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Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its sister group Cercopithecidae form the catarrhine clade, cladistically making them monkeys (though this is the subject of much debate). Apes do not have tails due to a mutation of the TBXT gene.[2] In traditional and non-scientific use, the term "ape" can include tailless primates taxonomically considered Cercopithecidae (such as the Barbary ape and black ape), and is thus not equivalent to the scientific taxon Hominoidea. There are two extant branches of the superfamily Hominoidea: the gibbons, or lesser apes; and the hominids, or great apes.

The family Hylobatidae, the lesser apes, include four genera and a total of 20 species of gibbon, including the lar gibbon and the siamang, all native to Asia. They are highly arboreal and bipedal on the ground. They have lighter bodies and smaller social groups than great apes.

The family Hominidae (hominids), the great apes, include four genera comprising three extant species of orangutans and their subspecies, two extant species of gorillas and their subspecies, two extant species of panins (bonobos and chimpanzees) and their subspecies, and humans in a single extant subspecies.[a][4][5]

Except for gorillas and humans, hominoids are agile climbers of trees. Apes eat a variety of plant and animal foods, with the majority of food being plant foods, which can include fruits, leaves, stalks, roots and seeds, including nuts and grass seeds. Human diets are sometimes substantially different from that of other hominoids due in part to the development of technology and a wide range of habitation. Humans are by far the most numerous of the hominoid species, in fact outnumbering all other primates by a factor of several thousand to one.

All non-human hominoids are rare and threatened with extinction. The eastern hoolock gibbon is the least threatened, only being vulnerable to extinction. Five gibbon species are critically endangered, as are all species of orangutan and gorilla. The remaining species of gibbon, the bonobo, and all four species of chimpanzees are endangered. The chief threat to most of the endangered species is loss of tropical rainforest habitat, though some populations are further imperiled by hunting for bushmeat. The great apes of Africa are also facing threat from the Ebola virus. Currently considered to be the greatest threat to survival of African apes, Ebola infection is responsible for the death of at least one third of all gorillas and chimpanzees since 1990.[6]

Name and terminology

"Ape", from Old English apa, is a word of uncertain origin.[b] The term has a history of rather imprecise usage-and of comedic or punning usage in the vernacular. Its earliest meaning was generally of any non-human anthropoid primate, as is still the case for its cognates in other Germanic languages.[c] Later, after the term " monkey" had been introduced into English, "ape" was specialized to refer to a tailless (therefore exceptionally human-like) primate. Thus, the term "ape" obtained two different meanings, as shown in the 1911 Encyclopædia Britannica entry: it could be used as a synonym for "monkey" and it could denote the tailless human-like primate in particular.[9]

Some, or recently all, hominoids are also called "apes", but the term is used broadly and has several different senses within both popular and scientific settings. "Ape" has been used as a synonym for "monkey" or for naming any primate with a human-like appearance, particularly those without a tail.[9] Biologists have traditionally used the term "ape" to mean a member of the superfamily Hominoidea other than humans, but more recently to mean all members of Hominoidea. So "ape"-not to be confused with "great ape"-now becomes another word for hominoid including humans.[5][d]

The taxonomic term hominoid is derived from, and intended as encompassing, the hominids, the family of great apes. Both terms were introduced by Gray (1825).[10] The term hominins is also due to Gray (1824), intended as including the human lineage (see also Hominidae#Terminology, Human taxonomy).

The distinction between apes and monkeys is complicated by the traditional paraphyly of monkeys: Apes emerged as a sister group of Old World Monkeys in the catarrhines, which are a sister group of New World Monkeys. Therefore, cladistically, apes, catarrhines and related contemporary extinct groups such as Parapithecidaea are monkeys as well, for any consistent definition of "monkey". "Old World Monkey" may also legitimately be taken to be meant to include all the catarrhines, including apes and extinct species such as Aegyptopithecus,[11][12][13][14][citation needed ] in which case the apes, Cercopithecoidea and Aegyptopithecus emerged within the Old World Monkeys.

The primates called "apes" today became known to Europeans after the 18th century. As zoological knowledge developed, it became clear that taillessness occurred in a number of different and otherwise distantly related species. Sir Wilfrid Le Gros Clark was one of those primatologists who developed the idea that there were trends in primate evolution and that the extant members of the order could be arranged in an ".. ascending series", leading from "monkeys" to "apes" to humans. Within this tradition "ape" came to refer to all members of the superfamily Hominoidea except humans. As such, this use of "apes" represented a paraphyletic grouping, meaning that, even though all species of apes were descended from a common ancestor, this grouping did not include all the descendant species, because humans were excluded from being among the apes.[e]

Traditionally, the English-language vernacular name "apes" does not include humans, but phylogenetically, humans (Homo) form part of the family Hominidae within Hominoidaea. Thus, there are at least three common, or traditional, uses of the term "ape": non-specialists may not distinguish between "monkeys" and "apes", that is, they may use the two terms interchangeably; or they may use "ape" for any tailless monkey or non-human hominoid; or they may use the term "ape" to just mean the non-human hominoids.

Modern taxonomy aims for the use of monophyletic groups for taxonomic classification;[15][f] Some literature may now use the common name "ape" to mean all members of the superfamily Hominoidea, including humans. For example, in his 2005 book, Benton wrote "The apes, Hominoidea, today include the gibbons and orang-utan ... the gorilla and chimpanzee ... and humans".[5] Modern biologists and primatologists refer to apes that are not human as "non-human" apes. Scientists broadly, other than paleoanthropologists, may use the term " hominin" to identify the human clade, replacing the term " hominid". See terminology of primate names.

See below, History of hominoid taxonomy, for a discussion of changes in scientific classification and terminology regarding hominoids.

Evolution

Although the hominoid fossil record is still incomplete and fragmentary, there is now enough evidence to provide an outline of the evolutionary history of humans. Previously, the divergence between humans and other extant hominoids was thought to have occurred 15 to 20 million years ago, and several species of that time period, such as Ramapithecus, were once thought to be hominins and possible ancestors of humans. But, later fossil finds indicated that Ramapithecus was more closely related to the orangutan; and new biochemical evidence indicates that the last common ancestor of humans and non-hominins (that is, the chimpanzees) occurred between 5 and 10 million years ago, and probably nearer the lower end of that range (more recent); see Chimpanzee-human last common ancestor (CHLCA).

Taxonomic classification and phylogeny

Genetic analysis combined with fossil evidence indicates that hominoids diverged from the Old World monkeys about 25 million years ago (mya), near the Oligocene-Miocene boundary.[16][17][18] The gibbons split from the rest about 18 mya, and the hominid splits happened 14 mya ( Pongo),[19] 7 mya ( Gorilla), and 3-5 mya ( Homo & Pan).[20] In 2015, a new genus and species were described, Pliobates cataloniae, which lived 11.6 mya, and appears to predate the split between Hominidae and Hylobatidae.[21][22][5][clarification needed ]

Catarrhini (31.0 Mya)

Hominoidea/apes (20.4 Mya)

Hominidae/great apes (15.7 Mya)

Homininae (8.8 Mya)

Hominini (6.3 Mya)

humans (genus Homo)

chimpanzees (genus Pan)

gorillas (genus Gorilla)

orangutans (genus Pongo)

gibbons/lesser apes (family Hylobatidae)

Traditional apes

Cercopithecoidea Old World monkeys

The families, and extant genera and species of hominoids are:

Superfamily Hominoidea[24]

History of hominoid taxonomy

The history of hominoid taxonomy is complex and somewhat confusing. Recent evidence has changed our understanding of the relationships between the hominoids, especially regarding the human lineage; and the traditionally used terms have become somewhat confused. Competing approaches to methodology and terminology are found among current scientific sources. Over time, authorities have changed the names and the meanings of names of groups and subgroups as new evidence - that is, new discoveries of fossils and tools and of observations in the field, plus continual comparisons of anatomy and DNA sequences - has changed the understanding of relationships between hominoids. There has been a gradual demotion of humans from being 'special' in the taxonomy to being one branch among many. This recent turmoil (of history) illustrates the growing influence on all taxonomy of cladistics, the science of classifying living things strictly according to their lines of descent.[citation needed ]

Today, there are eight extant genera of hominoids. They are the four genera in the family Hominidae, namely Homo, Pan, Gorilla, and Pongo; plus four genera in the family Hylobatidae (gibbons): Hylobates, Hoolock, Nomascus and Symphalangus.[24] (The two subspecies of hoolock gibbons were recently moved from the genus Bunopithecus to the new genus Hoolock and re-ranked as species; a third species was described in January 2017).[27])

In 1758, Carl Linnaeus, relying on second- or third-hand accounts, placed a second species in Homo along with H. sapiens: Homo troglodytes ("cave-dwelling man"). Although the term "Orang Outang" is listed as a variety - Homo sylvestris - under this species, it is nevertheless not clear to which animal this name refers, as Linnaeus had no specimen to refer to, hence no precise description. Linnaeus may have based Homo troglodytes on reports of mythical creatures, then-unidentified simians, or Asian natives dressed in animal skins.[28] Linnaeus named the orangutan Simia satyrus ("satyr monkey"). He placed the three genera Homo, Simia and Lemur in the order of Primates.

The troglodytes name was used for the chimpanzee by Blumenbach in 1775, but moved to the genus Simia. The orangutan was moved to the genus Pongo in 1799 by Lacépède.

Linnaeus's inclusion of humans in the primates with monkeys and apes was troubling for people who denied a close relationship between humans and the rest of the animal kingdom. Linnaeus's Lutheran archbishop had accused him of "impiety". In a letter to Johann Georg Gmelin dated 25 February 1747, Linnaeus wrote:

It is not pleasing to me that I must place humans among the primates, but man is intimately familiar with himself. Let's not quibble over words. It will be the same to me whatever name is applied. But I desperately seek from you and from the whole world a general difference between men and simians from the principles of Natural History. I certainly know of none. If only someone might tell me one! If I called man a simian or vice versa I would bring together all the theologians against me. Perhaps I ought to, in accordance with the law of Natural History.[29]

Accordingly, Johann Friedrich Blumenbach in the first edition of his Manual of Natural History (1779), proposed that the primates be divided into the Quadrumana (four-handed, i.e. apes and monkeys) and Bimana (two-handed, i.e. humans). This distinction was taken up by other naturalists, most notably Georges Cuvier. Some elevated the distinction to the level of order.

However, the many affinities between humans and other primates - and especially the "great apes" - made it clear that the distinction made no scientific sense. In his 1871 book The Descent of Man, and Selection in Relation to Sex, Charles Darwin wrote:

The greater number of naturalists who have taken into consideration the whole structure of man, including his mental faculties, have followed Blumenbach and Cuvier, and have placed man in a separate Order, under the title of the Bimana, and therefore on an equality with the orders of the Quadrumana, Carnivora, etc. Recently many of our best naturalists have recurred to the view first propounded by Linnaeus, so remarkable for his sagacity, and have placed man in the same Order with the Quadrumana, under the title of the Primates. The justice of this conclusion will be admitted: for in the first place, we must bear in mind the comparative insignificance for classification of the great development of the brain in man, and that the strongly marked differences between the skulls of man and the Quadrumana (lately insisted upon by Bischoff, Aeby, and others) apparently follow from their differently developed brains. In the second place, we must remember that nearly all the other and more important differences between man and the Quadrumana are manifestly adaptive in their nature, and relate chiefly to the erect position of man; such as the structure of his hand, foot, and pelvis, the curvature of his spine, and the position of his head.[30]

Changes in taxonomy and terminology

Humans the non-apes: Until about 1960, taxonomists typically divided the superfamily Hominoidea into two families. The science community treated humans and their extinct relatives as the outgroup within the superfamily; that is, humans were considered as quite distant from kinship with the "apes". Humans were classified as the family Hominidae and were known as the "hominids". All other hominoids were known as "apes" and were referred to the family Pongidae.[31]

The "great apes" in Pongidae: The 1960s saw the methodologies of molecular biology applied to primate taxonomy. Goodman's 1964 immunological study of serum proteins led to re-classifying the hominoids into three families: the humans in Hominidae; the great apes in Pongidae; and the "lesser apes" (gibbons) in Hylobatidae.[32] However, this arrangement had two trichotomies: Pan, Gorilla, and Pongo of the "great apes" in Pongidae, and Hominidae, Pongidae, and Hylobatidae in Hominoidea. These presented a puzzle; scientists wanted to know which genus speciated first from the common hominoid ancestor.

Gibbons the outgroup: New studies indicated that gibbons, not humans, are the outgroup within the superfamily Hominoidea, meaning: the rest of the hominoids are more closely related to each other than (any of them) are to the gibbons. With this splitting, the gibbons ( Hylobates, et al.) were isolated after moving the great apes into the same family as humans. Now the term "hominid" encompassed a larger collective taxa within the family Hominidae. With the family trichotomy settled, scientists could now work to learn which genus is 'least' related to the others in the subfamily Ponginae.

Orangutans the outgroup: Investigations comparing humans and the three other hominid genera disclosed that the African apes (chimpanzees and gorillas) and humans are more closely related to each other than any of them are to the Asian orangutans ( Pongo); that is, the orangutans, not humans, are the outgroup within the family Hominidae. This led to reassigning the African apes to the subfamily Homininae with humans-which presented a new three-way split: Homo, Pan, and Gorilla.[33]

Hominins: In an effort to resolve the trichotomy, while preserving the nostalgic "outgroup" status of humans, the subfamily Homininae was divided into two tribes: Gorillini, comprising genus Pan and genus Gorilla; and Hominini, comprising genus Homo (the humans). Humans and close relatives now began to be known as "hominins", that is, of the tribe Hominini. Thus, the term "hominin" succeeded to the previous use of "hominid", which meaning had changed with changes in Hominidae (see above: 3rd graphic, "Gibbons the outgroup").

Gorillas the outgroup: New DNA comparisons now provided evidence that gorillas, not humans, are the outgroup in the subfamily Homininae; this suggested that chimpanzees should be grouped with humans in the tribe Hominini, but in separate subtribes.[34] Now the name "hominin" delineated Homo plus those earliest Homo relatives and ancestors that arose after the divergence from the chimpanzees. (Humans are no longer classified as an outgroup, but are a branch, deep in the tree of the pre-1960s ape group).

Speciation of gibbons: Later DNA comparisons disclosed previously unknown speciation of genus Hylobates (gibbons) into four genera: Hylobates, Hoolock, Nomascus, and Symphalangus.[24][27] The ordering of speciation of these four genera are being investigated as of 2022.

Characteristics

Distinction from monkeys

Cladistically, apes, catarrhines, and extinct species such as Aegyptopithecus and Parapithecidaea, are monkeys,[citation needed ] so one can only specify ape features not present in other monkeys.

Unlike most monkeys, apes do not possess a tail. Monkeys are more likely to be in trees and use their tails for balance. While the great apes are considerably larger than monkeys, gibbons (lesser apes) are smaller than some monkeys. Apes are considered to be more intelligent than monkeys, which are considered to have more primitive brains.[35]

Behaviour

Diet

Apart from humans and gorillas, apes eat a predominantly frugivorous diet, mostly fruit, but supplemented with a variety of other foods. Gorillas are predominately folivorous, eating mostly stalks, shoots, roots and leaves with some fruit and other foods. Non-human apes usually eat a small amount of raw animal foods such as insects or eggs. In the case of humans, migration and the invention of hunting tools and cooking has led to an even wider variety of foods and diets, with many human diets including large amounts of cooked tubers ( roots) or legumes.[36] Other food production and processing methods including animal husbandry and industrial refining and processing have further changed human diets.[37] Humans and other apes occasionally eat other primates.[38] Some of these primates are now close to extinction with habitat loss being the underlying cause.[39][40]

Cognition

All the non-human hominoids are generally thought of as highly intelligent, and scientific study has broadly confirmed that they perform very well on a wide range of cognitive tests-though there is relatively little data on gibbon cognition. The early studies by Wolfgang Köhler demonstrated exceptional problem-solving abilities in chimpanzees, which Köhler attributed to insight. The use of tools has been repeatedly demonstrated; more recently, the manufacture of tools has been documented, both in the wild and in laboratory tests. Imitation is much more easily demonstrated in "great apes" than in other primate species. Almost all the studies in animal language acquisition have been done with "great apes", and though there is continuing dispute as to whether they demonstrate real language abilities, there is no doubt that they involve significant feats of learning. Chimpanzees in different parts of Africa have developed tools that are used in food acquisition, demonstrating a form of animal culture.[41]

See also

Notes

1. The hypothetical Proto-Germanic form is given as ^ *apōn (F. Kluge, Etymologisches Wörterbuch der Deutschen Sprache (2002), online version, s.v. "Affe"; V. Orel, A handbook of Germanic etymology (2003), s.v. "*apōn" or as *apa(n) (Online Etymology Dictionary (2001-2014), s.v. "ape"; M. Philippa, F. Debrabandere, A. Quak, T. Schoonheim & N. van der Sijs, Etymologisch woordenboek van het Nederlands (2003-2009), s.v. "aap"). Perhaps ultimately derived from a non-Indo-European language, the word might be a direct borrowing from Celtic, or perhaps from Slavic, although in both cases it is also argued that the borrowing, if it took place, went in the opposite direction.

2. "Any simian known on the Mediterranean during the Middle Ages; monkey or ape"; cf. ^ ape-ward: "a juggler who keeps a trained monkey for the amusement of the crowd." (Middle English Dictionary, s.v. "ape").

3. Definitions of ^ paraphyly vary; for the one used here see e.g. Stace 2010, pp. 106

4. Definitions of ^ monophyly vary; for the one used here see e.g. Mishler 2009, pp. 114

References

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2. ^ Grehan, J. R. (2006). "Mona Lisa smile: the morphological enigma of human and great ape evolution". Anatomical Record. 289B (4): 139-157. doi:10.1002/ar.b.20107. PMID 16865704.

3. ^ Benton, M. J. (2005). Vertebrate Palaeontology. Wiley-Blackwell. ISBN 978-0-632-05637-8., p. 371

4. ^ Rush, J. (23 January 2015). "Ebola virus 'has killed a third of world's gorillas and chimpanzees' - and could pose greatest threat to their survival, conservationists warn". The Independent. Archived from the original on 30 March 2015.

5. ^ Chisholm, Hugh, ed. (1911). "Ape" . Encyclopædia Britannica. Vol. 2 (11th ed.). Cambridge University Press. p. 160.

6. ^ Osman Hill, W. C. (1953). Primates Comparative Anatomy and Taxonomy I-Strepsirhini. Edinburgh Univ Pubs Science & Maths, No 3. Edinburgh University Press. p. 53. OCLC 500576914.

7. ^ Martin, W. C. L. (1841). A General Introduction to the Natural History of Mammiferous Animals, With a Particular View of the Physical History of man, and the More Closely Allied Genera of the Order Quadrumana, or Monkeys. London: Wright and Co. printers. pp. 340, 361.

8. ^ Bugge, J. (1974). "Chapter 4". Cells Tissues Organs. 87 (Suppl. 62): 32-43. doi:10.1159/000144209. ISSN 1422-6405.

9. ^ Springer; D. H. (1 July 2011). An Introduction to Zoology: Investigating the Animal World. Jones & Bartlett Publishers. p. 536. ISBN 978-0-7637-5286-6. Through careful study taxonomists today struggle to eliminate polyphyletic and paraphyletic groups and taxons, reclassifying their members into appropriate monophyletic taxa

10. ^ "Fossils may pinpoint critical split between apes and monkeys". 15 May 2013.

11. ^ Rossie, J. B.; Hill, A. (2018). "A new species of Simiolus from the middle Miocene of the Tugen Hills, Kenya". Journal of Human Evolution. 125: 50-58. doi:10.1016/j.jhevol.2018.09.002. PMID 30502897. S2CID 54625375.

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13. ^ Alba, D. M.; Fortuny, J.; Moyà-Solà, S. (2010). "Enamel thickness in the Middle Miocene great apes Anoiapithecus, Pierolapithecus and Dryopithecus". Proceedings of the Royal Society of London B: Biological Sciences. 277 (1691): 2237-2245. doi:10.1098/rspb.2010.0218. ISSN 0962-8452. PMC 2880156. PMID 20335211.

14. ^ Grabowski, M.; Jungers, W. L. (2017). "Evidence of a chimpanzee-sized ancestor of humans but a gibbon-sized ancestor of apes". Nature Communications. 8 (1): 880. Bibcode:2017NatCo...8..880G. doi:10.1038/s41467-017-00997-4. ISSN 2041-1723. PMC 5638852. PMID 29026075.

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21. ^ Frängsmyr, T.; Lindroth, S.; Eriksson, G.; Broberg, G. (1983). Linnaeus, the man and his work. Berkeley and Los Angeles: University of California Press. ISBN 978-0-7112-1841-3., p. 166

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Literature cited

Dawkins, R. (2005). The Ancestor's Tale (p/b ed.). London: Phoenix (Orion Books). ISBN 978-0-7538-1996-8.

Dixson, A. F. (1981). The Natural History of the Gorilla. London: Weidenfeld & Nicolson. ISBN 978-0-297-77895-0.

Mishler, Brent D (2009). "Species are not uniquely real biological entities". In Ayala, F. J. & Arp, R. (eds.). Contemporary Debates in Philosophy of Biology. pp. 110-122. doi:10.1002/9781444314922.ch6. ISBN 978-1-4443-1492-2.

Stace, C. A. (2010). "Classification by molecules: what's in it for field botanists?" (PDF). Watsonia. 28: 103-122. Archived from the original (PDF) on 26 July 2011.

Terry, M. W. (1977). "Use of common and scientific nomenclature to designate laboratory primates". In Schrier, A. M. (ed.). Behavioral Primatology: Advances in Research and Theory. Vol. 1. Hillsdale, N.J., USA: Lawrence Erlbaum.

External links

# data[].attributes.attachment_link.description
Toggle the table of contents From Wikipedia, the free encyclopedia Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its sister group Cercopithecidae form the catarrhine clade, cladistically making them monkeys (though this is the subject of much debate).

# data[].attributes.attachment_link.readable_text
A captive white tiger at the Singapore Zoo

The white tiger or bleached tiger is a leucitic pigmentation variant of the mainland Asian tiger. It is reported in the wild from time to time in the Indian states of Madhya Pradesh, Assam, West Bengal, Bihar, Odisha, in the Sunderbans region and especially in the former State of Rewa. It has the typical black stripes of a tiger, but its coat is otherwise white or near-white.

A white tiger at the Madrid Zoo

The white Bengal tigers are distinctive due to the color of their fur. The white fur is caused by a lack of the pigment pheomelanin, which is found in Bengal tigers with orange color fur. When compared to Bengal tigers, the white Bengal tigers tend to grow faster and heavier than the orange Bengal tiger.[citation needed ] They also tend to be somewhat bigger at birth, and as fully grown adults.[citation needed ] White Bengal tigers are fully grown when they are 2-3 years of age. White male tigers reach weights of 200 to 230 kilograms (440 to 510 lb) and can grow up to 3 meters (9.8 ft) in length. As with all tigers, the white Bengal tiger's stripes are like fingerprints, with no two tigers having the same pattern. The stripes of the tiger are a pigmentation of the skin; if an individual were to be shaved, its distinctive coat pattern would still be visible.

For a white Bengal tiger to be born, both parents must carry the unusual gene for white colouring, which only happens naturally about once in 10,000 births. Dark-striped white individuals are well-documented in the Bengal tiger subspecies ( Panthera tigris) as well as having been reported historically in several other subspecies. Currently, several hundred white tigers are in captivity worldwide, with about one hundred being found in India. Their unique white color fur has made them popular in entertainment showcasing exotic animals, and at zoos. Their rarity could be because the recessive allele is the result of a one-time mutation or because white tigers lack adequate camouflage, reducing their ability to stalk prey or avoid other predators. (Downes 2021)

(video) A white tiger in a zoo in Japan

Pseudo-melanistic white tiger

A white tiger's pale coloration is due to the lack of the red and yellow pheomelanin pigments that normally produce the orange coloration. This had long been attributed to a mutation in the gene for the tyrosinase (TYR) enzyme. A knockout mutation in this gene results in albinism, the ability to make neither pheomelanin (red and yellow pigments) nor eumelanin (black and brown pigments), while a less severe mutation in the same gene in other mammals results in selective loss of pheomelanin, the so-called Chinchilla trait. The white phenotype in tigers had been attributed to such a Chinchilla mutation in tyrosinase, and in the past white tigers were sometimes referred to as 'partial albinos'. While whole genome sequencing determined that such a TYR mutation is responsible for the white lion leucistic variant, a normal TYR gene was found in both white tigers and snow leopards. Instead in white tigers a naturally-occurring point mutation in the SLC45A2 transport protein gene was found to underlie its pigmentation. The resultant single amino acid substitution introduces an alanine residue that protrudes into the transport protein's central passageway, apparently blocking it, and by a mechanism yet to be determined this prevents pheomelanin expression in the fur. Mutations in the same gene are known to result in 'cream' coloration in horses, and play a role in the paler skin of humans of European descent. This is a recessive trait, meaning that it is only seen in individuals that are homozygous for this mutation, and that while the progeny of white tigers will all be white, white tigers can be also bred from colored Bengal tiger pairs in which each possesses a single copy of the unique mutation. Inbreeding promotes recessive traits and has been used as a strategy to produce white tigers in captivity, but this has also resulted in a range of other genetic defects.

The stripe color varies due to the influence and interaction of other genes. Another genetic characteristic makes the stripes of the tiger very pale; white tigers of this type are called snow-white or "pure white". White tigers, Siamese cats, and Himalayan rabbits have enzymes in their fur which react to temperature, causing them to grow darker in the cold. A white tiger named Mohini was whiter than her relatives in the Bristol Zoo, who showed more cream tones. This may have been because she spent less time outdoors in the winter. Kailash Sankhala observed that white tigers were always whiter in Rewa State, even when they were born in New Delhi and returned there. "In spite of living in a dusty courtyard, they were always snow white." A weakened immune system is directly linked to reduced pigmentation in white tigers.

Stripeless tigers

A white tiger with almost no stripes at The Mirage in Las Vegas, the United States of America

An additional genetic condition can result in near-complete absence of stripes, making the tiger almost pure white. One such specimen was exhibited at Exeter Change in England in 1820, and described by Georges Cuvier as "A white variety of Tiger is sometimes seen, with the stripes very opaque, and not to be observed except in certain angles of light." Naturalist Richard Lydekker said that, "a white tiger, in which the fur was of a creamy tint, with the usual stripes faintly visible in certain parts, was exhibited at the old menagerie at Exeter Change about the year 1820." Hamilton Smith said, "A wholly white tiger, with the stripe-pattern visible only under reflected light, like the pattern of a white tabby cat, was exhibited in the Exeter Change Menagerie in 1820.", and John George Wood stated that, "a creamy white, with the ordinary tigerine stripes so faintly marked that they were only visible in certain lights." Edwin Henry Landseer also drew this tigress in 1824.

The modern strain of snow white tigers came from repeated brother-sister matings of Bhim and Sumita at Cincinnati Zoo. The gene involved may have come from a Siberian tiger, their part-Siberian ancestor Tony. Continued inbreeding appears to have caused a recessive gene to become homozygous and produce the stripeless phenotype. About one fourth of Bhim and Sumita's offspring were stripeless. Their striped white offspring, which have been sold to zoos around the world, may also carry the gene for the stripeless trait. Because Tony's genome is present in many white tiger pedigrees, the gene may also be present in other captive white tigers. As a result, stripeless white tigers have appeared in zoos as far afield as the Czech Republic ( Liberec), Spain and Mexico. Stage magicians Siegfried & Roy were the first to attempt to selectively breed for stripeless tigers; they owned snow-white Bengal tigers taken from Cincinnati Zoo (Tsumura, Mantra, Mirage and Akbar-Kabul) and Guadalajara, Mexico (Vishnu and Jahan), as well as a stripeless Siberian tiger called Apollo.

In 2004, a blue-eyed, stripeless white tiger was born in a wildlife refuge in Alicante, Spain. Its parents are normal orange Bengals. The cub was named "Artico" ("Arctic").

Outside of India, inbred white tigers have been prone to crossed eyes, a condition known as strabismus, due to incorrectly routed visual pathways in the brains of white tigers. When stressed or confused, all white tigers cross their eyes. Strabismus is associated with white tigers of mixed Bengal and Siberian ancestry. The only pure-Bengal white tiger reported to be cross-eyed was Mohini's daughter Rewati. Strabismus is directly linked to the white gene and is not a separate consequence of inbreeding.

Kenny, a victim of inbreeding rescued by the Turpentine Creek Wildlife Refuge in October 2000.[20] He experienced many health problems over the course of his life and died in 2008.[21]

The orange litter-mates of white tigers are not prone to strabismus. Siamese cats and albinos of every species which have been studied all exhibit the same visual pathway abnormality found in white tigers. Siamese cats are also sometimes cross-eyed, as are some albino ferrets. The visual pathway abnormality was first documented in white tigers in the brain of a white tiger called Moni after he died, although his eyes were of normal alignment. The abnormality is that there is a disruption in the optic chiasm. The examination of Moni's brain suggested the disruption is less severe in white tigers than it is in Siamese cats. Because of the visual pathway abnormality, by which some optic nerves are routed to the wrong side of the brain, white tigers have a problem with spatial orientation, and bump into things until they learn to compensate. Some tigers compensate by crossing their eyes. When the neurons pass from the retina to the brain and reach the optic chiasma, some cross and some do not, so that visual images are projected to the wrong hemisphere of the brain. White tigers cannot see as well as normal tigers and suffer from photophobia, like albinos.

Other genetic problems include shortened tendons of the forelegs, club foot, kidney problems, arched or crooked backbone and twisted neck. Reduced fertility and miscarriages, noted by "tiger man" Kailash Sankhala in pure-Bengal white tigers, were attributed to inbreeding depression. A condition known as "star-gazing" (the head and neck are raised almost straight up, as if the affected animal is gazing at the stars), which is associated with inbreeding in big cats, has also been reported in white tigers.

There was a 200 kg (450 lb) male cross-eyed white tiger at the Pana'ewa Rainforest Zoo in Hawaii, which was donated to the zoo by Las Vegas magician Dirk Arthur. There is a picture of a white tiger which appears to be cross-eyed on just one side in the book Siegfried and Roy: Mastering the Impossible. A white tiger, named Scarlett O'Hara, who was Tony's sister, was cross-eyed only on the right side.

A male tiger named 'Cheytan', a son of Bhim and Sumita who was born at the Cincinnati Zoo, died at the San Antonio Zoo in 1992, from anaesthesia complications during root canal therapy. It appears that white tigers also react strangely to anaesthesia. The best drug for immobilizing a tiger is CI 744, but a few tigers, white ones in particular, undergo a re-sedation effect 24-36 hours later. This is due to their inability to produce normal tyrosinase, a trait they share with albinos, according to zoo veterinarian David Taylor. He treated a pair of white tigers from the Cincinnati Zoo at Fritz Wurm's safari park in Stukenbrock, Germany, for salmonella poisoning, which reacted strangely to the anaesthesia.

Mohini was checked for Chédiak-Higashi syndrome in 1960, but the results were inconclusive. This condition is similar to albino mutations and causes bluish lightening of the fur color, crossed eyes, and prolonged bleeding after surgery. Also, in the event of an injury, the blood is slow to coagulate. This condition has been observed in domestic cats, but there has never been a case of a white tiger having Chédiak-Higashi syndrome. There has been a single case of a white tiger having central retinal degeneration, reported from the Milwaukee County Zoo, which could be related to reduced pigmentation in the eye. The white tiger in question was a male named Mota on loan from the Cincinnati Zoo.

There is a myth that white tigers have an 80% infant mortality rate. However, the infant mortality rate for white tigers is no higher than it is for normal orange tigers bred in captivity. Cincinnati Zoo director Ed Maruska said:

"We have not experienced premature death among our white tigers. Forty-two animals born in our collection are still alive. Mohan, a large white tiger, died just short of his 20th birthday, an enviable age for a male of any subspecies, since most males live shorter captive lives. Premature deaths in other collections may be artifacts of captive environmental conditions...in 52 births we had four stillbirths, one of which was an unexplained loss. We lost two additional cubs from viral pneumonia, which is not excessive. Without data from non-inbred tiger lines, it is difficult to determine whether this number is high or low with any degree of accuracy."

Ed Maruska also addressed the issue of deformities:

"Other than a case of hip dysplasia that occurred in a male white tiger, we have not encountered any other body deformities or any physiological or neurological disorders. Some of these reported maladies in mutant tigers in other collections may be a direct result of inbreeding or improper rearing management of tigers generally."

A captive white tiger in Birmingham, United Kingdom

A captive white tiger in Yerevan Zoo, Armenia

Because of the extreme rarity of the white tiger allele in the wild, the breeding pool was limited to the small number of white tigers in captivity. According to Kailash Sankhala, the last white tiger ever seen in the wild was shot in 1958. Today there is a large number of white tigers in captivity. A white Amur tiger may have been born at Center Hill and has given rise to a strain of white Amur tigers. A man named Robert Baudy realized that his tigers had white genes when a tiger he sold to Marwell Zoo in England developed white spots, and bred them accordingly. The Lowry Park Zoo in Tampa Bay had four of these white Amur tigers, descended from Robert Baudy's stock.

It has also been possible to expand the white-gene pool by outcrossing white tigers with unrelated orange tigers and then using the cubs to produce more white tigers. The white tigers Ranjit, Bharat, Priya and Bhim were all outcrossed, in some instances to more than one tiger. Bharat was bred to an unrelated orange tiger named Jack from the San Francisco Zoo and had an orange daughter named Kanchana. Bharat and Priya were also bred with an unrelated orange tiger from Knoxville Zoo, and Ranjit was bred to this tiger's sister, also from Knoxville Zoo. Bhim fathered several litters with an unrelated orange tigress named Kimanthi at the Cincinnati Zoo. ankam Ranjeeth had several mates at the Omaha Zoo.

The last descendants of Bristol Zoo's white tigers were a group of orange tigers from outcrosses which were bought by a Pakistani senator and shipped to Pakistan. Rajiv, Pretoria Zoo's white tiger, who was born in the Cincinnati Zoo, was also outcrossed and sired at least two litters of orange cubs at Pretoria Zoo. Outcrossing is not necessarily done with the intent of producing more white cubs by resuming inbreeding further down the line. Outcrossing is a way of bringing fresh blood into the white strain. The New Delhi Zoo loaned out white tigers to some of India's better zoos for outcrossing, and the government had to impose a whip to force zoos to return either the white tigers or their orange offspring.

A white Bengal tiger at the Cincinnati Zoo

Siegfried & Roy performed at least one outcross. In the mid-1980s they offered to work with the Indian government in the creation of a healthier strain of white tigers. The Indian government reportedly considered the offer; however, India had a moratorium on breeding white tigers after cubs were born at New Delhi Zoo with arched backs and clubbed feet, necessitating euthanasia. Siegfried & Roy have bred white tigers in collaboration with the Nashville Zoo.

To better preserve genetic diversity and avoid genetic defects, the Association of Zoos and Aquariums barred member zoos from intentionally breeding to produce white tigers, white lions, or king cheetahs in a white paper adopted by the board of directors in July 2011. The paper explains that selecting for or against any particular allele would result in a loss of genetic diversity. Instead, the alleles should be maintained at their natural frequencies. Inbreeding to produce abnormal appearances can also produce congenital defects that impact health and welfare. Sometimes the traits themselves can cause problems, such as albinism's visual and neural effects. Additionally, animals with an abnormal appearance do not serve as well as ambassadors for their species in the zoos' mission to educate the public.

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3. Yun Sung Cho et al. (2013). "The tiger genome and comparative analysis with lion and snow leopard genomes", Nature Communications 4: 2433, doi:10.1038/ncomms3433

4. ^ Soejima M, Koda Y (January 2007). "Population differences of two coding SNPs in pigmentation-related genes SLC24A5 and SLC45A2". International Journal of Legal Medicine. 121 (1): 36-9. doi:10.1007/s00414-006-0112-z. PMID 16847698. S2CID 11192076.

5. ^ Leyhausen, Paul; Reed, Theodore H. (April 1971). "The white tiger: care and breeding of a genetic freak". Smithsonian.

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7. ^ Guillery, R.W.; Kaas, J.H. (22 June 1973). "Genetic abnormality of the visual pathways in a 'white tiger'". Science. 180 (92): 1287-9. Bibcode:1973Sci...180.1287G. doi:10.1126/science.180.4092.1287. PMID 4707916. S2CID 28568341.

8. ^ Bernays, M.E.; Smith, R. (1999). "Convergent strabismus in a white tiger". Australian Veterinary Journal. 77 (3): 152-5. doi:10.1111/j.1751-0813.1999.tb11220.x. PMID 10197239.

9. ^ Quinn, Patricia A. "Kenny and Willie". Turpentine Creek Wildlife Refuge. Archived from the original on 14 March 2007.

10. Gorham, Mary Ellen, DVM. Genetic defects do little to mar beauty of India's rare white tigers. March 1986

11. ^ Fischbacher, Siegfried; Horn, Roy Uwe Ludwig; Tapert, Annette; Roy, Siegfried and (1992). Siegfried and Roy: Mastering the Impossible. ISBN 0688105513.

12. Bush, Mitchell; Phillips, Lindsay G.; & Montali, Richard J. (1987) "Clinical Management of Captive Tigers", p. 186 in Ronald Lewis Tilson, Ulysses S. Seal (eds.) ^ Tigers Of The World, Biopolitics, Management, and Conservation of an Endangered Species, Noyes Publications, Park Ridge, New Jersey, USA, ISBN 0815511337.

13. ^ Maruska, Edward J. (1987) "White Tiger Phantom Or Freak?", Chapter 33, Part IV White Tiger Politics, in Ronald Lewis Tilson, Ulysses S. Seal (eds.) Tigers Of The World, Biopolitics, Management, and Conservation of an Endangered Species, Noyes Publications, Park Ridge, New Jersey, USA, ISBN 0815511337.

14. ^ Berrier, H.H.; Robinson, F.R.; Reed, T.H.; Gray, C.W. (1975). "The white tiger enigma". Veterinary Medicine/Small Animal Clinician. 70 (4): 467-472. PMID 1038910.

15. ^ Beehler, B.A.; Moore, C.P.; Picket, J.P. (1984). "Central retinal degeneration in a white Bengal tiger (Panthera tigris tigris)". Proc. Am. Assoc. Zoo Vet.

16. Iverson, S.J. (1982). "Breeding White Tigers". Zoogoer. 11: 5-12.

17. ^ Fischbacher, Siegfried; Horn, Roy Uwe Ludwig; Tapert, Annette (1992). Siegfried and Roy: mastering the impossible. New York: W. Morrow. ISBN 978-0688105518.

18. ^ "Welfare and Conservation Implications of Intentional Breeding for the Expression of Rare Recessive Alleles" (PDF). Association of Zoos & Aquariums. June 2011.

# data[].attributes.attachment_link.description
The white tiger or bleached tiger is a leucitic pigmentation variant of the mainland Asian tiger. It is reported in the wild from time to time in the Indian states of Madhya Pradesh, Assam, West Bengal, Bihar, Odisha, in the Sunderbans region and especially in the former State of Rewa.