Tortoiseshell is a

cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...

coat coloring named for its similarity to tortoiseshell material. Like calicoes, tortoiseshell cats are almost exclusively female. Male tortoiseshells are rare and are usually sterile.Atkins (2003), p.105 Tortoiseshell cats, or torties, combine two colors other than white, either closely mixed or in larger patches. The colors are often described as red and black, but the "red" patches can instead be orange, yellow, or cream, and the "black" can instead be chocolate, gray,

tabby A tabby is any domestic cat (''Felis catus'') with a distinctive 'M'-shaped marking on its forehead; stripes by its eyes and across its cheeks, along its back, and around its legs and tail; and (differing by tabby type), characteristic striped, ...

, or blue. Tortoiseshell cats with the

pattern as one of their colors are sometimes referred to as torbies or torbie cats.King, Ingrid. "'Tortitude' – The Unique Personality of Tortoiseshell Cats", ''The Conscious Cat''. consciouscat.net. August 17, 2009. Retrieved 2015-12-19
/ref> "Tortoiseshell" is typically reserved for particolored cats with relatively small or no white markings. Those that are predominantly white with tortoiseshell patches are described as tricolor, tortoiseshell-and-white (in the United Kingdom), or

calico Calico (; in British usage since 1505) is a heavy plain-woven textile made from unbleached, and often not fully processed, cotton. It may also contain unseparated husk parts. The fabric is far coarser than muslin, but less coarse and thick than ...

(in Canada and the United States). Cats with a tortoiseshell pattern and small blotches of white are sometimes referred to as "tortico," a

portmanteau A portmanteau word, or portmanteau (, ) is a blend of words This pattern is especially preferred in the Japanese Bobtail breed, and exists in the Cornish Rex group.

Patterns

Tortoiseshell cats have particolored coats with patches of various shades of red and black, and sometimes white. The size of the patches can vary from a fine speckled pattern to large areas of color. Typically, the more white a cat has, the more solid the patches of color. Dilution genes may modify the coloring, lightening the

fur Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket t ...

to a mix of cream and blue, lilac or fawn; the markings on tortoiseshell cats are usually

asymmetrical Asymmetry is the absence of, or a violation of, symmetry (the property of an object being invariant to a transformation, such as reflection). Symmetry is an important property of both physical and abstract systems and it may be displayed in pre ...

Occasionally

patterns of black and brown (eumelanistic) and red (phaeomelanistic) colors are also seen. These patched tabbies are often called a tortie-tabby, a torbie or, with large white areas, a caliby. Not uncommonly there will be a "split face" pattern with black on one side of the face and orange on the other, with a dividing line running down the bridge of the nose. Tortoiseshell coloring can also be expressed in the point pattern, referred to as a tortie point. Split face tortoiseshell cat

Genetics

Leonard Doncaster Leonard Doncaster (31 December 1877 – 28 May 1920) was an English geneticist and a lecturer on zoology at both Birmingham University and the University of Liverpool whose research work was largely based on insects. Early life Doncaster was ...

was the first to prove that tortoiseshell is the female heterozygote of orange and black, the corresponding male being orange. In the course of his studies he discovered that the rare tortoiseshell male is often sterile. Tortoiseshell and calico coats result from an interaction between genetic and developmental factors. The primary gene for coat color (B) for the colors brown, chocolate, cinnamon, etc., can be masked by the co-dominant gene for the orange color (O) which is on the

X Chromosome The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex ...

and has two

alleles An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chrom ...

, the orange (X^O) and not-orange (X^o), that produce orange

phaeomelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...

and black eumelanin pigments, respectively. (NOTE: Typically, the X for the chromosome is assumed from context and the alleles are referred to by just the uppercase O for the orange, or lower case o for the not-orange.) The tortoiseshell and

calico cat A calico cat is a domestic cat of any breed with a tri-color coat. The calico cat is most commonly thought of as being typically 25% to 75% white with large orange and black patches (or sometimes cream and grey patches, which is called a mut ...

s are indicated: Oo to indicate they are heterozygous on the O gene. The (B) and (O) genes can be further modified by a recessive dilute gene (dd) which softens the colors. Orange becomes cream, black becomes gray, etc. Various terms are used for specific colors, for example, gray is also called blue, orange is also called ginger. Therefore, a tortoiseshell cat may be a chocolate tortoiseshell or a blue/cream tortoiseshell or the like, based on the alleles for the (B) and (D) genes. The cells of female cats, which like other mammalian females have two X chromosomes (XX), undergo the phenomenon of

X-inactivation X-inactivation (also called Lyonization, after English geneticist Mary Lyon) is a process by which one of the copies of the X chromosome is inactivated in therian female mammals. The inactive X chromosome is silenced by being packaged into a ...

, in which one or the other of the X-chromosomes is turned off at random in each cell in very early development. The inactivated X becomes a

Barr body A Barr body (named after discoverer Murray Barr) or X-chromatin is an inactive X chromosome in a cell with more than one X chromosome, rendered inactive in a process called lyonization, in species with XY sex-determination (including huma ...

. Cells in which the chromosome carrying the orange (O) allele is inactivated express the alternative non-orange (o) allele, determined by the (B) gene. Cells in which the non-orange (o) allele is inactivated express the orange (O) allele. Pigment genes are expressed in melanocytes that migrate to the skin surface later in development. In bi-colored tortoiseshell cats, the melanocytes arrive relatively early, and the two cell types become intermingled, producing the characteristic brindled appearance consisting of an intimate mixture of orange and black cells, with occasional small diffuse spots of orange and black. In tri-colored calico cats, a separate gene interacts developmentally with the coat color gene. This spotting gene produces white, unpigmented patches by delaying the migration of the melanocytes to the skin surface. There are a number of alleles of this gene that produce greater or lesser delays. The amount of white is artificially divided into ''mitted'', '' bicolor'', ''harlequin'', and '' van'', going from almost no white to almost completely white. In the extreme case, no melanocytes make it to the skin and the cat is entirely white (but not an albino). In intermediate cases, melanocyte migration is slowed, so that the pigment cells arrive late in development and have less time to intermingle. Observation of tri-color cats will show that, with a little white color, the orange and black patches become more defined, and with still more white, the patches become completely distinct. Each patch represents a clone of cells derived from one original cell in the early embryo.Robinson, Roy. Genetics for Cat Breeders and Veterinarians. Publisher: Butterworth-Heinemann Medical 1991. A male cat, like males of other therian mammals, has only one X and one Y chromosome (XY). That X chromosome does not undergo X-inactivation, and coat color is determined by which allele is present on the X chromosome. Accordingly, the cat's coat will be either entirely orange or non-orange. Very rarely (approximately 1 in 3,000) a male tortoiseshell or calico is born; these typically have an extra X chromosome (XXY), a condition known in humans as

Klinefelter syndrome Klinefelter syndrome (KS), also known as 47,XXY, is an aneuploid genetic condition where a male has an additional copy of the X chromosome. The primary features are infertility and small, poorly functioning testicles. Usually, symptoms are sub ...

, and their cells undergo an X-inactivation process like in females. As in humans, these cats often are sterile because of the imbalance in sex chromosomes. Some male calico or tortoiseshell cats may be chimeras, which result from fusion in early development of two (fraternal twin) embryos with different color genotypes; these torties can pass only one color to their offspring, not both, according to which of the two original embryos its testes are descended from. Others are mosaics, in which the XXY condition arises after conception and the cat is a mixture of cells with different numbers of X chromosomes.

Gallery

File:Tortoiseshellshorthair.JPG, A domestic shorthair tortoiseshell cat. Individual white hairs and light-colored hair patches are visible, but they are small compared with the orange and black patches. File:Savannah, a Texas "caliby" cat.jpg, Tortie cat with a predominantly white undercoat, a "caliby" File:Blu-tortie-point-masch.jpg, Blue tortoiseshell

Birman The Birman, also called the "Sacred Cat of Burma",
Retrieved 16 April 2010 is a domestic calico cat A calico cat is a domestic cat of any breed with a tri-color coat. The calico cat is most commonly thought of as being typically 25% to 75% white with large orange and black patches (or sometimes cream and grey patches, which is called a mut ...

. File:A tortoiseshell cat's speckled paw-pads.jpg, Black and red mottling on the paw-pads of a tortoiseshell cat File:BabyRagdoll2.jpg, A 16-year-old female tortoiseshell ragdoll cat. While Tortie Ragdolls are actually

in color, the

nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. The principles of naming vary from the relatively informal conventions of everyday speech to the internationally ag ...

is different in this breed's descriptions of colors and patterns.

Folklore

In the folklore of several cultures, cats with tortoiseshell coloration are believed to bring

good luck Luck is the phenomenon and belief that defines the experience of improbable events, especially improbably positive or negative ones. The naturalistic interpretation is that positive and negative events may happen at any time, both due to rand ...

. In Ireland, tortoiseshell cats are considered to bring good luck to their owners. In the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

, tortoiseshells are sometimes referred to as ''money cats''. In Japan, tortoiseshell cats are considered to bring good luck against shipwrecks. There are some additional interpretations of the luck of tortoiseshell cats, such as the one in England that describes an announcement of misfortune when a strange tortoiseshell cat enters a house. In England, if a woman dreams of a tortoiseshell cat, it can be interpreted as a warning that she should take care of her so-called friends.

Behavior

One study found that tortoiseshell owners frequently believe their cats have increased attitude ("tortitude"); but there is little existing scientific evidence on the matter. One study found that there was not a relationship between coat color and tameness. However, a 2015 study from the University of California, Davis School of Veterinary Medicine surveying more than 1,200 cat guardians established links between a tortoiseshell coat pattern and a cat's inclination towards hissing, biting, chasing, and slapping/scratching their human companions, while a 2016 study showed an association with increased aggression and prey interest. According to celebrity cat expert Jackson Galaxy, tortoiseshell cats tend to have much more distinct personalities and are more sensitive to environmental stimuli. Based on the varying study results, assumptions cannot be made between cat coat color and personality. However, with some animals, such as domestic horses, silver foxes, deer mice, and rats, there are associations between personality and coat color and more research is needed to see if there is such an association in cats.

Notes

References

* Atkins, Carla. ''Cats: An Owner's Guide'' (2003). San Diego, California: Thunder Bay Press.

External links

"Tortoiseshell Cat Tortoiseshell Color Pattern, Tortie Cat"
at animal-world.com

tortiecats.free.fr
website showing the diversity of tortie and calico coats {{Cat nav Cat coat types