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The tiger (Panthera tigris) is the largest living cat species and a member of the genus Panthera native to Asia. It has a powerful, muscular body with a large head and paws, a long tail, and orange fur with black, mostly vertical stripes. It is traditionally classified into nine recent subspecies, though some recognise only two subspecies, mainland Asian tigers and island tigers of the Sunda Islands.
Throughout the tiger's range, it inhabits mainly forests, from coniferous and temperate broadleaf and mixed forests in the Russian Far East and Northeast China to tropical and subtropical moist broadleaf forests on the Indian subcontinent and Southeast Asia. The tiger is an apex predator and preys mainly on ungulates such as deer and wild boar, which it takes by ambush. It lives a mostly solitary life and occupies home ranges, which it defends from individuals of the same sex. The range of a male tiger overlaps with that of multiple females with whom he has reproductive claims. Females give birth to usually two or three cubs that stay with their mother for about two years. When becoming independent, they leave their mother's home range and establish their own.
The tiger is among the most popular of the world's charismatic megafauna. It has been kept in captivity since ancient times and has been trained to perform in circuses and other entertainment shows. The tiger featured prominently in the ancient mythology and folklore of cultures throughout its historic range and has continued to appear in culture worldwide.
The Old English tigras derives from Old French tigre, from Latin tigris, which was a borrowing from Classical Greek τίγρις 'tigris'.[4]In the 1st century BC, Roman scholar Marcus Terentius Varro argued that the word tigris originated from the Armenian language and means 'arrow', which is also the name of the fast-flowing river Tigris.[5] The Middle Persian tigr also has both meanings; however, today, the connection between 'arrow' and the river's name is doubted, and they are likely to be Latin homonyms.[6]
In 1758, Carl Linnaeus described the tiger in his work Systema Naturae and gave it the scientific name Felis tigris; his scientific description was based on descriptions by earlier naturalists such as Conrad Gessner and Ulisse Aldrovandi.[2] In 1929, the British taxonomist Reginald Innes Pocock subordinated the species under the genus Panthera, using the scientific name Panthera tigris.[7][8]
Following Linnaeus's first descriptions of the species, nine recent tiger subspecies have been proposed between the early 19th and early 21st centuries, the Bengal, Malayan, Indochinese, South China, Siberian, Caspian, Javan, Bali and Sumatran tigers.[9][10] The validity of several tiger subspecies was questioned in 1999 as most putative subspecies were distinguished on the basis of fur length and colouration, striping patterns and body size of specimens in natural history museum collections; since fur characteristics vary widely within populations, it was proposed to recognise only two tiger subspecies as valid, namely P. t. tigris in mainland Asia and the smaller P. t. sondaica in the Greater Sunda Islands.[11]
This two-subspecies proposal was reaffirmed in 2015 through a comprehensive analysis of morphological, ecological, and molecular traits of all putative tiger subspecies. The continental nominate subspecies P. t. tigris constitutes two clades: a northern clade composed of the Siberian and Caspian tiger populations, and a southern clade composed of all other mainland populations.[10]In 2017, the Cat Classification Task Force of the IUCN Cat Specialist Group revised felid taxonomy in accordance with the 2015 two-subspecies proposal and recognised only P. t. tigris and P. t. sondaica.[12] By contrast, results of a 2018 whole-genome sequencing study of 32 samples support at least six subspecies as the Bengal, Malayan, Indochinese, South China, Siberian and Sumatran tigers were found to be distinct monophyletic clades.[13] These results were corroborated in 2021 and 2023.[14][15]
The following tables are based on the classification of the species Panthera tigris provided in Mammal Species of the World,[9] and also reflect the classification recognised by the Cat Classification Task Force in 2017.[12]
The tiger shares the genus Panthera with the lion, leopard, jaguar and snow leopard. Results of genetic analysis indicate that the tiger and snow leopard are sister species whose lineages split from each other between 2.70 and 3.70 million years ago.[37] The tiger's full genome sequence was published in 2013. It was found to have repeated sequences that parallel those in other cat genomes and "an appreciably conserved synteny".[38]
The fossil species Panthera palaeosinensis of early Pleistocene northern China was described as a possible tiger ancestor when it was discovered in 1924, but modern cladistics place it as basal to modern Panthera.[39][36] Panthera zdanskyi, which lived around the same time and place, was suggested to be a sister taxon of the modern tiger when it was examined in 2014.[36] However, as of 2023, at least two recent studies considered P. zdanskyi likely to be a synonym of P. palaeosinensis, noting that its proposed differences from that species fell within the range of individual variation.[40][41] The earliest appearance of the modern tiger species in the fossil record are jaw fragments from Lantion in China that are dated to the early Pleistocene.[36] Middle- to late-Pleistocene tiger fossils were found throughout China, Sumatra and Java. Prehistoric subspecies include Panthera tigris trinilensis and P. t. soloensis of Java and Sumatra, and P. t. acutidens of China; late Pleistocene and early Holocene fossils of tigers were also found in Borneo and Palawan, Philippines.[42]
Results of a phylogeographic study indicate that all living tigers have a common ancestor that lived between 108,000 and 72,000 years ago.[28] A 2022 paleogenomic study of a Pleistocene tiger basal to living tigers concluded that modern tiger populations spread across Asia no earlier than 94,000 years ago. There is evidence of interbreeding between the lineage of modern mainland tigers and these ancient tigers.[43] The potential tiger range during the late Pleistocene and Holocene was predicted in a 2016 study using ecological niche modelling based on more than 500 tiger locality records combined with bioclimatic data. The resulting model shows a contiguous tiger range at the Last Glacial Maximum, indicating gene flow between tiger populations in mainland Asia. The tiger populations on the Sunda Islands and mainland Asia were possibly separated during interglacial periods.[44]
Captive tigers were bred with lions to create hybrids that share physical and behavioural qualities of both parent species; the liger is the offspring of a female tiger and a male lion, and the tigon the offspring of a male tiger and a female lion.[45] The lion sire passes on a growth-promoting gene, but the corresponding growth-inhibiting gene from the female tiger is absent, so that ligers grow far larger than either parent species. By contrast, the male tiger does not pass on a growth-promoting gene, and the lioness passes on a growth inhibiting gene; hence, tigons are around the same size as either species.[46] Breeding hybrids is considered unethical as they are susceptible to obesity and other birth defects.[45]
The tiger's coat is generally coarse and relatively thin, though the Siberian tiger has a thick winter coat.[47][52] It has a mane-like heavy growth of fur around the neck and jaws and long whiskers, especially in males.[47] Its colouration is generally orange but can vary from light yellow to dark red.[47][42][53] White fur covers the ventral surface, along with parts of the face.[47][54] It also has a prominent white spot on the back of the ears which are surrounded by black.[47] The tiger is marked with distinctive black or dark brown stripes, the patterns of which are unique for each individual.[47][55] The stripes are mostly vertical, but those on the limbs and forehead are horizontal. They are more concentrated towards the posterior and those on the trunk may or may not reach under the belly. The tips of stripes are generally sharp and some may split up or split and fuse again. Tail stripes are thick bands and a black tip marks the end.[56]
Stripes are likely advantageous for camouflage in vegetation with vertical patterns of light and shade, such as trees, reeds and tall grass.[55][57] This is supported by a 1987 Fourier analysis study which concluded that the spatial frequencies of tiger stripes line up with their environment.[58] The tiger is one of only a few striped cat species; it is not known why spotted patterns and rosettes are the more common camouflage patterns among felids.[59] The orange colour may also aid in concealment, as the tiger's prey are dichromats, and thus they may perceive the cat as green and blended in with the vegetation.[60] The white dots on the ear may play a role in communication.[47]
Pseudo-melanistic tigers with thick, merged stripes have been recorded in Simlipal National Park and three Indian zoos; population genetic analysis of Indian tiger samples revealed that this phenotype is caused by a mutation of a transmembrane aminopeptidase gene. Around 37% of the Simlipal tiger population has this feature, which has been linked to genetic isolation.[63]
The tiger historically ranged from eastern Turkey and northern Afghanistan to Indochina and from southeastern Siberia to Sumatra, Java and Bali.[47] As of 2022, it inhabits less than 7% of its historical distribution and has a scattered range that includes the Indian subcontinent, the Indochinese Peninsula, Sumatra, the Russian Far East and northeastern China.[1]As of 2020, India had the largest extent of global tiger habitat with 300,508 km2 (116,027 sq mi), followed by Russia with 195,819 km2 (75,606 sq mi).[64]
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