Friday, September 27, 2013


From Wikipedia, the free encyclopedia

Domestic cat[1]
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Felidae
Genus: Felis
Species: F. catus
Binomial name
Felis catus[2]
Linnaeus, 1758[3]
Felis silvestris catus (subjective synonym)[4]
Felis catus domestica (invalid junior synonym)[5]
The domestic cat[1][2] (Felis catus[2] or Felis silvestris catus[4]) is a small, usually furry, domesticated, and carnivorous mammal. It is often called the housecat when kept as an indoor pet,[6] or simply the cat when there is no need to distinguish it from other felids and felines. Cats are often valued by humans for companionship and their ability to hunt vermin and household pests.
Cats are similar in anatomy to the other felids, with strong, flexible bodies, quick reflexes, sharp retractable claws, and teeth adapted to killing small prey. Cat senses fit a crepuscular and predatory ecological niche. Cats can hear sounds too faint or too high in frequency for human ears, such as those made by mice and other small animals. They can see in near darkness. Like most other mammals, cats have poorer color vision and a better sense of smell than humans.
Despite being solitary hunters, cats are a social species, and cat communication includes the use of a variety of vocalizations (meowing, purring, trilling, hissing, growling and grunting) as well as cat pheromones and types of cat-specific body language.[7]
Cats have a rapid breeding rate. Under controlled breeding, they can be bred and shown as registered pedigree pets, a hobby known as cat fancy. Failure to control the breeding of pet cats by spaying and neutering, and the abandonment of former household pets, has resulted in large numbers of feral cats worldwide, requiring population control.[8]
Since cats were cult animals in ancient Egypt, they were commonly believed to have been domesticated there,[9] but there may have been instances of domestication as early as the Neolithic from around 9500 years ago (7500 BCE).[10]
A genetic study in 2007 revealed that domestic cats are descended from African wildcats (Felis silvestris lybica) c. 8000 BCE, in the Middle East.[9][11] According to Scientific American, cats are the most popular pet in the world, and are now found almost every place where people live.[12]

Nomenclature and etymology

Classification based on human interaction[13]
Population Food source Shelter Socialized
Pedigree Fed by guardian Human guardian Yes
Pet Fed by guardian Human homes Yes
Semi-feral General feeding Buildings Yes
Feral General feeding/foraging Buildings No
The English word cat (Old English catt) is in origin a loanword, introduced to many languages of Europe from Latin cattus[14] and Byzantine Greek κάττα, including Portuguese and Spanish gato, French chat, German Katze, Lithuanian katė and Old Church Slavonic kotka, among others.[15] The ultimate source of the word is Afroasiatic, presumably from Late Egyptian čaute,[16] the feminine of čaus "wildcat". The word was introduced, together with the domestic animal itself, to the Roman Republic by the 1st century BCE.[citation needed] An alternative word with cognates in many languages is English puss (pussycat). Attested only from the 16th century, it may have been introduced from Dutch poes or from Low German puuskatte, related to Swedish kattepus, or Norwegian pus, pusekatt. Similar forms exist in Lithuanian puižė and Irish puisín. The etymology of this word is unknown, but it may have simply arisen from a sound used to attract a cat.[17][18]
A group of cats is referred to as a "clowder" or a "glaring",[19] a male cat is called a "tom" or "tomcat"[20] (or a "gib",[21] if neutered), a female is called a "molly"[citation needed] or (especially among breeders) a "queen",[22] and a pre-pubescent juvenile is referred to as a "kitten". The male progenitor of a cat, especially a pedigreed cat, is its "sire",[23] and its female progenitor is its "dam".[24] In Early Modern English, the word kitten was interchangeable with the now-obsolete word catling.[25]
A pedigreed cat is one whose ancestry is recorded by a cat fancier organization. A purebred cat is one whose ancestry contains only individuals of the same breed. Many pedigreed and especially purebred cats are exhibited as show cats. Cats of unrecorded, mixed ancestry are referred to as domestic short-haired or domestic long-haired cats, by coat type, or commonly as random-bred, moggies (chiefly British), or (using terms borrowed from dog breeding) mongrels or mutt-cats.
While the African wildcat is the ancestral subspecies from which domestic cats are descended, and wildcats and domestic cats can completely interbreed, there are several intermediate stages between domestic pet and pedigree cats on the one hand and those entirely wild animals on the other. The semi-feral cat is a mostly outdoor cat that is not owned by any one individual, but is generally friendly to people and may be fed by several households. Feral cats are associated with human habitation areas and may be fed by people or forage in rubbish, but are typically wary of human interaction.[13]

Taxonomy and evolution

The wildcat, Felis silvestris, is the ancestor of the domestic cat.
The felids are a rapidly evolving family of mammals that share a common ancestor only 10–15 million years ago,[26] and include, in addition to the domestic cat, lions, tigers, cougars, and many others. Within this family, domestic cats (Felis catus) are part of the genus Felis, which is a group of small cats containing approximately seven species (depending upon classification scheme).[1][27] Members of the genus are found worldwide and include the jungle cat (Felis chaus) of southeast Asia, European wildcat (F. silvestris silvestris), African wildcat (F. s. lybica), the Chinese mountain cat (F. bieti), and the Arabian sand cat (F. margarita), among others.[28]
All the cats in this genus share a common ancestor that probably lived around 6–7 million years ago in Asia.[29] The exact relationships within the Felidae are close but still uncertain,[30][31] e.g. the Chinese mountain cat is sometimes classified (under the name Felis silvestris bieti) as a subspecies of the wildcat, like the North African variety F. s. lybica.[4][30] As domestic cats are little altered from wildcats, they can readily interbreed. This hybridization poses a danger to the genetic distinctiveness of wildcat populations, particularly in Scotland and Hungary, and possibly also the Iberian Peninsula.[32]
The domestic cat was first classified as Felis catus by Carolus Linnaeus in the tenth edition of his Systema Naturae in 1758.[1][3] However, because of modern phylogenetics, domestic cats are now usually regarded as another subspecies of the wildcat, Felis silvestris.[1][4][33] This has resulted in mixed usage of the terms, as the domestic cat can be called by its subspecies name, Felis silvestris catus.[1][4][33] Wildcats have also been referred to as various subspecies of F. catus,[33] but in 2003 the International Commission on Zoological Nomenclature fixed the name for wildcats as F. silvestris.[34] The most common name in use for the domestic cat remains F. catus, following a convention for domesticated animals of using the earliest (the senior) synonym proposed.[34] Sometimes the domestic cat has been called Felis domesticus[35] or Felis domestica,[1] as proposed by German naturalist J. C. P. Erxleben in 1777, but these are not valid taxonomic names and have been used only rarely in scientific literature,[36] because Linnaeus's binomial takes precedence.[37]
Cats have either a mutualistic or commensal relationship with humans. However, in comparison to dogs, cats have not undergone major changes during the domestication process, as the form and behavior of the domestic cat are not radically different from those of wildcats, and domestic cats are perfectly capable of surviving in the wild.[38][39] This limited evolution during domestication means that domestic cats tend to interbreed freely with wild relatives,[32] distinguishing them from other domesticated animals.[citation needed] Fully domesticated house cats also often interbreed with feral F. catus populations.[13] However, several natural behaviors and characteristics of wildcats may have pre-adapted them for domestication as pets.[39] These traits include their small size, social nature, obvious body language, love of play, and relatively high intelligence;[40]:12–17 they may also have an inborn tendency towards tameness.[39]
There are two main theories about how cats were domesticated. In one, people deliberately tamed cats in a process of artificial selection, as they were useful predators of vermin.[41] However, this has been criticized as implausible, because there may have been little reward for such an effort: cats generally do not carry out commands and, although they do eat rodents, other species such as ferrets or terriers may be better at controlling these pests.[4] The alternative idea is that cats were simply tolerated by people and gradually diverged from their wild relatives through natural selection, as they adapted to hunting the vermin found around humans in towns and villages.[4]
There is a population of Transcaucasus Black feral cats once classified as Felis daemon (Satunin, 1904), but now population is considered to be a part of domestic cat.[42]


The domesticated cat and its closest wild ancestor are both diploid organisms that possess 38 chromosomes[43] and roughly 20,000 genes.[44] About 250 heritable genetic disorders have been identified in cats, many similar to human inborn errors.[45] The high level of similarity among the metabolisms of mammals allows many of these feline diseases to be diagnosed using genetic tests that were originally developed for use in humans, as well as the use of cats as animal models in the study of the human diseases.[46][47]


Diagram of the general anatomy of a male
Domestic cats are similar in size to the other members of the genus Felis, typically weighing between 4–5 kg (8.8–11 lb).[30] However, some breeds, such as the Maine Coon, can occasionally exceed 11 kg (25 lb). Conversely, very small cats (less than 1.8 kg (4.0 lb)) have been reported.[48] The world record for the largest cat is 21.3 kg (47 lb).[49] The smallest adult cat ever officially recorded weighed around 1.36 kg (3.0 lb).[49] Feral cats tend to be lighter as they have more limited access to food than house cats. In the Boston area, the average feral adult male will scale 3.9 kg (8.6 lb) and average feral female 3.3 kg (7.3 lb).[50] Cats average about 23–25 cm (9–10 in) in height and 46 cm (18.1 in) in head/body length (males being larger than females), with tails averaging 30 cm (11.8 in) in length.[51]
Cats have seven cervical vertebrae as do almost all mammals; 13 thoracic vertebrae (humans have 12); seven lumbar vertebrae (humans have five); three sacral vertebrae like most mammals (humans have five because of their bipedal posture); and a variable number of caudal vertebrae in the tail (humans retain three to five caudal vertebrae, fused into an internal coccyx).[52]:11 The extra lumbar and thoracic vertebrae account for the cat's spinal mobility and flexibility. Attached to the spine are 13 ribs, the shoulder, and the pelvis.[52] :16 Unlike human arms, cat forelimbs are attached to the shoulder by free-floating clavicle bones which allow them to pass their body through any space into which they can fit their heads.[53]
Cat skull
The cat skull is unusual among mammals in having very large eye sockets and a powerful and specialized jaw.[54]:35 Within the jaw, cats have teeth adapted for killing prey and tearing meat. When it overpowers its prey, a cat delivers a lethal neck bite with its two long canine teeth, inserting them between two of the prey's vertebrae and severing its spinal cord, causing irreversible paralysis and death.[55] Compared to other felines, domestic cats have narrowly spaced canine teeth; which is an adaptation to their preferred prey of small rodents, which have small vertebrae.[55] The premolar and first molar together compose the carnassial pair on each side of the mouth, which efficiently shears meat into small pieces, like a pair of scissors. These are vital in feeding, since cats' small molars cannot chew food effectively.[54]:37
Cats, like dogs, are digitigrades. They walk directly on their toes, with the bones of their feet making up the lower part of the visible leg.[56] Cats are capable of walking very precisely, because like all felines they directly register; that is, they place each hind paw (almost) directly in the print of the corresponding forepaw, minimizing noise and visible tracks. This also provides sure footing for their hind paws when they navigate rough terrain. Unlike most mammals, when cats walk, they use a "pacing" gait; that is, they move the two legs on one side of the body before the legs on the other side. This trait is shared with camels and giraffes. As a walk speeds up into a trot, a cat's gait will change to be a "diagonal" gait, similar to that of most other mammals (and many other land animals, such as lizards): the diagonally opposite hind and forelegs will move simultaneously.[57]
Like almost all members of the Felidae family, cats have protractable and retractable claws.[58] In their normal, relaxed position the claws are sheathed with the skin and fur around the paw's toe pads. This keeps the claws sharp by preventing wear from contact with the ground and allows the silent stalking of prey. The claws on the forefeet are typically sharper than those on the hind feet.[59] Cats can voluntarily extend their claws on one or more paws. They may extend their claws in hunting or self-defense, climbing, kneading, or for extra traction on soft surfaces. Most cats have five claws on their front paws, and four on their rear paws.[60] The fifth front claw (the dewclaw) is proximal to the other claws. More proximally, there is a protrusion which appears to be a sixth "finger". This special feature of the front paws, on the inside of the wrists, is the carpal pad, also found on the paws of big cats and of dogs. It has no function in normal walking, but is thought to be an anti-skidding device used while jumping. Some breeds of cats are prone to polydactyly (extra toes and claws).[60] These are particularly common along the northeast coast of North America.[61]


Normal physiological values[62]:330
Body temperature 38.6 °C (101.5 °F)
Heart rate 120–140 beats per minute
Breathing rate 16–40 breaths per minute
As cats are familiar and easily kept animals, their physiology has been particularly well studied; it generally resembles that of other carnivorous mammals but displays several unusual features probably attributable to cats' descent from desert-dwelling species.[35] For instance, cats are able to tolerate quite high temperatures: Humans generally start to feel uncomfortable when their skin temperature passes about 38 °C (100 °F), but cats show no discomfort until their skin reaches around 52 °C (126 °F),[54]:46 and can tolerate temperatures of up to 56 °C (133 °F) if they have access to water.[63]
Cats conserve heat by reducing the flow of blood to their skin and lose heat by evaporation through their mouth. They do not sweat, and pant for heat relief only at very high temperatures[64] (but may also pant when stressed). A cat's body temperature does not vary throughout the day; this is part of cats' general lack of circadian rhythms and may reflect their tendency to be active both during the day and at night.[65]:1 Cats' feces are comparatively dry and their urine is highly concentrated, both of which are adaptations that allow cats to retain as much fluid as possible.[35] Their kidneys are so efficient that cats can survive on a diet consisting only of meat, with no additional water,[66] and can even rehydrate by drinking seawater.[65]:29[67]
Cats are obligate carnivores: their physiology has evolved to efficiently process meat, and they have difficulty digesting plant matter.[35] In contrast to omnivores such as rats, which only require about 4% protein in their diet, about 20% of a cat's diet must be protein.[35] Cats are unusually dependent on a constant supply of the amino acid arginine, and a diet lacking arginine causes marked weight loss and can be rapidly fatal.[68] Another unusual feature is that the cat cannot produce taurine, with taurine deficiency causing macular degeneration, wherein the cat's retina slowly degenerates, causing irreversible blindness.[35] Since cats tend to eat all of their prey, they obtain minerals by digesting animal bones, and a diet composed only of meat may cause calcium deficiency.[35]
A cat's gastrointestinal tract is adapted to meat eating, being much shorter than that of omnivores and having low levels of several of the digestive enzymes that are needed to digest carbohydrates.[69] These traits severely limit the cat's ability to digest and use plant-derived nutrients, as well as certain fatty acids.[69] Despite the cat's meat-oriented physiology, several vegetarian or vegan cat foods have been marketed that are supplemented with chemically synthesized taurine and other nutrients, in attempts to produce a complete diet. However, some of these products still fail to provide all the nutrients that cats require,[70] and diets containing no animal products pose the risk of causing severe nutritional deficiencies.[71]
Cats do eat grass occasionally. Proposed explanations include that grass is a source of folic acid or dietary fiber.[72]


Eyes of a tabby cat
Cats' whiskers are highly sensitive to touch.
Cats have excellent night vision and can see at only one sixth the light level required for human vision.[54]:43 This is partly the result of cat eyes having a tapetum lucidum, which reflects any light that passes through the retina back into the eye, thereby increasing the eye's sensitivity to dim light.[73] Another adaptation to dim light is the large pupils of cats' eyes. Unlike some big cats, such as tigers, domestic cats have slit pupils.[74] These slit pupils can focus bright light without chromatic aberration, and are needed since the domestic cat's pupils are much larger, relative to their eyes, than the pupils of the big cats.[74] Indeed, at low light levels a cat's pupils will expand to cover most of the exposed surface of its eyes.[75] However, domestic cats have rather poor color vision and (like most non-primate mammals) have only two types of cones, optimized for sensitivity to blue and yellowish green; they have limited ability to distinguish between red and green.[76] A 1993 paper found a response to mid-wavelengths from a system other than the rods which might be due to a third type of cone. However, this appears to be an adaptation to low light levels rather than representing true trichromatic vision.[77]
Cats have excellent hearing and can detect an extremely broad range of frequencies. They can hear higher-pitched sounds than either dogs or humans, detecting frequencies from 55 Hz up to 79 kHz, a range of 10.5 octaves; while humans can only hear from 31 Hz up to 18 kHz, and dogs hear from 67 Hz to 44 kHz, which are both ranges of about 9 octaves.[78][79] Cats do not use this ability to hear ultrasound for communication but it is probably important in hunting,[80] since many species of rodents make ultrasonic calls.[81] Cat hearing is also extremely sensitive and is among the best of any mammal,[78] being most acute in the range of 500 Hz to 32 kHz.[82] This sensitivity is further enhanced by the cat's large movable outer ears (their pinnae), which both amplify sounds and help a cat sense the direction from which a noise is coming.[80]
Cats have an acute sense of smell, which is due in part to their well-developed olfactory bulb and also to a large surface of olfactory mucosa, in cats this mucosa is about 5.8 square centimetres (0.90 sq in) in area, which is about twice that of humans and only 1.7-fold less than the average dog.[83] Cats are very sensitive to pheromones such as 3-mercapto-3-methylbutan-1-ol,[84] which they use to communicate through urine spraying and marking with scent glands.[85] Cats also respond strongly to plants that contain nepetalactone, especially catnip, as they can detect that substance at less than one part per billion.[86] This response is also produced by other plants, such as silver vine (Actinidia polygama) and the herb valerian; it may be caused by the smell of these plants mimicking a pheromone and stimulating cats' social or sexual behaviors.[87]
Cats have relatively few taste buds compared to humans. Domestic and wild cats share a gene mutation that keeps their sweet taste buds from binding to sugary molecules like carbohydrates, leaving them with no ability to taste sweetness.[88] Their taste buds instead respond to amino acids, bitter tastes and acids.[89]
To aid with navigation and sensation, cats have dozens of movable vibrissae (whiskers) over their body, especially their face. These provide information on the width of gaps and on the location of objects in the dark, both by touching objects directly and by sensing air currents; they also trigger protective blink reflexes to protect the eyes from damage.[54]:47

No comments:

Post a Comment