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Dogs
(Canis lupus familiaris.)
Dog" 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. The
dog (Canis lupus familiaris) is a domesticated subspecies of
the wolf, a mammal of the Canidae
family of the order Carnivora. The domestic dog (Canis
lupus familiaris) descends from one or more populations of wild wolves
(Canis lupus).The species was originally classified as Canis
familiaris by Linnaeus in 1758. It has been reclassified as a
subspecies of the gray wolf, Canis lupus, in 1993 by the
Smithsonian Institution and the American Society of Mammalogists.
It has been
suggested that dogs were first domesticated in East Asia, possibly
China
and taken to North America from
Asia
. Dogs migrated with
humans around the planet a variety of dog forms migrated with them.
Dogs are very social animals.
The domestic dog is one of the most widely-kept working and
companion animals in human history. It is estimated that there are 400,million
dogs in the world. The dog has
evolved into hundreds of breeds. It is
considered as a food source in some cultures.
The time of domestication in the late Upper Paleolithic close to the
Pleistocene/Holocene boundary, between 17,000 and 14,000 years ago.
Dogs are dichromats and have color vision equivalent to
red-green color blindness in humans
Some breeds, particularly the sighthounds, have a field of vision up to
270° (compared to 180° for humans), although broad-headed breeds with
short noses have a much narrower field of vision, as low as 180°
Dogs detect sounds as low as the 16 to 20 Hz frequency range (compared to
20 to 70 Hz for humans) and above 45 kHz (compared to 13 to 20 kHz for
humans), and in addition have a degree of ear mobility that
helps them to rapidly pinpoint the exact location of a sound.
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).
In domestic dogs, sexual maturity (puberty) begins to
happen around age 6 to 12 months for both males and females, although this
can be delayed until up to two years old for some large breeds.
Dogs bear their litters roughly 56 to 72 days
after fertilization, although the length of gestation can vary. An average
litter consists of about six puppies, though this number may vary widely
based on the breed of dog. Toy dogs generally produce from one to four
puppies in each litter, while much larger breeds may average as many as 12
pups in each litter.
Neutering (spaying females and castrating males) refers to
the sterilization of animals, usually by removal of the male's testicles
or the female's ovaries and uterus,
Dogs are able to healthily digest a variety of foods
including vegetables and grains, and in fact dogs can consume a large
proportion of these in their diet and can survive healthily on a reasonable vegetarian diet,if eggs and
milk products are included
As a rule of thumb, small breeds are longer-lived than large breeds, but
some of the longest lived large breeds have median longevities nearly as
large as those of the shortest lived small breeds, and some of the breeds
with the shortest longevities are medium-sized.The median longevity of most dog breeds is between 10 and 13 years. The
breed with the dubious distinction of the shortest lifespan is
the Dogue de Bordeaux with a median longevity of about 5.2 years, but
several breeds, including Miniature Bull Terrier, Bulldog, Nova Scotia
Duck Tolling Retriever, Bloodhound, Irish Wolfhound, Greater Swiss
Mountain Dog, Great Dane, and Mastiff, are nearly as short-lived, with
median longevities between 6 and 7 years. On the other end of the
spectrum, the longest-lived breeds, including Toy Poodle, Border Terrier,
Miniature Dachshund, Miniature Poodle, and Tibetan Spaniel, have median
longevities between 14 and 15 years.
Dogs are employed in various roles across the globe, proving invaluable
assets in areas such as
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search-and-rescue; law enforcement (including attack
dogs, sniffer dogs and tracking dogs);
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guards for livestock, people or property;
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herding; Arctic exploration sled-pullers;
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guiding the blind and acting as a pair of ears for the
deaf;
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assisting with hunting, and a great many other roles which
they may be trained to assume.
Most dogs rarely have to deal with complex tasks and are
unlikely to learn relatively complicated activities (such as opening
doors) unaided.
Some dogs (such as guide
dogs for the visually impaired) are specially trained to recognize and
avoid dangerous situations.
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