cm) long bone that serves as a strut between the scapula, shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on t ...

collarbone
—the horse's
forelimbs A limb (from the Old English ''lim''), or extremity, is a jointed, or prehensile A prehensile tail. Prehensility is the quality of an appendage An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes fr ...
are attached to the
spinal column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, c ...

spinal column
by a powerful set of muscles, tendons, and ligaments that attach the
shoulder blade The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder mak ...

shoulder blade
to the torso. The horse's four legs and hooves are also unique 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 made up of the
carpal bones The carpal bones are the eight small bones that make up the wrist (or carpus) that connects the hand to the forearm. The term "carpus" is derived from the Latin wikt:carpus#Latin, carpus and the Greek language, Greek wikt:καρπός#Ancient Gree ...

carpal bones
that correspond to the human
wrist In human anatomy The human body is the structure of a human being Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification, classification and ...

wrist
. Similarly, the
hock Hock may refer to: Common meanings: * Hock (wine), a type of wine * Hock (anatomy), part of an animal's leg * To leave an item with a pawnbroker People: * Hock (surname) * Richard "Hock" Walsh (1948-1999), Canadian blues singer Other uses: * A ty ...
contains bones equivalent to those in the human
ankle The ankle, or the talocrural region, is the region where the foot The foot (plural: feet) is an anatomical Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and liv ...

ankle
and
heel The heel is the prominence at the posterior end of the . It is based on the projection of one bone, the or heel bone, behind the articulation of the bones of the lower . Structure To distribute the compressive forces exerted on the heel dur ...

heel
. The lower leg bones of a horse correspond to the bones of the human hand or foot, and the
fetlock and the pastern The is a part of the leg of a horse The horse (''Equus ferus caballus'') is a domesticated odd-toed ungulate mammal. It belongs to the taxonomic family Equidae and is one of two Extant taxon, extant subspecies of wild horse, ' ...
(incorrectly called the "ankle") is actually the proximal
sesamoid bone In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any ind ...
s between the
cannon A cannon is a large-caliber A 45 ACP hollowpoint (Federal Cartridge, Federal HST) with two .22 Long Rifle, 22 LR cartridges for comparison In gun A gun is a ranged weapon designed to use a shooting tube ( gun barrel) to launc ...
bones (a single equivalent to the human
metacarpal In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the located between the of the fingers and the of the , which forms the connection to the . The metacarpal bones are analogous to the in the foot. Structure T ...
or
metatarsal bones The metatarsal bones, or metatarsus are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges The phalanges (singular: ''phalanx'' ) are digital bone A bone is a Stiffness ...
) and the
proximal phalanges The phalanges (singular: ''phalanx'' ) are digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electronics is a field of electronics Elec ...
, 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, hair, bone,
tendon A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant ...

tendon
s,
ligament A ligament is the Connective tissue#Types, fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body incl ...

ligament
s,
cartilage Cartilage (cartilaginous tissue) is a resilient and smooth elastic tissue Elastic is a word often used to describe or identify certain types of elastomer An elastomer is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-m ...

cartilage
, and the assorted specialized tissues that make up the
hoof A hoof ( or ), plural hooves ( or ) or hoofs , is the tip of a toe Toes are the digits (fingers) of the foot of a tetrapod. Animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology) ...

hoof
. Ensminger, pp. 21–25


Hooves

The critical importance of the feet and legs is summed up by the traditional adage, "no foot, no horse". Ensminger, p. 367 The
horse hoof A horse hoof is a structure surrounding the distal phalanx The phalanx ( grc, φάλαγξ; plural phalanxes or phalanges, , ''phalanges'') was a rectangular mass military formation, usually composed entirely of heavy infantry armed with sp ...

horse hoof
begins with the
distal phalanges The phalanges (singular: ''phalanx'' ) are digital bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vertebrate skeleton in animals. Bones protect the various organs of the body, produce red blood cell ...
, the equivalent of the human fingertip or tip of the toe, surrounded by
cartilage Cartilage (cartilaginous tissue) is a resilient and smooth elastic tissue Elastic is a word often used to describe or identify certain types of elastomer An elastomer is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-m ...

cartilage
and other specialized, blood-rich soft tissues such as the laminae. The exterior hoof wall and horn of the sole is made of keratin, the same material as a human Nail (anatomy), fingernail. The end result is that a horse, weighing on average , travels on the same bones as would 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 Farrier'' Image:Panamanian_farrier_at_work.jpg, Rasping the Horse hoof, hoof A farrier is a specialist in equine hoof care, including the trimming and balancing of horse, horses' horse hoof, hooves and the placing of horseshoe, s ...

farrier
. The hoof continually grows, and in most domesticated horses needs to be trimmed (and horseshoes reset, if used) every five to eight weeks, though the hooves of horses in the wild wear down and regrow at a rate suitable for their terrain.


Teeth

Horses are adapted to grazing. In an adult horse, there are 12 incisors at the front of the mouth, adapted to biting off the grass or other vegetation. There are 24 teeth adapted for chewing, the premolars and Molar (tooth), molars, at the back of the mouth. Stallions and geldings have four additional teeth just behind the incisors, a type of Canine tooth, canine teeth called "tushes". Some horses, both male and female, will also develop one to four very small Vestigiality, vestigial teeth in front of the molars, known as "wolf" teeth, which are generally removed because they can interfere with the bit (horse), bit. There is an empty interdental space between the incisors and the molars where the bit rests directly on the gums, or "bars" of the horse's mouth when the horse is bridled. An estimate of a horse's age can be made from looking at its teeth. The teeth continue to erupt throughout life and are worn down by grazing. Therefore, the incisors show changes as the horse ages; they develop a distinct wear pattern, changes in tooth shape, and changes in the angle at which the chewing surfaces meet. This allows a very rough estimate of a horse's age, although diet and veterinary care can also affect the rate of tooth wear. Ensminger, pp. 46–50


Digestion

Horses are herbivores with a digestive system adapted to a forage diet of grasses and other plant material, consumed steadily throughout the day. Therefore, compared to humans, they have a relatively small stomach but very long intestines to facilitate a steady flow of nutrients. A horse will eat of food per day and, under normal use, drink of water. Horses are not ruminants, they have only one stomach, like humans, but unlike humans, they can utilize cellulose, a major component of grass. Horses are hindgut fermentation, hindgut fermenters. Cellulose fermentation by symbiotic bacteria occurs in the cecum, or "water gut", which food goes through before reaching the large intestine. Horses cannot Vomiting, vomit, so digestion problems can quickly cause horse colic, colic, a leading cause of death. Horses do not have a gallbladder; however, they seem to tolerate high amounts of fat in their diet despite lack of a gallbladder.


Senses

The horses' senses are based on their status as predation, prey animals, where they must be aware of their surroundings at all times. Ensminger, pp. 309–310 They have the largest eyes of any land mammal, and are lateral-eyed, meaning that their eyes are positioned on the sides of their heads. This means that horses have a range of vision of more than 350°, with approximately 65° of this being binocular vision and the remaining 285° monocular vision. Horses have excellent day and night vision, but they have two-color, or Dichromacy, dichromatic vision; their color vision is somewhat like color blindness, red-green color blindness in humans, where certain colors, especially red and related colors, appear as a shade of green. Their Olfaction, sense of smell, while much better than that of humans, is not quite as good as that of a dog. It is believed to play a key role in the social interactions of horses as well as detecting other key scents in the environment. Horses have two olfactory centers. The first system is in the nostrils and nasal cavity, which analyze a wide range of odors. The second, located under the nasal cavity, are the Vomeronasal organs, also called Jacobson's organs. These have a separate nerve pathway to the brain and appear to primarily analyze pheromones. A horse's hearing is good, and the Auricle (anatomy), pinna of each ear can rotate up to 180°, giving the potential for 360° hearing without having to move the head. Noise impacts the behavior of horses and certain kinds of noise may contribute to stress: A 2013 study in the UK indicated that stabled horses were calmest in a quiet setting, or if listening to country or classical music, but displayed signs of nervousness when listening to jazz or rock music. This study also recommended keeping music under a volume of 21 decibels. An Australian study found that stabled racehorses listening to talk radio had a higher rate of gastric ulcers than horses listening to music, and racehorses stabled where a radio was played had a higher overall rate of ulceration than horses stabled where there was no radio playing. Horses have a great sense of balance, due partly to their ability to feel their footing and partly to highly developed proprioception—the unconscious sense of where the body and limbs are at all times. A horse's Somatosensory system, sense of touch is well-developed. The most sensitive areas are around the eyes, ears, and nose. Horses are able to sense contact as subtle as an insect landing anywhere on the body. Horses have an advanced sense of taste, which allows them to sort through fodder and choose what they would most like to eat, and their Prehensility, prehensile lips can easily sort even small grains. Horses generally will not eat poisonous plants, however, there are exceptions; horses will occasionally eat toxic amounts of poisonous plants even when there is adequate healthy food.


Movement

File:Muybridge horse walking animated.gif, ''Walk'' File:Trot animated.gif, ''Trot'' File:Muybridge_horse_pacing_animated.gif, ''Pace'' File:Canter animated.gif, ''Canter'' File:Muybridge race horse animated.gif, ''Gallop'' , record: All horses move naturally with four basic horse gait, gaits:#Harris, Harris, p. 32 *the four-beat Horse gait#Walk, walk, which averages ; *the two-beat Trot, trot or jog at (faster for harness racing horses); *the Canter and gallop, canter or lope, a three-beat gait that is ; *the Canter and gallop, gallop, which averages ,#Harris, Harris, pp. 47–49 but the world record for a horse galloping over a short, sprint distance is . Besides these basic gaits, some horses perform a two-beat horse gait, pace, instead of the trot.#Harris, Harris, p. 50 There also are several four-beat 'ambling' gaits that are approximately the speed of a trot or pace, though smoother to ride. These include the lateral Ambling#Rack, rack, Ambling, running walk, and tölt as well as the diagonal Ambling gait, fox trot. Ambling gaits are often genetic in some breeds, known collectively as gaited horses. These horses replace the trot with one of the ambling gaits.#Harris, Harris, pp. 50–55


Behavior

Horses are prey animals with a strong
fight-or-flight response The fight-or-flight-or-freeze or the fight-flight response (also called hyperarousal or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack Attack may refer to: Warfare and comba ...
. Their first reaction to a threat is to startle and usually flee, although they will stand their ground and defend themselves when flight is impossible or if 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. Most light horse riding breeds were developed for speed, agility, alertness and endurance; natural qualities that extend from their wild ancestors. However, through selective breeding, some breeds of horses are quite docile, particularly certain draft horses. Horses are herd animals, with a clear hierarchy of rank, led by a dominant individual, usually a mare. They are also social creatures that 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 Social grooming, grooming, and body language. Many horses will become difficult to manage if they are isolated, but with training, horses can learn to accept a human as a companion, and thus be comfortable away from other horses. Ensminger, pp. 305–309 However, when confined with insufficient companionship, exercise, or stimulation, individuals may develop stable vices, an assortment of bad habits, mostly Stereotypy (non-human), stereotypies of psychological origin, that include wood chewing, wall kicking, "weaving" (rocking back and forth), and other problems.


Intelligence and learning

Studies have indicated that horses perform a number of Cognition, cognitive tasks on a daily basis, meeting mental challenges that include foraging, food procurement and identification of individuals within a Social structure, social system. They also have good Spatial visualization ability, spatial discrimination abilities. They are naturally curious and apt to investigate things they have not seen before. Studies have assessed equine intelligence in areas such as problem solving, speed of learning, and memory. Horses excel at simple learning, but also are able to use more advanced cognitive abilities that involve categorization and concept learning. They can learn using habituation, Desensitization (psychology), desensitization, classical conditioning, and operant conditioning, and positive and negative reinforcement. One study has indicated that horses can differentiate between "more or less" if the quantity involved is less than four. Domesticated horses may face greater mental challenges than wild horses, because they live in artificial environments that prevent instinctive behavior whilst also learning tasks that are not natural. Horses are animals of habit that respond well to regimentation, and respond best when the same routines and techniques are used consistently. One trainer believes that "intelligent" horses are reflections of intelligent trainers who effectively use response conditioning techniques and positive reinforcement to train in the style that best fits with an individual animal's natural inclinations.


Temperament

Horses are mammals, and as such are warm-blooded, or endothermic creatures, as opposed to cold-blooded, or poikilothermic animals. However, these words have developed a separate meaning in the context of equine terminology, used to describe temperament, not Thermoregulation, body temperature. For example, the "hot-bloods", such as many horse racing, race horses, exhibit more sensitivity and energy,#Belknap, Belknap, p. 255 while the "cold-bloods", such as most draft horse, draft breeds, are quieter and calmer.#Belknap, Belknap, p. 112 Sometimes "hot-bloods" are classified as "light horses" or "riding horses", Ensminger, pp. 71–73 with the "cold-bloods" classified as "draft horses" or "work horses". Ensminger, p. 84 "Hot blooded" breeds include "oriental horses" such as the Akhal-Teke, Arabian horse, Barb horse, Barb and now-extinct Turkoman horse, as well as the
Thoroughbred The Thoroughbred is a list of horse breeds, horse breed best known for its use in Thoroughbred horse race, horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only t ...

Thoroughbred
, a breed developed in England from the older oriental breeds. Hot bloods tend to be spirited, bold, and learn quickly. They are bred for agility and speed. They tend to be physically refined—thin-skinned, slim, and long-legged. The original oriental breeds were brought to Europe from the Middle East and North Africa when European breeders wished to infuse these traits into racing and light cavalry horses. Whitaker, p. 43 Whitaker, pp. 194–197 Muscular, heavy
draft horse A draft horse (US), draught horse (UK) or dray horse (from the Old English ''dragan'' meaning "to draw or haul"; compare Dutch language, Dutch ''dragen'' and German language, German ''tragen'' meaning "to carry" and Danish language, Danish ''d ...

draft horse
s are known as "cold bloods", as they are bred not only for strength, but also to have the calm, patient temperament needed to pull a plow or a heavy carriage full of people. They are sometimes nicknamed "gentle giants".#Price, Price, p. 15 Well-known draft breeds include the Belgian horse, Belgian and the Clydesdale horse, Clydesdale. Some, like the Percheron, are lighter and livelier, developed to pull carriages or to plow large fields in drier climates.#Bongianni, Bongianni, entry 87 Others, such as the Shire horse, Shire, are slower and more powerful, bred to plow fields with heavy, clay-based soils. Ensminger, pp. 124–125 The cold-blooded group also includes some pony breeds. "
Warmblood Warmbloods are a group of middle-weight horse types and breeds primarily originating in Europe and registered with organizations that are characterized by open studbook policy, studbook selectionStudbook selection is a process used in certain ...
" breeds, such as the Trakehner or Hanoverian horse, Hanoverian, developed when European carriage and horses in warfare, war horses were crossed with Arabians or Thoroughbreds, producing a riding horse with more refinement than a draft horse, but greater size and milder temperament than a lighter breed. Certain pony breeds with warmblood characteristics have been developed for smaller riders. Warmbloods are considered a "light horse" or "riding horse". Today, the term "Warmblood" refers to a specific subset of sport horse breeds that are used for competition in
dressage Dressage ( or ; a French term, most commonly translated to mean "training") is a form of horse riding performed in exhibition and competition, as well as an art sometimes pursued solely for the sake of mastery. As an equestrian The word equestr ...
and show jumping. Strictly speaking, the term "Warmblood, warm blood" refers to any crossbreeding, cross between cold-blooded and hot-blooded breeds.#Belknap, Belknap, p. 523 Examples include breeds such as the Irish Draught or the Cleveland Bay. The term was once used to refer to breeds of light riding horse other than Thoroughbreds or Arabians, such as the Morgan horse.#Price, Price, p. 18


Sleep patterns

Horses are able to sleep both standing up and lying down. In an adaptation from life in the wild, horses are able to enter light sleep by using a "stay apparatus" in their legs, allowing them to doze without collapsing. Horses sleep better when in groups because some animals will sleep while others stand guard to watch for predators. A horse kept alone will not sleep well because its instincts are to keep a constant eye out for danger. Unlike humans, horses do not sleep in a solid, unbroken period of time, but take many short periods of rest. Horses spend four to fifteen hours a day in standing rest, and from a few minutes to several hours lying down. Total sleep time in a 24-hour period may range from several minutes to a couple of hours, mostly in short intervals of about 15 minutes each. Ensminger, p. 310. The average sleep time of a domestic horse is said to be 2.9 hours per day. Horses must lie down to reach Rapid eye movement sleep, 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, although horses may also suffer from that disorder.


Taxonomy and evolution

The horse Adaptation, adapted to survive in areas of wide-open terrain with sparse vegetation, surviving in an ecosystem where other large grazing animals, especially ruminants, could not. Horses and other equids are odd-toed ungulates of the Order (biology), order Perissodactyla, a group of mammals that was dominant during the Tertiary period. In the past, this order contained 14 Family (biology), families, but only three—
Equidae Equidae (sometimes known as the horse family) is the of s and related animals, including the extant horses, s, and s, and many other known only from s. All species are in the ', which originated in North America. Equidae belongs to the order ...
(the horse and related species), Tapiridae (the tapir), and Rhinocerotidae (the rhinoceroses)—have survived to the present day. The earliest known member of the family Equidae was the ''Hyracotherium'', which lived between 45 and 55 million years ago, during the Eocene period. It had 4 toes on each front foot, and 3 toes on each back foot. The extra toe on the front feet soon disappeared with the ''Mesohippus'', which lived 32 to 37 million years ago. Over time, the extra side toes shrank in size until they vanished. All that remains of them in modern horses is a set of small Vestigiality, vestigial bones on the leg below the knee, known informally as splint bones. Their legs also lengthened as their toes disappeared until they were a hooved animal capable of running at great speed. By about 5 million years ago, the modern ''Equus'' had evolved. Equid teeth also evolved from browsing on soft, tropical plants to adapt to browsing of drier plant material, then to grazing of tougher plains grasses. Thus proto-horses changed from leaf-eating forest-dwellers to grass-eating inhabitants of semi-arid regions worldwide, including the steppes of Eurasia and the Great Plains of North America. By about 15,000 years ago, ''Equus ferus'' was a widespread holarctic species. Horse bones from this time period, the late Pleistocene, are found in Europe, Eurasia, Beringia, and North America. Yet between 10,000 and 7,600 years ago, the horse became extinct in North America and rare elsewhere. The reasons for this extinction are not fully known, but one theory notes that extinction in North America paralleled human arrival. Another theory points to climate change, noting that approximately 12,500 years ago, the grasses characteristic of a steppe ecosystem gave way to shrub tundra, which was covered with unpalatable plants.


Wild species surviving into modern times

A truly
wild horse The wild horse (''Equus ferus'') is a species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular ...

wild horse
is a species or subspecies with no ancestors that were ever domesticated. Therefore, most "wild" horses today are actually
feral horse A feral horse is a free-roaming horse The horse (''Equus ferus caballus'') is a domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over t ...
s, animals that escaped or were turned loose from domestic herds and the descendants of those animals. Only two wild subspecies, the tarpan and the Przewalski's horse, survived into recorded history and only the latter survives today. The Przewalski's horse (''Equus ferus przewalskii''), named after the Russian explorer Nikolai Przhevalsky, is a rare Asian animal. It is also known as the Mongolian wild horse; Mongolian people know it as the ''taki'', and the Kyrgyz people call it a ''kirtag''. The subspecies was presumed extinct in the wild between 1969 and 1992, while a small breeding population survived in zoos around the world. In 1992, it was reestablished in the wild due to the conservation efforts of numerous zoos. Today, a small wild breeding population exists in Mongolia.#Dohner, Dohner, pp. 298–299 There are additional animals still maintained at zoos throughout the world. The question of whether the Przewalski's horse was never domesticated was challenged in 2018 when DNA studies of horses found at Botai culture cites revealed captured animals with DNA markers of an ancestor to the Przewalski's horse. The study concluded that the Botai animals appear to have been an independent domestication attempt involving a different wild population from all other domesticated horses. However, the question of whether all Przewalski's horses descend from this domesticated population is unresolved, as only one of seven modern Przewalski’s horses in the study shared this ancestry. The tarpan or European wild horse (''Equus ferus ferus'') was found in Europe and much of Asia. It survived into the historical era, but became Extinction, extinct in 1909, when the last captive died in a Russian zoo.#Dohner, Dohner, p. 300 Thus, the genetic line was lost. Attempts have been made to recreate the tarpan, which resulted in horses with outward physical similarities, but nonetheless descended from domesticated ancestors and not true wild horses. Periodically, populations of horses in isolated areas are speculated to be Relict (biology), relict populations of wild horses, but generally have been proven to be feral or domestic. For example, the Riwoche horse of Tibet was proposed as such, but testing did not reveal genetic differences from domesticated horses. Similarly, the Sorraia of Portugal was proposed as a direct descendant of the Tarpan based on shared characteristics,#Edwards, Edwards, pp. 104–105 but genetic studies have shown that the Sorraia is more closely related to other horse breeds and that the outward similarity is an unreliable measure of relatedness.


Other modern equids

Besides the horse, there are six other species of genus ''Equus'' in the Equidae family (biology), family. These are the ass or donkey, ''Equus asinus''; the mountain zebra, ''Equus zebra''; plains zebra, ''Equus quagga''; Grévy's Zebra, Grévy's zebra, ''Equus grevyi''; the kiang, ''Equus kiang''; and the onager, ''Equus hemionus''. Horses can crossbreed with other members of their genus. The most common Hybrid (biology), hybrid is the mule, a cross between a "jack" (male donkey) and a
mare A mare is an adult female Female (symbol: ♀) is the sex of an organism that produces the large non-mobile ovum, ova (egg cells), the type of gamete (sex cell) that fuses with the Sperm, male gamete during sexual reproduction. A female ...

mare
. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). Other hybrids include the zorse, a cross between a zebra and a horse. With rare exceptions, most hybrids are infertility, sterile and cannot reproduce.


Domestication

The horse was likeliest domesticated in central Asia before 3500 BC. . Two major sources of information are used to determine where and when the horse was first domesticated and how the domesticated horse spread around the world. The first source is based on Paleontology, palaeological and archaeological discoveries; the second source is a comparison of DNA obtained from modern horses to that from bones and teeth of ancient horse remains. The earliest archaeological evidence for the domestication of the horse comes from sites in Ukraine and Kazakhstan, dating to approximately 3500–4000 BC. By 3000 BC, the horse was completely domesticated and by 2000 BC there was a sharp increase in the number of horse bones found in human settlements in northwestern Europe, indicating the spread of domesticated horses throughout the continent. The most recent, but most irrefutable evidence of domestication comes from sites where horse remains were interred with chariots in graves of the Sintashta and Petrovka settlement, Petrovka cultures c. 2100 BC. A 2021 genetic study suggested that most modern domestic horses descend from the lower Volga region, Volga-Don region. Ancient DNA, Ancient horse genomes indicate that these populations influenced almost all local populations as they expanded rapidly throughout Eurasia, beginning about 4200 years ago. It also shows that certain adaptations were strongly selected for because of equestrianism, horse riding, and that equestrian material culture, including Sintashta culture, Sintashta spoke-wheeled chariots, spread with the horse. Domestication is also studied by using the genetic material of present-day horses and comparing it with the genetic material present in the bones and teeth of horse remains found in archaeological and palaeological excavations. The variation in the genetic material shows that very few wild stallions contributed to the domestic horse, while many mares were part of early domesticated herds. This is reflected in the difference in genetic variation between the DNA that is passed on along the paternal, or sire line (Y-chromosome) versus that passed on along the maternal, or dam line (mitochondrial DNA). There are very low levels of Y-chromosome variability, but a great deal of genetic variation in mitochondrial DNA. There is also regional variation in mitochondrial DNA due to the inclusion of wild mares in domestic herds. Another characteristic of domestication is an increase in coat color variation. In horses, this increased dramatically between 5000 and 3000 BC. Before the availability of DNA techniques to resolve the questions related to the domestication of the horse, various hypotheses were proposed. One classification was based on body types and conformation, suggesting the presence of four basic prototypes that had adapted to their environment prior to domestication. Another hypothesis held that the four prototypes originated from a single wild species and that all different body types were entirely a result of selective breeding after domestication. However, the lack of a detectable substructure in the horse has resulted in a rejection of both hypotheses.


Feral populations

Feral horses are born and live in the wild, but are descended from domesticated horses. Many populations of
feral horse A feral horse is a free-roaming horse The horse (''Equus ferus caballus'') is a domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over t ...
s exist throughout the world. Studies of feral herds have provided useful insights into the behavior of prehistoric horses, as well as greater understanding of the instincts and behaviors that drive horses that live in domesticated conditions. There are also semi-feral horses in many parts of the world, such as Dartmoor and the New Forest in the UK, where the animals are all privately owned but live for significant amounts of time in "wild" conditions on undeveloped, often public, lands. Owners of such animals often pay a fee for grazing rights.


Breeds

The concept of purebred bloodstock and a controlled, written breed registry has come to be particularly significant and important in modern times. Sometimes purebred horses are incorrectly or inaccurately called "thoroughbreds".
Thoroughbred The Thoroughbred is a list of horse breeds, horse breed best known for its use in Thoroughbred horse race, horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only t ...

Thoroughbred
is a specific breed of horse, while a "purebred" is a horse (or any other animal) with a defined Pedigree chart, pedigree recognized by a breed registry. Ensminger, p. 424 Horse breeds are groups of horses with distinctive characteristics that are transmitted consistently to their offspring, such as equine conformation, conformation, color, performance ability, or disposition. These inherited traits result from a combination of natural crosses and artificial selection methods. Horses have been Selective breeding, selectively bred since their
domestication Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that sec ...
. An early example of people who practiced selective horse breeding were the Bedouin, who had a reputation for careful practices, keeping extensive pedigrees of their Arabian horses and placing great value upon pure bloodlines. These pedigrees were originally transmitted via an oral tradition. In the 14th century, Carthusian monks of southern Spain kept meticulous pedigrees of bloodstock lineages still found today in the Andalusian horse. Breeds developed due to a need for "form to function", the necessity to develop certain characteristics in order to perform a particular type of work.#Sponenberg, Sponenberg, p. 155 Thus, a powerful but refined breed such as the Andalusian developed as riding horses with an aptitude for
dressage Dressage ( or ; a French term, most commonly translated to mean "training") is a form of horse riding performed in exhibition and competition, as well as an art sometimes pursued solely for the sake of mastery. As an equestrian The word equestr ...
. Heavy draft horses were developed out of a need to perform demanding farm work and pull heavy wagons. Other horse breeds had been developed specifically for light agricultural work, carriage and road work, various sport disciplines, or simply as pets.#Sponenberg, Sponenberg, p. 162 Some breeds developed through centuries of crossing other breeds, while others descended from a single foundation stock, foundation sire, or other limited or restricted foundation bloodstock. One of the earliest formal registries was General Stud Book for Thoroughbreds, which began in 1791 and traced back to the foundation bloodstock for the breed. There are more than 300 horse breeds in the world today.


Interaction with humans

Worldwide, horses play a role within human cultures and have done so for millennia. Horses are used for leisure activities, sports, and working purposes. The Food and Agriculture Organization (FAO) estimates that in 2008, there were almost 59,000,000 horses in the world, with around 33,500,000 in the Americas, 13,800,000 in Asia and 6,300,000 in Europe and smaller portions in Africa and Oceania. There are estimated to be 9,500,000 horses in the United States alone. The American Horse Council estimates that horse-related activities have a direct impact on the economy of the United States of over $39 billion, and when indirect spending is considered, the impact is over $102 billion. In a 2004 "poll" conducted by Animal Planet, more than 50,000 viewers from 73 countries voted for the horse as the world's 4th favorite animal. Communication between human and horse is paramount in any equestrian activity; to aid this process horses are usually ridden with a
saddle The saddle is a supportive structure for a rider of an animal, fastened to by a . The most common type is the equestrian saddle designed for a . However, specialized saddles have been created for en, s and other animals. It is not known p ...

saddle
on their backs to assist the rider with balance and positioning, and a bridle or related headgear to assist the rider in maintaining control. Sometimes horses are ridden without a saddle, and occasionally, horses are trained to perform without a bridle or other headgear. Many horses are also Driving (horse), driven, which requires a horse harness, harness, bridle, and some type of horse-drawn vehicle, vehicle.


Sport

Historically, equestrians honed their skills through games and races. Equestrian sports provided entertainment for crowds and honed the excellent horsemanship that was needed in battle. Many sports, such as
dressage Dressage ( or ; a French term, most commonly translated to mean "training") is a form of horse riding performed in exhibition and competition, as well as an art sometimes pursued solely for the sake of mastery. As an equestrian The word equestr ...
, eventing and show jumping, have origins in horses in warfare, military training, which were focused on control and balance of both horse and rider. Other sports, such as rodeo, developed from practical skills such as those needed on working ranches and Station (Australian agriculture), stations. Sport hunting from horseback evolved from earlier practical hunting techniques. Horse racing of all types evolved from impromptu competitions between riders or drivers. All forms of competition, requiring demanding and specialized skills from both horse and rider, resulted in the systematic development of specialized breeds and equipment for each sport. The popularity of equestrian sports through the centuries has resulted in the preservation of skills that would otherwise have disappeared after horses stopped being used in combat. Horses are trained to be ridden or driven in a variety of sporting competitions. Examples include show jumping,
dressage Dressage ( or ; a French term, most commonly translated to mean "training") is a form of horse riding performed in exhibition and competition, as well as an art sometimes pursued solely for the sake of mastery. As an equestrian The word equestr ...
, three-day eventing, combined driving, competitive driving,
endurance riding Endurance riding is an equestrianism, equestrian sport based on controlled long-distance races. It is one of the international competitions recognized by the International Federation for Equestrian Sports, FEI. There are endurance rides worldw ...

endurance riding
, Gymkhana (equestrian), gymkhana, rodeos, and fox hunting. Horse shows, which have their origins in medieval European fairs, are held around the world. They host a huge range of classes, covering all of the mounted and harness disciplines, as well as halter (horse show), "In-hand" classes where the horses are led, rather than ridden, to be evaluated on their conformation. The method of judging varies with the discipline, but winning usually depends on style and ability of both horse and rider. Sports such as polo 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 requires specialized training to participate, 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 task.#Edwards, Edwards, p. 360 Examples of these sports of partnership between human and horse include jousting, in which the main goal is for one rider to unseat the other, and buzkashi, a team game played throughout Central Asia, the aim being to capture a goat carcass while on horseback. Horse racing is an equestrian sport and major international industry, watched in almost every nation of the world. There are three types: "flat" racing; Steeplechase (horse 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. A major part of horse racing's economic importance lies in the Gambling#Parimutuel betting, gambling associated with it.


Work

There are certain jobs that horses do very well, and no technology has yet developed to fully replace them. For example, mounted police horses are still effective for certain types of patrol duties and 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 search and rescue, mounted teams to locate people, particularly hikers and children, and to provide disaster relief assistance. Horses can also be used in areas where it is necessary to avoid vehicular disruption to delicate soil, such as nature reserves. They may also be the only form of transport allowed in wilderness areas. Horses are quieter than motorized vehicles. Law enforcement officers such as park rangers or game wardens may use horses for patrols, and horses or mules may also be used for clearing trails or other work in areas of rough terrain where vehicles are less effective. Although machinery has replaced horses in many parts of the world, an estimated 100 million horses, donkeys and mules are still used for agriculture and transportation in less developed areas. This number includes around 27 million working animals in Africa alone. Some land management practices such as cultivating and logging can be efficiently performed with horses. In agriculture, less fossil fuel is used and increased environmental conservation occurs over time with the use of working animal, draft animals such as horses. Logging with horses can result in reduced damage to soil structure and less damage to trees due to more selective logging.


Warfare

Horses have been used in warfare for most of recorded history. The first archaeological evidence of horses used in warfare dates to between 4000 and 3000 BC, and the use of horses in warfare was widespread by the end of the Bronze Age. Whitaker, pp. 30–31 Although mechanization has largely replaced the horse as a weapon of war, horses are still seen today in limited military uses, mostly for ceremonial purposes, or for reconnaissance and transport activities in areas of rough terrain where motorized vehicles are ineffective. Horses have been used in the 21st century by the Janjaweed militias in the War in Darfur.


Entertainment and culture

Modern horses are often used to reenact many of their historical work purposes. Horses are used, complete with equipment that is authentic or a meticulously recreated replica, in various live action historical reenactments of specific periods of history, especially recreations of famous battles. Horses are also used to preserve cultural traditions and for ceremonial purposes. Countries such as the United Kingdom still use horse-drawn carriages to convey royalty and other VIPs to and from certain culturally significant events. Public exhibitions are another example, such as the Budweiser Clydesdales, seen in parades and other public settings, a team of
draft horse A draft horse (US), draught horse (UK) or dray horse (from the Old English ''dragan'' meaning "to draw or haul"; compare Dutch language, Dutch ''dragen'' and German language, German ''tragen'' meaning "to carry" and Danish language, Danish ''d ...

draft horse
s that pull a beer wagon similar to that used before the invention of the modern motorized truck. Horses are frequently used in television, films and literature. They are sometimes featured as a major character in films about particular animals, but also used as visual elements that assure the accuracy of historical stories. Both live horses and Cultural icon, iconic images of horses are used in advertising to promote a variety of products. The horse frequently appears in coats of arms in heraldry, in a variety of poses and equipment. The mythology, mythologies of many cultures, including Greco-Roman mythology, Greco-Roman, Hindu mythology, Hindu, Islamic mythology, Islamic, and Norse mythology, Norse, include references to both normal horses and those with wings or additional limbs, and multiple myths also call upon the horse to draw the chariots of the Moon and Sun. The horse also Horse in Chinese mythology, features prominently in Chinese mythology, and it appears in the 12-year cycle of animals in the Chinese astrology, Chinese zodiac related to the Chinese calendar.


Therapeutic use

People of all ages with physical and mental disabilities obtain beneficial results from an association with horses. Therapeutic riding is used to mentally and physically stimulate disabled persons and help them improve their lives through improved balance and coordination, increased self-confidence, and a greater feeling of freedom and independence. 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
International Federation for Equestrian Sports The International Federation for Equestrian Sports (, FEI) is the international sport governing body, governing body of equestrianism, equestrian sports. The FEI headquarters are in Lausanne, Switzerland. An FEI code of conduct protects the wel ...
(FEI). Hippotherapy and therapeutic horseback riding are names for different physical, occupational, and speech therapy treatment strategies that utilize equine movement. In hippotherapy, a therapist uses the horse's movement to improve their patient's cognitive, coordination, balance, and fine motor skills, whereas therapeutic horseback riding uses specific riding skills. Horses also provide psychological benefits to people whether they actually ride or not. "Equine-assisted" or "equine-facilitated" therapy is a form of experiential psychotherapy that uses horses as companion animals to assist people with mental illness, including anxiety disorders, psychotic disorders, mood disorders, behavioral difficulties, and those who are going through major life changes. There are also experimental programs using horses in prison settings. Exposure to horses appears to improve the behavior of inmates and help reduce recidivism when they leave.


Products

Horses are raw material for many products made by humans throughout history, including byproducts from the horse slaughter, slaughter of horses as well as materials collected from living horses. Products collected from living horses include mare's milk, used by people with large horse herds, such as the Mongols, who let it ferment to produce kumis. Horse blood was once used as food by the Mongols and other nomadic tribes, who found it a convenient source of nutrition when traveling. Drinking their own horses' blood allowed the Mongols to ride for extended periods of time without stopping to eat. The drug Premarin is a mixture of estrogens extracted from the urine of pregnant mares (pregnant mares' urine), and was previously a widely used drug for hormone replacement therapy. The tail hair of horses can be used for making bow (music), bows for string instruments such as the violin, viola, cello, and double bass. Horse meat has been used as food for humans and carnivore, carnivorous animals throughout the ages. Approximately 5 million horses are slaughtered each year for meat worldwide. It is eaten in many parts of the world, though consumption is taboo in some cultures, and a subject of political controversy in others. Horsehide leather has been used for boots, gloves, A-2 jacket, jackets, Baseball (ball), baseballs, and baseball gloves. Horse hooves can also be used to produce animal glue. Horse bones can be used to make implements. Specifically, in Italian cuisine, the horse tibia is sharpened into a probe called a ''spinto'', which is used to test the readiness of a (pig) ham as it cures. In Asia, the saba is a horsehide vessel used in the production of kumis.


Care

Horses are grazing animals, and their major source of nutrients is good-quality forage from hay or pasture. They can consume approximately 2% to 2.5% of their body weight in dry feed each day. Therefore, a adult horse could eat up to of food. Sometimes, concentrated feed such as Cereal, grain is fed in addition to pasture or hay, especially when the animal is very active. When grain is fed, equine nutritionists recommend that 50% or more of the animal's diet by weight should still be forage. Horses require a plentiful supply of clean water, a minimum of to 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 routine
hoof A hoof ( or ), plural hooves ( or ) or hoofs , is the tip of a toe Toes are the digits (fingers) of the foot of a tetrapod. Animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology) ...

hoof
care from a
farrier : ''The Farrier'' Image:Panamanian_farrier_at_work.jpg, Rasping the Horse hoof, hoof A farrier is a specialist in equine hoof care, including the trimming and balancing of horse, horses' horse hoof, hooves and the placing of horseshoe, s ...

farrier
, as well as vaccinations to protect against various diseases, and horse teeth, dental examinations from a
veterinarian A veterinarian (vet), also known as a veterinary surgeon or veterinary physician, is a medical professional who practices veterinary medicine by treating diseases, disorders, managing reproductive health and injuries in non-human animal ...
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 agricultural fencing, fences to be safely contained. Regular horse grooming, grooming is also helpful to help the horse maintain good health of the hair coat and underlying skin.#Giffin, Giffin, p. 90


See also

* Glossary of equestrian terms * Lists of horse-related topics


References


Sources

* * * * * * * * * * * *


Further reading

*


External links


"Ancient horse bone yields oldest DNA sequence"
* * {{Authority control Horses, Animal-powered transport Mammals described in 1758 Taxa named by Carl Linnaeus Equus (genus) Herbivorous mammals Horse subspecies Livestock National symbols of Burkina Faso National symbols of Lesotho National symbols of Mongolia National symbols of Nigeria National symbols of Turkmenistan Pack animals Symbols of New Jersey