Filing Code 4700
Date Issued March 19 7 7
U.S. DEPARTMENT OF THE INTERIOR
Bureau of Land Management
U.S. DEPARTMENT OF AGRICULTURE
U.S. Forest Service
WILD, FREE-ROAMING HORSES - STATUS OF PRESENT KNOWLEDGE
by Mark Zarn, Thomas Heller and
Kay Collins, Research Biologist
Denver Public Library
no . 294 Additional copies of Technical Notes are ava
liable from DSC, Federal Center Building 50, Denver, Colo.. 80225
4u /, «5r66&5/T qL
TABLE OF CONTENTS
Species Description 1
Size of Horses 5
Length of Life 5
Aging Horses 5
Population Characteristics 7
Population Status 9
Origin and History of Wild Horses 11
Origin of Wild Horses 11
Domestication of the Horse 12
Influence of Horses on History 13
The Horse in America 14
The Wild Horse Controversy 15
Sexual Behavior in Females 17
Sexual Behavior in the Stallion . 19
Reactions of Other Horses to Mating 20
Food Habits 20
Smell and Taste 25
Tactile Sensations 27
Social Organization and Behavior 28
Family Groups 31
Home Range 32
Postures and Facial Expressions 35
i 2 f¥
TABLE OF CONTENTS (Cont'd)
Sleep and Rest 39
Eliminative Behavior 40
Scent or Visual Boundary Marking 41
Water and Watering Behavior 42
Foal Behavior 43
Coprophagy in Foals 45
Predation and Disease 45
Competition and Relationships with Other Animals . . 48
Relationships with Other Animals 48
Wild Horse Management 49
Population Management 49
Population Control 51
Methods of Capture 51
Management Plans 53
Current Problems 53
Advantages of Wild Horses 53
Disadvantages of Wild Horses 54
Research Needs ..... 54
Current Research 54
Designated Wild Horse Ranges 54
Legislation Concerning Wild Horses 55
Organizations Concerned With the Welfare of Wild
Literature Cited 66
Appendix 1 Labeled Points of the Horse
Appendix 2 Three Types of Lumbar Vertebrae Found in Wild Horses
Appendix 3 Coat Color in Horses
Appendix 4 Gaits of the Horse, Drawn from Cine Film
Appendix 5 Features of Equid Evolution: Skull, Foot Structure,
Dentition and Diet
Appendix 6 List of Plants Making up 2% or More of the Diet of
Wild Horses in the Western United States
Appendix 7 Historical Distribution of Horses
Appendix 8 Map Showing Distribution of Wild Horses in the
Western United States
The purpose of this report is to provide personnel of the U. S.
Forest Service and U. S. Bureau of Land Management with a
literature review and summary of available information on wild
The scientific and recorded factual information on America's
wild horses is extremely limited. Klingel (1972), who has
spent many years studying the wild Equidae of Africa, states
that, except for social organization, all members of the genus
are very much alike. As a result, many portions of this tech-
nical note were summarized from data on domestic horses or
from data on other members of the Equidae . Therefore, the
validity of much of the information as it applies to America's
wild horses will have to stand the test of future research.
Only a relatively small number of people know very much about
wild horses. Certain individuals such as ranchers and those
few who have chased them, lived near, or been around them all
their lives often possess a remarkable store of knowledge on
their habits and general ecology. Thus, there is a consider-
able amount of anecdotal information that cannot be quoted
because it cannot be verified.
The problems of management are extremely complicated. We are
not dealing with a homogenous population of wild animals. At
the extremes are those horses that have been in the wild for
many generations and are capable of surviving under the harshest
of conditions. At the other end are those animals only a step
or two away from domestication that have not as yet fully
adapted to their environment. Management of horses as truly
wild animals would consider little or no interference by man;
however, this approach could be hazardous and is almost an
impossibility under the increasing pressures for various land
uses. Other types of management, related to game animals or
to livestock, are hamstrung by lack of biological data and may
be restricted by special interest groups or the emotional issues
General . The family Equidae , to which the horse belongs,
also includes donkeys, zebras, onagers and all their ancestors
back to eohippus. All the living Equidae represent a single
genus, Equus , with six species. Domestic horses and their wild
relatives form one species; the asses, both domestic and wild,
another; the onagers a third; zebras comprise the other three
The genus Equus includes all members of the family Equidae
and their immediate ancestors during the last Ice Age. Equus
caballus includes only the domestic horse and wild relatives so
closely related to it that they are capable of interbreeding and
producing fertile offspring (Simpson, 1951).
The andulusian horse that came to America was reconstructed from
old paintings and records by Cabrera. The animal was small to
medium in type, rather close to the ground, had a wide chest,
ample barrel, a muscular, rather short neck, and a rounded
sloping croup with a low- set tail. The latter two character-
istics are also typical of Barb points (Simpson, 1951).
The Spanish Barb Wild Horse Research Farm describes the Barb:
it is small (under 14 hands) and weighs about 800 pounds. The
front legs join the deep narrow chest in a reversed V. The
withers are low. The ergots are small or non-existent, the
chestnuts small, smooth, and soft and do not peel as they do
on draft breeds. The croup is low with the back legs well under
it. The back is short with 17 pairs of ribs and either five
lumbar vertebrae or the sixth fused to the fifth. The head is
small, not over 18 inches from the pole to the end of the nasal
bone. The ears are small, rimmed with black; light hair grows
out of the center of the ear. The muzzle is also small and
has crescent-shaped nostrils.
Colors are solid, roan, or grulla, which shades from slate to
mouse brown. The mane, tail, hooves and legs below the knee
are black. The hair on the back of the legs grows in a curl
and comb .
The present-day wild horse, due to many years of cross breeding
with abandoned, lost or stolen domestic breeds is, in most
cases, little different than any other domestic light horse
(Beebe and Johnson, 1964). Ryden (1970) states that there are
only a few hundred pure-blooded descendants of the original
Spanish horses and these are in captivity in special registers
in North and South America. She also states that the Spanish
horse's traits often appear in animals that have as little as
3.0 percent Spanish ancestry.
The significance of the number of lumbar vertebrae to determine
whether a horse has Spanish ancestry or not is open to question.
Stecher (1962) studied the lateral joints in the caudal lumbar
region of horses. He examined the skeletal remains of 245
horses of nine species obtained from various sources. The
horses were classified according to whether they had five or
six lumbar vertebrae. Skeletal specimens included the domestic
horse, the arabian, the Shetland pony, Przewalski's horse, the
hybrid mule, two species of asses and two of zebras. The Shet-
land pony was the only species in which all samples (eight)
contained six lumbar vertebrae; the Hemoine ( Equus hemoinus ) ,
the Mongolian wild ass, was the only species in which all
samples (nine) contained five lumbar vertebrae. Skeletons of
ten arabians showed three with five and seven with six verte-
brae. Two domestic horses had five and one half, and one
Grevy's zebra ( Equus grevyi) had seven lumbar vertebrae.
Edwards (1970) states that arabian horses, regardless of their
purity, do not always have five lumbar vertebrae any more than
Przewalski's horse always had five or six. It depended on who
you were talking to.
Howell (1945) wrote that the American Museum of Natural History
stated in a letter to him that the proper number of lumbar
vertebrae for the arabian is five while that of other horses is
six. The statement was qualified by stating that the point
which constitutes a lumbar vertebrae is its transverse processes
whereas a dorsal vertebrae is determined by the attachments of
ribs in place of transverse processes. Therefore, it is safer
to say that arab horses have 23 dorso-lumbars while other
varieties have 24.
Feist (1971) and Hall (1972) reported skeletal examples of
three types of lumbar vertebrae in the Pryor Mountain horses.
The Barb type have five lumbar vertebrae and 17 pairs of ribs;
the Andulusian have five and a half, with the last three fused;
and the modern breeds of today (except the Arabian) have six
lumbar vertebrae with no fusion. Appendix 2 depicts three
types of lumbar vertebrae found in equids.
Colors . Since local color names vary from one geographical
area to another, it is difficult to portray true horse colors
The original Andulusian horse encompasses the entire range of
horse colors. Spotting occurs, but is not especially character-
istic (Simpson, 1951). Smith (1841) wrote that all South
American feral horses bore the stamp of the domesticated races
of old Spain. His personal observations indicated that they
were mostly of similar color though every color seen in Europe
existed among them. Grey, or shades of grey, were most common
in the northern mountain regions, and shades of bay in the
pampas. Black was the rarest color. Hoyt (1886), an old
mustanger, wrote that ninety percent of the feral horses on
the panhandle of Texas were bay, dark brown, or black, and that
other colors were rare. Cook (1919), writing in 1870, stated
that on the plains area east of the Rockies, color in wild
mustangs consisted of cream, buckskin or mouse and that black
stripes above the knees or hocks and along the middle of the
back from mane to tail commonly occurred. Worcester (1945, p.
416), in an historical review of Spanish horses among the
Indians, stated that David Thompson, an early explorer, commented
on hoof color in Indian horses: "The yellow hoof with white
hair is a brittle hoof and soon wears away; for this reason, as
much as possible, the natives take only black-hoofed horses on
their war expeditions."
Gremmel (1939), writing in the Journal of Heredity , stresses
physical differences in horse coat colors from an histological
point of view. He lists the basic colors and the patterns that
occur within these basics (see Appendix 3).
Dobie (1952) devoted a chapter to the dun color in wild horses
The dun and the stripe are always waiting to come
back. All colors but gray and roan are, in bio-
logical language, recessive to dun. I cannot draw up
tables of dates and numbers, but to me it is evident
that for three and a half centuries, say from 1520 to
1880, dun was progressively emerging over the American
continents among descendents of horses marked sparsely
by that color when Spaniards planted them. Before that
time selective breeding had driven the dun color into
hiding; feral life brought it back.
There is a wild coat pattern gene in horses. Przewalski's
horse is not uniform black but has a distinctly concealing
color. The general body color is a neutral gray but peripheral
areas, including mane, tail, dorsal stripe and legs, are black.
The primitive type coat color depends upon four dominant genes.
Recessive mutations have modified each of them. However, they
form the basis of domestic color varieties, many of which would
be unable to survive in wild populations because they lack
concealing value (Castle, 1954). Feist (1971) listed eight
basic colors for the Pryor Mountain horses. Variations to these
basics that appear on legs, manes or tails were classified as
secondary markings. Hall (1972, p. 19) noted that the Pryor
Mountain herd seemed to be reverting back to the original
mustang type. Among other characteristics he refers to color.
"The reversion of colors to the blue corn, buckskins, and bays
with line stripes down their back, along their withers and on
There are many reports that stallions often show color prefer-
ences for the mares they select for their harems and will reject
those whose color does not meet their requirements (Dobie, 1952;
Feist, 1971; Ryden, 1970). Since color vision has not been
scientifically established in horses (Hafez, e_t al, 1969;
Smythe, 1966), the selection of certain colored mares may be
based on brightness or intensity rather than hue.
Size of horses . There are no extensive records of wild
horse sizes or weights. The original Spanish horse was small,
rarely attaining 15 hands. Some of the Indian mounts reached
only 12 to 13 hands. Present-day stallions seldom exceed 1000
pounds, and mares may be as light as 700 pounds (Ryden, 1970).
In the Pryor Mountain herd, females averaged 600 to 750 pounds
and males, 800 to 850 pounds (Hall, 1972). Cook (1919), who
wrote of the period from 1870 to 1880, estimated that the
average wild horse weighed about 800 pounds. Schwartz (1949)
reported that wild horses sold to fox ranches and other outlets
that buy horses for slaughter averaged between 750 and 850
pounds but some of them weighed as much as 1250 pounds. Horses
from the North often weighed more than those from the South due
to more draft blood from escapees of the World War I period;
however, the horses in certain parts of Oregon were small,
averaging 800 pounds in weight. The Fort Apache herds, which
had as high a percentage of wild mustang blood as any, averaged
about 650 to 700 pounds (Wyman, 1945).
A factor affecting the growth of wild horses, and one of the
reasons many of them remain smaller than domestic horses, is
their restricted diet. They rarely eat grain like domestic
horses, and their diet is often deficient in minerals and
vitamins, plus the fact that salt and adequate water are not
always available to them (Beebe and Johnson, 1964). Other
writers also mention inadequate and poor quality of food as a
reason for the small size of wild horses (Ensminger, 1951; Hall,
1972; Ryden, 1970).
The maturation rate in wild horses is slower than in domestic
horses. Two- and three-year-old horses often appear to be
yearlings (Ryden, 1970; Hall, 1972).
Length of life in wild horses . There is little data on
the lifespan of horses in the wild state. Domestic horses
that reach their twenties are considered old; however, it is
not uncommon for horses to reach their thirties and some have
been recorded that survived past forty years of age (Simpson,
1951). The maximum life span of horses in the Pryor Mountains
is ten to fourteen years and their maximum breeding period is
five to six years (Hall, 1972). Dobie (1952) relates that
Black Kettle, a famous and legendary wild horse that was cap-
tured past his prime, lived to about thirty years of age.
Aging horses . The age of horses is generally determined
by the amount of wear of their teeth. The mature male has forty
teeth; a young animal, male or female, has twenty- four teeth.
The mature female lacks tushes and therefore has thirty-six
teeth. In horses up to five years of age the numbers of perma-
nent and milk teeth are noted. From six to twelve years, age
is estimated by the number of cups or indentations in the
incisor teeth. After twelve years, age may be judged by the
cross section and slant of the incisors. Learning to determine
age in horses is a matter of practical experience. When a
horse exceeds twelve years, even the most experienced investi-
gators have difficulty in determining accurate age (Ensminger,
1951). Horses that live in areas of sandy or gritty soils
show increased dental wear. Under these conditions a six- year-
old horse may appear to be ten years old (Bone, 1964).
Locomotion . It is only since the development of the camera
that man has learned accurately how a horse coordinates its
four legs during execution of the various speeds of movement.
Horsemen recognize as many as twelve gaits in horses, but these
are all variations of the walk, trot, pace and gallop. The pace
is included because a few horses pace naturally. The canter,
which is a slow gallop, usually has to be taught. The lope,
recognized by western horsemen, is a smooth gallop or canter
which sometimes verges on a four-beat rhythm similar to a run-
The walk has a four-beat cadence with the succession of foot-
falls being left-fore, right-hind, right-fore, left-hind. The
body is alternately supported on three and on two legs. The
trot is a faster gait with a two-beat cadence where the diagonal
legs move together so that the sequence of feet striking the
ground is left- fore, right-hind followed by right-fore, left-
hind. Twice in each stride there is an interval when all four
feet are off the ground. The pace has similar rhythm to the
trot but the two legs of the same side, not the diagonals, move
together. It is a slow, broken pace tending toward a walk.
The gallop is the horse's fastest gait and differs from the
others in not being symmetrical on the two sides. It may be
led either on one side or the other. The cadence is three
beat, with a broken rhythm that occurs as beat, pause, beat,
quick double beat, beat, pause, etc. The pause represents the
short period when all four feet are off the ground, which
occurs only once in each stride. The sequence of footfall for
the left lead is left-fore, right-hind, left-hind and right-fore,
the latter two almost together with the hind foot slightly
ahead. The right-hind foot is lifted almost immediately as the
left hind foot comes down and before the right fore foot strikes.
Normally, at no time are three of the horse's feet on the
ground. The right lead is a mirror image of the left lead. In
an extended gallop there may be four beats, as opposed hind
and fore feet strike at perceptible intervals; however, the
break after the placing of the lead foot still distinguishes
the cadence. Horses can be taught to lead either right or left
or to change from one lead to the other while galloping. This
is important if the animal is to turn rapidly, because a horse
making a sharp left turn on the right lead is liable to fall
(Simpson, 1951; Tricker and Tricker, 1966).
Few horses jump regularly unless they are taught. This may be
due in part to their lack of binocular vision which prevents
them from judging the correct take-off distances (Hafez et al,
Drawings from a motion picture strip (Appendix 4) depict leg
positions of the horse while walking, trotting and galloping.
Some of the properties of a collective group of organisms or
populations are density, birth rate, death rate, age distri-
bution, biotic potential, dispersion and growth form. Genetic
characteristics such as adaptiveness , reproductive fitness, and
persistence (leaving descendants over long periods of time) are
also directly related to populations (Odum, 1971).
There are three major age groups in a population, the pre-
reproductive, the reproductive and the post- reproductive. In
a rapidly growing population, growth may be exponential due to
a high birthrate and each successive generation will be more
numerous. This results graphically in a pyramid age structure.
The graphic representation of a stable population is bell shaped,
The pre-reproductive and reproductive age groups are fairly
equal in size and the post- reproductive age group remains small.
If the birth rate is drastically reduced the reproductive,
post- reproductive age groups increase proportionally which
results in an urn-shaped graph representative of a declining
population (Boughey, 1968).
Odum (1971) describes characteristics of populations in regard
to age structure. An expanding population contains a large
proportion of young animals; a stationary population a more
even distribution of age classes; a declining population a large
proportion of old individuals.
The population density of wild horses, like that of any other
animals, must be in tune with and not exceed the carrying
capacity of the available habitat. Other than this general
observation and the limited data that Hall (1972) and Feist
(1971) collected on the Pryor Mountain horses, there is no
scientific information available on optimum population levels,
the results of overcrowding, competition, or the effects of a
degrading habitat. However, there is evidence that wild horse
densities could be reduced, through improper management and
control, to a level that could lead to their extinction either
locally or nationally.
There is a critical population size that varies from species
to species. Once the population density of a particular species
goes below this level it is doomed to extinction regardless of
efforts to save it. Prime examples are the passenger pigeon
which died out completely even though hunting had ceased and
there were still several thousand remaining birds scattered
over North America; the Heath hen, although rigorously protected
(after the population level had become small) , suffered the
Since their social life plays an important part in locating
feeding areas, raising their young and defending against
enemies, gregarious animals such as the ungulates are particu-
larly susceptible to the danger of extinction when their density
reaches a certain level. A number of factors may determine
this critical population size. Three of the more important of
these are: (1) males fail to find females due to low density,
(2) courtship behavior is inhibited by local low population
density, (3) the remaining population is too small to resist
predators and competitors (Ziswiler, 1967). Erhenfeld (1972)
adds another factor: the population size may be too small for
reproduction to compensate for losses from disease, climatic
conditions, or natural disasters.
Distribution of Wild Horses
The public land administered by the Bureau of Land Management
and the U. S. Forest Service that contain habitat for wild
horses are located in Arizona, California, Colorado, Idaho,
Montana, Nevada, New Mexico, Utah and Wyoming. The largest
concentrations of wild horses are in Nevada, Wyoming and Oregon.
Their distribution is generally limited to areas where accessi-
bility is limited, population of humans is sparse, and the
terrain rugged. Their range is also limited by availability
of forage, water and the numbers of fences or barriers that
restrict movement. The total extent of wild horse habitat on
lands not federally administered is not known. Thousands of
acres of these lands are not fenced and the wild horses have
access to them.
Populations of wild horses in the grassland biome are small, a
few have been reported in New Mexico and in Montana. The
greatest numbers inhabit the cold desert and the pinon- juniper
type of the woodland-brushland biome. Seasonally, in some areas
they range into the montane coniferous forest biome. In general
this biome is too cold in the winter for the horses to remain
there year round. See map, appendix 8-.
The proceedings of the first National Advisory Board meeting
for wild horses and burros (January 1973) reported an estimated
total of 2000 horses on Forest Service controlled lands and
16,878 horses on Bureau of Land Management controlled lands.
Both agencies state that 1975 population estimates, as presented
below, are of much higher quality than their earlier data due
primarily to more intensive efforts and improved methods of
censusing. Bureau of Land Management controlled lands are
listed by state; Forest Service lands by forest region. Data
on state, private and other lands is not available. (See map,
Appendix 8) .
Bureau of Land Management Wild Horse Inventory Data as of May 1, 1975
(Prepared by Milton Frei, U.S. Bureau of Land Mgt., Denver, Colo.)
Estimates of Population
* Includes animals claimed, proof of ownership
still has to be determined under Section 5 of
the 1971 Wild Horse and Burro Act
National Forest Wild Free-Roaming Horse Inventory Data (Estimate)
(Adapted from a letter dated April 15, 1975, from the Assistant
Director for Environmental Coordination, U.S. Forest Service)
Region National Forest as of 1-1-75 Claimed
1 Custer 8
Apache- Si tgreaves
Region Total 234
Region Total 879
Malheur 174 44
Ochoco 60 1
Region Total 234 45
GRAND TOTAL 2,755 74
O rigin and History of Wild Horses
Origin . Present-day horses of all kinds have descended from
a small, four-toed, rodent-like creature whose name many people
are familiar with, eohippus, or the dawn horse. The correct
scientific name, however, is Hyracotherium . This came about
because early scientists (1838) did not recognize that the
fossil remains of a small animal found near Suffolk, England
was related to horses, and compared the remains to the Hyraxes,
which the fossils closely resembled. Hyraxes are comparable
in size and external appearance to rodents and lagomorphs. When
similar fossils were found in North America at a later date the
principle of evolution had become well established and they
were recognized as horse ancestors. Charles Marsh of Yale
University gave them the euphonius name, eohippus. Since
Hyracotherium is much the older of the two names, under the
rules of zoological nomenclature it is the correct one to use.
Eohippus lived at the same time in both Europe and North America,
appearing in both places at the very beginning of the Eocene.
No direct ancestors of eohippus have been found on either
continent. There were several species of eohippus which varied
greatly in size, the smallest being not much over 10 inches in
height at the shoulder, the largest about 20 inches. Four toes
occurred on the front foot of eohippus, each ending in a
separate small hoof. The hind foot had only three functional
toes. The animal was already distinctly herbivorous, with
teeth modified for browsing rather than grazing (Simpson, 1951).
In the beginning of the Cenozoic Era of geologic time (70 to 75
million years ago) the British Isles and North America were
attached as part of the supercontinent of Laurasia, which also
included Greenland and Europe north of the Alps and east to the
Himalayas. During the long period when Laurasia was separating,
animals were able to migrate back and forth on the land bridges
that still connected Europe and North America. During this time
eohippus evolved and occupied both North America and Europe.
Not long after this the continents separated and migration
ceased. In Europe for an unknown reason eohippus became extinct.
In North America through a period of about fifty million years
eohippus evolved into Mercyhippus , an animal with high crowned
teeth which permitted it to graze rather than browse. It was
also larger, about the size of a small pony of today.
After Mercyhippus there is a gap in the fossil records from
about six million years ago to about 600,000 B.C., during which
time Mercyhippus evolved into Equus caballus , the true horse,
having a single toe on each foot. No fossil remains of horses
have been found in North America for the pleistocene epoch, the
Great Ice Age. The scanty records that were available came
mostly from Eurasia. Perhaps when the ice melted, fossil records
were washed away in the huge floods that followed. Equus
caballus may have evolved from some of its North American
ancestors that crossed the land bridge which connected Alaska
and Siberia during this period. Changes in conditions which
are still unclear brought the horse back to North America about
600,000 B.C. Fossil records dating from this time to about
7000 B.C. have been found in many places on the North American
continent. After 7000 B.C., horses again vanished along with
several other species of large grasseaters. There was no such
extinction of species in Europe. As the ice sheet melted,
Europe warmed and the forests encroached on the grasslands.
Grazing herds were forced eastward onto the steppes of southern
Russia and western Asia. Tribes of early hunters followed the
herds, became semi-nomadic and by 5000 B.C. had hunting dogs
and had domesticated the onager (Asian wild ass) and reindeer
(Simpson, 1951; Haines, 1971). Appendix 5 depicts features of
Domestication of the horse . By about 4000 B.C. two, and
possibly three, species of E. caballus had developed in the
Eurasian grasslands. Around the Black and Caspian Seas the
"Tarpan" and in Mongolia or Manchuria Przewalski's horse had
developed. A third subspecies, depicted as a forest horse, was
larger than the other two and existed in Polish forests until
the middle of the eighteenth century. Disagreement exists as
to whether it was a true subspecies.
Truly wild horses were common from Europe through central Asia
in early historic times. The European breed called "Tarpan" is
now extinct and it is uncertain if Przewalski's horse survives
in pure form. There is general agreement, however, that the
"Tarpan" was the first domesticated horse.
Later, Indo-Europeans invaded the region from the southeast and
possibly tamed a few horses. By 4000 B.C. they were using
horses to pull carts. Horse culture spread north and east into
Mongolia and turned many tribes into nomads. About 2000 B.C.
tribesmen from the Asian steppes crossed the Iranian plateau
with horses and overran the entire near east. A thousand years
later horses appeared in North Africa, west to Gibraltar, and
north and west through Europe as far as Scandinavia, Spain,
France, and the British Isles. The earliest records of horses
in Greece appear about 1700 B.C., in Egypt, 1600 B.C. and in India,
1500 B.C. By 1000 B.C., and possibly earlier, they had reached
Spain. The first horses that were imported from north of the
Caucasus were small, stocky animals, more commonly used for
pulling carts and chariots than riding. Later the Egyptians
involved in trading and breeding horses crossed these with the
more fleet horses that came from the Libyans or Numidians of
There are several theories concerning the development of modern
horses. One of the most popular at present is that all the
light, fast, Mediterranean and mideastern horses arose from a
single original stock now represented by the Arabian. If this
is true, the Numidian horses now represented by the Barb (named
from Barbary, an old African country west of Libya) were of
common origin with the Arabian. The Barb and Arabian, however,
as far back as they can be traced, are of distinct types. They
are both light and fast, but the former lacks the wedge-shaped
head, the dished profile and protruding eyes of the Arabian.
Both supposedly have 23 lumbar vertebrae, whereas 24 is the
usual number in all other breeds .
A heavy horse capable of carrying armored knights was first
developed in Germany, France and the British Isles. The early
horse of Spain was a heavy breed similar to those used in
France and Germany. When the Moors invaded and conquered Spain,
the Spaniards recognized the superiority of Moor horses which
were mostly Barb with perhaps some mix of Arabian. They crossed
their own Norse Dun breed with the Barb-Arabian mixture. The
product, called the Jennet, was so superior that for the next
several centuries Spain was renowned for the quality of its
horses, especially those from the Andulusia area of Spain.
The Andulusian type is the breed that was first brought to
the new world by Spanish conquistadors. Later it escaped onto
our western plains and the pampas of South America and became
the wild horse of the West and of Argentina (Simpson, 1951;
Ryden, 1970; Haines, 1971).
Influence of horses on history . Since their domestication,
horses have had a profound influence on history. Perhaps the
most significant has been the use of horses in warfare. They
have been involved in every war up until recent times, and only
within the present century has the development of horses for
military use ceased to be the main concern of breeders.
The Mohammedan and Mongolian conquests were made possible by
horses. In the seventeenth century the Mohammedans were stopped
by the Franks only because the Franks were clad in armor and
mounted on heavy, strong horses. The Mongolians were never
really stopped; their empire collapsed because of its unwieldy
Horses since ancient time have been important sources of power
for agriculture and transportation, for recreation, as status
symbols or emblems of wealth and authority, for food, leather,
and other products. The horse is still essential as a source
of rural power and transportation in many countries.
The American nation was built on horsepower and even today, when
the horse is no longer essential, it remains a part of our
culture. The mechanized age lessened the importance of the
horse as a principle factor in American development, but it
still has use for riding, hunting, recreation and as an animal
that people like to be associated with (Simpson, 1951).
The horse in America . It is difficult to state flatly how
or where horses first escaped or were stolen from the Spaniards
and reverted to a wild state. On Columbus' second voyage in
1493 he landed horses from Andulusia in the West Indies. Ponce
de Leon brought horses from Cuba or Puerto Rico to the coast
of Florida in 1521. Cortez carried horses with him when he
discovered the Aztec civilization in 1519. Horses were intro-
duced into the pampas of South America by Pedro Mendoza in 1535.
However, it is likely that wild horses which later covered the
pampas came from Chile and not from the small number Mendoza
abandoned. During the early years of exploration, horses were
sent in nearly every ship leaving Spanish ports. The Spaniards
also established breeding farms in the West Indian colonies of
Cuba, Puerto Rico and Santo Domingo, and stocked them with the
finest stallions and brood mares that had been brought out of
Spain. So many horses were transported that Spain finally
placed an embargo on the animals because they lacked enough
horses for home use. At one critical point horses were in such
short supply that the breeding farms in the West Indies were
forced to import more Barbs from North Africa, thus the Barb
was once again introduced into the line (Simpson, 1951; Ryden,
1970; Haines, 1971).
Indian tribes in Texas and New Mexico were probably the first to
obtain horses. The Apaches and Comanches got horses by raiding
the Spanish camps; they sold or bartered horses to other tribes
as did Spanish and French traders. Soon horses spread to the
Navajos, Zunis, Utes, and other tribes in the Southwest and
thence to tribes in the southern plains and northern plains.
By 1750 even the Blackfoot Indians in Canada had horses (Smith,
There are no reliable estimates of the number of feral horses
in the U. S. during the late 1700 's to early 1800' s. This was
the time of maximum horse population. McKnight (1959) estimates
anywhere between 2 and 5 million. The greatest numbers occurred
in the Southwest, with the most densely populated ranges in
west central Texas.
The introduction of barbed wire and fencing marked the end of
the wild horses on the Great Plains and significantly reduced
their numbers elsewhere. At the end of the 19th century most
wild horse concentrations were to be found west of the Rocky
The Boer War in South Africa created a large demand for horses.
Thousands of wild horses were caught and shipped to Africa, and
since many died en route or were killed in action, the demand
continued until the war ended in 1902. During World War I,
amateur and professional horse hunters found they could sell
all the wild horses they could catch.
In the early 1920' s four new markets developed that helped fur-
ther decrease wild horse herds: the use of horse meat for
chicken feed, pet foods, human food and an increase in horse
use by southern farmers when cotton prices dropped and tractors
became too expensive. The demand was partly supplied by trained
mustangs captured from wild bands.
The blood of remaining wild herds was further diluted during
the depression of the thirties. Large numbers of marginal
farmers and ranchers went out of business. These early settlers,
unable to sell their domestic horses, released or abandoned
them. Many of these joined the roving bands of wild horses.
The passage of the Taylor Grazing Act in 1934 also affected
wild horses, since stockmen became reluctant to share their
assigned grazing areas with wild horses. As a result, ranchers,
professional horse catchers, and the federal agencies cooperated
on drives to remove the horses. When this Act became law it
was estimated that there were some 150,000 wild horses remaining
on public lands in the eleven western states.
World War II brought temporary relief but after the war, efforts
to rid the range of wild horses was again initiated. During
the late 1940' s and 50' s, over 100,000 horses were removed from
Nevada rangelands, while smaller numbers were removed from
other western ranges (Denhardt, 1948; McKnight, 1959; Smith,
1969; Ryden, 1970). (See historical distribution of wild
horses, Appendix 7)
The wild horse controversy . The controversy over wild
horses simmered for many years. Public concern for the plight
of the wild horse gradually increased as people became aware
that the methods of capture were barbarous, the treatment
brutal and inhumane, and the final product, pet or chicken food.
During the 1920' s chicken feed producers in California persuaded
the railroads to ship horses as "chicken feed" thus eliminating
the need for humane treatment during transit.
One of the results, and the primary one, was a rash of articles
and stories in national magazines and in the news media about
wild horses. Millions of people who had never heard of wild
horses were now concerned and they reacted by writing letters
to their elected representatives (McKnight, 1959).
Several different philosophies concerning wild horses emerged.
One group, including many stockmen and trained scientists do
not consider the wild horse wild. They claim it is a mixture
of many breeds of the domestic horse-- that the blood of the
original Spanish horse is so diluted as to be almost nonexistent.
They also consider it a nuisance and a pest. Another group
favors native wildlife and where there is competition they feel
that the horse should be removed or rigidly controlled. A
very large number of people view the wild horse as a symbol of
the old West and that all wild horses should remain wherever they
are. A more moderate group leans toward multiple use. They
feel that the wild lands are for the use of all animals and
that the condition of the land and vegetation has first prior-
ity but that there is a place for the wild horse. They are
strongly opposed to brutality or inhumane treatment when popu-
lations have to be controlled (Crain, 1973; McKnight, 1959).
As a result of continued public concern, Congress has passed
two federal laws to protect wild horses. Public Law 86-234, passed
in 1959, prohibits pollution of water holes for trapping and the
use of aircraft or motorized vehicles to capture or kill wild
horses. Public Law 92-195, passed in 1971, places wild horses
and burros roaming on national resource lands under the juris-
diction of the Secretaries of Interior and Agriculture for
protection, management and control. It provides a penalty for
harassing, capturing, killing or selling wild horses or burros
and prohibits the processing of either animal into any commercial
product. It also provides for the establishment of an advisory
board to make recommendations to the Secretaries on management
and protection of wild horses and burros. The above statute
omits national parks and monuments.
The first advisory board, composed of nine members, met on four
occasions during their initial year, 1973. Meetings were held
in Salt Lake City, Utah; Denver, Colorado; Billings, Montana;
and Lake Havasu City, Arizona. All of the meetings were open
to the public. The members of the first advisory board are
Dr. Charles Wayne Cook 4800 Venturi Lane
Fort Collins, CO 80521
Mrs. Velma Johnston 140 Greenstone Dr.
Reno, NV 89503
Mrs. Paul Twyne 629 River Bend Rd.
Great Falls, VA 22066
Dr. Roger Hungerford
University of Arizona
Tucson, AZ 85721
Mr. Ed Pierson
Mr. Ben Glading
Dr. Floyd W. Frank
Mr. Roy Young
Mr. Dean Prosser, Jr,
Laporte, CO 85035
1413 El Tejon Way
Sacramento, CA 95826
1395 Walenta Way
Moscow, ID 83843
P. 0. Box 588
Elko, NV 89801
P. 0. Box 206
Cheyenne, WY 82001
Sexual behavior in females . During diestrous, if the
stallion attempts to mount, the mare displays defensive reactions
varying from aggressiveness to disinterest. As estrous approaches,
the mare may allow the stallion to smell and bite her. When
ready to copulate, the tail is lifted and held to the side, the
pelvis lowered and the hind legs spread. The intensity of
estrous behavior varies between individual mares and peaks just
before ovulation (Hafez et al, 1969). The behavior of adult
pony mares in full estrous was usually passive after a stallion
had shown interest. They stand quietly with hind legs straddled,
tail raised and often turn their head to touch the stallion's
muzzle. On occasions they squeal, urinate in small amounts or
paw the air with the forefeet (Tyler, 1972).
Domestic mares generally show estrous at 15 to 24 months of age.
The estrous periods recur at approximate 21-day intervals within
a range of 18 to 27 days. The length of the estrous period
varies from 5 to 8 days but may be longer in early spring. The
average gestation period is 340 days plus or minus 30 days.
Postpartum estrous usually occurs seven to eleven days after
foaling (Ensminger, 1951).
Under domestication the average conception rate of horses is
less than 50 percent. In the wild state, when horses had access
to good forage and water it was not uncommon for the conception
rate to be as high as 90 percent (Ensminger, 1951). The method
of determining the conception rate for wild horses was not
Within the body of literature on horses, there is inconsistency
pertaining to the nature and length of the breeding seasons.
The terms "polyestrous" and "breeding season" are often mis-
interpreted. Mares can be classified into three categories,
monoestrous, true polyestrous and transitory polyestrous. Wild
breeds are monoestrous. They exhibit several estrous cycles
during a restricted breeding season that coincides with the
longest days of the year. Wild mares may show sexual receptivity
throughout the year but they do not necessarily breed all year
round (Berliner, 1958; Hafez et al, 1969). Clegg and Ganong
(1969) report that domestic mares will breed at any season if
they are well fed. When mares are maintained on grass they
frequently show anestrous during the winter. They suggest
that nutritional factors are partly responsible. The mare is
predominantly a spring breeder; therefore she would be expected
to respond to increasing rather than decreasing day length
(Clegg and Ganong, 1969). A wild mare will go barren until
the following year if she is not bred in the spring or early
summer (Feist, 1971).
Burkhardt (1947) studied the influence of light on the repro-
ductive activity of domestic mares. He divided anestrous mares
into four groups. One group received artificial illumination
to increase day length. Another group was exposed to ultra-
violet light applied to the flank and belly. The mares in this
latter group had their eyes hooded. Estrous appeared in the
group receiving extended day length about 30 days earlier than
the control. The estrous cycle of those receiving light on the
flank and belly was normal. The author suggested that since
irradiation of the ovaries did not alter the estrous cycle, the
receptor organ was probably the eye. Nishikawa et a_l (1952)
exposed anestrous mares to increased day length from mid-
November until the end of February. They concluded that light
was a factor but not the only one controlling reproductive
activity in mares.
Hall (1972) says that the majority of mares in the Pryor Mountain
herd do not enter estrous until they are three years old. He
does not think that these horses have adjusted their estrous
cycles to the optimum period for foal survival. He relates
reproductivity to nutrition since the first foals (1971 and
1972) were observed in April and the majority of the mares were
through foaling by mid-July. When the horses have been on
green spring forage a sufficient time for their nutritional
state to improve they enter estrous. Their reproductive period
starts at about four and ends at about nine years of age.
Tyler (1972) reported that most pony mares foaled for the first
time when three or four years old but some not until they were
five years old. Very few of the 141 mares that were 3 years
old or more foaled in each of the 3 years of study. Foaling
in alternate years was common; so were abortions during the late
autumn, winter and early spring.
Sexual behavior in the stallion . There are three distinct
phases of sexual behavior in the stallion: courtship, erection
and mounting, and intromission and ejaculation. Sex drive is
manifested throughout the year. Courtship is important for
successful mating because the stallion depends upon erotic
stimuli to achieve vascular engorgement of the penis. This is
elicited by visual, auditory, tactile, and olfactory sensory
modalities. The relative importance of these varies among
species (Hafez et al, 1962). During courtship the stallion,
after smelling the mare, exhibits the flehmen posture and some-
times snorts or whinnies and nibbles or licks the mare before
mounting (Hafez £t al, 1969; Feist, 1971; Tyler, 1972). True
precopulatory behavior of stallions was often very brief.
Usually it was longer with young mares than with older, more
experienced mares. The older mares also rejected sexual advances
by colts and bit or kicked at them when they attempted sniffing.
Adult stallions chased colts away from adult estrous mares but
allowed them to copulate with young females up to 4 years of
age (Tyler, 1972).
Blakeslee (1974) was told by the owners of the free-roaming
appaloosa horses that they had observed only one instance of a
foal being killed by a stallion, and this occurred in a fenced
enclosure. Tyler (1972) stated that three stallions were
probably responsible for the death of six foals and the injury
of several others. She attributed these actions to frustration-
induced aggression caused by mares (who were not in full estrous)
rejecting the stallions' sexual advances.
Proper copulatory patterns are apparent in many stallions at 10
to 12 months of age. However, domestic stallions are generally
not placed in service until three years of age (Enflminger, 1951;
Hafez et al, 1962). In the Pryor Mountain herd, Hall (1972)
states that the testes of stallions do not descend until they are
three years of age.
Reproductive activity in the stallion, like the mare, is also
influenced by light. Reduced light diminished the quantity
and quality of semen whereas increased light produced an
opposite reaction (Nishikawa &t_ _al, 1952).
Foaling . With normal presentation a domestic mare foals in
fifteen to thirty minutes. The foal is usually born while the
mare is lying on her side with her legs stretched out. In
normal birth the front feet with heels down appear first,
followed by the nose which rests on the front legs. The hind
legs and feet are last (Ensminger, 1951).
Blakeslee (1974) reported that she was advised by the owners of
the free- roaming appaloosa horses that any birth on the open
range lasting much longer than 10 minutes meant that the mare
was having difficulty. Tyler (1972) observed a pony birth that
was completed within 25 minutes from the time the mare lay down.
Appaloosa mares generally gave birth while lying in an upright
position with the forelegs stretched out in front and the body
weight resting on the sternum (Blakeslee, 1974). New Forest
ponies delivered while lying fully recumbent (Tyler, 1972).
Blakeslee (1974) stated that appaloosa mares showed no preference
for a birth site other than to tend to avoid the night grazing
area because most mares foaled at night. Birth sites with
respect to vegetation or topography were not determined because
all observed births were on the winter range which was flat to
rolling, and the surrounding vegetation similar. She also
reported that appaloosa mares almost without exception isolated
themselves before giving birth, and the dominant mares went
greater distances from the group than the subordinate mares.
Feist (1971) did not observe any births within the Pryor Mountain
herd but did find foal skeletons in secluded areas. Tyler (1972)
reported that pony mares chose a variety of birth sites, some-
times secluded, sometimes near their group companions or close
to busy roads. Dobie (1952) and Ryden (1971) stated that the
only time wild stallions permit a mare to leave the group is when
she is about to foal.
Dominant appaloosa mares spent longer times at the birth site
and did not rejoin their family groups with their foals as soon
as subordinate mares. Mares in their last month of pregnancy
or geldings sometimes adopted the foals of primiparous or
subordinate mares. When this occurred the foal, being unable
to nurse, usually died. Some parturient mares permit another
mare to accompany and remain near them at the birth site. This
associate is nearly always a mare without a foal of her own
Reaction of other horses to mating . Tyler (1972) observed
yearlings, foals and sometimes dominant pony mares attempt to
prevent mating by either kicking at the stud or estrous mare or
by placing themselves between the mare and stud. Feist (1971)
observed other mares kicking at both the estrous mare and stud,
and Blakeslee (1974) observed other mares kicking at the stud.
Neither writer reported interference by foals or yearlings.
Probably the most important change that occurred in horse
evolution was the transition from a browsing to a grazing
animal. The teeth of early horses were efficient for eating a
large variety of foods as long as the food was soft and did not
wear down the teeth too rapidly. Early horses could not have
lived on grass even if it were available because it would have
worn out their teeth at an early age. As grasses became more
abundant (determined from fossil grass seeds) many browsing
animals unable to adapt, disappeared. The horse exploited this
change by evolving teeth that permitted them to change from
browsing to grazing. The present tooth pattern of equids
developed during the Miocene and has not changed greatly since
that time. After the new type of dentition was developed,
horses could eat most any vegetable matter including harsh
prairie grasses. Three main changes occurred: tooth patterns
changed to permit grinding, crown height increased to give
longer life to the teeth, and a cementum layer developed. The
cement filled the valleys and pits in the teeth and prevented
food from lodging and decaying; it also prevented the brittle
enamel crests of the teeth from breaking. The tooth system of
the present-day horse is highly specialized for eating grass
which, due to its high silica content, is a very harsh food.
As a result, the teeth of horses wear down rapidly. As they
wear, the teeth in the upper jaw move down and those in the
lower jaw move up so that a grinding surface is maintained at
the same level. When the teeth are worn to the roots and can
no longer grind, the horse will starve. Generally, however,
most wild horses die of other causes before this occurs (Simpson,
As the teeth of horses changed, undoubtedly digestive adapta-
tions also occurred, but since fossil records leave no evidence
this cannot be substantiated (Simpson, 1951).
Although the horse is a grazer he can eat and apparently survive
on a wide variety of foods. In various parts of the world
horses are fed grapevines, leaves of lime, lawn clippings,
garden refuse, garbage, bamboo leaves, and even dried fish
The digestive tract of the horse is smaller than that of a
ruminant and is not able to handle as much roughage. However,
since bacterial action similar to that in a ruminant takes place
in the caecum and colon, the horse does not need high quality
protein in its diet. This is not true of young colts, however,
since much less bacterial synthesis takes place (Ensminger, 1951).
The esophageal and intestinal opening of the horse are close
together, thus water passes quickly through the stomach and
small intestine. No food leaves the horse's stomach until it
is about two thirds full. As the horse eats, partially digested
food passes out into the small intestine in a continuous stream--
as a result, up to three times the capacity of the stomach may
pass out during a large meal. Emptying of the stomach slows
only when eating stops, and the stomach is never empty unless
the horse has not eaten for several days. Some of the digested
food is absorbed by the stomach but most absorption takes place
in the intestines. Within the small intestine the food
remains quite fluid and passes through rapidly.
The large intestine is divided into five components: the
caecum, large colon, small colon, rectum, and anus. Some
bacterial action and synthesis of vitamins takes place in the
caecum, but the greater part of digestion, including bacterial
action and absorption of nutrients, occurs within the large
colon (Hanauer, 1973).
The efficiency of the extraction of protein from foods of
various composition is similar for cattle and horses (Glover
and Duthie, 1958). There are important differences, however,
in the mechanism of digestion between horses and ruminants.
The ruminant maximizes the use of protein at the expense of
energy. The mechanical and chemical breakdown of plant cells
within the rumen is so thorough that relatively complete
extraction of the cell contents takes place. This process of
recycling for efficiency limits the passage of food through
the digestive tract. When the ingested food contains large
quantities of lignified cell walls the rate of passage is
slowed and the overall assimilation of protein may be quite
low. Under these conditions the animal may not be able to meet
its maintenance requirements unless it has the opportunity to
selectively graze components of the vegetation that contain
cells with thin walls and a high concentration of protein.
In the horse, fermentation of cellulose occurs in the colon
and large intestine, but the simple stomach remains the prin-
cipal site of protein extraction. The slow process of cell
breakdown that occurs in the ruminant is avoided and proteins
are quickly assimilated as amino acids. The horse achieves
almost equal efficiency with the ruminant in protein extraction
through quantity rather than quality. Food passes through its
digestive system almost twice as fast as it does in a cow;
therefore, the horse can support itself on forage too low in
protein to support a cow or other large ruminant, but it must
maintain a much higher rate of intake (Bell, 1970, 1971).
In general the smaller the animal the higher is its metabolic
rate. However, there is a degree of overlap between ruminants
and non- ruminants from the effect of body size on metabolic
rate. For relative maintenance (per unit weight per unit time)
small animals need more protein and energy than large animals.
They will lose weight more rapidly and be less competitive than
a larger animal if they are both on a submaintenance diet. The
reverse is true for an absolute maintenance (per animal per
unit time) diet. With equal quality of food intake the smaller
animal needs less food and as a result has more time to eat
enough for maintenance. The smaller animal can thus afford to
be more selective in its grazing habits and survive on a
sparse food supply that would starve the larger animal (Bell,
The year-round food habits of present-day wild horses have
never been extensively studied. In some areas where these
animals still survive, their habitat includes rough terrain,
sparse vegetation and adverse climate. It is possible that
the food habits of these animals are considerably different
from the animals that live in less harsh environments.
Hansen (1975, personal communication) reports that he has been
unable to find a single scientific publication on the diet of
the domestic or wild horse on pasture or rangeland. His
studies indicate that, under ordinary range conditions, 80 to
95% of the diet (on a dry-weight basis) of wild horses consists
of grasses and grasslike plants and that they consume more
browse than they do forbs. Appendix 6 lists some of the plants
Hansen has found to be common in wild horse diets in the western
Captured wild horses of both Asia and America do not readily
change their dietary habits to include concentrated feeds as
do their domestic counterparts (Hafez et al, 1962).
Dobie (1952) wrote that captured wild horses preferred cotton-
wood bark to grain and that they were very adept at pawing
through snow for their food. Hall (1972) made random feeding
site observations during 1968 and 1969 on the Pryor Mountain
herd. The major food item during spring, summer and fall con-
sisted of grasses. During the winter they utilized brushy
species, primarily saltbush ( Atriplex spp.), rabbitbush
( Chrysothamnus spp.) and big sagebrush ( Artemisia tridentata ) ,
along with any remaining grass.
In Britain, Tyler (1972) conducted behavioral studies on the
semi-wild herds of New Forest ponies. The herds are annually
harvested for the sale of certain animals, primarily yearlings
and foals, and the numbers of stallions are controlled. Other
than this they lead a wild existence, remain free and forage
for themselves throughout the year.
Their habitat consisted of deciduous woodland, heathland, grass-
land, valley bogs, and open water in ponds, ditches and
The bulk of the ponies 1 food during the summer was purple moor
grass, Molinia caerulea , along with small amounts of Agrostis ,
Festuca , Lolium and Cynosurus spp. Certain animals spent much
time wading in ponds grazing Glyceria spp., Carex spp. and most
small flowering plants. Bracken ( Pteridium aquilinum ) was the
only other food plant eaten in quantity. Between autumn and
spring, leaves and shoots of brambles (Rubus spp.), oak ( Quercus
robar) and beech ( Fagus sylvatica ) were eaten.
The normal daily pattern of the ponies was completely disrupted
when acorns were abundant as they spent most of the day foraging
for these. In 1964 the deaths of 42 ponies were attributed to
poisoning from eating acorns. When snow was on the ground
leaves of holly ( Ilex aquifolium ) and gorse ( Ulex europaeus )
provided almost the only food. These plants were grazed as
high as the animals could reach (approximately 8 feet).
The author reported that when hay was fed during the winter
there were a few groups of ponies that never approached the
hay piles and apparently did not recognize it as food.
Feist (1971) spoke only qualitatively on feeding habits of the
Pryor Mountain herd. Grass was preferred but in short supply
so that the animals were forced to supplement their diet with
other types of vegetation. Where water was abundant they ate
marsh grasses, weeds and forbs. Among woody plants, he observed
horses grazing the new growth of saltbush, greasewood ( Sarcobatus
vermiculatus ) , black sage brush ( Artemisia nova ) and on rare
occasions Utah juniper ( Juniperus osteosperma ) and mountain
mahogany ( Cercocarpus spp.). He noted horses pawing up and
eating the roots of winter fat ( Eurotia lanata ) and two species
of milkvetch ( Astragalus kentrophyta and A. gilviflorus ) . He
also reported sighting a mature, an immature and a yearling
female eating old feces from a stud pile during the summer
Appaloosa horses grazed for 1% to 3 hours before resting, and
on the summer range they spent much less time grazing during the
day than they did on the winter range. They were observed
grazing practically all species of grass plus elk thistle
(Cirsium spp.) and lichens and bark from quaking aspen ( Populus
tremuloides ) . Although sagebrush, shrubby cinquefoil ( Potentilla
fruticosa L.) and prickly pear cactus ( Opuntia polycantha Haw.)
were abundant they were never observed eating these species
When short of grass, domestic horses will eat leaves of trees
and shrubs and peel bark from young trees (Smythe, 1966).
Colostrum, the milk secreted by the mare the first few days
after partruition, is very important to the newborn foal. It
is not only different in chemical composition from the mare's
normal milk but contains antibodies to protect against certain
infections, and it serves as a natural purgative (Ensminger,
Vision . The horse is color blind and sees the landscape
ahead as a mosaic of various shades of gray caused by differently
lighted areas. Its eyes are incapable of breaking up a visual
image into individual items such as trees, grass, fences, etc.
The horse recognizes movement through changes in brightness,
tone, and the relationship of the moving subject to fixed
objects. Any object that remains perfectly still may go
The eyes of the horse are set on the side of the head so that
each eye receives a different scene. When the images are
superimposed the horse views a flat panorama. The eye lens is
non-elastic and the retina is arranged on a slope with the
bottom of the retina nearer the lens than the top. Neither the
cornea nor the lens of the horse's eye is truly shaped, thus
horses suffer from astigmatism; they have trouble focusing on
a subject a little way ahead and therefore often mistake a
harmless object as something dangerous. To focus on objects
at different distances the horse raises or lowers its head so
that the correct part of the retina is on the subject. Although
the horse possesses eye muscles to turn the eye in various
directions, they are seldom used primarily because of the posi-
tions of the eye and the fact that the neck is long and moveable.
Generous movement of the head is absolutely necessary if the
horse is to focus its eyes properly. When grazing, the horse
is able to view objects from every direction by moving its head.
Objects to the rear can be seen between its legs. A horse sees
most and farthest when it stands still with head erect and the
forehead and muzzle perpendicular to the ground. In this
position it can probably see all the landscape for several
hundred yards around by alternate use of frontal and lateral
vision. Horses move the head into position to look straight
ahead and the ears point forward. When a horse is paying
attention to objects on either side of the body it cannot see
very well in front of the body; in like manner when it is
staring straight ahead it cannot see what goes on on either side
Smell and taste . It is often difficult to disassociate
taste from smell in horses. Some horses will accept a strong
smell and refuse on taste, whereas others will reject strong
smelling substances without tasting. Domestic horses have a
liking for salt, sugar, and honey. They dislike most strongly
aromatic substances such as peppermint, eucalyptus, thyme, and
fats or anything of a meaty nature.
The true nostrils of the horse open into the nasal chamber which
contains large turbinated bones that are very brittle and covered
with mucous membranes. The nasal surfaces contain areas of
closely packed smell buds and olfactory nerve endings. They
also have a false nostril which runs upward as a blind pouch.
Horses are nose breathers with the nostril size varying con-
siderably among individuals. They do not open their mouths or
drop the tongue until completely exhausted (Smythe, 1966).
The muzzle of the horse is soft skinned, flexible and capable
of receiving environmental stimuli. Sensory cells and nerve
endings embedded in the connective tissues of the lips and
nostrils plus the long bristling hairs that stick out in all
directions are each capable of receiving sensory stimuli. The
region of the lips and nose perform functions of the hand in
man. The nose of the zebra is far more useful for orientation
and warning against surprise attack than is the eye (Burkhardt
et al, 1967).
The soft palate of the horse is large and somewhat pendulous.
It is used to block the open end of the larynx to prevent
choking when the horse is eating or drinking. It may also drop
into the pharynx and limit mouth breathing when the horse is
exhausted or nearly so.
Stallions have an acute sense of smell and can smell a mare in
estrous at a considerable distance if she is upwind (Smythe,
The horse's ability to smell distant water has saved the lives
of many early riders. Old time mustangers, when following a
band of wild horses, were very careful not to change their
clothing because their odor would change. Most horses can
smell snakes, and there are reports of a horse that could track
deer. South American horses gallop about in the dark and avoid
the burrows of hundreds of Vizcacha ( Lagidium spp.) holes,
probably by smelling them (Dobie, 1952).
Domestic horses will eat a great variety of drugs one would
expect them to refuse. They are apparently unable to discrimi-
nate between edible and poisonous plants and, being unable to
vomit, they are unable to get rid of the poisonous ones (Hafez
et al, 1969).
Hearing . Horses hear over a great range of frequencies and
can pick up sounds too slight for human ears. They have the
advantage of a long neck and concave ears that can be moved in
any direction to not only detect sound but also to pinpoint the
origin. There appears to be a connection between the ears and
nose of the horse because when the ears prick the nostrils
dilate. When a horse's ears are laid back on the neck it is
either a sign of temper or an indication of stress such as
The pitch ranges of hearing in most domestic animals is known;
however, horses are an exception. There has been little
experimental work done on their hearing.
Horses communicate with each other and other animals with a
number of vocalizations and sounds. Mares communicate to their
foals with a wide variety of low- toned whinnies, each of which
appear to convey a different meaning (Smythe, 1966). Dobie
(1952) states that the scream of a stallion is one of the most
terrifying sounds in nature and constitutes a warning to all
other animals and stallions within hearing distance.
Domestic horses appreciate sounds from humans, and there are
many stories of grooms who became famous by their abilities to
calm frenzied horses by talking, whispering or hissing to them.
Highly strung horses are often excited or alarmed by sounds
that are unfamiliar such as escaping steam, fireworks, thunder,
or even the rustling of paper.
Horses can sense very slight ground vibrations through their
legs and feet. When grazing, these vibrations are felt through
the limbs, teeth, jaws and bones of the head. The footsteps
of a man can be picked up long before they become audible
(Smythe, 1966). South American gaucho horses which lived in a
semi-wild state expressed great fear of Indian attacks. They
would often come running home when an imminent Indian attack
was still a day's ride away. A few frontiersmen trained their
horses to fear the odor of Indians (Dobie, 1952).
Tactile sensations . In order to maintain its normal body
temperature of about 100.3° F., the horse sweats and shivers.
It has the ability to sweat at a moment's notice from exertion,
fear, or excitement. The muscular exertions expanded when
working or running hard in such a large animal makes this a
necessity. Sweat glands in the horse occur in the neck, certain
parts of the back, the shoulders, axillae, and groin; however,
there are no sweat glands in the skin of the limbs except
between the hind thighs. Foam forms on the body and limbs
after continued exertion when sweat pours from the suboriferous
skin ducts, and there is a considerable amount of heat loss
through water vapor from the breath.
The ability of the horse to fairly rattle his skin to dislodge
insects or when rising from the ground to remove adhering
particles from the skin is well known. This is made possible
by the panniculus muscle which covers the greater part of the
body beneath the skin. The same muscle is involved in shiver-
ing, which the horse uses to increase surface temperatures when
it is cold.
Many horses respond very rapidly and often vigorously to skin
stimuli; the neck and shoulders, the skin of the lower limbs
especially around the feet and the coronets, the heel at the
rear of the pastern, and the skin on the ribs and flanks are
very sensitive. Most horses appreciate scratching on the skin
of the withers and gentle patting of the neck and face (Smythe,
Horses have certain skin areas that are extremely sensitive to
certain irritants, either vapor, solids or liquids. These
include the lips and skin of the muzzle, the skin inside the
elbows, groin, beneath the tail, the eyelids and their con-
junctive areas, plus the skin surrounding the nasal openings
(Hafez et al, 1969).
Social Organization and Behavior
General . Behavioral and social studies of truly wild horses
are nonexistent, and it is only within the last decade or so
that very limited attempts to study the wild horses of the
American West has been attempted.
Some form of close aggregation of groups of individuals or
"clumping" is common among herbivores. Animals aggregate for
protection from predators, mating, and facility in feeding.
However, according to Allee's principle, each species has an
optimum aggregation value. Densities above or below this value
tend to act as factors in population regulation (Boughey, 1968).
The social organization of wild horses is different than that of
most ungulates. All wild horses belong to a harem or family
group controlled by a dominant male, with the exception of
adolescent males that have been ejected from the harem by the
lead stallion, which form into small bachelor groups or bands.
Any wild horse seen by itself is either an adolescent male, a
male that has reached maturity and is trying to capture its
own harem, or a crippled, diseased animal unable to keep up
with the group. Hall (1975) states that a lone animal normally
is an old stud that has lost his harem. He never observed one
of these older animals in a bachelor group.
Each harem also contains a top-ranking mare that governs daily
activity. She leads the group to forage and water and is second
to the stallion in command. Whenever the group runs to escape
danger this mare takes the lead with the stallion bringing up
the rear (Dobie, 1952; Ryden, 1970). Hall (1972) reported
during the 1971 roundup of the Pryor Mountain horse herd that
when a band was harassed, the lead stallion was the first to go
off by himself. This was observed repeatedly. He also commented
that the instinct to follow in wild horses was very strong. When
a band lost its lead mare the remaining horses were often
The stallion's functions are to breed, keep the group intact,
prevent social strife, defend against other males of the same
species, and defend against any danger that threatens the
family group (Dobie, 1952; Ryden, 1970). Hall (1975) doubts
that the stallion will defend against any danger threatening
the group other than that posed by a competing stallion.
The protection and defense of a family group or harem by any
animal has three main functions. It distributes the animals
over the available environment, provides for the selection of
the strongest male by fighting (which affects the progeny), and
offers defense for the young (Lorenz, 1963).
Stallions control their groups by biting, kicking, and by a
threatening posture that includes elongating and arching the
neck and weaving the head back and forth. This threatening
posture is generally all that is necessary to make any member
of the group obey (Ryden, 1970).
Klingel (1972) states that a number of behavioral patterns are
almost identical in the Equidae . In their social organization,
however, there are considerable differences; two basic patterns
exist. The plains zebra (E. quagga ) , the mountain zebra (E.
zebra ) , the horse (E. przewalski ) and possibly the asiatic wild
ass (E. hemionus) live in harem groups composed of one to several
mares led by a dominant stallion. Surplus stallions form groups
of their own. The young leave the family group in a set pattern,
and do not establish territories. These social units move
freely over their home ranges which they share peacefully with
conspecifics. In opposition to this type of social behavior,
Grevy's zebra (E_. grevyi ) and the wild ass (E. af ricanus ) dis-
play no personal attachments between any individuals other than
mare-foal relationships. The animals often occur singly, in
stallion groups, mare groups, mare-foal groups and mixed herds.
The groups are variable and their composition may change at any
time. Some of the stallions are territorial but do not prevent
conspecifics from entering their territory as long as they do
not interfere with the mating activities of the territorial
stallion. They only defend territories when there is an estrous
mare near the boundary. Only the territorial male will court a
mare at any one time because all the other males are subordinate
to him. There is no order of dominance or leadership among
adults. All adult individuals seem to be of equally low rank
and only the mare and her foal ever search for each other when
they are separated.
Aggressiveness . Individual aggressiveness in vertebrates
towards members of the same species is expressed in two ways:
defense of a given territory and the establishment of hier-
archies of precedence within social groups (Collias, 1970).
Due to the potential danger, most mammals avoid fighting if
possible. They generally resort first to aggressive display
and threats which often result in submission or appeasement
by the weaker opponent. Fighting seldom results in the death
of the loser unless the environment is overcrowded. An unsound
environment distorts the normal patterns of social behavior
(Scott, 1958). There are many examples of increased aggression
in crowded populations (Mathews, 1964). Crowding may also
produce a reverse reaction when it exceeds certain levels, and
animals may become passive and nonreactive (Southwick, 1970).
When wild horses reached their peak numbers during the last
century they often existed in crowded environments (Dobie, 1952),
In the Pryor Mountains, Hall (1972) reports that they still do,
which may account for the sometimes conflicting reports on
behavioral patterns at different times and places among wild
Many stallions are very domineering and keep close watch over
members of their group. Only during foaling will the stud
permit a mare to leave the band so that she can find a secluded
spot to foal (Dobie, 1952; Ryden, 1970). Hall (1972) reported
that some mares appeared to be fickle and were observed away
from their group for several days at a time. He also observed
extreme variation in the amount of time mares remained away from
the group during foaling (one day to several weeks). He attrib-
uted this variation to the strength of her bonds with the group.
If a mare with foal falls behind during an escape attempt the
stud may kill the foal by breaking its neck or he may force the
mare to abandon it. Studs also may often display threatening
gestures toward humans while the band is escaping. If another
stallion approaches the harem, the two stallions posture with
tails arched and heads pressed together staring at each other
until one backs down. If a fight ensues, they rear on their
hind legs, ears back and mouth agape. They strike with their
forefeet, bite for the jugular and often wheel and kick. During
the encounter they shriek, snort and scream. If one falls he
is stomped by the other. The winning stud seldom chases his
rival for more than a short distance (Dobie, 1952; Hall, 1972;
The intolerance for other males is greater during the breeding
season than it is at other times and reaches its lowest ebb
during the winter months (Hall, 1972).
All age classes of appaloosas threaten foals, but adult mares
are more aggressive toward foals not their own than are other
age groups (Blakeslee, 1974). All pony mares were aggressive
to strange foals and either threatened, kicked or bit them if
they came close (Tyler, 1972). Feist (1971) did not find any
consistent pattern of dominant hierarchy among the individual
mares of the various bands in the Pryor Mountain horses. Ex-
hibition of authority by one mare over another appeared to
depend on a particular situation and the superior dominance of
the stud overshadowed any formation of hierarchy among the
mares. Hall (1972), who spent a great deal more time with
these horses than Feist, reported a definite recognizable
hierarchy within each band and that, once established, it
remained fairly constant. Blakeslee (1974) stated that, among
adult females, neither age, size, weight, nor length of time in
the group determined dominance. The only observed character-
istic common to dominant mares was their tendency to be aggres-
sive. Tyler (1972) noted kicking fights between pony mares on
several occasions, presumably to establish or maintain dominance.
The rank order of mares, once established, was very stable and
a mare dominant over another mare in one situation was never
subordinate to the same mare in another situation. It was
also noted that a subordinate mare rarely challenged a previously
established more dominant mare. The length of time a mare lived
in a group was not important in determining rank, and a foal
shared status with its mother only when it was close to her.
The rank order of mares in any one group or where several groups
were considered was a simple linear one, but with large numbers
the order was complicated by triangular relationships within
the hierarchy. In one group of eight dominant mares there was
a significant correlation between their size and rank. However,
this did not hold true with other groups and neither size nor
age explained the high position of some mares in hierarchies.
Dominance between stallions and mares varied. Stallions always
dominated where food was concerned but not in all other situa-
Family groups . The number of mares, yearlings and colts
controlled by a stallion varies. Dobie (1952) reports viewing
as many as a hundred horses in a group but adds that 15 to 20
was the usual size. Other reports state that normal groups
consist of one to eight mares exclusive of colts and yearlings
(Hoyt, 1886). Wild horse bands in the Pryor Mountains and in
Nevada averaged three to four animals composed of a stallion,
lead mare, subordinate mares, yearlings, or colts (Hall, 1972;
Pellegrini, 1971). When wild horses are frightened or stampede,
the bands may join together into one large herd controlled by a
single stallion. However, the large bands again separate into
individual harems when they stop running (Dobie, 1952; Ryden,
Stallion colts are usually ejected from the band at an early
age, about two to four years. The age at which they are
expelled seems to depend on the aggressiveness of the dominant
stallion. These young males may remain alone near where they
were born until they can join up with a bachelor group. If
they join together they are controlled by a dominant stallion
in a loosely organized group. Early writers reported as many
as 25 of these young males in a band. Later reports indicate
two to five animals varying from two to five years of age.
When stallions approach the age and size at which they can
capture a harem of their own they may leave the group and
remain alone (Dobie, 1952; Hall, 1972; Ryden, 1970).
Hall (1972, 1975) stated that there was often a considerable
interchange of animals between harems. Many such interchanges
were observed in the Pryor Mountain study. He relates the
interchanges and the small band size to the sex ratio (607 o males,
407 o females) , and to overcrowding. He reported that in some
areas in Utah the band size averages six animals. In these
cases the sex ratio is about equal and there is no evidence
Klingel (1965) reported that family groups among the plains
zebra (Equus quagga ) are extremely stable and are not held
together by the dominant stallion. In five observed cases
where the lead stallion disappeared, the groups remained
together until subsequently taken over by another stallion.
Sometimes large harems have two stallions; both may breed, but
one is always dominant. When the herd is in flight this second
stallion runs abreast and forward of the male in command (Dobie,
1952; Hall, 1972; Ryden, 1972).
Home range . In any discussion of home ranges or territories
of America's wild horses it is well to remember that these two
items may be those imposed or strongly influenced by man. Field
studies that will enable us to understand the diversity of ways
these animals use the space available to them are virtually
Every species of mammal has a home range of some type. These
home ranges may be stationary or they may change with conditions.
The ranges often overlap and migratory animals may have more
than one home range. A home range may be defined as the area
over which an animal or a group of animals travel in pursuit of
routine activity. It may have no clearly defined boundaries
but it must produce the energy requirements of the specific
group of animals that occupy it. It implies a self-imposed
restriction of movement (Burt, 1943).
Estes (1974) claims that the actions of zebras are found in all
members of the horse family; therefore, the only truly wild
member of the Equidae that may furnish clues as to how wild
horses once lived is the plains or Burchell's zebra (Equus
Burchelli). There are still over a half million of these
animals on the savannah of northern South Africa and the southern
Sudan. During their annual migrations herds of zebras may
stretch across the grasslands as far as one can see.
Plains zebras live in stable families, or harems, of mares and
foals, with each family of six to sixteen members controlled
and defended (mostly from other males) by one stallion. Large
troops of zebras are made up of these units plus bachelor herds
which mainly consist of immature stallions.
Both Feist (1971) and Hall (1972) reported on home ranges within
the Pryor Mountain herd. Hall observed that the ranges varied
seasonally with an individual band using as many as five areas.
He observed at least 17 bands of horses using the same area at
least part of the time. These actions were attributed to con-
gestion and lack of adequate forage. Feist reported that home
ranges were relatively well defined and adhered to and only
rarely did a band leave their home range. Pellegrini (1970)
reported that the home range of the three bands most extensively
studied in the Wassuk Range of Nevada confined their activity
to cube-shaped areas, while the home range of lone horses was
linear along the boundaries of two adjacent home ranges. Among
the New Forest ponies, home range depended on the topography
and the nature of the habitat. Four requirements for a home
range were necessary: grazing area, shelter, water and shade.
When these were close together the home ranges were often small
(200 acres). The home ranges of the different groups were very
stable and though they were often almost identical or overlapped,
each group tended to use a different part of the grazing area
When the wild horses were at their peak during the last century
many writers reported large herds. Early maps of Texas marked
the territory between the Rio Grande and Nueces Rivers as "vast
herds of wild horses." A Franciscan missionary reported that
when crossing an area uninhabited by people the wild horses were
so abundant that their trails made the area look like the most
populated in the world and that all the grass was gone. Within
these large herds, however, the individual bands or harem groups
retained their identity (Dobie, 1952).
Lorenz (1963) lists several species of animals (bison, antelope,
and horses) which do not maintain strict home ranges or display
territorial jealousy if there is enough food for all.
Indians depended on the home range instinct to hold their semi-
wild herds on reservation lands, but not all horses reveal this
trait and as a result many of them reverted to a wild state
Mustangs confine their feeding and flights from danger to
certain boundary lines. This fact was well known to plainsmen
who made a business of catching wild horses (Cook, 1919).
Smith (1841) stated that the genuine wild horse is migratory,
moving north in the summer and returning in early fall. The
mixed races (feral horses) move to pastures rather than to
points of the compass.
Territoriality . A territory in animal populations may be
defined as that part of the home range which is protected from
individuals of the same species either by fighting or by other
aggressive action. Territoriality is so widespread among the
vertebrates and in many of the invertebrates that it must be
considered a basic animal characteristic. Although it is not
found in all animals nor is it always developed within strict
boundaries among the animals that possess it, the potential
is there whether the animal displays the characteristic or
not (Burt, 1943).
There is only scant evidence to indicate the degree of terri-
toriality displayed by wild horses.
Pellegrini (1971), in his study of Nevada herds, concluded that
wild horses establish a territory even though no special section
of the home range exists as a defended area. Hall (1972) reports
that horses in the Pryor Mountains do not establish territories,
and he is convinced that they are not territorial. The indi-
vidual bands maintain a "sphere of intolerance," an area near
the harem or family group in which the dominant male will
defend against other males. This "sphere" (the distance within
which another stallion may approach the harem) expands during the
breeding season and contracts after it is over. During the
winter months it may be almost nonexistent.
Feist (1971), reporting on the same herd of horses, concluded
that the bands or studs do not exhibit territorial behavior.
They do, however, maintain a spacing between bands. In all
observations this spacing was related to distance between bands
and never to the defense of a ground area.
The dominant males of the plains zebra do not defend a territory.
They control moveable property rather than real estate (Estes,
Vocalizations . Waring (1971) states that social inter-
actions are common among both feral and domestic horses. These
interactions occur through visual, auditory, olfactory,
gustatory and tactile cues. He warns against using any single
means of communication out of context. To fully understand
the importance of sounds, all other means of communication
must be identified and understood.
Using American Saddle Bred horses as subjects, he tape recorded
their vocalizations, then by spectrographic patterns he divided
them into seven basic categories. Identified were squeals,
nickers, whinnies, groans, blows, snorts, and snores-- the first
four vocal, the latter three non- vocal. Breed variability may
exist, but it probably falls within the basic sound categories
Squeals: express threats. Nickers: anticipatory sounds prior
to being fed; stallions in courtship; and by mares when foals
are in jeopardy. Whinnies: uttered during distress or inquiry.
Groans: issued during discomfort or anguish. Blows: express
alarm or aid olfactory investigation. Snorts: used in conflict
situations-- they may express relief or disgust. Snores: pro-
duced during inhalation, two types were detected--one of short
duration uttered prior to emitting an alarm blow, the second,
of longer duration, produced while the animal was prone. The
author indicates that all of these sounds are used by either
Feist (1971) identified four definite vocalizations in the
Pryor Mountain herd: the snort, neigh, nicker, and scream. He
observed the snort as a danger signal used mostly by stallions,
seldom by mares. The neigh was used as a distress call primarily
by mares and younger horses of either sex. Studs used the
neigh to call animals that had strayed or when they were in a
build-up to a fight. The nicker was used in closed communica-
tion and courtship. The scream was emitted exclusively by
studs during fights.
Hafez et al (1962) identifies the snort as a danger signal, the
neigh or whinny as a distress call, and the nicker as a sign of
relief or for closed communication and courtship.
Tyler (1972) reported that the squeal was most commonly uttered
by mares when a stallion approached and sniffed them. Mares
also squealed when fighting or when displaying aggressiveness.
Stallions only occasionally squealed when fighting.
Postures and facial expressions . Tyler (1972) states that
six expressions are recognized in equids but they are not all
seen in true horses. She describes five of these expressions
among the New Forest semi-wild ponies.
Ponies yawned by holding their mouths wide open with the upper
and lower teeth exposed and ears forward. Yawning occurred
before or after resting, when mares in estrous were being
sniffed by stallions, in stallions after copulating, and in
foals after suckling.
The greeting expression occurred when two group companions or
a stallion and a mare met; they sometimes extended their heads
and touched each other's muzzle and lips. These often developed
into threat postures when the ponies laid back their ears. The
greeting expression was also used as a preliminary to mutual
During the flehmen posture the animal extends its neck and curls
the upper lip so that the teeth are exposed. Schneider (1930,
1931, 1932a, b) described the flehmen in a wide variety of
ungulates. Hafez et al (1969) states that this expression
commonly takes place during the precopulatory patterns of many
ungulates. Estes (1974) states that during the flehmen, urinary
odors are apparently assayed in an accessory olfactory system
specialized to detect concentrations of sex hormones. In the
New Forest ponies (Tyler, 1972) the expression was always
observed as a reaction to some smell: by stallions after
sniffing a mare; by stallions, mares or foals after sniffing
urine; by mares or other ponies after sniffing fresh placentae
or by any pony at the sight of another showing the flehmen
posture. Blakeslee (1974) stated that the flehmen posture was
exhibited by foals, yearlings, and adults in a variety of
situations other than smelling urine on the ground. The
posture was induced by touching the nose of a horse with a
human hand and by sight of another horse urinating, or by the
sight of another horse exhibiting the flehmen posture. Feist
(1971) observed 55 situations of this action in the Pryor
Mountain herd. All of them were related to olfactory responses
and all of them were by males.
The threat expression is characterized by backward-directed
ears and was first described by Antonius (1937). Tyler states
that it is absent in asses, half-asses, and Grevy's zebra
(Equus grevyi ) ♦ The true horses do not draw up the corners of
the mouth as do the other species of zebra. In the New Forest
ponies mild threats were exhibited by slightly laying back the
ears, but intense threats were expressed with the ears flat
back and sometimes the mouth slightly open, and occurred just
before a dominant pony attempted to bite a subordinate pony.
Stallions also used the threat gesture when driving mares by
stretching the neck toward the ground, ears flat, and swaying
the head back and forth. Ryden (1970) observed similar actions
when stallions threatened or drove mares.
Zeeb (1959) described the snapping expression. It is character-
ized by stretching of the neck with the ears slightly back and
down, the corners of the mouth drawn back partly exposing the
teeth, and the lower jaw in motion up and down. Tyler (1972)
stated that the expression was common in the New Forest ponies
when foals or yearlings were threatened or approached by adult
mares or stallions. It occurred in a variety of occasions,
most of which seemed to be released by fear. Occasionally it
was a response of foals and even yearlings to approaching cows.
Although it was regarded as a submissive expression it had no
effect in preventing older animals from carrying out their
threats. Foals and yearlings were often bit or kicked by mares
even after they had made the snapping response. Feist (1971)
recorded 21 instances of this behavior by young males to the
dominant stallion. Ordinarily the stallion made no recognition
of the submissive behavior.
Grooming . Domestic horses, unlike cattle, do not groom
each other but they may nibble each other along the withers or
stand head to tail and flick flies off each other's faces.
Nibbling of the withers is usually a sign of recognition and
often may be noted when two animals meet after an interval
(Hafez e_t al, 1969).
Trumler (1958) classified grooming in zebras as follows: local-
ized muscle contractions; shaking; striking one part of the
body against another or against the ground; rubbing (includes
rolling); scratching; nibbling; and social or mutual grooming.
Feist (1971) stated that mutual grooming was a common part of
the daily activities in the Pryor Mountain wild herd, accomplished
by pulling the lips back and using the incisor teeth to groom
the neck, withers, base of the mane and on down to the rump.
Horses also groomed one side, then switched to groom the other
side. Mutual grooming occurred only between herd members and
almost all grooming combinations were observed except between
the stud and immature males. Tyler (1972) observed all the
above forms of grooming in the semi-wild New Forest ponies.
Mutual grooming was a response to insect infestations, shedding
of hair, or as a means of social contact. Each pony had only
a small number of partners with which it groomed. These part-
ners were usually related, unrelated group companions, or
members of two closely associated groups. The usual grooming
partner of a foal was its mother, another sibling or another
foal. Mutual grooming bouts were most often initiated by the
subordinate animal and ended by the dominant animal. Mutual
grooming was a common activity among all age classes of appa-
loosas. All observations of grooming were within their
particular group, and there was no consistent pattern of
preference for certain partners (Blakeslee, 1974).
Feist (1971) observed 81 cases of rolling, 50 of which were in
dust and 31 in mud and water. Although yearlings and foals
rolled, no female yearlings or foals were observed rolling in
dust or mud. Dusting sites were scattered throughout the range
and were used by all bands or horses that passed by. Ponies
usually rubbed against fixed objects such as stumps, trees or
wooden bridges. When insects were abundant they spent long
periods stamping, kicking at their bellies, shaking and lashing
their tails or rolling. Rolling often occurred at the end of
a resting period or when they encountered wet grass after a
rain, patches of bare ground or sawdust. No special sites were
reserved for rolling (Tyler, 1972). Appaloosa horses choose
specific pieces of ground for rolling places, and these were
so well used that they were denuded of vegetation and covered
with dust. Rolling in water was common for all age classes as
was rubbing against trees or other fixed objects (Blakeslee,
Play . Hie word play is a human concept applied to any
activity other than work. The term is difficult to apply to
wild animal activity or behavior; since animals do not work
(in the human sense of the word) they cannot be said to play.
Human play no longer has survival value; however, in animals
it must be assumed that it does have value. Play occurs
among animals only when they are free of environmental or
physiological stresses. It is a widely held view that play
is preparation for adult activity, and the animals that have an
opportunity to play prior to becoming adults have a selective
advantage over those animals that are denied this opportunity.
However, it has never been clearly shown that animals prevented
from playing are less efficient as adults than those that play
(Loizos, 1966). Play increases locomotive skills and may be
used to test social dominance (Hafez e_t al, 1969).
Feist (1971) reported that play among foals of the same band
and foals of other bands occurred regularly. This was tolerated
by the studs if the juveniles returned to their own bands after
playing. Play involved running, kicking, sudden stops and
starts, and head tossing. Foals were observed playing at all
times of the day but primarily in early evening when tempera-
tures had cooled. Play among other age groups was rare and if
started was quickly ended by the dominant male. Tyler (1972)
reported that play in young foals took the form of the foal
galloping to and from its mother or making irregular circles
around her. It bucked and kicked as it galloped. Sometimes
the foal reared up at its mother or pulled at her mane and
neck. Young foals were very inquisitive and often sniffed or
nibbled at strange objects and then rushed back to their
mother. Play between foals did not occur before their second
or third week. After this period, play between foals became
more common. Foals nibbled, groomed, or chased one another
and kicked out with their hind legs and bucked or reared as
they galloped. The play of colts older than four weeks differed
from that of fillies. Colts spent long periods play fighting,
rearing, pawing and attempting to bite. Most play fights
between colts contained all the components of true fighting
between adults. Play between fillies which often ended as
mutual grooming was much less common than play between colts
or between colts and fillies. Both colt and filly foals showed
interest in stallions and often attempted to approach them.
Most stallions were very tolerant and usually ignored the foals.
Play fights were observed between stallions and colts but never
between stallions and colts over two years old. Blakeslee
(1974) observed similar play among foals but did not report any
differences between the play of males and females.
Sleep and rest . In lying down the horse brings all of its
legs under the body, bends its knees and hocks and permits the
chest to touch the ground before the hind quarters. When down,
the horse either rests on one side of its chest with a fore and
hind leg underneath or it lies on its side with all legs
stretched out. In getting up, the forelegs are stretched out
first followed by the rear legs pushing up the hindquarters.
The horse may sleep very soundly for seven hours out of twenty-
four, mostly during the heat of the day. Horses sleep standing
up or laying down; however, it is rare to see all horses in a
group laying down at the same time; one is always alert (Hafez
et al, 1969). Many horses sleep on their feet and some graze
all night (Ensminger, 1951). Ruckebusch et al (1970) studied
behavior and physiological responses of horses during sleep.
They state that sleeping while standing was rare in experimental
animals but appeared to be frequent in animals maladjusted or
insecure in their surroundings. Dobie (1952) wrote that wild
horses never lie down altogether, many sleep on their feet and
lay down only to roll. He relates the story of an old-time
horseman who told him that wild horses napped regularly three
times during the night, at about nine, eleven and just before
dawn. Feist (1971) observed a number of situations in which
horses rested or were sleeping. Foals spent a great deal of
time sleeping while lying down; this decreased as they grew
older. Mature animals only occasionally lay down and no obser-
vations were made of an entire band lying down. Yawning and
stretching often occurred following sleep or rest. Pellegrini
(1971) stated that horses in the Wassuk range of Nevada travelled
little during the night. They either stayed near water or in
sheltered areas, apparently sleeping most of the time. They
also rested or slept in shaded areas during the day. Both foals
and adults spend more time resting during the winter than in
the summer (Blakeslee, 1974; Tyler, 1972). The latter author
attributed this difference to increased food availability during
Pawing . The original function of pawing was part of the
horse's nutritive behavior and always occurred together with
an olfactory investigation (Odberg, 1972).
Horses paw through snow to obtain grass or they may paw to
remove undesirable objects (stones, cactus) that interfere with
or block their efforts to reach desirable forage plants. Paw-
ing was also used to search for water from dried waterways
where it was common for early cowboys to find holes dug by
horses as much as eight feet deep. Pawing is also their means
of breaking ice to obtain water (Boone, 1933; Dobie, 1952;
Odberg, 1972; Smythe, 1966).
Horses paw for various other reasons. They have often been
observed sniffing and pawing the areas where they are about
to roll. Pawing may occur during the threatening behavior when
two males meet and they may also paw during courtship if thwarted
in their attempts to mate. Pawing and sniffing often accompany
investigation of stud piles. Foals sometimes paw when they are
frustrated in their attempts to feed, and mares may paw before
foaling. Domestic horses paw at the sight of unreachable food
given by humans or while waiting for an action they feel or
"know" is going to happen (before a race) , or they may paw from
boredom or nervousness when they are in their stable (Boone,
1933; Dobie, 1952; Odberg, 1972).
Eliminative behavior . Vigorous adult horses defecate 5 to
12 times, and urinate 7 to 11 times per day (Hafez e_t al , 1969).
Tyler (1972) estimated frequency of elimination in the New
Forest ponies. Adult mares defecated on an average of once in
just over 2 hours and urinated once every 4 to 4% hours. Foals
urinated about once per hour in the first week or so, but this
gradually dropped to the same frequency as adults when they
were about a year old. Stallions frequently sniffed piles of
feces and then defecated or less commonly urinated on the pile.
Sometimes they did this several times in succession on different
piles of feces.
Horses, unlike cattle, stop whatever they are doing to urinate
or defecate. They maintain a characteristic stance according
to sex when eliminating; and after elimination the stallion,
but not the mare, smells the eliminative product (Hafez et al,
1969). Ponies stopped grazing to urinate but merely raised
their tails and continued to graze while defecating (Tyler,
Feist (1971) believes that there is much more significance in
the eliminative behavior of wild horses than there is in
domestic horses. Particularly important is the action of the
stud in relation to other horses in the band and to other
studs. The stud's urination behavior is directed to excrements
of the mare, whereas his defecation behavior is used primarily
for the stud pile. Feist further believes that this behavior
is dominance- linked.
Blakeslee (1974) found no evidence of dominance display by
appaloosa stallions connected with eliminative behavior nor did
they accumulate stud piles like wild horses.
Scent or visual boundary markin g. The fact that wild horses
deposit their fecal matter in one place and thus create piles
of manure commonly referred to as "stud piles" is well known.
There is little evidence as to the exact purpose of this type
of behavior. It may be a form of scent marking, visual boundary
marking or both.
Dobie (1952) gives an account of the many early explorers,
historians, and others who were amazed at the numerous piles of
horse dung that lined the trails used by wild horses on both
the South American pampas and on the western prairie. He states
that a stallion's dung piles constitute a visual and olfactory
notice to other stallions that he had been there.
Shenkel (1947) concluded that scent marking legitimizes the
leader, marks his territory and aids in making new acquaintances.
Lyall-Watson (1964) interprets scent marking differently, stating
that scent marking aids the animal in maintaining familiarity
with his environment and assures him that he is within his
home range. This interpretation suggests that scent marking is
not used as an aggressive display for territorial defense even
though it would be effective in maintaining a territory.
Pellegrini (1971) indicated that mares and colts also accumu-
late dung piles and that these piles probably served as
boundary markers. Hall (1972) discounts the purpose of stud
piles for marking territory because the Pryor Mountain horses
are not territorial and the piles appeared to be randomly
scattered. Feist (1971) agrees with Hall. "If five bands
passed by a particular pile on a trail or on a feeding area
in one day it would be rare if all of the studs did not defecate
with accompanying posturing on that pile."
Zebra stallions mark only the feces of mares in estrous
(Klingel, 1969, 1972). He suggested that scent marking in
zebras is vestigial behavior and probably inherited from terri-
torial ancestors. The same author later reported that the
marking behavior of the non- territorial equids has no known
function. Kleiman (1966) distinguished scent marking from
true elimination by three factors, one of which was directional
posture. Pony stallions, when marking, oriented their elimina-
tive products toward other piles of feces. They often walked
from one pile of feces to another stopping to eliminate on
several piles. Stallions usually defecated when marking; mares
and foals more commonly urinated (Tyler, 1972). Both Feist
(1971) and Tyler (1972) reported that the amount eliminated by
stallions when marking was controlled and expelled in small
quantities, compared with true elimination. Feist observed
stallions stepping over a mare's excretion and urinating in a
short but strong blast. Stallions were also observed defecating
up to three times during a short period while fighting. Tyler
noted that there was no evidence that marking had any effect on
Water and watering behavior . There is no data available
on the amount of water needed or consumed by wild horses under
their various habitat conditions. (Ensminger (1951) states that
the average domestic horse will consume about 12 gallons per
day. Stoddart et al (1975) quotes from early research on
domestic horses and lists 10-12 gallons per day.
Among wild horses Feist (1971) noted no consistent watering
schedule by any band. Generally each band visited a water hole
once a day except during very hot weather when they watered
twice a day. Over most of the range, horses were always within
four or five miles of a water hole. The time spent at water
holes rarely exceeded 30 minutes. Pellegrini (1971) observed
territorial behavior of wild horses in Nevada at water holes.
When two bands arrived simultaneously one band was dominant.
The less dominant band did not water until the other band had
left the area. Hall (1972) states that in the cooler months
horses trail a considerable distance to water but during the
warm periods of late June, July, and August they concentrate
on water. Frei (1975) states that wild horses in eastern
Nevada will trail as far as 10 to 15 miles to water and seldom
stay any closer to water than three miles. When temperatures
reach their maximum (95° F.) during the summer the horses water
every other day. Actual drinking time generally does not exceed
3-4 minutes per horse, and they rarely remain near the water
hole more than 5 minutes after drinking. Appaloosa horses
rarely remained long at watering places, usually no longer than
a half hour. Although the horses used well worn trails going
to and from water, they had no set pattern for time of arrival.
They trailed to water at a certain time for several days in
succession and then changed their schedule (Blakeslee, 1974).
Charles Goodnight, a scout during the Civil War, told Dobie
(1952) that wild horses, unless severely disturbed, did not
graze more than five miles from water and that they watered at
the same spot each day. During droughts wild horses of the
South American pampas sometimes became so frantic that upon
finding water they piled into it on top of each other, drowning
and trampling to death large numbers (Dobie, 1952). Smith (1841)
reports similar behavior in South American wild horses during
drought periods. The thirsty animals trampled each other so
furiously that thousands of skeletons lined their watering
places. He suggested that these actions were probably a means
of population control.
Foal behavior . The following has been extracted from a
paper by Waring (1970) who studied foal behavior in American
Within seconds of birth the foal raises its head and assumes a
sternal position. By pawing and by motions of the head and
neck the foal attempts to move away from the mare; this drags
the hind legs free of the mare's vagina and eventually severs
the umbilical cord.
Within 15 minutes the foal attempts to rise but often not until
three-quarters of an hour has passed do the hind legs flex
sufficiently to permit it to stand. The eyes, open at birth,
show distinct binocular orientation by 25 minutes. The mare
vocalizes to her foal within minutes after birth, and auditory
orientation of the foal occurs within 45 minutes. The initial
stance is unsteady and the foal shifts frequently to maintain
its balance. Suckling motions have been observed within 55
minutes. Nursing depends partly on the mare's willingness to
stand still or position herself so the foal can find her
nipples. Some foals nurse soon after standing and some do not
succeed until almost 2 hours old. Defecation may occur prior
to one hour of age and urination a few hours later.
At one hour of age the foal commonly shows ability in standing
and moving about, can see and hear, can eliminate, express
curiosity and care-seeking behavior. During the second hour the
colt perfects its walking and shows evidence of its attachment
to its mother; the mare and colt may vocally respond to each
other's sounds. Sleep begins as short naps and increases until
it occupies much of the foal's early life. Fear of new objects
begins. When it is two hours old, the foal may walk easily,
lie down, nurse, follow its mother, vocalize, seek shelter
beside her, express fear, and sleep.
By half a day it can walk, trot, gallop, combat insects (by
use of its tail or by kicking and nipping) , urinate in a
manner characteristic of its sex, exhibit short periods of
animated play, and consume small amounts of forage. The mare-
to-foal bond begins soon after birth and is stronger than the
reciprocal. When the two are separated, the mare may show
extreme excitement, but the foal exhibits disorientation more
Tyler (1972) observed foal behavior of the semi-wild ponies.
Almost immediately after birth an observed foal had pushed its
muzzle and a foreleg through the amniotic membranes. Within
five minutes it attempted to stand, but this was thwarted by
the mare's vigorous licking action. It stood within 33 minutes
and suckled successfully 52 minutes after birth. Most mares
began to lick their foals a few minutes after birth and con-
tinued to do so for as long as a half hour. On the foals' first
day the mares are very possessive and keep the foals away from
all other ponies. On the second day the foals are usually able
to recognize their mothers by smell, and the mares become less
protective. A few foals ate or nibbled at grass on their first
day, and some were observed in such activities as rubbing,
rolling, scratching, stamping, shaking and nibbling. They also
yawned and displayed the flehmen posture and snapping expression,
First-week foals seldom strayed more than 25 yards from their
mothers and even those up to 5 months old spent less than 107 o
of their time more than 50 yards away from her. When a foal
approached its mother to suckle, it often nickered, laid back
its ears and tossed its head. The foal then moved in front of
the mother pushing under her head before it attempted to suckle.
It did this regardless of the direction of approach. The close
relationship between the mare and her yearling continued even
though the mare had a new colt. The yearling rested near its
mother, groomed with her and followed her. Weaning usually
occurred when foals were about a year old or at the time of
the birth of a new foal. The author observed one pony mare
which allowed her yearling to nurse after the birth of her
foal, but considered this behavior atypical. Blakeslee (1974)
stated yearlings were not generally allowed to nurse after the
birth of the new foal. However, if a mare did not foal, her
yearling frequently continued to nurse.
Tyler (1972) reported that until their third or fourth month,
pony foals, due to their short necks, straddled their forelegs
to graze. The average amount of time spent. grazing by foals
increased from 3.5 minutes per hour the first week to 16.3
minutes per hour after the fourth month. Foals in their
twelfth and thirteenth months spent a mean of 44.4 minutes per
The author also reported that after birth, licking of the fetal
fluids by the mare from herself and the foal seemed to be very
important. After a mare has licked her foal, she is able to
discriminate between it and other foals, and a relationship
between mother and young becomes established. The great attrac-
tion to the fetal fluids was shown by a pony mare whose colt
fell into a ditch soon after birth. The foal was rescued and
moved a few yards away from the mother, but the mare remained
near the ditch and the placenta. When the colt was carried back
to her she began to lick it and a normal relationship was
Blakeslee (1974) stated that foals pull at and mouth various
plants when one or more days old; however, they do not swallow
the plant material until their teeth have cut through the gums
at about the fifth day. Grooming in foals did not occur until
they were about a month old, and the initial bouts usually
were with their mothers. Very young foals had trouble drinking
from streams, and it took them several days to learn to proper-
ly spread their forelegs and retain their balance while drinking.
Coprophagy in foals . Tyler (1972) reported that coprophagy
was common in pony foals up to three or four weeks old. The
feces eaten almost always belonged to the foal's mother, but
on two occasions a foal was observed eating its own feces.
Blakeslee (1974) also reported young foals eating feces,
usually their mothers'. Older foals did not eat feces. Hafez
et al (1962) report that adult domestic horses reject the
feces of their own kind but that foals eat a considerable amount
of fresh feces of adult horses. They attribute this behavior
to the need for proper bacterial flora for the foal's intestines,
Predation and Disease
Predation. As far as is known, there are no scientific
studies of predation on wild horses. The mountain lion (Felis
concolor ) is the only large predator remaining within their
habitat that is capable of killing an adult horse. It is
possible that coyotes could kill foals if they were unprotected.
Feral dogs, when hunting in packs, certainly have the capability
to attack and kill horses, but whether they do or do not has
never been reported.
The only natural enemies of horses are mountain lions and wolves,
All horses are afraid of bears but even in California where
grizzlies were once numerous, they killed few horses. Wolves
sometimes attacked horses but they preferred buffalo and after
these were gone they turned to cattle. The natural prey of
the mountain lion is deer, but once they had tasted horsemeat
(especially foal) it became one of their favorite foods (Dobie,
Young and Goldman (1946) cite instances of mountain lions prey-
ing on horses in Arizona, Colorado and New Mexico. Raising
colts and even maintaining a herd of adult horses was impossible
in some areas due to lion predation. Once lions came addicted
to horse flesh they often abandoned all caution. The writers
also note that mountain lions are exceptionally fond of burro
Diseases, pests and parasites . Outbreaks of diseases or
infestations by pests and parasites within a wild animal popu-
lation are often important indicators of other problems. These
may be related to habitat, poor nutrition, overcrowding,
competition, injury, harassment, or other reasons.
The more common afflictions of domestic horses, unless other-
wise indicated, have been adapted fromEnsminger (1951). It
is possible that any one or more of the diseases could be
present in or transmitted to wild horse herds. Symptoms,
treatment and details are beyond the scope of this technical
Equine abortion: Causes may be grouped into four categories
those resulting from infection by Salmonella abortivoequina ;
those from streptococci infection which gains entrance through
the genital tract; a virus or epizootic type which is highly
contagious; and those abortions that occur from miscellaneous
causes which cannot be classified into the above categories.
These may vary from accidents or injuries to nutritional or
Equine encephalomyelitis (sleeping sickness): a disease
carried by 4 immunological, distinct filtrable viruses. It is
vectored by 13 members of 3 genera of mosquitos of which Culex
tarsalis is the most likely carrier. It may also be carried
by spotted fever ticks ( Dermacentor venustus ) and assassin bugs
( triatoma spp . ) .
Equine infectious anemia (swamp fever): a very serious
blood disease of horses and mules. It is caused by a specific
virus that may stay in the host for years. Treatment has been
Infectious adenitis: Also referred to as strangles or
distemper, the disease is caused by a bacterial streptococcii.
Transmission is usually by the inhalation or ingestion of the
infected discharges. It is highly contagious and the organisms
may live outside the animal's body for as long as six months.
Glanders or farcy: A very old disease of bacterial origin.
It may be diagnosed through the "mallein test." No cure is
Dourine: A chronic venereal disease of horses and asses
commonly termed equine syphilis. It is caused by a protozoa
and is spread mostly through mating, but may be transmitted
by biting insects.
In 1930 the Bureau of Animal Industry reported that 177o of the
wild horses on the San Carlos Apache Indian lands were infected
with dourine. Later tests indicated 80% of the horses in the
high country were infected. The Federal Bureau of Animal
Husbandry removed about 500 horses from Nevada wild herds in
1935 because of the presence of the disease (Wyman, 1945). The
Bureau of Land Management in 1974 reported a suspected out-
break of the same disease in wild horses near China Lake,
Rabies: caused by a filtrable virus which usually occurs
from injected saliva in a bite wound; an acute infectious
disease of horses and all other warm-blooded animals, including
Anthrax: also infectious to all warm-blooded animals. The
bacillus of anthrax can survive in the soil for very long periods,
It was the first disease in which immunization was accomplished
by an attenuated culture by Pasteur in 1881.
Tetanus: Caused by an extremely powerful toxin liberated
by the tetanus organisms ( Clostridium tetanii ) . The organism
is found in certain soils, horse dung, and sometimes in human
Periodic opthalmia, or moon blindness: the most common
cause of blindness in horses and mules. It is an inflammation
of the inner portion of the equine eye and its associated
structures. Horses of all ages are susceptible, and it may
occur in one or both eyes (Roby et al , 1956).
Parasites: The species and degree of harm vary in different
parts of the world. They may be located in practically every
tissue and cavity of the body. Some are specifically localized,
others are migratory through different parts of the body. The
most important of these are: the bot flies, of which there are
three species; the strongyles with six species, the larger of
which are commonly referred to as bloodworms or redworms; the
ascarids or roundworms; two species of pinworms; four species
of stomach worms; the screw worm, largely confined to the
south and southwest; blowflies; ringworm; lice; mites; and
Poisonous plants: Horses often eat and may be poisoned by
many species of poisonous plants. Some plants may be eaten
over extended periods before producing ill effects, others
that contain acute poisons may produce visible symptoms or
death soon after being eaten (Huffman e_t _al, 1956).
In addition, horses are subject to colds, laryngitis, bronchitis,
pneumonia and pleurisy (Hanauer, 1973).
Competition and Relationships With Other Animals
Competition . The extent, nature and degrees of competition
between wild horses and other domestic or wild animals for
habitat components such as food, water, space and cover or other
requirements has never been investigated. Cook (1968), writing
on the nutritive content of range forage for domestic ruminants,
stated that the most critical period for grazing animals that
inhabit seasonal ranges are those months between December and
April when inclement weather and perhaps poor range conditions
cause animals to lose weight excessively. When range conditions
are poor, the degree of utilization of the forage increases
and the digestibility and nutrient content decreases because
animals are forced to eat the less nutritious parts of the
plants. Thus nutritional deficiencies are common on winter
ranges of the intermountain region. The above would also
apply to wild horses in varying degrees over much of their
range. Since wild horses are on the range year round, at some
season or seasons they occupy the same range as domestic live-
stock, elk, deer, and antelope. If, during these periods,
forage is in short supply the various classes of herbivores
will compete, and it is likely that the less dominant animals
will suffer the most.
Hansen (1975) does not think that wild horses compete strongly
with mule deer ( Odocoileus hemionus) or antelope on most ranges,
but he would expect them to compete with cattle since their
diets appear to be 60 to 98 percent similar. They may compete
moderately with domestic sheep, bighorn sheep (Ovis canadensis )
and elk ( Cervus canadensis ) .
Both the Bureau of Land Management and the Forest Service
report competition between wild horses, domestic livestock,
and big game animals. Generally these reports have centered
around forage supply.
Cook (1975) states that in many areas where wild horses now
occur the habitat is unsuitable for year-round feed requirements,
Under the provisions of the Wild Horse Act they cannot be moved
to suitable areas if that particular area did not previously
contain wild horses. The author estimates that wild horses
are increasing 20 to 30% per year, and under these conditions
many of them will starve and the range will deteriorate. Cook
feels that starvation, disease, and deterioration of the
environment may not be acceptable management measures.
Relationships with other animals . Documented information
on the relationships between wild horses and other animals is
In 1828 a Mexican surveying party reported that between Laredo
and San Antonio, Texas, deer and wild horses grazed together
in large numbers. When wild horses were frightened and ran in
large bands, they were sometimes joined by antelope ( Antilocapra
americana ) (Dobie, 1952). Ryden (1970) stated that wild horses
and buffalo ( Biso n americana ) often grazed together and that
antelope used the horses for sentries to warn them of danger.
During severe winters cattle often followed the horse herds so
they could graze in areas the horses had opened up. Other
reports conflict with these statements. Linsdale and Tomich
(1953) reported that mule deer ( Odocoileus hemionus columbianus )
moved away when horses grazed too close to them. Both Blakeslee
(1974) and Tyler (1972) wrote that free-roaming appaloosas and
semi-wild ponies, respectively, dominated cattle. Tyler ob-
served a yearling pony threaten a fallow deer doe ( Dama dama )
that was grazing near it.
McKnight (1959) wrote that many of the respondents to his
questionnaire stated that wild horses abused livestock, some-
times killing or crippling them and sometimes excluding them
from watering places.
Wild Horse Management
(The following sections on Population Management and Population
Control were contributed by Milton Frei of the Bureau of Land
Management, Denver, Colorado.)
Population management . The management of wild horses
presents a new challenge to public land administration agencies
such as the Bureau of Land Management and the U. S. Forest
Service. Heretofore management responsibilities of these
agencies have been limited to animal habitat rather than the
Although the concept of wild horse population management is a
relatively new one, the principles of animal population manage-
ment are well documented and can be applied directly to wild
The first step in managing wild horse populations is to deter-
mine the number of animals to manage in any particular area.
The determination of this number must be based on available
habitat and consideration of other animal species or resource
Once the number of wild horses to be retained for management
has been determined, the next step is to analyze those factors
which have molded the population into what it is today. It
must be true that over the long run, as many wild horses die
as are born. This is the same scheme that nature has built
into all of her animal species. Therefore, before management
of wild horse populations can begin, the factors of population
dynamics (productivity, mortality, sex ratio and age structure)
must be collected and understood. These factors can then be
analyzed to determine the forces which have shaped the popula-
tion and to predict the numerical abundance of wild horses in
The first step in a wild horse population analysis is to deter-
mine if the population is stable, increasing or decreasing.
The following formula represents one method for determining
the stability of a wild horse population:
A = Estimated number of adults in population (1 year and older)
B = Foal/100 adults (percent)
F = Number of foals
Zf = Mortality of foals (percent)
Nf = Mortality of foals (number)
Za = Mortality of adults (percent)
Na = Mortality of adults (number)
Y = Total population estimate (adults and foals)
P = Projected population
I = Population increase or decrease
(A) (B) = F
(F) (Zf) = Nf
(A) (Za) = Na
A + F = Y
Y - (Nf + Na) = P
P - A = I (increase or decrease). If P is less
than A, reverse P and A in formula. Values
will then be decrease in population.
I = Population increase where P> A
I = Population decrease where P< A
Once the stability of a wild horse population has been deter-
mined, it is necessary to analyze other population data prior
to actual manipulation of the population. For example, if the
population is determined to be increasing in total numbers and
it is desirable to decrease total numbers, an analysis can be
made as to the ratio of male animals to female animals in the
total population. It may be possible to decrease the produc-
tivity of wild horses by increasing the number of male animals
in relation to the number of female animals.
In another example, if the population is determined to be stable,
it is important to understand the reasons why. It may be that
births are equalling deaths or that the population is on the
brink of disaster. In this example, an analysis can be made
as to the age structure of the population. If the age structure
is balanced (i.e. all age classes adequately represented),
nothing more in the way of management need be done. However,
if one or more age classes are lacking or totally missing, it
may indicate that the missing age classes must be restored if
the population is to survive.
Population control. Control of wild horse populations
differs from control of big game populations in that they are
not a huntable or game species. Shooting of wild horses by
persons other than officials of the Bureau of Land Management
or U. S. Forest Service is prohibited by federal law and is
Control of wild horses is also restricted in that it is a
violation of federal law to use aircraft or motorized vehicles
to capture or kill a wild horse. As a result, the only tech-
niques available to capture the animals alive involve time-
consuming techniques such as water trapping, dry trapping,
roping and immobilizing. This is complicated by the fact that
many areas are too rough or have too many water sources for
these techniques to be effective.
Disposing of wild horses which have been captured presents
additional complications in population control. If animals are
destroyed the problem arises as to what should be done with
their carcasses. It is against federal law to convert the
remains of wild horses into commercial use. If live animals
are given away to private individuals for keeping under humane
conditions, the problem arises as to transfer of title to the
animal. It is not possible to transfer title to wild horses
and as a result, many individuals are reluctant to keep a wild
horse under those conditions. In addition, wild horses are
just as their name suggests, "wild." Full-grown horses are
very powerful animals and can be extremely dangerous when
placed in the hands of unexperienced individuals.
Methods of capture . Hall (1974) has prepared a paper on
wild horse capture techniques based primarily on experience
gained during the herd reduction program on the Pryor Mountain
wild horse range. Rather than attempt to repeat, the reader
is referred to this publication. The author states that many
of the methods described will prove too costly in terms of
manpower and money to capture large numbers of horses for
population reductions. However, as far as is known, this is
the only publication of its kind in existence.
Other states, notably Wyoming, Nevada, and Oregon, have had
experience in gathering wild horses. The Bureau of Land
Management in Wyoming presented a paper to the National Advisory
Board for wild, free-roaming horse and burros at their September
1974 meeting in Reno, Nevada on the techniques and problems of
wild horse capture.
The methods used to capture wild horses after World War II and
prior to the enactment of PL 92-195 have been described else-
where. Methods of capture used by the early horse catchers
included creasing, roping, snaring and running the animals into
some type of corral or trap. Shooting a horse in the upper
part of the neck close to the spinal column was termed creasing.
The shock stunned the animal so that he was immobile until he
could be tied. The method was more legend than truth. Old
mustangers related that for every horse caught by this method
fifty were killed. Horses were snared by attaching a loop of
rope to a long pole. The rider rode alongside the horse and
dropped the loop over his head. He then dismounted and choked
the horse to the ground. Lassoing or roping did not become a
common method of capture until late in the 19th century. Corrals
or traps were of all types, depending upon the available material
and the topography such as narrow canyons or ravines. Brush was
often piled fan shaped as wings to guide the horses into the
trap (Dobie, 1952).
Hoyt (1886) describes wild horse capture techniques on the
Texas panhandle. The horses were chased for 5 or 6 days by
relays of saddle horses and riders until they were so exhausted
they would mill rather than run when a rider approached. They
were then roped and clog chains attached to their legs. Part
of the clog was a free length of chain which wrapped itself
around the forelegs if the horse attempted to run. All horses
except yearlings and two-year-olds were clogged. The stallions
were captured first and castrated at the time the clogs were
attached. The horses were driven to water once a day and
allowed to graze only at night so that they would spend the
hours of darkness eating rather than attempting to escape.
Ryden (1970) was told by old timers that early mustangers in
the Wyoming Red Desert captured wild mares, tamed them, then
sewed their nostrils together with rawhide until they could
only partially breathe. The mares were then released to run
with their old band. Since they could not run fast they slowed
the whole band and the horses were easier to capture. Another
method used was to bend a horseshoe around a captured mare's
ankle and then release her. The horseshoe did not bother her
when she walked but when she ran it banged against her other
legs and slowed her. These mares were used over and over
Both James and Catlin writing in 1823 and 1838, respectively,
relate that the Comanches could tame and ride a wild horse
within a day or so of capture. A small party of well-mounted
Indians would hide in a narrow ravine or some other concealed
area while the other members of the tribe would drive the horses
into the ambush area. Each horse was captured with a lasso or
noosed rope around the neck. They were then quickly thrown and
their heels tied together.
Wild horse management plans . Both the U. S. Forest Service
and the Bureau of Land Management have developed plans for pro-
tection, management and control of wild horses. Both agencies
have land use planning systems that evaluate the resource and
then develop integrated planning and management for all the
multiple uses of the land area under consideration. These
include the vegetative and watershed conditions, wildlife needs,
livestock use, recreational use, and other legitimate demands.
Current problems . From various reports these include:
rapidly expanding populations that, due to the restrictions of
PL 92-195, will demand costly and inefficient means of control;
lack of biological data on wild horses; lack of valid censusing
and population data; lack of funds and manpower needed for
intense management; competition between livestock, elk, deer,
and antelope for forage and habitat; problems of disposing of
excess horses; management and control of horses on intermingled
lands (federal, private, state or other ownership); stallions
stealing privately owned mares; highway hazards (Wyoming Bureau
of Land Management reports that at least 10 horses were killed
by cars in 1974); and recreationists have complained of being
chased by wild horses.
Cook (1975) concluded that the Wild Horse and Burro Act was
short sighted. The bill essentially has no control measures
and as a result wild horses will continue to increase to the
detriment of the resource; the bill should be amended to permit
the use of aircraft by the agencies for roundups and control;
the excess horses cannot be sold or given away; and there is
no provision to permit complete removal of horses from some
areas of unsuitable year-round habitat.
Advantages of wild horses . There are certain advantages
to having wild horses on the range. Due to their inefficient
digestive system they aid in spreading plants by the distribu-
tion of feces that contain viable seeds. Their feces distri-
bution also fertilizes the soil and aids germination of seeds.
Horses aid livestock and other herbivores by breaking ice
covering water holes in the winter and help all animals by
breaking trails through snow. They provide an esthetic value
to the western range that has never been exceeded by any other
animal (Dobie, 1952; McKnight, 1959; Ryden, 1970). Horses
graze very selectively and can utilize grasses too coarse for
most other domestic animals (Stoddart e_t ajL, 1975). The removal
of coarse forage material exposes finer, more succulent feed for
other herbivores. Frei (1975) claims that wild horses use
range lands more efficiently than cattle. They travel much
greater distances in search of forage and do not excessively
utilize vegetation near water because they do not remain near
watering sources for long periods like cattle.
Disadvantages of wild horses . McKnight (1959) listed
about a dozen problems associated with wild horse from respond-
ents to his questionnaire. Heading the list was competition
with livestock for forage and water. Other problems were com-
petition with big game, overgrazing, trampling, heavy grazing
during the spring, leading tame horses into the wilds, destroy-
ing range improvements, tearing down fences, excluding other
animals from water, molesting livestock, roiling or dirtying
water holes, and breaking into cropland and grazing. Stoddart
et al (1975) states that horses constantly seek fresh feed and
are capable of cropping forage very closely because they have
both upper and lower incisor teeth. When horses are confined
in small pastures no other animal can match their impact.
Research needs . All aspects of wild horse ecology need
research, and so it is difficult to assign priorities. However,
if management of wild horses is to be meaningful to the land
managers in the near future, it would appear that research into
year-round habitat requirements would assume great importance.
Also desperately needed are data on population dynamics and
competition with other animals.
Current research . At present neither the Department of
Agriculture nor of the Interior are funding any research on
wild horses. Eastern Montana College at Billings, Montana,
and Colorado State University at Fort Collins, Colorado, are
presently engaged in wild horse research that is privately
funded. Results have not as yet been published.
Designated wild horse ranges . In 1962 the Secretary of
the Interior established a 435,000-acre refuge for wild horses
in southern Nevada. The area is northwest of Las Vegas in the
northeast corner of Nellis Air Force Base.
In 1968 the Secretary of the Interior established a 31,000-acre
wild horse range in the Pryor Mountains of south-central
Montana. The area adjoins the Wyoming state line and the
Bighorn Canyon National Recreation Area.
Legislation concerning wild horses and burros . Congress
has passed two Federal laws to protect wild horses. Public Law
86-234, passed in 1959, makes it illegal to use aircraft or
motorized vehicles to capture or kill wild horses. Public Law
92-195, passed in 1971, places wild horses and burros roaming
on national resource lands under the jurisdiction of the Secre-
taries of the Interior and of Agriculture Departments for pro-
tection, management and control. It provides a penalty for
harassing, capturing, killing, or selling wild horses, and
prohibits the processing of wild horses into any commercial
product. The maximum penalty consists of a fine of $2,000 and
imprisonment for one year. The Act of 1971 provides for the
establishment of an advisory board to make recommendations on
the management and protection of wild horses and burros.
Under the laws of the various states, wild horses are not
recognized as game animals or wildlife. They are considered
as "estrays" or abandoned animals and are not included under
the provisions of the Taylor Grazing Act.
Cooperative agreements for the protection and management of
wild horses and burros are authorized between the Secretaries
of Interior or Agriculture and state and local government
agencies and with other landowners.
Organizations concerned with the welfare of wild horses . The
inclusion of all the people, groups, animal welfare organizations
or others that have aided and supported the wild horse cause would
be extremely lengthy. Therefore, the organizations listed below
include only those that are directly and exclusively concerned
with the preservation and welfare of the wild horse.
1. American Horse Protection Association
Washington, D. C. 20007
2. American Mustang Association
3. Canadian Wildhorse Society
Richmond, British Columbia
4. International Society for the Protection of Mustangs
Reno , Nevada
5. National Mustang Association
Newcastle, Utah 84756
6. Spanish Barb Wild Horse Research Farm
248 N. Main Street
Porterville, California 93257
7. The Spanish Mustang Registry
8. Wild Horse Organized Assistance
Reno , Nevada
Glossary . All modern horse breeds are called either hot,
cold, or warm bloods. The hot bloods, small, swift and tempera-
mental developed from the Arab horse. The cold blood, larger,
more placid, developed in northern Europe during the middle
ages to carry armored knights. The warm bloods are a mixture
of the two (Ryden, 1970).
Hand - the system of measuring a horse's height. A hand is
four inches or the width of an adult man's hand across the
thumb. The term dates back to ancient times (Howard, 1965).
Mustang - a corruption of the Spanish word Mesteno, which refers
to an animal that belongs to everyone and not to any particular
person. The term was first applied to horses that had escaped
and became wild in the Southwest. In a short time all feral
and semi- feral horses were referred to as mustangs. The name
was also applied to certain domesticated horses. When feral
horses were caught and broken, the word also came to mean cow
pony (McKnight, 1959).
Cayuse - the term applied to any horses that resembled Indian
stock or to cow ponies that were wild. The name originated
from the Cayuse Indians of Idaho (a tribe now extinct) who
were known for the numbers of horses they possessed (Dobie,
Estray - "any steer, heifer, bull, stag, cow, calf, horse, mare,
gelding, or colt not wearing a brand (Ryden, 1970).
Labeled Points or Parts of a Horse
Three Types of Lumbar Vertebrae Found in Horses
Coat Colors in Horses
Adapted from Gremmel, 1939
A. Basic Colors
I. Black - body color is true black (disregarding weathering)
1. Black - true black without light areas
2. Seal brown - black with light areas to include
muzzle, under eyes, flank, and inside of upper legs,
termed "light points."
II. Bay - shades from tan to brown, with black mane and
tail and often with black lower legs:
1. Mahogany bay - the brown shades of bay, often
2. Blood bay - the red shades of bay
3. Sandy bay - the light shades of bay
III. Chestnut - shades from yellow gold to dark brown, mane
and tail not black but approximately the color of
1. Liver chestnut - the dark shades, some appearing
dark brown with an auburn hue
2. Sorrel - the red shades; sometimes in the lighter
shades the mane and tail are of the color described
as "crushed strawberry."
IV. Ysabella - a color group having flax or silver manes
1. Red ysabella - red sorrel-like; flax mane and
2. Palomino - a golden yellow; silver mane and tail
3. Pseudo-albino - very light cream to white; silver
mane and tail; often have "glass" or blue eyes
B. Color Patterns
I. Gray - causes gradual displacement of colored hair by
white hair as age advances:
1. Iron or steel gray - usually a high percentage of
colored hair, indicating a young animal
2. Dapple gray - having the colored hair in such
distribution as to give a dappled effect
3. White - almost devoid of colored hair
II. At certain ages gray, black roan, and gray roan are
practically indistinguishable, but true genetic
differences exist. Gray is foaled solid color; any
roan is foaled roan; and gray roan whitens with age
the same as does gray.
Roan, a more or less uniform mixture of colored and
white hairs, occurs in a number of combinations:
1. Black roan - black and white hairs mixed, usually
2. Blue roan - usually described as black and white
hairs mixed, but almost invariably having some
3. Bay or red roan - roaned bay.
4. Chestnut or strawberry roan - roaned chestnut.
5. Paint roan - roaning imposed on the colored areas
6. Dun roan - roan in combination with the dun factor
7. Gray roan - roan in combination with the gray
III. Dun - always with dorsal stripe; often zebra stripes
on legs and transverse stripe over withers and
shoulders; coat appears diluted:
1. Mouse dun - dun imposed on black, seal brown,
dark mahogany bay, and dark liver chestnut, giving
a smoky effect.
2. Buckskin dun - dun imposed on blood and sandy bay.
3. Claybank dun - dun imposed on sorrel.
IV. Paint or pied - irregular colored and white areas:
1. Piebald - white and black
2. Skewbald - white and any color other than black
Gray, roan, dun, and pied or paint may be in any
Movement on Land
Adapted from Tricker and Tricker, 1966
Three Gaits of the Horse, Drawn from Cine Film
Evolution of the Horse: Teeth, Skulls and Feet
Adapted from World of Wildlife
Br — a^cQ i
Plant Species Comprising at Least 2% or More of the Diet
of Wild Horses in the Southwest Desert Vegetation Types
Adapted from Hansen, 1975
Prosopsis julif lora
green spangletop grass
Plant Species Comprising at Least 2% or More of the Diet
of Wild Horses for the Foothills and Northern Desert Shrub
Vegetation Types in Western States
needle and thread grass
The Spread of the Horse to the Western World
Adapted from Smith, 1969
The spread of the horse
to the western world
Allee, W. C. 1931. Animal Aggregations: A Study in General
Sociology. University of Chicago Press, Chicago. 431 p.
Anonymous. 1971. Family: Equidae. World of Wildlife . 1(5):
Anonymous. 1974. Description of the Barb . Spanish Barb Wild
Horse Research Farm. Porterville, California. 2 p.,
Antonius, 0. 1937. Uber Herdenbildung und Paarungs eigentum-
lichkeiten der Einhufer. Z. Tierpsychol. , 1:259-289.
Beebe, B. F. and J. R. Johnson. 1964. American Wild Horses .
David McKay, New York, 180 p.
Bell, R. H. V. 1970. The use of the herb layer by grazing
ungulates in the Serengeti, p. 111-124. In: A. Watson,
ed. , Animal Populations in Relation to their Food Resources .
. 1971. A grazing ecosystem in the Serengeti.
Scientific American . 225(1) :86-93.
Berliner, V. R. 1969. The estrous cycle of the mare, p. 267.
In: H. H. Cole and P. T. Cupps, eds., Reproduction in
Domestic Animals. Academic Press, New York.
Blakeslee, J. K. 1974. Mother- Young Relationships and Related
Behavior Among Free-Ranging Appaloosa Horses . M. S. Thesis,
Idaho State University. 113 p.
Bone, Jesse F. 1964. The age of the horse. Southwest Veter-
inarian . 17(4):269-272.
Boone, A. R. 1933. The wild herd passes. Travel . 60(4):20-23,
Boughey, A. S. 1968. Ecology of Populations . Macmillan, New
York. 135 p.
Burkhardt, D. , W. Schleidt, and H. Altner. 1967. Signals in
the Animal World . McGraw-Hill, New York. 150 p.
Burkhardt, J. 1947. Transition from anestrus in the mare and
the effects of artificial lighting. Journal of Agricultural
Burt, W. H. 1943. Territoriality and home range concepts as
applied to mammals. Journal of Mammalogy . 24:346-352.
Castle, W. E. 1954. Coat color inheritance in horses and in
other mammals. Genetics. 39(l):35-44.
Catlin, George. 1838. Commanche horses, p. 145-150. In: J. F.
Dobie, M. C. Boatright and H. H. Ransom, Mustangs and Cow
Horses . 1965, 2nd ed. Southern Methodist University Press,
Clegg, M. T. and W. F. Ganong. 1969. Environmental factors
affecting reproduction, p. 473-488. In: H. H. Cole and
P. T. Cupps , eds., Reproduction in Domestic Animals . Academic
Press, New York.
Collias, N. E. 1970. Aggressive behavior among vertebrate
animals, p. 14-39. In: C. H. Southwick, ed. , Animal
Aggression : Selected Readings. Van Nostrand Reinhold,
Cook, C. W. and L. F. Harris. 1968. Nutritive Value of Seasonal
Ranges . Utah State University Agricultural Experiment
Station Bulletin #472. Logan, Utah. 55 p.
Cook, C. W. 197 5. Wild horses and burros: a new management
problem. Rangeman ' s Journal . 2(1):19-21.
Cook, J. H. 1919. Wild horses of the plains. Natural History .
Crain, Carolyn. 1973. Saving the Symbol of the West: The
Wild Horses . Unpublished bibliographic essay. 18 p.
Denhardt, R. M. 1948. The Horse of the Americas . University
of Oklahoma Press, Norman, Oklahoma. 286 p.
Dobie, J. F. 1952. The Mustangs . Little, Brown and Company,
Boston. 376 p.
Edwards, Gladys Brown. 1970. The long and short of it.
Arabian Horse World . 10:87-94.
Ehrenfeld, D. W. 1972. Conserving Life on Earth . Oxford
University Press, New York. 360 p.
Ensminger, M. E. 1951. Horse Husbandry . Interstate Printers
and Publishers, Danville, Illinois. 336 p.
Estes, R. D. 1974. Zebras offer clues to the way wild horses
once lived. Smithsonian. 5(8) : 100-107 .
Feist, J. D. 1971. Behavior of Feral Horses in the Pryor
Mountain Wild Horse Range . M. S. Thesis, University of
Michigan. 129 p.
Frei, Milton. 1975. Personal communication. U. S. Department
of the Interior, Bureau of Land Management, Denver, Colorado,
Glover, J. and D. W. Duthie. 1958. The nutritive ratio crude
protein relationships in ruminant and non-ruminant digestion,
Journal of Agricultural Science . 50:227-229.
Gremmel, F. 1939. Coat color in horses. Journal of Heredity .
Hafez, E. S. E., M. Williams and S. Wierzbowski. 1962. The
behaviour of horses, p. 370-396. In: E. S. E. Hafez, The
Behaviour of Domestic Animals . Williams and Wilkins,
. 1969. The behaviour of horses, p. 391-416. In:
E. S. E. Hafez, The Behaviour of Domestic Animals . Williams
and Wilkins, Baltimore.
Haines, Francis. 1971. Horses in America . Thomas Y. Crowell,
New York. 213 p.
Hall, R. 1972. Wild Horse: Biology and Alternatives for
Management, Pryor Mountain Wild Horse Range . Bureau of Land
Management, Billings District. 67 p.
1974. Wild Horse Capture Techniques . Bureau of
Land Management, Utah State Office, Salt Lake City, Utah.
^ . 1975. Personal communication, U. S. Department
of the Interior, Bureau of Land Management, Salt Lake City,
Hanauer, Elsie. 1973. The Science of Equine Feeding . A. S.
Barnes, New York. 78 p.
Hansen, R. M. 1975. Personal communication. Department of
Range Science. Colorado State University, Fort Collins,
Howard, R. W. 1965. The Horse in America . Follett, Chicago.
Howell, C. E. 1945. Vertebrae in Arabian horses. California
Cultivator. Vol. 92:520. Sept. 29.
Hoyt, H. S. 1886. Mustanging on the staked plains, p. 96-101.
In: J. F. Dobie, M. C. Boatright and H. H. Ransom, eds.,
Mustangs and Cow Horses . 1965, 2nd ed. Southern Methodist
University Press, Dallas.
Huffman, W. T. , E. A. Moran, and W. Binns. 1956. Poisonous
Plants. In: Yearbook of Agriculture Animal Diseases .
U. S. Department of Agriculture, Washington, D. C. 118-130.
James, T. J. 1823. Comanche Horses, pp. 143-144. In:
J. Frank Dobie, Mody C. Boatright and Harry H. Ransom,
Mustangs and Cov Horses . 1965. 2nd Ed. Southern Methodist
University Press, Dallas, Texas.
Kleiman, Devra. 1966. Scent marking in the Canidae. p. 167-177
In: P. A. Jewell and Caroline Loizos, eds. Play, Explora -
tion and Territory in Mammals . Academic Press, New York.
Klingel, H. 1965. Notes on the biology of the plains zebra,
Equus quagga boehmi . East African Wildlife Journal . 3:86-88.
1969. Reproduction in the plains zebra, Equus
Burchellis boehmi : behavior and ecological factors.
Journal Reprod. Fert ., Suppl. 6:339-345.
1972. Social behaviour of African Equidae .
Zoological Africa . 7 (1) : 175-185.
Linsdale, J. M. and P. Q. Tomich. 1953. A Herd of Mule Deer ,
Odocoileus hemionus columbianus . A record of observations
made on the Hastings Natural History Reservation. Berkeley
and Los Angeles.
Loizos, Caroline. 1966. Play in mammals, p. 1-9. In: P. A.
Jewell and Caroline Loizos, eds., Play, Exploration and
Territory in Mammals . Academic Press, New York.
Lorenz, K. 1963. On Aggression . Marjorie Kerr Wilson, trans.
Harcourt, Brace and World, New York. 306 p.
Lyall-Watson, M. 1964. The Ethology of Food Hoarding in
Mammals . Ph.D. Dissertation, University of London.
Mathews, H. L. 1964. Overt fighting in mammals, p. 23-32. In:
J. D. M'Carthy and F. J. Ebling, eds., The Natural History
of Aggression . Academic Press, New York.
McKnight, T. L. 1959. The feral horse in Anglo-America.
Geographical Review . 49:506-525.
Nishikawa, Y. , T. Svjie and N. Haracla. 1952. 35 Animal Breed-
ing Abstracts. 22:103. Bulletin National Institute of
Agricultural Science Series G3 . 1954.
Odberg, F. 0. 1972. An Interpretation of Pawing by the Horse
(Equus caballus L.): Displacement Activity and Original
Functions . Revised part of a B.S. Thesis, State University
of Gent, Belgium. 12 p.
Odum, E. P. 1970. Fundamentals of Ecology . 3rd ed. Saunders,
Philadelphia. 574 p.
Pelligrini, S. W. 1971. Home Range, Territoriality and Move -
ment Patterns of Wild Horses in the Wassuk Range of Western
Nevada . M.S. Thesis, University of Nevada, Reno. 39 p.
Roby, T. 0. and L. 0. Mott. 1956. Diseases and parasites
affecting horses and mules, p. 531-533. In: Yearbook of
Agriculture Animal Diseases . U. S. Department of Agriculture,
Ruckebusch, U. , P. Barbey and P. Guillemot. 1970. Les etats de
Sommeil chez le Cheval ( Equus caballus ) . C. R. Seances Soc .
Biol. Filiales . 164(3) :658-665.
Ryden, Hope. 1970. America's Last Wild Horses . Dutton, New
York. 311 p.
Schenkel, R. 1947. Expression Studies of Wolves. Behaviour .
M. 1930. Das Flehmen I. Zool. Gart. Lpz . 3:183-
1931. Das Flehmen II. Zool. Gart. Lpz . 4:349-364.
1932a. Das Flehmen III. Zool. Gart. Lpz . 5:
1932b. Das Flehmen IV. Zool. Gart. Lpz . 5:287-
Schwartz, B. 1949. A kingdom for wild horses. Nature Magazine .
Scott, J. P. 1958. Aggression . University of Chicago Press,
Chicago, 111. 149 p.
Simpson, G. G. 1951. Horses; The Story of the Horse Family in
the Modern World and through Sixty Million Years of History .
Oxford University Press, New York. 247 p.
Smith, B. 1969. The Horse in the West . World Publishing Com-
pany, New York. 255 p.
Smith, C. H. 1841. Feral horses of America, p. 173-185. In:
C. H. Smith, The Naturalist's Library, Mammalia Vol. XII .
Horses . W. H. Lizars, Edinburgh.
Smythe, R. H. 1966. The Mind of the Horse . Stephen Greene
Press, Brattleboro, Vermont. 123 p.
Southwick, C. H. 1970. Conflict and violence in animal societies,
p. 1-13. In: C. H. Southwick, ed. , Animal Aggression:
Selected Readings . Van Nostrand Reinhold, New York.
Stecher, R. M. 1962. Lateral facets and lateral joints in the
lumbar spine of the horse. American Journal of Veterinary
Research . 23(96) : 934-947 .
Stoddart, L. A., A. D. Smith, T. W. Box. 1975. Range Manage -
ment . McGraw-Hill. New York. 532 p.
Tricker, R. A. R. and B. J. K. Tricker. 1967. The Science of
Movement . American Elsevier, New York. 284 p.
Trumler, E. 1958. Beobachtungen and den Bohm-zebras des Georg
von Opel-Friegeheges fur Tierforschung. I. Das Paarungvser-
halten. Saugetierk Mitt . 6:1-48.
Tyler, S. 197 2. The Behavior and Social Organization of New
Forest Ponies. Animal Behavior Monographs . 5(2):84-196.
U. S. Department of the Interior, Bureau of Land Management.
1973. Environmental Impact Statement and Proposed Manage -
ment Regulations for Wild Free-Roaming Horses and Burros .
. 1974. Livestock Grazing Management on National
Resource Lands . Final Environmental Impact Statement. 3 vols.
U. S. Department of the Interior, U. S. Department of Agriculture,
June, 1974. A Report to Congress by the Secretary of the
Interior and the Secretary of Agriculture on Administration
of the Wild Free-Roaming Horse and Burro Act: P.L. 92-195 .
U. S. Department of the Interior, Bureau of Land Management and
U. S. Department of Agriculture, Forest Service. 1973.
Proceedings of the National Advisory Board for Wild Free -
Roaming Hors es and Burros . 7 p. 14 appendices.
Waring, G. H. 1970. Perinatal behavior of foals (Equus caballus)
Paper presented at 50th Annual Meeting of the American
Society of Mammalogists. June 18, 1970. College Station,
1970. Primary socialization of the foal (Equus
caballus ) . Paper presented at the Animal Behavior Society
at the 21st Annual AIBS meeting. Indiana University,
Bloomington, Indiana, August 29, 1970.
. 1971. Sounds of the horse (Equus caballus).
Paper presented to the Ecological Society of America. 22nd
Annual American Institute of Biological Sciences meeting,
Colorado State University, Fort Collins, Colorado. Sept. 2,
Worcester, D. E. 1945. Spanish horses among the plains tribes.
Pacific Historical Review . 14:409-417.
World of Wildlife. 1971. Vol. 1, part 5. Orbis Publishing
Ltd. , London.
Wyman, Walker D. 1945. The Wild Horse of the West . Caxton
Printers, Caldwell, Idaho. 348 p.
Young, S. P. and E. A. Goldman. 1946. The Puma, Mysterious
American Cat . American Wildlife Institute, Washington, D.C.
Zeeb, K. 1959. Die Unterlegenheitsgebarde' des noch nicht
ausgewachsenen Pferdes, ( Equus caballus ) . Z. Tierpsychol . ,
Ziswiler, V. 1967. Extinct and Vanishing Animal s. Revised
English Edition by F. and P. Bunnell. Springer-Verlag.