An odd-eyed cat has one blue eye and one eye either green, yellow, amber, or brown. This is a feline form of complete heterochromia, [1] [2] a condition that occurs in some other animals, including humans. There is also sectoral (partial) heterochromia, where two different colours occur within the same iris. The condition most commonly affects solid white cats, but may be found in cats of any coat colour. [3] [4] [5]
The odd-eyed colouring is caused when either the epistatic (recessive) white gene or dominant white (which masks any other colour genes and turns a cat completely solid white) [3] or the white spotting gene (which is the gene responsible for bicolour coats) [4] prevents melanin (pigment) granules from reaching one eye during development, resulting in a cat with one blue eye and one green, yellow, amber, or brown eye. Approximately 15–40% of the solid white cats have one or two blue eyes. [3]
The odd-eye condition only rarely occurs in cats that lack both the dominant white and the white spotting gene. [3] These cats carry a dominant blue eye-gene, which is not linked to coat colouration. A famous example of this case is the extinct Ojos Azules cat. [3] [5]
Odd-eyes are found in all domestic cats, and are not linked to a specific breed. However, odd-eyed cats are popular within several breeds, including Van cat, Turkish Van, Turkish Angora, Sphynx, Persian, Oriental Shorthair, Japanese Bobtail and Khao Manee. In the Japanese Bobtail, odd-eyed cats are most frequently found in calico individuals. [6]
As with some other newborn mammals, all cats are blue-eyed as kittens, [7] and may change as the newborn ages. The differences in an odd-eyed kitten's eye colour might not be noticeable, except upon close inspection. Odd-eyed kittens have a different shade of blue in each eye. The colour of the odd eye changes over a period of months, for example, from blue to green to yellow or from green to blue to yellow, until it reaches its final, adult colour.
There is a common misconception that all odd-eyed cats are born deaf in one ear. This is not true, however, solid white (completely white) cats with one or two blue eyes do have a higher incidence of genetic deafness, with the white gene occasionally causing the degeneration of the cochlea, beginning a few days after birth. [8] In odd-eyed white cats, the ear on the blue-eyed side may be deaf, while the other ear usually has normal hearing. [3]
The established link between deafness and odd-eyes is found in the link between deafness, blue eyes and solid white coats. There are multiple different genes responsible for blue (incl. odd eyes), and several of these genes are not linked to white coats or deafness (e.g., "Siamese" colourpoint-gene, Ojos Azules-gene, etc.). For example solid white blue-eyed Foreign White or Ojos Azules cats are not linked to deafness. Deafness depends on the cat's genotype (genetic make-up), and not its phenotype (physical appearance). Therefore, not all solid white cats with one or two blue eyes are deaf. It is not advisable to breed from deaf white cats, as this would pass the trait along. BAER-testing (Brainstem Auditory Evoked Response) is used to test deafness in cats. [3] [5]
Scientists estimate that about 10–20% of non-blue-eyed solid white cats of are born deaf, or become deaf as part of the feline aging process, while about 30–40% of the solid white odd-eyed cats are deaf. For solid white cat with two blue eyes, 60–80% are deaf. [3] [9] Cats are classified as deaf, when one or both ears are affected by deafness.
In flash photographs, odd-eyed cats typically show a red-eye effect in the blue eye, but not in the other eye. This is due to the combined effect of the (normal) presence of a tapetum lucidum in both eyes and the absence of melanin in the blue eye. The tapetum lucidum produces eyeshine in both eyes, but in the non-blue eye a layer of melanin over the tapetum lucidum selectively removes some colours of light.
The Atatürk Forest Farm and Zoo in Ankara has a breeding program to preserve pure solid white Turkish Angora cats. [10] [11] The zoo specifically prized the odd-eyed Angoras, as the Turkish folklore suggests that "the eyes must be as green as the lake and as blue as the sky". [12]
Prophet Muhammad's pet Angora, Muezza, was reputed to be an odd-eyed cat. [11]
The mascot of the 2010 FIBA World Championship, hosted by Turkey, was an anthropomorphised odd-eyed Van cat named "Bascat". [13]
The Siamese cat is one of the first distinctly recognised breeds of Asian cat. Derived from the Wichianmat landrace, one of several varieties of cats native to Thailand, the original Siamese became one of the most popular breeds in Europe and North America in the 19th century. Siamese cats have a distinctive colourpoint coat, resulting from a temperature-sensitive type of albinism.
A bicolor cat is a cat with white fur combined with fur of some other color, for example solid black, tabby, or colorpointed. There are various patterns of a bicolor cat. These range from the Van-patterned to a solid color with a throat locket or medallion. Bicolor coats are found in many cat breeds, as well as being common in domestic longhair and domestic shorthair cats.
The Turkish Van is a semi-long-haired, standardised breed of domestic cat, which was developed in the United Kingdom from a selection of cats obtained from various cities of modern Turkey, especially southeast Turkey. The breed is rare, is one of the larger breeds, and is distinguished by the Van pattern, where the colour is restricted to the head and the tail, and the rest of the cat is white; this is due to the expression of the piebald white spotting gene, a type of partial leucism. A Turkish Van may have blue or amber eyes, or be odd-eyed.
The iris is a thin, annular structure in the eye in most mammals and birds, responsible for controlling the diameter and size of the pupil, and thus the amount of light reaching the retina. In optical terms, the pupil is the eye's aperture, while the iris is the diaphragm. Eye color is defined by the iris.
The American Bobtail is an uncommon breed of domestic cat which was developed in the late 1960s. It is most notable for its stubby "bobbed" tail about one-third to one-half the length of a normal cat's tail. This is the result of a cat body type genetic mutation affecting the tail development, similar to that of a Manx cat. The breed is not related to other short-tailed breeds, such as the Cymric cat, or the Japanese Bobtail or Kurilian Bobtail, despite the similar name and physical type—the breeding programs are entirely unrelated, and the genetic mutation causing the bobbed tail are known to be different, as the mutation causing the American Bobtail's short tail is dominant; comparatively, the Japanese Bobtail, for example, has a tail mutation that is recessive.
The Japanese Bobtail is a breed of domestic cat with an unusual bobtail more closely resembling the tail of a rabbit than that of other cats. The breed was first developed in Japan, and registered officially in the 1960s. The breed has been known in Japan for centuries, and it frequently appears in traditional folklore and art. Japanese Bobtails are believed to be derived from domestic and feral populations of kinked-tailed cats widespread throughout Southeast Asia and southern China.
The tapetum lucidum is a layer of tissue in the eye of many vertebrates and some other animals. Lying immediately behind the retina, it is a retroreflector. It reflects visible light back through the retina, increasing the light available to the photoreceptors.
The Burmese cat is a breed of domestic cat, originating in Burma, believed to have its roots near the Thai-Burma border and developed in the United States and Britain.
Cat coat genetics determine the coloration, pattern, length, and texture of feline fur. The variations among cat coats are physical properties and should not be confused with cat breeds. A cat may display the coat of a certain breed without actually being that breed. For example, a Neva Masquerade could wear point coloration, the stereotypical coat of a Siamese.
Heterochromia is a variation in coloration most often used to describe color differences of the iris, but can also be applied to color variation of hair or skin. Heterochromia is determined by the production, delivery, and concentration of melanin. It may be inherited, or caused by genetic mosaicism, chimerism, disease, or injury. It occurs in humans and certain breeds of domesticated animals.
The Siberian is a centuries-old landrace of domestic cat in Russia, and recently developed as a formal breed with standards promulgated the world over since the late-1980s. Since 2006, the breed is recognised for registry and championship status with all major cat registries.
The Turkish Angora is a breed of domestic cat. Turkish Angoras are one of the ancient, natural breeds of cat, having originated in central Anatolia. The breed has been documented as early as the 17th century. Outside of the United States, the breed is usually referred to as simply the Angora or Ankara cat. These cats have slender and elegant bodies.
The Snowshoe is a rare breed of domestic cat originating in the United States of America in the 1960s. The Snowshoe is a short-haired bicolour colourpoint breed. Snowshoes were first produced when a Siamese breeder's cat gave birth to three kittens with white feet. The breeder, Dorothy Hinds-Daugherty, then began a breeding program to produce what were originally called "Silver Laces", crossing the strangely marked Siamese cats with bicolour American Shorthair cats and other breeds. Despite having existed for 45 years, Snowshoes are rare due to the difficulty of reproducing the correct coat markings.
Ojos Azules was a breed of shorthaired domestic cat with unusual blue or odd eyes caused by a dominant blue eye (DBE) genetic mutation. The breed came in all coat colors; however, only particolors, colorpoints, and intermediate colors with a characteristic white tail tip were permitted. The breed also had a semi-longhaired coat variety, the Ojos Azules Longhair. Due to the lethal side effects of the Ojos Azules gene, breeders stopped working with this blue eye mutation.
The Oriental Longhair is a variety of domestic cat closely related to the Oriental Shorthair. The Oriental Longhair in some registries, such as The International Cat Association (TICA), it is considered a separate breed. In others, such as the Cat Fanciers' Association (CFA), it is a division, along with the short-haired variety, of a merged breed, the Oriental. With no globally recognised naming convention, other cat fanciers may refer to this type as Foreign Longhair, Javanese or Mandarin. It was formerly known as the British Angora before being renamed in 2002 by British cat fanciers in order to avoid confusion with the Turkish Angora.
The Neva Masquerade is a breed or sub-breed of long-haired domestic cat, which originates in Russia. It is the sister breed or colourpoint variant of the Siberian cat, a centuries-old Russian landrace. The colourpoint markings are the result of a colourpoint gene originally found in Siamese cats. The Neva Masquerade is believed to be derived from crossing the Siberian cat with Asian colourpoint cats, such as the Siamese or Thai, or possibly cats related to those, such as the colourpointed Persian cats. Some cat registries may classify the Neva Masquerade as a colourpoint variety or sub-breed of the Siberian cat, while others consider it to be a separate sister breed. Regardless of its classification, all Neva Masquerade cats are selectively bred and pedigreed today in all major cat fancier and breeder organisations under the Siberian (Forest) cat or Neva Masquerade. This means that all Neva Masquerade cats are purebred cats with a formally registered ancestry.
Cat senses are adaptations that allow cats to be highly efficient predators. Cats are good at detecting movement in low light, have an acute sense of hearing and smell, and their sense of touch is enhanced by long whiskers that protrude from their heads and bodies. These senses evolved to allow cats to hunt effectively at dawn and dusk.
Acromelanism or point coloration is a genetically determined, temperature-dependent pigmentation pattern, with full expression only occurring on legs, ears, tail, face and scrotum. It is most recognized as the coloration of Siamese and related breeds of cat, but can be found in dogs, rabbits, rats, mice, sheep, guinea pigs, minks, and gerbils.
Congenital sensorineural deafness occurs commonly in domestic cats with a white coat. It is a congenital deafness caused by a degeneration of the inner ear. Deafness is far more common in white cats than in those with other coat colours.
The Persian cat, also known as the Persian Longhair, is a long-haired breed of cat characterised by a round face and short muzzle. The first documented ancestors of Persian cats might have been imported into Italy from Khorasan as early as around 1620, however, this has not been proven. Instead, there is stronger evidence for a longhaired cat breed being exported from Afghanistan and Iran from the 19th century onwards. Persian cats have been widely recognised by the North-West European cat fancy since the 19th century, and after World War II by breeders from North America, Australia and New Zealand. Some cat fancier organisations' breed standards subsume the Himalayan and Exotic Shorthair as variants of this breed, while others generally treat them as separate breeds.
