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Nomenclature and etymology

The word cat derives from Old English catt, which belongs to a group of related words in European languages, including Welsh cath, Spanish gato, Basque katu, Byzantine Greek kátia, Old Irish cat, German Katze, and Old Church Slavonic kotka. The ultimate source of all these terms is Late Latin catus, cattus, catta "domestic cat", as opposed to feles "European wildcat". It is unclear whether the Greek or the Latin came first, but they were undoubtedly borrowed from an Afro-Asiatic language akin to Nubian kadís and Berber kaddîska, both meaning "wildcat".[12] This term was either cognate with or borrowed from Late Egyptian čaus "jungle cat, African wildcat" (later giving Coptic šau "tomcat"),[13] itself from earlier Egyptian tešau "female cat"[14] (vs. miew "tomcat").[15] The term puss (as in pussycat) may come from Dutch poes or from Low German Puuskatte, dialectal Swedish kattepus, or Norwegian pus, pusekatt, all of which primarily denote a woman and, by extension, a female cat.[16]

A group of cats is referred to as a "clowder", a male cat is called a "tom" (or a "gib", if neutered), and a female is called a "molly" or "queen". The male progenitor of a cat, especially a pedigreed cat, is its "sire", and its female progenitor is its "dam". An immature cat is called a "kitten" (which is also an alternative name for young rats, rabbits, hedgehogs, beavers, squirrels and skunks). In medieval Britain, the word kitten was interchangeable with the word catling. A cat whose ancestry is formally registered is called a pedigreed cat, purebred cat, or a show cat. In strict terms, a purebred cat is one whose ancestry contains only individuals of the same breed. A pedigreed cat is one whose ancestry is recorded, but may have ancestors of different breeds. Cats of unrecorded mixed ancestry are referred to as domestic longhairs and domestic shorthairs or commonly as random-bred, moggies, mongrels, or mutt-cats.

Taxonomy and evolution

The wildcat Felis silvestris is a close relative of the domestic cat.

The Felids are a rapidly evolving family of mammals that share a common ancestor only 10-15 million years ago,[17] 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 seven species.[1][18] Members of the genus are found worldwide and include the Jungle Cat (Felis chaus) of southeast Asia, the African Wildcat (Felis silvestris lybica), the Chinese Mountain Cat (Felis silvestris bieti) and the Arabian Sand Cat (Felis margarita).[19] All the cats in this genus share a common ancestor that probably lived around six million years ago in Asia.[20] Although the exact relationships within the Felidae are still uncertain,[21][22] both the Chinese Mountain Cat and the African Wildcat are close relations of the domestic cat and are both classed as subspecies of the Wildcat Felis silvestris.[4][21] As domestic cats are little altered from wildcats, they can readily interbreed. This hybridization may pose a danger to the genetic distinctiveness of wildcat populations, particularly in Scotland and Hungary.[23]

The domestic cat was first classified as Felis catus by Carolus Linnaeus in the tenth edition of his Systema Naturae of 1758.[2][24] However, due to modern phylogenetics, domestic cats are now usually regarded as another subspecies of the Wildcat Felis silvestris.[4][24][25] 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] Wildcats have also been referred to as various subspecies of F. catus,[25] but in 2003 the International Commission on Zoological Nomenclature fixed the name for Wildcats as F. silvestris.[26] 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.[26] Sometimes the domestic cat is called Felis domesticus,[27] although this is not a valid scientific name.[28]

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.[29][30] Several natural behaviors and characteristics of Wildcats may have preadapted them for domestication as pets.[30] These traits include their small size, social nature, obvious body language, love of play and relatively high intelligence.[31] All the small Felids may also have an inborn tendency towards tameness.[30]

There are two main models for how cats were domesticated. In one model, people deliberately tamed cats in a process of artificial selection, as they were useful predators of vermin.[32] However, some theorists find this implausible, because there may have been little reward for such an effort: cats 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 in human settlements.[4]

Anatomy

Diagram of the general anatomy of a male cat

Domestic cats are similar in size to the other members of the genus Felis, typically weighing between 4 kilograms (8 lb 13 oz) and 5 kilograms (11 lb 0 oz).[21] However, some breeds, such as the Maine Coon, can exceed 11 kilograms (25 lb). Conversely, very small cats (less than 1.8 kilograms (3 lb 15 oz)) have been reported.[33] The world record for the largest cat is 21.297 kilograms (46 lb 15.2 oz).[34] The smallest adult cat ever officially recorded weighed around 1.36 kilograms (3 lb).[35] Cats average about 23–25 centimeters (9–10 in) in height and 46 centimeters (18.1 in) in head/body length (males being larger than females), with tails averaging 30 centimeters (11.8 in) in length.[36]

Cats have 7 cervical vertebrae like almost all mammals, 13 thoracic vertebrae (humans have 12), 7 lumbar vertebrae (humans have 5), 3 sacral vertebrae like most mammals (humans have 5 because of their bipedal posture), and a variable number of caudal vertebrae in the tail (humans retain 3 to 5 caudal vertebrae, fused into an internal coccyx).[37] 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.[38] Unlike human arms, cat forelimbs are attached to the shoulder by free-floating clavicle bones, which allows them to pass their body through any space into which they can fit their heads.[39]

Skull of a domestic cat.

The cat skull is unusual among mammals in having very large eye sockets and a powerful and specialized jaw.[40] Within the jaw, cats have teeth adapted for killing prey and tearing meat. When they overpower prey, a cat delivers a lethal neck bite with its two long canine teeth that insert between two of the prey's vertebrae and sever its spinal cord, causing irreversible paralysis and death.[41] 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.[41] 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.[42]

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.[43] 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.

Like almost all members of the Felidae family, cats have protractable claws.[44] In their normal, relaxed position the claws are sheathed with the skin and fur around the 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.[45] 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 (bedspreads, thick rugs, etc.). It is also possible to make a cooperative cat extend its claws by carefully pressing both the top and bottom of the paw.

Most cats have five claws on their front paws, and four on their rear paws.[46] 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 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 polydactylyism, and may have eight or even ten toes.[46] These are particularly common along the North-East coast of North America.[47]

Senses

Cat's eye. Cats have extremely sensitive vision, particularly in dim light.

Cats have excellent night vision and can function at only one-sixth the light level required for human vision.[48] 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.[49] Another adaptation to dim light is the large pupils of cats' eyes. Unlike some big cats, such as tigers, domestic cats have slit pupils.[50] 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.[50] Indeed, at low light levels a cat's pupils will expand to cover most of the exposed surface of its eyes.[51] However, domestic cats have rather poor color vision and can only see two colors: blue and green, and are less able to distinguish between red and green,[52] although they can achieve this in some conditions.[53]
Cats' whiskers are highly sensitive to touch.

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.[54][55] Cats do not use this ability to hear ultrasound for communication but it is probably important in hunting,[56] since many species of rodents make ultrasonic calls.[57] Cats' hearing is also extremely sensitive and is among the best of any mammal,[54] being most acute in the range of 500 Hz to 32 kHz.[58] 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.[56]

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 cm2 in area, which is about twice that of humans and only 1.7-fold less than the average dog.[59] Cats respond strongly to the smell of nepetalactone, a compound found in catnip, and can detect this substance at less than one part per billion.[60] Cats are also sensitive to pheromones such as 3-Mercapto-3-methylbutan-1-ol,[61] which they use to communicate through urine spraying and marking with scent glands.[62]

Due to a mutation in an early cat ancestor, one of two genes necessary to taste sweetness may have been lost by the cat family.[63] Their taste buds instead respond to amino acids, bitter tastes and acids.[64] To aid with navigation and sensation, cats have dozens of movable vibrissae (whiskers) over their body, especially their face. These provide information 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.[65]

Genetics

The domesticated cat and its closest wild ancestor are both diploid organisms that possess 38 chromosomes[67] and roughly 20,000 genes.[68] About 250 heritable genetic disorders have been identified in cats, many similar to human inborn errors.[69] 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 in the study of the human diseases.[70][71] An interesting example of a mutation that is shared among all felines, including the big cats, is a mutant chemosensor in their taste buds that prevents them from tasting sweetness, which may explain their indifference to fruits, berries, and other sugary foods.[63] In some breeds of cats congenital deafness is very common, with most white cats (but not albinos) being affected, particularly if they also have blue eyes.[66] The genes responsible for this defect are unknown, but the disease is studied in the hope that it may shed light on the causes of hereditary deafness in humans.[72]

Since a large variety of different coat patterns exist within the various cat breeds, the cat is an excellent animal to study the coat genetics of hair growth and coloration.[73] Several genes interact to produce cats' hair color and coat patterns. Different combinations of these genes give different phenotypes. For example, the enzyme tyrosinase is needed to produce the dark pigment melanin and Burmese cats have a mutant form that is only active at low temperatures, resulting in color appearing only on the cooler ears, tail and paws.[74] A completely inactive gene for tyrosinase is found in albino cats, which therefore lack all pigment.[75] Hair length is determined by the gene for fibroblast growth factor 5, with inactive copies of this gene causing long hair.[76]

The Cat Genome Project, sponsored by the Laboratory of Genomic Diversity at the U.S. National Cancer Institute Frederick Cancer Research and Development Center in Frederick, Maryland, aims to help the development of the cat as an animal model for human hereditary and infectious diseases, as well as contributing to the understanding of the evolution of mammals.[71] This effort led to the publication in 2007 of an initial draft of the genome of a Abyssinian cat called Cinnamon.[68] The existence of a draft genome has led to the discovery of several cat disease genes,[68] and even allowed the development of cat genetic fingerprinting for use in forensics.[77]

Physiology

As a familiar and easily-kept animal, the physiology of cats has been particularly well studied and is generally similar to that of other carnivorous mammals.[27] However, several features of cats' physiology are unusual and are probably due to their descent from desert-dwelling species.[27] For instance, cats are able to tolerate quite high temperatures, with humans starting to feel uncomfortable when their skin temperature passes about 44.5 °C (112 °F), in contrast cats show no discomfort until their skin reaches around 52 °C (126 °F).[79] Unusually, 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 in both day and night.[80] As well as being tolerant of high temperatures, cats' feces are usually dry and their urine is also highly concentrated, both of which are adaptations that allow cats to retain as much fluid as possible.[27] Indeed, their kidneys are so efficient that cats can survive on a diet consisting only of meat, with no additional water,[81] and can even rehydrate by drinking seawater.[82][83]
A cat carrying a house mouse.

Cats are obligate carnivores: their physiology has evolved to efficiently process meat, and they have difficulty digesting plant matter.[27] 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.[27] 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.[84] Another unusual feature is that the cat also cannot produce the amino acid taurine, with taurine deficiency causing macular degeneration, where the cat's retina slowly degenerates, causing irreversible blindness.[27] 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.[27]

A cat's digestive tract is also 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.[85] These traits severely limits the cat's ability to digest and use plant-derived nutrients, as well as certain fatty acids.[85] 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,[86] and diets containing no animal products pose the risk of causing severe nutritional deficiencies.[87]

Health

In captivity, an average life expectancy for indoor cats at birth is 14 years,[88] although the oldest known cat, Creme Puff, lived to age 38.[89] Having a cat neutered confers some health benefits, since castrated males cannot develop testicular cancer, spayed females cannot develop uterine or ovarian cancer, and both have a reduced risk of mammary cancer.[90] The lifespan of feral cats is hard to determine accurately, although one study reported a median age of 4.7 years, with a range between 0 to 10 years.[91]

Diseases

Cats can suffer from a wide range of health problems, including infectious diseases, parasites, injuries and chronic disease. Vaccinations are available for many of these diseases, and domestic cats are regularly given treatments to eliminate parasites such as worms and fleas.
Poisoning

In addition to obvious dangers such as rodenticides, insecticides and weed killers, cats may be poisoned by many chemicals that are usually considered safe.[92] This is because their livers are less effective at some forms of detoxification than those of other animals, including humans and dogs.[27][93] Some of the most common causes of poisoning in cats are antifreeze and rodent baits.[94] It has also been suggested that cats may be particularly sensitive to environmental pollutants.[92][95] When a cat has a sudden or prolonged serious illness without any obvious cause, it is therefore possible that it has been exposed to a toxin.

Human medicines should never be given to cats. For example, the painkiller paracetamol (also called acetaminophen), sold under brand names such as Tylenol and Panadol is extremely toxic to cats: even very small doses can be fatal and need immediate treatment.[96][97] Even aspirin, which is sometimes used to treat arthritis in cats, is much more toxic to them than to humans and must be administered cautiously.[92] Similarly, application of minoxidil (Rogaine) to the skin of cats, either accidentally or by well-meaning owners attempting to counter loss of fur, has sometimes been fatal.[98] Essential oils can be toxic to cats and there have been reported cases of serious illnesses caused by tea tree oil, and tea tree oil-based flea treatments and shampoos.[99]

Other common household substances that should be used with caution around cats include mothballs and other naphthalene products.[92] Phenol-based products are often used for cleaning and disinfecting near cats' feeding areas or litter boxes: such as Pine-Sol, Dettol (Lysol) or hexachlorophene,[92] but these can sometimes be fatal.[100] Ethylene glycol, often used as an automotive antifreeze, is particularly appealing to cats, and as little as a teaspoonful can be fatal.[101] Some human foods are toxic to cats; for example theobromine in chocolate can cause theobromine poisoning, although few cats will eat chocolate.[102] Large amounts of onions or garlic are also poisonous to cats.[92] Many houseplants are also dangerous,[103] such as Philodendron species and the leaves of the Easter Lily, which can cause permanent and life-threatening kidney damage.[104]

Sociability

Social grooming in a pair of cats.

Although wildcats are solitary, the social behavior of domestic cats is much more variable and ranges from widely-dispersed individuals to feral cat colonies that form around a food source, based on groups of co-operating females.[108][109] Within such groups one cat is usually dominant over the others.[110] Each cat in a colony holds a distinct territory, with sexually active males having the largest territories, which are about ten times larger than those of female cats and may overlap with several females' territories.[62] These territories are marked by urine spraying, by rubbing objects at head height with secretions from facial glands and by defecation.[62] Between these territories are neutral areas where cats watch and greet one another without territorial conflicts. Outside these neutral areas, territory holders usually chase away stranger cats, at first by staring, hissing, and growling, and if that does not work, by short but noisy and violent attacks. Despite some cats cohabiting in colonies, cats do not have a social survival strategy, or a pack mentality and always hunt alone.[111]

As part of cat sociability they use a variety of vocalizations for communication, including meowing, purring, trilling, hissing, growling, squeaking, chirping, clicking, and grunting.[9] Their types of body language: position of ears and tail, relaxation of whole body, kneading of paws, are all indicators of mood. The tail and ears are particularly important social signal in cats, with a raised tail acting as a friendly greeting.[112][113] Tail raising also indicates the cat's position in the group's social hierarchy, with dominant individuals raising their tails less often than subordinate animals.[113] Nose-touching is also a common greeting and may be followed by social grooming, which is solicited by one of the cats raising and tilting its head.[109] However, some pet cats are poorly socialized. In particular older cats may show aggressiveness towards newly-arrived kittens, which may include biting and scratching; this type of behavior is known as Feline Asocial Aggression.[114]

For cats, life in proximity with humans (and other animals kept by humans) amounts to a "symbiotic social adaptation". They may express great affection towards their human companions, especially if they imprint on them at a very young age and are treated with consistent affection. It has been suggested that, ethologically, the human keeper of a cat functions as a sort of surrogate for the cat's mother, and that adult domestic cats live their lives in a kind of extended kittenhood, a form of behavioral neoteny.[115]

Grooming

The hooked papillae on a cat tongue act like a hairbrush to help clean and detangle fur.

Cats are known for their cleanliness, spending many hours licking their coats.[116] The cat's tongue has backwards-facing spines about 500 micrometres long, which are called papillae. These are quite rigid, as they contain keratin.[117] These spines allow cats to groom themselves by licking their fur, with the rows of papillae acting like a hairbrush. Some cats, particularly longhaired cats, occasionally regurgitate hairballs of fur that have collected in their stomachs from grooming. These clumps of fur are usually sausage-shaped and about two to three centimeters long. Hairballs can be prevented with remedies that ease elimination of the hair through the gut, as well as regular grooming of the coat with a comb or stiff brush.[116

Fighting

Cats intimidate opponents by arching their backs, raising their fur, turning sideways, and hissing.

In domestic cats, males are more likely to fight than females.[118] In feral cats, the most common reason for cat fighting is when two males are competing to mate with a female: here most fights will be won by the heavier male.[119] Another possible reason for fighting in domestic cats is when the cats have difficulties in establishing a territory within a small home.[118] Female cats will also fight over territory or to defend their kittens. Spaying females and neutering males will decrease or eliminate this behavior in many cases.
Fighting cats make themselves appear more impressive and threatening by raising their fur and arching their backs, thus increasing their apparent size.[112] Attacks usually comprise powerful slaps to the face and body with the forepaws as well as bites, but serious damage is rare; usually the loser runs away with little more than a few scratches to the face, and perhaps the ears. Cats will also throw themselves to the ground in a defensive posture to rake their opponent's belly with their powerful hind legs.[120]
Normally, serious injuries from fighting will be limited to infections of scratches and bites, though these can occasionally kill cats if untreated. In addition, bites are probably the main route of transmission of feline immunodeficiency virus (FIV).[121] Sexually active males will usually be in many fights during their lives, and often have decidedly battered faces with obvious scars and cuts to the ears and nose.

Hunting and feeding

A domestic cat eating a captured bird.

Cats feed on small prey, primarily birds and rodents.[122] Feral cats and house cats that are free-fed tend to consume many small meals in a single day, although the frequency and size of meals varies between individuals.[111] Cats use two hunting strategies, either stalking prey actively, or waiting in ambush until an animal comes close enough to be captured. Although it is not certain, the type of strategy used may depend on the prey species in the area, with for example, cats waiting in ambush outside burrows, but tending to actively stalk birds.[123]

Most breeds of cat have a noted fondness for settling in high places, or perching. In the wild, a higher place may serve as a concealed site from which to hunt; domestic cats may strike prey by pouncing from such a perch as a tree branch, as does a leopard.[124] Other possible explanations include that height gives the cat a better observation point, allowing it to survey its territory. During a fall from a high place, a cat can reflexively twist its body and right itself using its acute sense of balance and flexibility.[125] This is known as the cat's "righting reflex". It always rights itself in the same way, provided it has the time to do so, during a fall. The height required for this to occur is around 90 cm (3 feet). Cats without a tail also have this ability, since a cat mostly moves its hind legs and relies on conservation of angular momentum to set up for landing, and the tail is in fact little used for this feat.[126]
A domestic cat eating a captured bird.

One poorly understood element of cat hunting behavior is the presentation of prey to human owners. Ethologist Paul Leyhausen proposed that cats adopt humans into their social group, and share excess kill with others in the group according to the local pecking order, in which humans are placed at or near the top.[127] However, anthropologist and animal scientist Desmond Morris, in his 1986 book Catwatching, suggests that when cats bring home mice or birds, they are teaching their human to hunt, or helping their human as if feeding "an elderly cat, or an inept kitten".[128] However, this proposal is inconsistent with the fact that male cats also bring home prey, despite males having no involvement with raising kittens.[123]

Domestic cats select food based on its temperature, smell and texture, strongly disliking chilled foods and responding most strongly to moist foods rich in amino acids, which are similar to meat.[87][111] Cats may reject novel flavors (a response termed neophobia) and learn quickly to avoid foods that have tasted unpleasant in the past.[111] They may also avoid sugary foods and milk; since they are lactose intolerant, these sugars are not easily digested and may cause soft stools or diarrhea.[111][129] They can also develop odd eating habits. Some cats like to eat or chew on other things, most commonly wool, but also plastic, paper, string, or even coal. This condition is called pica and can threaten their health, depending on the amount and toxicity of the items eaten.[130][131

Play

Domestic cats, especially young kittens, are known for their love of play. This behavior mimics hunting and is important in helping kittens learn to stalk, capture, and kill prey.[132] Cats will also engage in play fighting, with each other and with humans. This behavior may be a way for cats to practice the skills needed for real combat, and might also reduce any fear they associate with launching attacks on other animals.[133]

Due to the close similarity between play and hunting, cats prefer to play with objects that resemble prey, such as small furry toys that move rapidly, but rapidly lose interest (they become habituated) in a toy they have played with before.[134] Cats also tend to play with toys more when they are hungry.[135] String is often used as a toy, but if it is eaten it can become caught at the base of the cat’s tongue and then move into the intestines, this is a medical emergency as it can cause serious illness and death.[136] Due to the risks posed by cats eating string, it is sometimes replaced with a laser pointer's dot, which cats may chase.[137] While concerns have been raised about the safety of these lasers, Professor John Marshall, an ophthalmologist at St Thomas' Hospital, has stated that it would be "virtually impossible" to blind a cat with a laser pointer.[138]

Reproduction

When cats mate, the male tom bites the scruff of the female's neck as she assumes a position conducive to mating.

Female cats are seasonally polyestrous, which means they may have many periods of heat over the course of a year, the season beginning in January or February and ending in late October. Heat periods occur about every two weeks and last about 4 to 7 days.[139] Multiple males will be attracted to a female in heat. The males will fight over her, and the victor wins the right to mate. At first, the female will reject the male, but eventually the female will allow the male to mate. The female will utter a loud yowl as the male pulls out of her. This is because a male cat's penis has a band of about 120-150 backwards-pointing spines, which are about one millimeter long;[140] upon withdrawal of the penis, the spines rake the walls of the female's vagina, which is a trigger for ovulation. After mating, the female will wash her vulva thoroughly. If a male attempts to breed with her at this point, the female will attack him. After about 20 to 30 minutes, once the female is finished grooming, the cycle will repeat.[139]

Because ovulation is not always triggered by a single mating, females may not be impregnated by the first male with which they mate.[141] Furthermore, cats are superfecund; that is, a female may mate with more than one male when she is in heat, with the result that different kittens in a litter may have different fathers.[139]

A kitten with newly-open eyes.

The gestation period for cats is between 64–67 days, with an average length of 66 days.[142] The size of a litter averages three to five kittens, with the first litter usually smaller than subsequent litters. Kittens are weaned at between six and seven weeks, and cats normally reach sexual maturity at 5–10 months (females) and to 5–7 months (males), although this can vary depending on breed.[139] Females can have two to three litters per year, so may produce up to 150 kittens in their breeding span of around ten years.[139]

Cats are ready to go to new homes at about 12 weeks old,[143] or when they are ready to leave their mother. Cats can be surgically sterilized (spayed or castrated) as early as 7 weeks to limit unwanted reproduction.[144] This surgery also prevents undesirable sex-related behavior, such as aggression, territory marking (spraying urine) in males and yowling (calling) in females. Traditionally, this surgery was performed at around six to nine months of age, but it is increasingly being performed prior to puberty, at about three to six months.[145] In the USA approximately 80% of household cats are neutered.[146]

Ecology

Habitats

Cats are a cosmopolitan species and are found across much of the world.[29] They are extremely adaptable and are now present on all the continents (including Antarctica) and on 118 of 131 main groups of islands.[147][148] Feral cats can live in forests, grasslands, tundra, coastal areas, agricultural land, scrublands, urban areas and wetlands.[149] Their habitats even include small oceanic islands with no human inhabitants.[150] However, this ability to thrive in almost any terrestrial habitat has led the cat's designation as one of the world's worst invasive species.[151] Despite this general adaptability, the close relatives of domestic cats, the African Wildcat (Felis silvestris lybica) and the Arabian Sand Cat (Felis margarita) both inhabit desert environments,[4] and domestic cats still show similar adaptations and behaviors.[27]

Impact on prey species

Feral cat eating a cottontail rabbit.

To date, there are few scientific data available to assess the impact of cat predation on prey populations. Cat numbers in the UK are growing annually and their abundance is far above the ‘natural’ carrying capacity, due to their population sizes being independent of their prey’s dynamics – i.e. cats are ‘recreational’ hunters.[152] Population densities can be as high as 2000 individuals per km2[153] and the current trend is an increase of 0.5 million cats annually.

Even well-fed domestic cats may hunt and kill, mainly catching small mammals, but also birds, amphibians, reptiles, fish and invertebrates.[122][154] Hunting by domestic cats may be contributing to the decline in the numbers of birds in urban areas, although the importance of this effect remains controversial.[155] In the wild, the introduction of feral cats during human settlement can threaten native species with extinction.[150] In many cases controlling or eliminating the populations of non-native cats can produce a rapid recovery in native animals.[156] However, the ecological role of introduced cats can be more complicated: for example, cats can control the numbers of rats, which also prey on birds' eggs and young, so in some cases eliminating a cat population can actually accelerate the decline of an endangered bird species in the presence of a mesopredator, controlled by cats.[157]

In the Southern Hemisphere, cats are a particular problem in landmasses such as Australasia, where cat species have never been native and there were few equivalent native medium-sized mammalian predators.[158] Native species such as the New Zealand Kakapo and the Australian Bettong, for example, tend to be more ecologically vulnerable and behaviorally "naive" to predation by feral cats.[159] Feral cats have had a major impact on these native species and have played a leading role in the endangerment and extinction of many animals.[160]

Impact on birds

It has been claimed that the domestic cat is a significant predator of birds. Current UK assessments indicate that they may be accountable for an estimated 64.8 million bird deaths each year.[122] Certain species appear more susceptible than others; for example, 30% of house sparrow mortality is linked to the domestic cat.[161] In the recovery of ringed robins and dunnocks, it was also concluded that 31% of deaths were a result of cat predation.[162]
On islands, birds can contribute as much as 60% of a cat’s diet.[163] In nearly all cases, however, the cat cannot be identified as the sole cause for reducing the numbers of island birds, and in some instances eradication of cats has caused a ‘mesopredator release’ effect;[164] where the suppression of top carnivores creates an abundance of smaller predators that cause a severe decline in their shared prey. Domestic cats are, however, known to be a contributing factor to the decline of many species; a factor that has ultimately led, in some cases, to extinction. The South Island Piopio; Chatham Islands Rail;[162] the Auckland Islands Merganser;[165] and the common diving petrel[166] are a few from a long list, with the most extreme case being the elimination of the flightless Stephen Island Wren, by a single cat.[167]
Some of the same factors that have promoted adaptive radiation of island avifauna over evolutionary time appear to promote vulnerability to non-native species in modern time. The susceptibility inherent of many island birds is undoubtedly due to evolution in the absence of mainland predators, competitors, diseases and parasites. In addition to lower reproductive rates and extended incubation periods.[168] The loss of flight, or reduced flying ability is also characteristic of many island endemics.[169] These biological aspects have increased vulnerability to extinction in the presence of introduced species, such as the domestic cat.[170] Equally, behavioural traits exhibited by island species, such as ‘predatory naivety’[171] and ground-nesting,[168] have also contributed to their susceptibility.

Domesticated cats

Cats are a common companion animal in Europe and North America, and their worldwide population exceeds 500 million.[10] In 1998 there were around 43 million cats in Western Europe, 33 million in Eastern Europe, seven million in Japan and three million in Australia.[172] A 2007 report stated that about 37 million US households owned cats, with an average of 2.2 cats per household giving a total population of around 82 million.[173] This is slightly more than the 72 million pet dogs in this country.[173] Although cat ownership has commonly been associated with women,[174] a 2007 Gallup poll reported that men and women were equally likely to own a cat.[175] The ratio of pedigree/purebred cats to random-bred cats varies from country to country. However, generally speaking, purebreds are less than ten percent of the total population.[176]
A cat pelt.

According to the Humane Society of the United States, as well as being kept as pets, cats are also used in the international fur trade.[177] About 24 cats are needed to make a cat fur coat, although cat fur is also used in gloves, hats, shoes, blankets and stuffed toys.[178] This use has now been outlawed in several countries, including the United States, Australia and the European Union.[179] However, some cat furs are still made into blankets in Switzerland as folk remedies that are believed to help rheumatism.[180]

It has long been common for cats to be eaten in some parts of China and in some other Asian countries. According to the Chengdu Business Daily, people in southern China's Guangdong province ate 10,000 cats a day.[181] Animal People estimates that 4 million cats are killed and consumed in Asia every year.[182]

Domesticated varieties

The concept of a cat breed appeared in Britain during the late 19th century.[183] The current list of cat breeds is quite large: with the Cat Fanciers' Association recognizing 41 breeds, of which 16 are "natural breeds" that probably emerged before humans began breeding pedigree cats, while the others were developed over the latter half of the 20th century.[29] The owners and breeders of show cats compete to see whose animal bears the closest resemblance to the "ideal" definition and standard of the breed (see selective breeding). Because of common crossbreeding in populated areas, many cats are simply identified as belonging to the homogeneous breeds of domestic longhair and domestic shorthair, depending on their type of fur. In the United Kingdom and Australasia, non-purebred cats are referred in slang as moggies (derived from "Maggie", short for Margaret, reputed to have been a common name for cows and calves in 18th century England and latter applied to housecats during the Victorian era).[184] In the United States, a non-purebred cat is sometimes referred to in slang as a barn or alley cat, even if it is not a stray. Cats come in a variety of colors and patterns. These are physical properties and should not be confused with a breed of cat. Some original cat breeds that have a distinct phenotype that is the main type occurring naturally as the dominant domesticated cat type in their region of origin are sometimes considered as subspecies and also have received names as such in nomenclature, although this is not supported by feline biologists. Some of these cat breeds are:

* F. catus anura - the Manx
* F. catus siamensis - the Siamese
* F. catus cartusenensis - the Chartreux
* F. catus angorensis - the Turkish Angora

Coat patterns

Cat coat genetics can produce a variety of coat patterns. Some of the most common are:

Bicolor, Tuxedo and Van

This pattern varies between the tuxedo cat which is mostly black with a white chest, and possibly markings on the face and paws/legs, all the way to the Van pattern (so named after the Lake Van area in Turkey, which gave rise to the Turkish Van breed), where the only colored parts of the cat are the tail (usually including the base of the tail proper), and the top of the head (often including the ears). There are several other terms for amounts of white between these two extremes, such as Harlequin or jellicle cat. Bicolor cats can have as their primary (non-white) color black, red, any dilution thereof, and tortoiseshell (see below for definition).

Tabby cat

Striped, with a variety of patterns. The classic blotched tabby (or marbled) pattern is the most common and consists of butterflies and bullseyes. The mackerel or striped tabby is a series of vertical stripes down the cat's side (resembling the fish). This pattern broken into spots is referred to as a spotted tabby. Finally, the tabby markings may look like a series of ticks on the fur, thus the ticked tabby, which is almost exclusively associated with the Abyssinian breed of cats. The worldwide evolution of the cat means that certain types of tabby are associated with certain countries; for instance, blotched tabbies are quite rare outside NW Europe, where they are the most common type.

Tortoiseshell and Calico

A Chilean torbie cat.

This cat is also known as a Calimanco cat or Clouded Tiger cat, and by the nickname "tortie." In the cat fancy, a tortoiseshell cat is randomly patched over with red (or its dilute form, cream) and black (or its dilute blue) mottled throughout the coat. Additionally, the cat may have white spots in its fur, which make it a "tortoiseshell and white" cat or, if there is a significant amount of white in the fur and the red and black colors form a patchwork rather than a mottled aspect, the cat will be called a calico. All calicos are tortoiseshell (as they carry both black and red), but not all tortoiseshells are calicos (which requires a significant amount of white in the fur and patching rather than mottling of the colors). The calico is also sometimes called a tricolor cat. The Japanese refer to this pattern as mi-ke (meaning "triple fur"), while the Dutch call these cats lapjeskat (meaning "patches cat"). A true tricolor must consist of three colors: a reddish color, dark or light; white; and one other color, typically a brown, black, or blue.[185] Both tortoiseshell and calico cats are typically female because the coat pattern is the result of differential X chromosome inactivation in females (which, as with all normal female mammals, have two X chromosomes). Conversely, cats where the overall color is ginger (orange) are commonly male (roughly in a 3:1 ratio). In a litter sired by a ginger tom, the females will be tortoiseshell or ginger. Male tortoiseshells can occur as a result of chromosomal abnormalities (often linked to sterility) or by a phenomenon known as mosaicism, where two early stage embryos are merged into a single kitten.

Colorpoint

Female tortoiseshell-and-white cat

The colorpoint pattern is most commonly associated with Siamese cats, but may also appear in any domesticated cat. A colorpointed cat has dark colors on the face, ears, feet, and tail, with a lighter version of the same color on the rest of the body, and possibly some white. The exact name of the colorpoint pattern depends on the actual color, so there are seal points (dark brown), chocolate points (warm lighter brown), blue points (dark gray), lilac or frost points (silvery gray-pink), red or flame points (orange), and tortie (tortoiseshell mottling) points, among others. This pattern is the result of a temperature sensitive mutation in one of the enzymes in the metabolic pathway from tyrosine to pigment, such as melanin; thus, little or no pigment is produced except in the extremities or points where the skin is slightly cooler. For this reason, colorpointed cats tend to darken with age as bodily temperature drops; also, the fur over a significant injury may sometimes darken or lighten as a result of temperature change.

The tyrosine pathway also produces neurotransmitters, thus mutations in the early parts of that pathway may affect not only pigment, but also neurological development. This results in a higher frequency of cross-eyes among colorpointed cats, as well as the high frequency of cross-eyes in white tigers.

White cats

True albinism (a mutation of the tyrosinase gene) is quite rare in cats. Much more common is the appearance of white coat color due to a lack of melanocytes in the skin. A higher frequency of deafness in white cats is due to a reduction in the population and survival of melanoblast stem cells, which in addition to creating pigment producing cells, develop into a variety of neurological cell types. White cats with one or two blue eyes have a particularly high likelihood of being deaf.

Smoke cats

The bottom eighth of each hair is white or creamy-white, with the rest of the hair being a solid color. Genetically this color is a non-agouti cat with the dominant inhibitor gene; a non-agouti version of the silver tabby. Smoke cats will look solid colored until they move, when the white undercoat becomes apparent. It is mostly found in pedigreed cats (especially longhair breeds) but also present in some domestic longhaired cats.

Body types

Cats can also come in several body types, ranging between two extremes:

Oriental

Not a specific breed, but any cat with an elongated slender build, almond-shaped eyes, long nose, large ears (the Siamese and Oriental Shorthair breeds are examples of this).

Foreign

less slender than the oriental type, but nevertheless a cat with a slight build and generally athletic look. Typical example breeds would be the Abyssinian cat and the Turkish Angora. Some people consider the foreign and oriental body types as being the same, however.

Semi-Foreign

More or less the middle range of body conformation types, this type of cat is less slender without being stocky. Example breeds would be the Devon Rex and the Egyptian Mau.

Semi-Cobby

these cats look more rounded without looking too stocky. Example breeds would be the American Shorthair and British Shorthair.

Cobby

Any cat with a short, muscular, compact build, roundish eyes, short nose, and small ears. Persian cats and Exotic cats are two prime examples of such a body type.

Effects on human health

Because of their small size, domesticated house cats pose little physical danger to adult humans. However, in the USA cats inflict about 400,000 bites per year, with 90% of these bites coming from provoked animals; this number represents about one in ten of all animal bites.[186] Many cat bites will become infected,[187] sometimes with serious consequences such as cat-scratch disease, or, more rarely, rabies.[186] Cats also pose a danger to pregnant women and immunosuppressed individuals, since their feces can transmit toxoplasmosis.[188] A large percentage of cats are infected with this parasite, with infection rates ranging around from 40 to 60% in both domestic and stray cats worldwide.[189][190][191]

Allergic reactions to cat dander and/or cat saliva are common.[192] Some humans who are allergic to cats—typically manifested by hay fever, asthma, or a skin rash—quickly acclimate themselves to a particular animal and live comfortably in the same house with it, while retaining an allergy to cats in general.[193] Whether the risk of developing allergic diseases such as asthma is increased or decreased by cat ownership is uncertain.[194][195] Some owners cope with this problem by taking allergy medicine, along with bathing their cats frequently, since weekly bathing will reduce the amount of dander shed by a cat.[196] There have also been attempts to breed hypoallergenic cats, which would be less likely to provoke an allergic reaction.[197]

As well as posing health risks, interactions with cats may improve health and reduce physical responses to stress: for example the presence of cats may moderate increased blood pressure.[198] Cat ownership may also improve psychological health by providing emotional support and dispelling feelings of depression, anxiety and loneliness.[199] Indeed, their ability to provide companionship and friendship are common reasons given for owning a cat.[175]

Indoor scratching

Close-up of a cat's claw, with the quick clearly visible

A natural behavior in cats is to periodically hook their front claws into suitable surfaces and pull backwards. This marks territory, exercises their legs, as well as cleaning and sharpening their claws.[200] Indoor cats benefit from being provided with a scratching post so that they are less likely to use carpet or furniture which they can easily ruin.[201] Commercial scratching posts typically are covered in carpeting or upholstery, but some authorities[who?] advise against this practice, as not making it clear to the cat which surfaces are permissible and which are not; they suggest using a plain wooden surface, or reversing the carpeting on the posts so that the rougher texture of the carpet backing is a more attractive alternative to the cat than the floor covering. Scratching posts made of sisal rope or corrugated cardboard are also common.
Close-up of a cat's claw, with the quick clearly visible

Although scratching can serve cats to keep their claws from growing excessively long, their nails can be trimmed if necessary with a small nail trimmer designed for humans, or a small pair of electrician's diagonal cutting pliers, or a guillotine type cutter specifically designed for animal nail trimming. Care must always be taken to avoid cutting the quick of the claw, analogous to cutting into the tip of a finger and equally painful and bloody. The position of the quick can be easily seen through the translucent nail of a cat with light colored claws but not in cats with dark colored nails, who therefore require carefully trimming of only small amounts from the nails.

Another response to indoor scratching is onychectomy, commonly known as declawing. This is a surgical procedure to remove the claw and first bone of each digit of a cat's paws. Declawing is most commonly only performed on the front feet. A related procedure is tendonectomy, which involves cutting a tendon needed for cats to extend their claws.[202] Declawing is a major surgical procedure and can produce pain, infections and permanent lameness.[202] Since this surgery is not performed for the benefit of the animal, it is controversial and remains uncommon outside of North America.[203] In many countries, it is prohibited by animal welfare laws. Although widely practiced in the US, declawing is ethically controversial within the American veterinary community.[204] Both the Humane Society of the United States and the American Society for the Prevention of Cruelty to Animals strongly discourage or condemn the procedure.[205]

Waste

Toilet-trained house cat

Cats bury their urine and feces. Indoor cats are usually provided with a litter box containing litter, typically bentonite, but sometimes other absorbent material such as shredded paper or wood chips, or sometimes sand or similar material. It should be cleaned daily and changed often, depending on the number of cats in a household and the type of litter; if it is not kept clean, a cat may be fastidious enough to find other locations in the house for urination or defecation. This may also happen for other reasons; for instance, if a cat becomes constipated and defecation is uncomfortable, it may associate the discomfort with the litter box and avoid it in favor of another location.

Daily attention to the litter box also serves as a monitor of the cat's health. Bentonite or clumping litter is a variation which absorbs urine into clumps which can be sifted out along with feces, and thus stays cleaner longer with regular sifting, but has sometimes been reported to cause health problems in some cats.[206] Those with toxoplasmosis-infected cats living in habitat areas of sea otters[207] may wish to dispose of droppings in the trash, rather than flushing them down the toilet.[208] Some cats can be trained to use the human toilet, eliminating the litter box and its attendant expense, unpleasant odor, and the need to use landfill space for disposal. Training may involve four to six weeks of incremental moves, such as moving and elevating the litter box until it is near the toilet, as well as employing an adapter such as a bowl or small box to suspend the litter above the toilet bowl.[209] When training is complete, the cat uses the toilet by squatting on the toilet seat over the bowl.

Feral cats

American feral farm cat.

Feral cats are wild cats that are unfamiliar with humans and roam freely in urban or rural areas.[210] The numbers of feral cats are not known, but estimates of the US feral population range from 25 to 60 million.[210] Feral cats may live alone, but most are found in large groups called feral colonies, which occupy a specific territory and are usually associated with a source of food.[211] Famous feral cat colonies are found in Rome around the Colosseum and Forum Romanum, with cats at some of these sites being fed and vetted by volunteers.[212]

Public attitudes towards feral cats vary widely: ranging from seeing them as free-ranging pets, to regarding them as vermin.[213] One common approach to reducing the feral cat population is termed trap-neuter-return, where the cats are trapped, neutered, immunized against rabies and the feline leukemia virus, and then released. Before releasing them back into their feral colonies, the attending veterinarian often nips the tip off one ear to mark the feral as neutered and inoculated, since these cats may be trapped again.[211] Volunteers continue to feed and give care to these cats throughout their lives, and not only is their lifespan greatly increased, but behavior and nuisance problems, due to competition for food, are also greatly reduced.[211]

History and mythology

Egyptian sculpture at the Louvre

Traditionally, historians tended to think that ancient Egypt was the site of cat domestication, due to the clear depictions of house cats in Egyptian paintings about 3,600 years old.[4] However, in 2004, a Neolithic grave was excavated in Shillourokambos, Cyprus that contained the skeletons, laid close to one another, of both a human and a cat. The grave is estimated to be 9,500 years old, pushing back the earliest known feline-human association significantly.[6][214][215] The cat specimen is large and closely resembles the African wildcat (Felis silvestris lybica), rather than present-day domestic cats. This discovery, combined with genetic studies, suggest that cats were probably domesticated in Cyprus and the Near East, in the Fertile Crescent around the time of the development of agriculture.[4]

In ancient Egypt cats were sacred animals, with the Bast often depicted in cat form, sometimes taking on the warlike aspect of a lioness.[216] The Romans are often credited with introducing the domestic cat from Egypt to Europe.[217] However, it is possible that cats were already kept in Europe prior to the Roman Empire, as they may have already been present in Britain in the late Iron Age.[32] Domestic cats were spread throughout much of the rest of the world during the Age of Discovery, as they were carried on sailing ships to control shipboard rodents and as good-luck charms.[217]

Several ancient religions believed that cats are exalted souls, companions or guides for humans, that they are all-knowing but are mute so they cannot influence decisions made by humans. In Japan, the Maneki Neko is a cat that is a symbol of good fortune. Although there are no sacred species in Islam, some writers have stated that Muhammad had a favorite cat, Muezza.[218] He is reported to have loved cats so much that "he would do without his cloak rather than disturb one that was sleeping on it".[219]

Freyja—the goddess of love, beauty, and fertility in Norse mythology—is depicted as riding a chariot drawn by cats.

Many cultures have negative superstitions about cats. An example would be the belief that a black cat "crossing your path" leads to bad luck, or that cats are witches' familiars used to augment a witch's powers and skills. This led to the widespread extermination of cats in Europe in medieval times. The Black Plague was spread by fleas carried by infected rats, and the killing of cats ostensibly caused an increase in the rat population. The killing of cats in Medieval Ypres is commemorated in the innocuous present-day Kattenstoet (cat parade).

According to a myth in many cultures, cats have nine (or sometimes seven) lives. The myth is attributed to the natural suppleness and swiftness cats exhibit to escape life-threatening situations.[220] Also lending credence to this myth is that falling cats often land on their feet because of an inbuilt automatic twisting reaction and are able to twist their bodies around to land feet first, though they can still be injured or killed by a high fall.[221]