Dogs
Dogs
Dogs
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Labrador Retriever, a breed of domestic dog
The dog is a
canine
mammal of the
Order
Carnivora. Dogs were first
domesticated from
wolves at least
12,000 years ago[1]
but perhaps as long as 150,000 years ago based on recent genetic fossil evidence
and DNA evidence[2].
In this time, the dog has developed into hundreds of breeds with a great degree
of variation. For example, heights at the
withers range
from just a few inches (such as the
Chihuahua) to roughly three feet (such as the
Irish Wolfhound), and colors range from white to black, with reds, grays
(usually called blue), and browns occurring in a tremendous variation of
patterns. Dogs, like humans, are highly
social animals and
pack
hunters; this similarity in their overall behavioral design accounts for
their trainability, playfulness, and ability to fit into human households and
social situations. Dogs fill a variety of roles in human society and are often
trained as
working
dogs. For dogs that do not have traditional jobs, a wide range of
dog sports
provide the opportunity to exhibit their natural skills. In many countries, the
most common and perhaps most important role of dogs is as
companions. Dogs have
lived with and worked with humans in so many roles that their loyalty has earned
them the
sobriquet "man's best friend." Conversely, some cultures consider dogs to be
unclean. In other cultures, some dogs are used as food.
Terminology
Puppies engage in
teething on almost anything.
Dog, in common usage, refers to the domestic dog, Canis lupus
familiaris (originally classified as Canis familiaris by
Linnaeus in 1758, but reclassified as a subspecies of the
wolf, Canis
lupus, by the
Smithsonian Institution and the
American Society of Mammalogists in 1993). The word is sometimes used to
refer collectively to any
mammal
belonging to the family
Canidae (as
in "the dog family"), such as
wolves,
foxes and
coyotes.
- Dog is also a term used by breeders to specifically denote a
male domestic
dog.
- Bitch
is a female
dog.
- Pack is used to denote a group of dogs.
- Puppy is a juvenile dog.
- Pooch, Poochie, Dogay, Pup, Pupsie,
Doggy, Doggie or Doglet are all informal and
affectionate terms for a dog often used by children.
- Canine in common usage is a synonym for dog or an adjective
meaning dog; for example, in the common expression "canine companion".
Many additional terms are used for dogs that are not purebred; see
Terms for mixed-breed dogs.
Physical characteristics
- Main articles:
Dog
anatomy
Although selective breeding has changed the appearance of many breeds, all
dogs retain the basic ingredients from their distant ancestors. Like most other
predatory mammals, the dog has powerful muscles, a
cardiovascular system that supports both sprinting and endurance, and teeth
for catching, holding, and tearing. Its skeleton provides the ability to run and
leap. They have small, tight feet, and walk on their toes.
Intelligence
Among dog lovers, dogs are generally valued for their intelligence.
Anecdotal
evidence suggests that dogs have a reasonably high intelligence. For a detailed
discussion on what dog intelligence is, see
dog intelligence.
Diet
This
English Springer Spaniel is enjoying a bone.
See also:
Dog
health
Presently, there is academic discussion as to whether domestic dogs are
omnivores
or
carnivores. The classification in the Order
Carnivora
does not necessarily mean that a dog's diet must be restricted to
meat. Unlike an
obligate carnivore, such as a
cat, a dog is not
dependent on meat protein in order to fulfill its dietary requirements. Dogs are
able to healthily digest a variety of foods including
vegetables
and grains, and
in fact can consume a large proportion of these in its diet. Wild canines not
only eat available plants to obtain key
amino
acids, but may also obtain nutrients from vegetable matter from the stomach
contents of their
herbivorous prey. Domestic dogs can survive healthily on a reasonable and
carefully designed
vegetarian
diet, particularly if
eggs
and milk products
are included. Some sources suggest that a dog fed on a stict vegetarian diet may
develop dilated cardiomyopathy since it lacks L-carnitine.[3]
In the wild these diets are typically pursued in the absence of available
meat. It has also been noted that extremely stressful conditions, such as the
Iditarod
race and scientific studies of similar conditions, suggest that high-protein
diets including meat help prevent damage to muscle tissue. This research is also
true of other mammals.
Dogs sometimes eat grass, a harmless activity. Explanations abound, but
rationales such as that it neutralizes acid are just guesses. Eating grass might
make the dog vomit, so one explanation is that dogs eat grass to remove unwanted
content from their stomachs.
Treats
Many dogs consider anything given to them directly by hand to be a treat,
even the food they are accustomed to at meal time. Such dogs might consider
anything dropped by humans, including small but indigestible objects (such as
marbles, coins, rings, etc.), to be treats as well, which could be dangerous to
the dogs when ingested.
For a discussion on one use of treats in training, see
clicker training.
Dangerous substances
Some foods commonly enjoyed by humans are dangerous to dogs, including
chocolate
(Theobromine
poisoning),
onions, grapes
and raisins,
Macadamia nuts, and
hops. Some human medications, such as
acetaminophen/paracetamol (Tylenol), are highly toxic to dogs.
Dogs also may find some poisons attractive, including
antifreeze
and snail bait.
Reproduction
Among professional breeders, dogs are only allowed to mate for a specific
purpose. Sometimes dogs are bred to create puppies to sell, or sometimes to
carry on an award-winning purebred line. Breeders who do this are usually
experienced in this process. Dog breeders have access to records which allow
them to accurately guess which characteristics will "breed true" in a particular
dog. Dog breeders also have accurate information on the complexities of the
reproductive process for the breed of dog that they are accustomed to handling.
Dog owners may accidentally allow their pets to breed without regard to
bloodlines.
Fertility
As with most domesticated species, one of the first and strongest effects
seen from selective breeding is selection for cooperation with the breeding
process as directed by humans. In domestic dogs, one of the behaviours that is
noted is the abolition of the pair bond seen in wild canines. The ability of
female domestic dog to come into
estrus at any
time of the year and usually twice a year is also valued. The amount of time
between cycles varies greatly among different dogs, but a particular dog's cycle
tends to be consistent through her life. This is also called in season or
in heat. Conversely, undomesticated canine species experience estrus once
a year, typically in late winter.
Menarche
Most bitches come into season for the first time between 6 and 12 months,
although some larger breeds delay until as late as 2 years. Like most mammals,
the age that a bitch first comes into season is mostly a function of her current
body weight as a proportion of her body weight when fully mature. The different
rates of maturation are responsible for the
menarche,
not the chronological age.
Pregnancy and litters
Catahoula Leopard Dog nursing litter of puppies
A general rule of thumb is that a mammal will produce half as many offspring
as the number of teats on the mother. This rule is altered in domesticated
animals since larger litters are often favoured for economic reasons. Dogs bear
their litters roughly 9 weeks after
fertilization. An average litter consists of about six puppies,
though this number may vary widely based on the breed of dog. Since a mother can
only provide nutrients and care to a limited number of offspring, humans must
assist in the care and feeding when the litter exceeds approximately eight
puppies. Some breeds have been developed to emphasize certain physical traits
beyond the point at which they can safely bear litters on their own. For
example, the
Bulldog often requires
artificial insemination and almost always requires
cesarean section for giving birth.
Spaying and neutering
Spaying or neutering refers to the removal of the male
testicles
or the female ovaries
and uterus, in
order to remove the capability to procreate, and to kill the
libido.
Dog experts advise that dogs not intended for further breeding should be
spayed or neutered so that they do not have undesired puppies. Unwanted puppies
are abandoned, eaten, or sometimes disposed of in an inhumane fashion. It is
also common for adult stray dogs who are placed in animal shelters to be
euthanized due to lack of space and resources.
Spaying and neutering can also help prevent hormone-driven diseases such as
breast cancer and prostate cancer, as well as undesired hormone-driven
behaviors. The hormonal changes involved are sure to change the animal's
personality somewhat, and some object to this angle as the sterilization in
itself could be carried out without the excision of organs.
Contrary to myth, it is not required for a female dog to either experience a
heat cycle or have puppies before spaying, and likewise, a male dog does not
need the experience of mating before neutering; these myths are responsible for
numerous unnecessary health problems and unwanted puppies. A female dog can
become pregnant on her first heat cycle (which can take place as early as six
months), and should be kept away from intact male dogs, including littermates,
over the age of 4 months. Many veterinarians recommend that owners neuter/spay
their pets around the age of 5 months.
Attributes
Modern dog
breeds show more variation in size, appearance, and behavior than any other
domestic animal. Within the range of extremes, dogs generally share attributes
with their wild ancestors, the
wolves. Dogs are
predators
and
scavengers, possessing sharp teeth and strong jaws for attacking, holding,
and tearing their food.
Sight
Dogs were thought to be
dichromats
and thus, by human standards,
color
blind.1,
2 New research is now
being explored that suggests that dogs may actually see some colour, but not to
the extent that humans do. It has also been suggested that dogs see in varieties
of purple/violet and yellow shades. Because the lenses of dogs' eyes are flatter
than humans', they cannot see as much detail; on the other hand, their eyes are
more sensitive to light and motion than humans' eyes. Some breeds, particularly
the best
sighthounds, have a field of vision up to 270° (compared to 100° to 120° for
humans), although broad-headed breeds with their eyes set forward have a much
narrower field of vision, as low as 180°.1,
2
Hearing
Dogs detect sounds as low as the 16 to 20
Hz frequency
range (compared to 20 to 70 Hz for humans) and as high as 70,000 to 100,000 Hz
(compared to 20,000 Hz for humans)2,
and in addition have a degree of ear mobility that helps them to rapidly
pinpoint the exact location of a sound. They can identify a sound's location
much faster than a human can, and they can hear sounds up to four times the
distance that humans can.
Scenting
Dogs are predators suited to chasing after, leaping at, and killing
prey. (pictured:
Weimaraner)
Dogs have nearly 220 million smell-sensitive cells over an area about the
size of a pocket
handkerchief (compared to 5 million over an area the size of a
postage stamp for humans). Some breeds have been selectively bred for
excellence in detecting scents, even compared to their canine brethren. Other
than the oversimplified obvious, i.e. chemical compounds that affect
chemical sensors in the nose, what a dog actually detects when he is scenting is
not really understood; although once a matter of debate, it now seems to be well
established that dogs can distinguish two different types of scents when
trailing, an air scent from some person or thing that has recently passed by, as
well as a ground scent that remains detectable for a much longer period. The
characteristics and behavior of these two types of scent trail would seem, after
some thought, to be quite different, the air scent being intermittent but
perhaps less obscured by competing scents, whereas the ground scent would be
relatively permanent with respect to careful and repetitive search by the dog,
but would seem to be much more contaminated with other scents. In any event, it
is established by those who train tracking dogs that it is impossible to teach
the dog how to track any better than it does naturally; the object instead is to
motivate it properly, and teach it to maintain focus on a single track and
ignore any others that might otherwise seem of greater interest to an untrained
dog. An intensive search for a scent, for instance searching a ship for
contraband, can actually be very fatiguing for a dog, and the dog must be
motivated to continue this hard work for a long period of time.
Direction and spatial sense
It has been observed that a lost dog can often find its way home, sometimes
traveling over long distances.
Weather detection
Dogs also have the ability to sense inclement weather (mainly
thunderstorms) many miles away. This is due to their keen ability to detect
fluctuations in
barometric pressure and can explain a dog's anxiety before and during a
storm. The evolutionary ability of sensing weather can be traced back to when
wolves used it to move the pack into proper shelter before a dangerous storm.
Dog health
- Main articles:
Dog
health
Dogs are susceptible to various diseases, ailments, and poisons, some of
which affect humans in the same way, others of which are unique to dogs.
Diseases
Diseases commonly associated with dogs include
rabies
(hydrophobia),
canine parvovirus, and
canine distemper, and
pulmonic stenosis, although there are many others.
Parasites
Common external parasites are various species of
fleas,
ticks, and
mites. Internal
parasites include
hookworms,
tapeworms,
roundworms,
and
heartworms.
Common physical disorders
Some breeds of dogs are also prone to certain genetic ailments, such as
hip
dysplasia,
luxating patellas,
cleft
palate,
blindness, or
deafness. Dogs are also susceptible to the same ailments that humans are,
including
diabetes,
epilepsy,
cancer, and
arthritis.
Gastric torsion and
bloat is a
dangerous problem in some large-chested breeds.
Behavior
Some dogs can be trained to retrieve
All dogs have a tremendous capacity to learn complex social behavior and to
interpret varied body language and sounds, and, like many predators, can react
to and learn from novel situations. The requirements of coordinating complex
social behavior requires that canines have the ability to sense and deliver a
wide variety of cues via body language, more so than for even humans, who can
use language for the same purpose. Physiologically, this correlates with such
features as a large number of nerves innervating the facial muscles of dogs,
allowing subtle control of a wide variety of facial expressions; in contrast to
cats, for instance,
who have many fewer nerves governing their facial muscles, resulting in a
smaller repertoire or "vocabulary" of expressions. This ability to read and
deliver nonverbal cues makes dogs expert at reading human beings, as well, often
even more so than other humans are, who rely on language. Most dog owners have a
large collection of stories about their dogs recognizing individuals by their
footsteps outside the door, and so on.
Interactions between Dogs and Humans
- Main articles:
Dog
society
The relationship between dogs and humans is rooted in history and dogs
coexist with humans in a variety of ways. Dogs thrive in small social groups or
packs
which, from their viewpoint, can include humans. Dog society can be thought of
as dog packs characterized by a companionate hierarchy, in which each individual
has a rank, and in which there is intense loyalty within the group. Dogs thrive
in human society because their relationships with humans mimic their natural
social patterns. The dog is always aware of its rank relative to other
individuals in the group. An assertive dog may consider itself the alpha animal,
considering its human master to be subordinate.
Dogs as working partners
Many breeds of dogs, but not least German Shepherd,
Labrador Retriever, and Border Collie are commonly used as
working
dogs. There are
service
dogs,
guard dogs,
hunting
dogs, and
herding
dogs. Dogs have served as
guides
for the blind,
as commandos,
and have flown into
outer
space. Most modern working dogs are put in positions which capitalize on
their sensory or strength and endurance advantages over normal humans. Dogs are
also used for searching for or rescuing people and animals, such as in
avalanches, at disaster sites, and for missing people or pets.
Dogs as hunting and sporting partners
Many people compete with their dogs in a variety of
dog sports,
including
agility,
flyball, and many others. This often strengthens the bond between human and
dog, since they must trust one another in a variety of environments and must
learn how the other works and thinks.
Setters in
particular have a long history as upland gun dogs. They have a native ability to
discover and "hold" upland game birds; to freeze them momentarily on the ground
with their silent, elongated pointing stance. Once the hunter approaches, at his
command they will flush the birds to fly and for the hunter to shoot at.
As water dogs, the
retrievers
are unsurpassed. They can spend long hours in a
duck blind
and, after the hunter has fired at multiple ducks or geese, they can visually
spot and remember the location of downed birds. At command, they dive into the
icy water, swim out and retrieve the birds one by one. They can follow hand,
verbal, and whistle commands at great distance as the hunter directs them to the
downed bird. They typically have large, gentle muzzles to mitigate any potential
damage to the game.
When trained,
beagles are particularly adept at chasing through thick briars and brush
after rabbits. Many
hound breeds are excellent at treeing raccoons during hunting season.
Hunters with dogs report the satisfaction that the dogs seem to exhibit.
Excitement is evident as they see the hunters load weapons, take to the field,
and begin the hunt.
Dogs as pets
A 9 year old English
Collie
cross. Some say
mongrels make the best pets
Relationships between humans and dogs are often characterized by strong
emotional bonds. Consequently, dogs are popular as
pets and companions,
independent of any
utilitarian considerations. Many dog owners consider having unconditional
acceptance from a friend who is always happy to see them to be quite
utilitarian, particularly if the dog also leads them to regular exercise.
Empirically, dogs are quite dependent on human companionship and may suffer poor
health in its absence. Many dogs are reported to have
separation anxiety if their owner is away for an extended period of time.
Some research demonstrates that dogs are able to convey a depth of emotion
not seen to the same extent in any other animal; this is purportedly due to
their closely-knit development with modern man, and the survival-benefits of
such communication as dogs became more dependent on humans for sustenance.
Nevertheless, it is often unwise to
anthropomorphize the responses of dogs. Despite understandably positive
interpretations by dog owners, it is questionable whether these animals are
truly capable of feeling emotions on a human level. More research is needed to
determine the
intelligence level of dogs, and the motivations behind their responses to
their masters.
Attacks on humans and livestock
- Main articles:
Dog
attack
Humans have a tendency to anthropomorphize animals, particularly pets such as
dogs, which are generally portrayed as being "man's best friend". Animals are
often given attributes such as "loyal", "cute", and "guardian", but these all
have the potential to lure people into a false sense of security.
After thousands of years of domestication and selective breeding for dogs
whose aggression towards humans goes no further than a ferocious bark that
strongly indicates dislike of a human behavior, most dogs are unlikely to attack
people. However, their sharp teeth and claws can inflict injury in an attack; a
large dog can knock a human down. Provocation can range from something as
seemingly innocuous as a toddler pulling a dog's tail, in which case the dog
might nip to discourage the behavior, to something completely transparent to
humans, such as an odor or a movement that sets a dog off, to blatant human
aggression or violence towards a dog, causing it to defend itself. There are
hundreds of shades of provocation that may or may not lead to an attack upon a
human. Canine aggression upon humans is ordinarily not tolerated, but any human
aggression against an animal having formidable means of self-defense is
foolhardy in the extreme.
With formidable skills and weapons as hunters as well as large and unfussy
appetites, dogs often menace livestock and wildlife. In most jurisdictions, dogs
are destroyed for killing other creatures, so dogs should be prevented from any
encounter with livestock or wildlife that might lead to a predatory response.
The same creatures that
wolves, coyotes,
and foxes attack as
prey, especially sheep and poultry, are similarly attractive prey to dogs.
Abandoned dogs
Wild dogs are shot by farmers in an effort to protect
livestock.
Bodies are sometimes tied to fences as warning to other dogs, especially in
rural United States and
Canada.
Abandoned domestic dogs who become
feral are
particularly dangerous; they lack the survival skills of wild canines, as well
as the genetic and learned fear of the humans' world. Feral dogs often form
predatory packs that attack livestock and occasionally also prove dangerous to
humans.
In the UK, it is illegal to kill dogs, even if they are on your private land;
you are required to contact your local
Police Force,
DogsTrust, or the local branch of the
RSPCA, who will
arrange its collection.
Ancestry and history of domestication
This ancient mosaic, likely Roman, shows a large dog with a collar
hunting a lion.
Molecular systematics indicate that the domestic dog (Canis lupus
familiaris) descends from one or more populations of wild wolves (Canis
lupus). As reflected in the
nomenclature, dogs are a subspecies of wolf and are thus still able to
interbreed.
The relationship between man and canine has deep roots.
Wolf remains have
been found in association with
hominid
remains dating from 400,000 years ago. Converging archaeological and genetic
evidence indicate a time of
domestication in the late
Upper Paleolithic close to the
Pleistocene/Holocene
boundary, between 17,000 and 14,000 years ago.
Fossil bone
morphologies and genetic analysis of current and ancient dog and wolf
populations have not yet been able to conclusively determine whether all dogs
descend from a single domestication event, or whether dogs were domesticated
independently in more than one location. Domesticated dogs may have interbred
with local populations of wild wolves on several occasions (so-called
introgression).
The earliest dog fossils, two crania from Russia and a mandible from Germany,
date from 13,000 to 17,000 years ago. Their likely ancestor is the large
northern
Holarctic wolf, Canis lupus lupus. Remains of smaller dogs from
Mesolithic
(Natufian)
cave deposits in the Middle East, dated to around 12,000 years ago, have been
interpreted as descendants of a lighter Southwest Asian wolf, Canis lupus
arabs. Rock
art and skeletal remains indicate that by 14,000 years ago, dogs were
present from North Africa across Eurasia to North America. Dog burials at the
Mesolithic
cemetery of
Svaerdborg in Denmark suggest that in ancient Europe dogs were valued
companions.
Genetic analyses have so far yielded divergent results. Vilà, Savolainen, and
colleagues (1997) concluded that dogs split off from wolves between 75,000 and
135,000 years ago, while a subsequent analysis by Savolainen et al. (2002)
indicated a "common origin from a single gene pool for all dog populations"
between 40,000 and 15,000 years ago in East Asia. Verginelli et al. (2005),
however, suggest both sets of dates must be reevaluated in light of recent
findings showing that poorly calibrated molecular clocks have systematically
overestimated the age of geologically recent events. On balance, and in
agreement with the archaeological evidence, 15,000 years ago is the most likely
time for the wolf-dog divergence.
Verginelli examined ancient
DNA evidence from
five prehistoric Italian
canids
carbon-dated to between 15,000 and 3,000 years old, 341 wolves from several
populations worldwide, and 547 purebred dogs. Their results indicate multiple
independent origins of dogs and/or of frequent interbreeding between early
proto-dogs and wolves throughout a vast geographic range. The detailed history
remains unexplored and until further evidence is available, the following
section on wolf ancestors must be considered purely speculative.
Wolf ancestors
Although all wolves belong to the species
Canis
lupus, there are (or were) many subspecies that had developed a
distinctive appearance, social structure, and other traits. For example, the
Japanese wolf and the
Eastern Timber Wolf posses different distinctive colouration, hunting and
social structures.
The
Indian Wolf is thought to have contributed to the development of more breeds
of dogs than other subspecies. Many of today's wild dogs, such as the
dingo, the
dhole and
pariah dogs,
are descended from this wolf.
The
Indian wolf is also thought to have bred with descendants of the European
wolf to create the
Mastiffs and
eventually leading to the development of such diverse breeds as the
Pug, the
Saint Bernard, and the
Bloodhound.
The
Tibetan Mastiff is an example of an ancient breed.
The
European wolf, in turn, may have contributed many of its attributes to the
Spitz dog types,
most terriers,
and many of today's
sheepdogs.
The
Chinese wolf is probably ancestor to the
Pekingese
and toy spaniels,
although it is also probable that descendants of the Chinese and European wolves
encountered each other over the millennia, contributing to many of the oriental
toy breeds.
The
Eastern Timber Wolf is a direct ancestor to most, if not all, of the North
American northern
sled dog
types. This interbreeding still occurs with dogs living in the
Arctic region,
where the attributes of the wolf that enable survival in a hostile environment
are valued by humans. Additionally, unintentional crossbreeding occurs simply
because dogs and wolves live in the same environment. The general
reproductive isolation which is required to define dogs and wolves as
separate species is purely a result of lack of opportunity, stemming from a
general mutual unfamiliarity, suspicion, mistrust, and fear.
The
phenotypic characteristic that distinguish a wolf from a dog are tenuous.
Wolves typically have a "brush tail" and erect ears. While some dog breeds
possess one of these characteristics, they rarely possess both.
Speed of domestication
Current research indicates that domestication, or the attributes of a
domesticated animal,
can occur much more quickly than previously believed. Domestication of a
wild dog may occur within one or two human generations with deliberate
selective breeding. It is also now generally believed that initial
domestication was not attained solely by human desire intervention but through
mutual desire. Wild canines who scavenged around human habitations received more
food than their more skittish or fearful counterparts. Canines who attacked
people or their children were likely killed or driven away, while those more
friendly animals survived. Canines would have been beneficial by chasing away
other vermin or
scavengers.
With their sharp senses, they would also be valuable as an alarm against
marauding predators. The relationship is theorized to have developed in this
way.
Dog breeds
There are numerous
dog breeds,
over 800 being recognized by various
kennel
clubs worldwide. As all dog breeds have been derived from mixed-breed dog
populations, the term "purebred" has meaning only with respect to a certain
number of generations. Many dogs, especially outside the United States and
Western Europe, belong to no recognized breed.
A few basic
breed types have evolved gradually during the domesticated dog's
relationship with man over the last 10,000 or more years, but most modern breeds
are of relatively recent derivation. Many of these are the product of a
deliberate process of
artificial selection. Because of this, some breeds are highly specialized,
and there is extraordinary morphological diversity across different breeds.
Despite these differences, dogs are able to distinguish dogs from other kinds of
animal.
The definition of a dog breed is a matter of some controversy. Some groups
use a definition that ultimately requires extreme
inbreeding
to qualify due to the low
gene pool.
Dogs that are bred in this manner often end up with severe health or behavioural
problems. Other organizations define a breed more loosely, such that an
individual may be considered of one breed as long as 75% of its parentage is of
that breed. These considerations come into play among breeders who enter their
dogs in dog
shows. Even prize-winning
purebred
dogs sometimes possess crippling
genetic defects due to
inbreeding.
These problems are not limited to
purebred
dogs and can affect mixed-breed populations. The behavior and appearance of a
dog of a particular breed can be predicted fairly accurately, while mixed-breed
dogs show a broader range of innovative appearance and behavior.
In February 2004, the Canine Studies Institute in
Aurora,
Ohio, arranged recognized breeds of dogs into ten categories.
Mixed-breed dogs or
Mongrels are
dogs that do not belong to specific breeds, being mixtures of two or more in
variant percentages. Mixed breeds, or dogs with no purebred ancestry, are not
inherently "better" or "worse" than purebred dogs as companions,
pets,
working
dogs, or competitors in
dog sports.
Sometimes mixed-breed dogs are deliberately bred, for example, the Cockapoo, a
mixture of Cocker Spaniel and Miniature
Poodle. Such
deliberate crosses may display
hybrid
vigor and other desirable traits, but can also lack one or more of the
desired traits of their parents, such as temperament or a particular color or
coat. However, without genetic testing of the parents, the crosses can sometimes
end up inheriting genetic defects that occur in both parental breeds.
Deliberately crossing two or more breeds is also a manner of establishing new
breeds.
Neoteny in the rapid evolution of diverse dog breeds
This rapid evolution of dogs from wolves is an example of
neoteny or
paedomorphism. As with many species, the young wolves are more social and
less dominant
than adults; therefore, the selection for these characteristics, whether
deliberate or inadvertent, is more likely to result in a simple retention of
juvenile characteristics into adulthood than to generate a complex of
independent new changes in behavior. This is true of many domesticated animals,
including human beings themselves, who have many characteristics similar to
young bonobo.
This paedomorphic selection naturally results in a retention of juvenile
physical characteristics as well. Compared to wolves, many adult dog breeds
retain such juvenile characteristics as soft fuzzy fur, round torsos, large
heads and eyes, ears that hang down rather than stand erect, etc.;
characteristics which are shared by most juvenile
mammals, and
therefore generally elicit some degree of protective and nurturing behavior
cross-species from most adult mammals, including humans, who term such
characteristics "cute" or "appealing".
The example of canine neoteny goes even further, in that the various breeds
are differently neotenized according to the type of behavior that was selected.
-
Livestock guardian dogs retain the most juvenile characteristics: they
stay close to home with their foster "litter" (which might include a flock
of
sheep), rather than going out hunting, they have almost no predatory
behavior (which would be disastrous in the vicinity of such a natural prey
stimulus as sheep), they respond to perceived threats with a lot of
vocalization and attempts to alert and engage the dominant individuals in
their "pack" (i.e. humans) whenever possible, engaging in actual
combat only as a last resort. In addition, they retain very juvenile
physical characteristics such as round bodies and heads, soft coats, ears
that hang down, and so on, which do not elicit fear responses from the sheep
in the way that an appearance similar to that of an adult wolf would.
(Compare to the physical appearance of the
border collie, a sheep
herding
dog, whose physical configuration is closer to that of an adult wild canine
and who therefore has a greater capacity to frighten sheep into a desired
pattern of movement, along with the more adult aggressive temperament to do
so).
- Gun dog
breeds used in hunting—that is,
pointers,
setters,
spaniels, and
retrievers—have an intermediate degree of paedomorphism; they are at the
point where they share in the pack's hunting behavior, but are still in a
junior role, not participating in the actual attack. They identify potential
prey and freeze into immobility, for instance, but refrain from then
stalking the prey as an adult predator would do next; this results in the
"pointing" behavior for which such dogs are bred. Similarly, they seize dead
or wounded prey and bring it back to the "pack", even though they did not
attack it themselves, that is, "retrieving" behavior. Their physical
characteristics are closer to that of the mature wild canine than the
sheepdog breeds, but they typically do not have erect ears, etc.
-
Scenthounds maintain an intermediate body type and behavior pattern that
causes them to actually pursue prey by tracking their scent, but tend to
refrain from actual individual attacks in favor of vocally summoning the
pack leaders (in this case, humans) to do the job. This contrasts with
sighthounds, who pursue and attack perceived prey on sight, and who
maintain the mature canine body type with erect ears, lean bodies, and adult
coats.
- Terriers
similarly have adult aggressive behavior, famously coupled with a lack of
juvenile submission, and display correspondingly adult physical features
such as erect ears, although many breeds have also been selected for size
and sometimes
dwarfed legs to enable them to pursue prey in their burrows.
- The least paedomorphic behavior pattern may be that of the
basenji,
bred in Africa
to hunt alongside humans almost on a peer basis; this breed is often
described as highly independent, neither needing nor appreciating a great
deal of human attention or nurturing, often described as "catlike" in its
behavior. It too has the body plan of an adult canine predator.
Of course, dogs in general possess a significant ability to modify their
behavior according to experience, including adapting to the behavior of their
"pack leaders"—again, humans. This allows them to be trained to behave in a way
that is not specifically the most natural to their breed; nevertheless, the
accumulated experience of thousands of years shows that some combinations of
nature and nurture are quite daunting, for instance, training
whippets to
guard flocks of sheep.
See also
References and further reading
- Abrantes, Roger (1999). Dogs Home Alone. Wakan Tanka, 46 pages.
ISBN 0966048423 (paperback).
- 1A&E Television Networks (1998). Big Dogs, Little Dogs:
The companion volume to the A&E special presentation, A Lookout Book, GT
Publishing.
ISBN 1-57719-353-9 (hardcover).
- 2Alderton, David (1984). The Dog, Chartwell Books.
ISBN 0-89009-786-0.
- Brewer, Douglas J. (2002) Dogs in Antiquity: Anubis to Cerberus: The
Origins of the Domestic Dog, Aris & Phillips
ISBN 0856687049
- Cunliffe, Juliette (2004). The Encyclopedia of Dog Breeds.
Parragon Publishing.
ISBN 0-75258-276-3.
- Donaldson, Jean (1997). The Culture Clash. James & Kenneth
Publishers.
ISBN 1888047054 (paperback).
- Fogle, Bruce, DVM (2000). The New Encyclopedia of the Dog. Doring
Kindersley (DK).
ISBN 0-7894-6130-7.
- Milani, Myrna M. (1986). The Body Language and Emotion of Dogs: A
practical guide to the Physical and Behavioral Displays Owners and Dogs
Exchange and How to Use Them to Create a Lasting Bond, William Morrow,
283 pages.
ISBN 0688128416 (trade paperback).
-
Pfaffenberger, Clare (1971). New Knowledge of Dog Behavior.
Wiley,
ISBN 0876057040 (hardcover); Dogwise Publications, 2001, 208 pages,
ISBN 1929242042 (paperback).
- Savolainen, P. et al. (2002). Genetic Evidence for an East Asian Origin
of Domestic Dogs. Science 298. 5598: 1610–1613.
- Shook, Larry (1995). "Breeders Can Hazardous to Health",The Puppy
Report: How to Select a Healthy, Happy Dog, Chapter Two, pp. 13–34.
Ballantine, 130 pages,
ISBN 0345384393 (mass market paperback); Globe Pequot, 1992,
ISBN 1558211403 (hardcover; this is much cheaper should you buy).
- Shook, Larry (1995). The Puppy Report: How to Select a Healthy, Happy
Dog, Chapter Four, "Hereditary Problems in Purebred Dogs", pp. 57–72.
Ballantine, 130 pages,
ISBN 0345384393 (mass market paperback); Globe Pequot, 1992,
ISBN 1558211403 (hardcover; this is much cheaper should you buy).
- Thomas, Elizabeth Marshall (1993). The Hidden Life of Dogs
(hardcover), A Peter Davison Book, Houghton Mifflin.
ISBN 0395669588.
- Verginelli, F. et al. (2005). Mitochondrial DNA from Prehistoric Canids
Highlights Relationships Between Dogs and South-East European Wolves.
Mol. Biol. Evol. 22: 2541–2551.
-
^ Vilà, C. et al. (1997).
Multiple and ancient origins of the domestic dog. Science 276:1687–1689.
(Also
"Multiple and Ancient Origins of the Domestic Dog")
-
^ Small animal internal
medicine, RW Nelson, Couto page 107
External links
- General info
- Genetics and origins
- Training and behavior
- Breed listings from major
kennel clubs
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