iger
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This article is about the feline. For other uses, see Tiger (disambiguation).
"Tigress" redirects here. For other uses, see Tigress (disambiguation).
| Tiger Temporal range: Early Pleistocene – Recent | |
|---|---|
 | |
| A Bengal tiger (P. tigris tigris) in India'sRanthambhore National Park. | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Family: | Felidae |
| Genus: | Panthera |
| Species: | P. tigris |
| Binomial name | |
| Panthera tigris (Linnaeus, 1758) | |
| Subspecies | |
 | |
| Historical distribution of tigers (pale yellow) and 2006 (green).[2] | |
| Synonyms | |
Tigris striatus Severtzov, 1858 Tigris regalis Gray, 1867 | |
The tiger (Panthera tigris) is the largest cat species, reaching a total body length of up to 3.3 metres (11 ft) and weighing up to 306 kg (670 lb). Their most recognizable feature is a pattern of dark vertical stripes on reddish-orange fur with lighter underparts. They have exceptionally stout teeth, and their canines are the longest among living felids with a crown height of as much as 74.5 mm (2.93 in) or even 90 mm (3.5 in).[4] In zoos, tigers have lived for 20 to 26 years, which also seems to be their longevity in the wild.[5] They are territorial and generally solitary but social animals, often requiring large contiguous areas of habitat that support their prey requirements. This, coupled with the fact that they are indigenous to some of the more densely populated places on earth, has caused significant conflicts with humans.
Tigers once ranged widely across Asia, from Turkey in the west to the eastern coast of Russia. Over the past 100 years, they have lost 93% of their historic range, and have been extirpated from southwest and central Asia, from the islands of Java and Bali, and from large areas of Southeast and Eastern Asia. Today, they range from the Siberian taiga to open grasslands and tropical mangrove swamps. The remaining six tiger subspecies have been classified as endangered by IUCN. The global population in the wild is estimated to number between 3,062 to 3,948 individuals, with most remaining populations occurring in small pockets that are isolated from each other. Major reasons for population decline include habitat destruction, habitat fragmentation and poaching.[1] The extent of area occupied by tigers is estimated at less than 1,184,911 km2 (457,497 sq mi), a 41% decline from the area estimated in the mid-1990s.[6]
Tigers are among the most recognisable and popular of the world's charismatic megafauna. They have featured prominently in ancientmythology and folklore, and continue to be depicted in modern films and literature. Tigers appear on many flags, coats of arms, and asmascots for sporting teams.[7] The Bengal tiger is the national animal of Bangladesh and India.[8]
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Taxonomy and etymology
In 1758, Linnaeus first described the species in his work Systema Naturae under the scientific name Felis tigris.[3] In 1929, the British taxonomist Reginald Innes Pocock subordinated the species under the genus Panthera using the scientific name Panthera tigris.[9]
The word Panthera is probably of Oriental origin and retraceable to the Ancient Greek word panther, the Latin word panthera, the Old French word pantere, most likely meaning "the yellowish animal", or from pandarah meaning whitish-yellow. The derivation from Greek pan- ("all") and ther ("beast") may be folk etymology that led to many curious fables.[10]
The word "tiger" is retraceable to the Latin word tigris meaning a spotted tigerhound of Actaeon.[11] The Greek word tigris is possibly derived from a Persian source.[12]
Characteristics and evolution
The oldest remains of a tiger-like cat, called Panthera palaeosinensis, have been found in China and Java. This species lived about 2 million years ago, at the beginning of the Pleistocene, and was smaller than a modern tiger. The earliest fossils of true tigers are known from Java, and are between 1.6 and 1.8 million years old. Distinct fossils from the early and middle Pleistocene were also discovered in deposits from China, and Sumatra. A subspecies called the Trinil tiger(Panthera tigris trinilensis) lived about 1.2 million years ago and is known from fossils found at Trinilin Java.[13]
Tigers first reached India and northern Asia in the late Pleistocene, reaching eastern Beringia (but not the American Continent), Japan, and Sakhalin. Fossils found in Japan indicate that the local tigers were, like the surviving island subspecies, smaller than the mainland forms. This may be due to the phenomenon in which body size is related to environmental space (see insular dwarfism), or perhaps the availability of prey. Until theHolocene, tigers also lived in Borneo, as well as on the island of Palawan in the Philippines.[14]
Characteristics
Tigers are muscular, have powerful forequarters, and especially in males, a large head. The ground coloration of their fur varies between tawny and xanthine orange or cinnamon brown in the southernmost populations, to between ochraceous-orange or zinc orange or capucine orange in the northernmost populations. The face is framed by long hairs that form whiskers, which are more conspicuous in males. The ventral parts are usually white. The body is marked with black or chaetura black stripes of various length, breadth and form. The pupils are circular with yellow irises. The rather small ears are rounded and black on their dorsal side with a conspicuous white central spot.[4] These spots, calledocelli, play an important role in intraspecific communication.[15]
The pattern of stripes is unique to each animal, these unique markings can be used by researchers to identify individuals (both in the wild and captivity), much in the same way that fingerprints are used to identify humans. It seems likely that the function of stripes is camouflage, serving to help tigers conceal themselves amongst the dappled shadows and long grass of their environment as they stalk their prey. The stripe pattern is also found on the skin of the tiger. If a tiger were to be shaved, its distinctive camouflage pattern would be preserved.
The tiger are the most variable in size of all big cats, even more so than the leopard and much more so than lions.[16] The Bengal, Caspianand Siberian tiger subspecies represent the largest living felids, and rank among the biggest felids that ever existed. Females vary in size from 240 to 275 cm (94 to 108 in), weigh 85 to 167 kg (190 to 370 lb) with a greatest length of skull ranging from 268 to 318 mm (10.6 to 12.5 in). Males vary in size from 270 to 330 cm (110 to 130 in), weigh 170 to 306 kg (370 to 670 lb) with a greatest length of skull ranging from 316 to 383 mm (12.4 to 15.1 in). Body size of different populations seems to be correlated with climate—Bergmann's Rule—and can be explained from the point of view of thermoregulation.[4] Large male Siberian tigers can reach a total length of more than 3.5 m (11 ft) "over curves", 3.3 m (11 ft) "between pegs" and a weight of 306 kg (670 lb). This is considerably larger than the size reached by the smallest living tiger subspecies, the Sumatran tiger, which reach a body weight of 75 to 140 kg (170 to 310 lb). At the shoulder, tigers may variously stand 0.7 to 1.22 m (2.3 to 4.0 ft) tall.[5]
Tigresses are smaller than the males in each subspecies, although the size difference between male and female tigers tends to be more pronounced in the larger tiger subspecies, with males weighing up to 1.7 times more than the females.[17] In addition, male tigers have wider forepaw pads than females. Biologists use this difference to determine gender based on tiger tracks.[18] The skull of the tiger is very similar to that of the lion, though the frontal region is usually not as depressed or flattened, with a slightly longer postorbital region. The skull of a lion has broader nasal openings. However, due to the amount of skull variation in the two species, usually, only the structure of the lower jaw can be used as a reliable indicator of species.[19]
Subspecies
There are nine subspecies of tiger, three of which are extinct. Their historical range in Bangladesh, Siberia, Iran, Afghanistan, India, China, andsoutheast Asia, including three Indonesian islands is severely diminished today. The surviving subspecies, in descending order of wild population, are:
- The Bengal tiger (Panthera tigris tigris) lives in India, Nepal, Bhutan and Bangladesh, and is the most common subspecies with populations estimated at less than 2,500 adult individuals. In 2011 the total population of adult tigers is estimated at 1,520–1,909 in India, 440 in Bangladesh, 155 in Nepal and 75 in Bhutan.[20] It lives in alluvial grasslands, subtropical and tropical rainforests, scrub forests, wet and dry deciduous forests, and mangroves. Male Bengal tigers had a total length, including the tail, of 270 to 310 cm (110 to 120 in), while females range from 240 to 265 cm (94 to 104 in). The weight of males range from 175 to 260 kg (390 to 570 lb), while that of the females range from 100 to 181 kg (220 to 400 lb).[4][21] In northern India and Nepal, tigers tend to be of larger size. Males often average 235 kilograms (520 lb), while females average 141 kilograms (310 lb).[22] In 1972, Project Tiger was founded in India aiming at ensuring a viable population of tigers in the country and preserving areas of biological importance as a natural heritage for the people.[23] But the illicit demand for bones and body parts from wild tigers for use in Traditional Chinese medicine is the reason for the unrelenting poachingpressure on tigers on the Indian subcontinent.[24] Between 1994 and 2009, the Wildlife Protection Society of India has documented 893 cases of tigers killed in India, which is just a fraction of the actual poaching and illegal trade in tiger parts during those years.[25] An area of special conservation interest lies in the Terai Arc Landscape in the Himalayan foothills of northern India and southern Nepal, where 11protected areas comprising dry forest foothills and tall grass savannas harbor tigers in a 49,000 square kilometres (19,000 sq mi) landscape. The goals are to manage tigers as a single metapopulation, the dispersal of which between core refuges can help maintain genetic, demographic, and ecological integrity, and to ensure that species and habitat conservation becomes mainstreamed into the rural development agenda. In Nepal, a community-based tourism model has been developed with a strong emphasis on sharing benefits with local people and on the regeneration of degraded forests. The approach has been successful in reducing poaching, restoring habitats, and creating a local constituency for conservation.[26]
- The Indochinese Tiger (Panthera tigris corbetti), also called Corbett's tiger, is found in Cambodia, China, Laos, Burma, Thailand, andVietnam. These tigers are smaller and darker than Bengal tigers: Males weigh from 150–190 kg (330–420 lb) while females are smaller at 110–140 kg (240–310 lb). Their preferred habitat is forests in mountainous or hilly regions. According to government estimates of national tiger populations, the subspecies numbers around a total of 350 individuals.[27] All existing populations are at extreme risk from poaching, prey depletion as a result of poaching of primary prey species such as deer and wild pigs, habitat fragmentation and inbreeding. In Vietnam, almost three-quarters of the tigers killed provide stock for Chinese pharmacies.
- The Malayan Tiger (Panthera tigris jacksoni), exclusively found in the southern part of the Malay Peninsula, was not considered a subspecies in its own right until 2004. The new classification came about after a study by Luo et al. from the Laboratory of Genomic Diversity Study,[28] part of the National Cancer Institute of the United States. According to official government figures, the population in the wild may number around 500 individuals, but is under considerable poaching pressure. The Malayan tiger is the smallest of the mainland tiger subspecies, and the second smallest living subspecies, with males averaging about 120 kg and females about 100 kg in weight. The Malayan tiger is a national icon in Malaysia, appearing on its coat of armsand in logos of Malaysian institutions, such as Maybank.
- The Sumatran Tiger (Panthera tigris sumatrae) is found only on the Indonesian island of Sumatra, and is critically endangered.[29] It is the smallest of all living tiger subspecies, with adult males weighing between 100–140 kg (220–310 lb) and females 75–110 kg (170–240 lb).[30] Their small size is an adaptation to the thick, dense forests of the island of Sumatra where they reside, as well as the smaller-sized prey. The wild population is estimated at between 400 and 500, seen chiefly in the island's national parks. Recent genetic testing has revealed the presence of unique genetic markers, indicating that it may develop into a separate species,[specify] if it does not go extinct.[31] This has led to suggestions that Sumatran tigers should have greater priority for conservation than any other subspecies. While habitat destruction is the main threat to existing tiger population (logging continues even in the supposedly protected national parks), 66 tigers were recorded as being shot and killed between 1998 and 2000, or nearly 20% of the total population.
- The Siberian tiger (Panthera tigris altaica), also known as the Amur tiger, inhabits the Amur-Ussuri region of Primorsky Krai andKhabarovsk Krai in far eastern Siberia.[32] It ranks among the biggest felids that ever existed with a head and body length of 160–180 cm (63–71 in) for females and 190–230 cm (75–91 in) for males, plus a tail of about 60–110 cm (24–43 in) and an average weight of around 227 kg (500 lb) for males. Siberian tigers have thick coats and a paler golden hue and fewer stripes.[4] The heaviest wild Siberian tiger weighed 384 kg (850 lb) but according to Mazák this record is not reliable.[5] In 2005, there were 331–393 adult-subadult Siberian tigers in the region, with a breeding adult population of about 250 individuals. The population has been stable for more than a decade, but partial surveys conducted after 2005 indicate that the Russian tiger population is declining.[33] At the turn of the century, the phylogeneticrelationships of tiger subspecies was re-assessed, and a remarkable similarity between the Siberian and Caspian tiger observed indicating that the Siberian tiger population is the genetically closest living relative of the extinct Caspian tiger, and strongly implying a very recent common ancestry for the two groups.[34]
- The South China tiger (Panthera tigris amoyensis), also known as the Amoy or Xiamen tiger, is the most critically endangered subspecies of tiger and is listed as one of the 10 most endangered animals in the world.[35] One of the smaller tiger subspecies, the length of the South China tiger ranges from 2.2–2.6 m (87–100 in) for both males and females. Males weigh between 127 and 177 kg (280 and 390 lb) while females weigh between 100 and 118 kg (220 and 260 lb). From 1983 to 2007, no South China tigers were sighted.[36] In 2007 a farmer spotted a tiger and handed in photographs to the authorities as proof.[36][37] The photographs in question, however, were later exposed as fake, copied from a Chinese calendar and digitally altered, and the “sighting” turned into a massive scandal.[38][39][40]
In 1977, the Chinese government passed a law banning the killing of wild tigers, but this may have been too late to save the subspecies, since it is possibly already extinct in the wild. There are currently 59 known captive South China tigers, all within China, but these are known to be descended from only six animals. Thus, the genetic diversity required to maintain the subspecies may no longer exist.[citation needed] Currently, there are breeding efforts to reintroduce these tigers to the wild.[citation needed]
Extinct subspecies
- The Bali tiger (Panthera tigris balica) was limited to the Indonesian island of Bali, and was the smallest subspecies with a weight of 90–100 kg (200–220 lb) in males and 65–80 kg (140–180 lb) in females.[5] Bali tigers were hunted to extinction — the last Bali tiger, an adult female, is thought to have been killed at Sumbar Kima, West Bali on 27 September 1937. There is no Bali tiger in captivity. The tiger still plays an important role in Balinese Hinduism.
- The Caspian tiger (Panthera tigris virgata), also known as the Hyrcanian tiger or Turan tigerwas found in the sparse forest habitats and riverine corridors west and south of the Caspian Seaand west through Central Asia into the Takla-Makan desert of Xinjiang, and has been recorded in the wild until the early 1970s.[41] The Amur tiger is the genetically closest living relative of the Caspian tiger.[34]
- The Javan tiger (Panthera tigris sondaica) was limited to the island of Java, and has been recorded until the mid-1970s.[42] Javan tigers were larger than Bali tigers; males weighed 100–140 kg (220–310 lb) and females 75–115 kg (170–250 lb).[43] After 1979, there were no more confirmed sightings in the region of Mount Betiri.[44] An expedition to Mount Halimun Salak National Park in 1990 did not yield any definite, direct evidence for the continued existence of tigers.[45]
Hybrids
Further information: Panthera hybrid, Liger and Tiglon
Hybridisation among the big cats, including the tiger, was first conceptualised in the 19th century, when zoos were particularly interested in the pursuit of finding oddities to display for financial gain.[46] Lions have been known to breed with tigers (most often the Amur and Bengalsubspecies) to create hybrids called ligers and tigons.[47] Such hybrids were once commonly bred in zoos, but this is now discouraged due to the emphasis on conserving species and subspecies. Hybrids are still bred in private menageries and in zoos in China.
The liger is a cross between a male lion and a tigress.[48] Because the lion sire passes on a growth-promoting gene, but the corresponding growth-inhibiting gene from the female tiger is absent, ligers grow far larger than either parent. They share physical and behavioural qualities of both parent species (spots and stripes on a sandy background). Male ligers are sterile, but female ligers are often fertile. Males have about a 50% chance of having a mane, but, even if they do, their manes will be only around half the size of that of a pure lion. Ligers are typically between 10 to 12 feet in length, and can be between 800 and 1,000 pounds or more.[48]
The less common tigon is a cross between the lioness and the male tiger.[49]
Colour variations
White tigers
Main article: White tiger
There is a well-known mutation that produces the white tiger, technically known as chinchilla albinistic,[50] an animal which is rare in the wild, but widely bred in zoos due to its popularity. Breeding of white tigers will often lead to inbreeding (as the trait is recessive). Many initiatives have taken place in white and orange tiger mating in an attempt to remedy the issue, often mixing subspecies in the process. Such inbreeding has led to white tigers having a greater likelihood of being born with physical defects, such as cleft palates and scoliosis (curvature of the spine).[51][52]Furthermore, white tigers are prone to having crossed eyes (a condition known as strabismus). Even apparently healthy white tigers generally do not live as long as their orange counterparts. Recordings of white tigers were first made in the early 19th century.[53] They can only occur when both parents carry the rare gene found in white tigers; this gene has been calculated to occur in only one in every 10,000 births. The white tiger is not a separate sub-species, but only a colour variation; since the only white tigers that have been observed in the wild have been Bengal tigers[54](and all white tigers in captivity are at least part Bengal), it is commonly thought that the recessive gene that causes the white colouring is probably carried only by Bengal tigers, although the reasons for this are not known.[51][55] Nor are they in any way more endangered than tigers are generally, this being a common misconception. Another misconception is that white tigers are albinos, despite the fact that pigment is evident in the white tiger's stripes. They are distinct not only because of their white hue; they also have blue eyes.
Golden tabby tigers
Main article: Golden tabby
In addition, another recessive gene may create a very unusual "golden tabby" colour variation, sometimes known as "strawberry." Golden tabby tigers have light gold fur, pale legs and faint orange stripes. Their fur tends to be much thicker than normal.[56] There are extremely few golden tabby tigers in captivity, around 30 in all. Like white tigers, strawberry tigers are invariably at least part Bengal. Some golden tabby tigers, called heterozygous tigers, carry the white tiger gene, and when two such tigers are mated, can produce some stripeless white offspring. Both white and golden tabby tigers tend to be larger than average Bengal tigers.
Other colour variations
There is no authenticated case of a black tiger, with the possible exception of one dead specimen examined in Chittagong in 1846.[57] There are unconfirmed reports of a "blue" or slate-coloured tiger, the Maltese tiger. Largely or totally black tigers are assumed, if real, to be intermittent mutations rather than distinct species.[50]
Distribution and habitat
In the past, tigers were found throughout Asia, from the Caucasus and the Caspian Sea to Siberia and the Indonesian islands of Java, Bali andSumatra. During the 20th century, tigers have been extirpated in western Asia and became restricted to isolated pockets in the remaining parts of their range. Today, their fragmented and partly degraded range extends from India in the west to China and Southeast Asia. The northern limit of their range is close to the Amur River in south eastern Siberia. The only large island inhabited by tigers today is Sumatra.[1]
Tigers were extirpated on the island of Bali in the 1940s, around the Caspian Sea in the 1970s, and on Java in the 1980s. Loss of habitat and the persistent killing of tigers and tiger prey precipitated these extirpations, a process that continues to leave forests devoid of tigers and other large mammals across South and Southeast Asia. Since the beginning of the 21st century, their historical range has shrunk by 93%. In the decade from 1997 to 2007, the estimated area known to be occupied by tigers has declined by 41%.[58]
Fossil remains indicate that tigers were present in Borneo and Palawan in the Philippines during the late Pleistocene and Holocene.[59][60]
Tiger habitats will usually include sufficient cover, proximity to water, and an abundance of prey. Bengal tigers live in many types of forests, including wet, evergreen, the semi-evergreen of Assam and eastern Bengal; the mangrove forest of the Ganges Delta; the deciduous forest of Nepal, and the thorn forests of the Western Ghats. Compared to the lion, the tiger prefers denser vegetation, for which its camouflage colouring is ideally suited, and where a single predator is not at a disadvantage compared with the multiple felines in a pride.
Biology and behaviour
Territorial behaviour
Adult tigers lead solitary lives and congregate only on an ad hoc and transitory basis when special conditions permit, such as plentiful supply of food. They establish and maintain home ranges. Resident adults of either sex tend to confine their movements to a definite area of habitat, within with they satisfy their needs, and in the case of tigresses, those of their growing cubs. Those sharing the same ground are well aware of each other's movements and activities.[57]
The size of a tiger's home range mainly depends on prey abundance, and, in the case of male tigers, on access to females. A tigress may have a territory of 20 km2 (7.7 sq mi), while the territories of males are much larger, covering 60 to 100 km2 (23 to 39 sq mi). The range of a male tends to overlap those of several females.[citation needed]
Tigers are strong swimmers, and are often found bathing in ponds, lakes, and rivers. During the extreme heat of the day, they often cool off in pools. They are able to carry prey through the water.
The relationships between individuals can be quite complex, and it appears that there is no set "rule" that tigers follow with regards to territorial rights and infringing territories. For instance, although for the most part tigers avoid each other, both male and female tigers have been documented sharing kills. George Schaller observed a male tiger share a kill with two females and four cubs. Females are often reluctant to let males near their cubs, but Schaller saw that these females made no effort to protect or keep their cubs from the male, suggesting that the male might have been the father of the cubs. In contrast to male lions, male tigers will allow the females and cubs to feed on the kill first. Furthermore, tigers seem to behave relatively amicably when sharing kills, in contrast to lions, which tend to squabble and fight. Unrelated tigers have also been observed feeding on prey together. The following quotation is from Stephen Mills' book Tiger, as he describes an event witnessed by Valmik Thapar and Fateh Singh Rathore in Ranthambhore National Park:[61]
A dominant tigress they called Padmini killed a 250 kg (550 lb) male nilgai – a very large antelope. They found her at the kill just after dawn with her three 14-month-old cubs and they watched uninterrupted for the next ten hours. During this period the family was joined by two adult females and one adult male – all offspring from Padmini's previous litters and by two unrelated tigers, one female the other unidentified. By three o'clock there were no fewer than nine tigers round the kill.
When young female tigers first establish a territory, they tend to do so fairly close to their mother's area. The overlap between the female and her mother's territory tends to wane with increasing time. Males, however, wander further than their female counterparts, and set out at a younger age to mark out their own area. A young male will acquire territory either by seeking out a range devoid of other male tigers, or by living as a transient in another male's territory until he is old and strong enough to challenge the resident male. The highest mortality rate (30–35% per year) amongst adult tigers occurs for young male tigers who have just left their natal area, seeking out territories of their own.[61]
Male tigers are generally more intolerant of other males within their territory than females are of other females. For the most part, however, territorial disputes are usually solved by displays of intimidation, rather than outright aggression. Several such incidents have been observed, in which the subordinate tiger yielded defeat by rolling onto its back, showing its belly in a submissive posture.[62] Once dominance has been established, a male may actually tolerate a subordinate within his range, as long as they do not live in too close quarters.[61] The most violent disputes tend to occur between two males when a female is in oestrus, and may result in the death of one of the males, although this is a rare occurrence.[61][62]
To identify his territory, the male marks trees by spraying of urine and anal gland secretions, as well as marking trails with scat. Males show a grimacing face, called the Flehmen response, when identifying a female's reproductive condition by sniffing their urine markings. Like the otherPanthera cats, tigers can roar. Tigers will roar for both aggressive and non-aggressive reasons. Other tiger vocal communications include moans, hisses, growls and chuffs.
Tigers have been studied in the wild using a variety of techniques. The populations of tigers were estimated in the past using plaster casts of their pugmarks. This method was criticized as being inaccurate.[63] Attempts were made to use camera trapping instead. Newer techniques based on DNA from their scat are also being evaluated. Radio collaring has also been a popular approach to tracking them for study in the wild.
Hunting and diet
In the wild, tigers mostly feed on larger and medium sized animals. Sambar, gaur, chital, barasingha, wild boar, nilgai and both water buffaloand domestic buffalo are the tiger's favoured prey in India. Sometimes, they also prey on leopards, pythons, sloth bears and crocodiles. In Siberia the main prey species are manchurian wapiti, wild boar, sika deer, moose, roe deer, and musk deer. In Sumatra, sambar, muntjac, wild boar, and malayan tapir are preyed on. In the former Caspian tiger's range, prey included saiga antelope, camels, caucasian wisent, yak, and wild horses. Like many predators, they are opportunistic and will eat much smaller prey, such as monkeys, peafowls, hares, and fish.
Adult elephants are too large to serve as common prey, but conflicts between tigers and elephants do sometimes take place. A case where a tiger killed an adult Indian Rhinoceros has been observed. Young elephant and rhino calves are occasionally taken. Tigers also sometimes prey on domestic animals such as dogs, cows, horses, and donkeys. These individuals are termed cattle-lifters or cattle-killers in contrast to typical game-killers.[64]
Old tigers, or those wounded and rendered incapable of catching their natural prey, have turned into man-eaters; this pattern has recurred frequently across India. An exceptional case is that of the Sundarbans, where healthy tigers prey upon fishermen and villagers in search of forest produce, humans thereby forming a minor part of the tiger's diet.[65] Tigers will occasionally eat vegetation for dietary fiber, the fruit of the Slow Match Tree being favoured.[64]
Tigers are thought to be nocturnal predators, hunting at night.[66] However, in areas where humans are absent, they have been observed via remote controlled, hidden cameras hunting during the daylight hours.[67] They generally hunt alone and ambush their prey as most other cats do, overpowering them from any angle, using their body size and strength to knock large prey off balance. Even with their great masses, tigers can reach speeds of about 49–65 kilometres per hour (35–40 miles per hour), although they can only do so in short bursts, since they have relatively little stamina; consequently, tigers must be relatively close to their prey before they break their cover. Tigers have great leaping ability; horizontal leaps of up to 10 metres have been reported, although leaps of around half this amount are more typical. However, only one in twenty hunts ends in a successful kill.[66]
When hunting large prey, tigers prefer to bite the throat and use their forelimbs to hold onto the prey, bringing it to the ground. The tiger remains latched onto the neck until its prey dies of strangulation.[15] By this method, gaurs and water buffalos weighing over a ton have been killed by tigers weighing about a sixth as much.[68] With small prey, the tiger bites the nape, often breaking the spinal cord, piercing the windpipe, or severing thejugular vein or common carotid artery.[69] Though rarely observed, some tigers have been recorded to kill prey by swiping with their paws, which are powerful enough to smash the skulls of domestic cattle,[64] and break the backs of sloth bears.[70]
During the 1980s, a tiger named "Genghis" in Ranthambhore National Park was observed frequently hunting prey through deep lake water,[71] a pattern of behaviour that had not been previously witnessed in over 200 years of observations. Moreover, he appeared to be extraordinarily successful for a tiger, with as many as 20% of hunts ending in a kill.
Reproduction
Mating can occur all year round, but is generally more common between November and April.[72] A female is only receptive for a few days and mating is frequent during that time period. A pair will copulate frequently and noisily, like other cats. The gestation period is 16 weeks. The litter size usually consists of around 3–4 cubs of about 1 kilogram (2.2 lb) each, which are born blind and helpless. The females rear them alone, sheltering them in dens such as thickets and rocky crevices. The father of the cubs generally takes no part in rearing them. Unrelated wandering male tigers may even kill cubs to make the female receptive, since the tigress may give birth to another litter within 5 months if the cubs of the previous litter are lost.[72] The mortality rate of tiger cubs is fairly high – approximately half do not survive to be more than two years old.[72]
There is generally a dominant cub in each litter, which tends to be male but may be of either sex.[71] This cub generally dominates its siblings during play and tends to be more active, leaving its mother earlier than usual. At 8 weeks, the cubs are ready to follow their mother out of the den, although they do not travel with her as she roams her territory until they are older. The cubs become independent around 18 months of age, but it is not until they are around 2–2½ years old that they leave their mother. Females reach sexual maturity at 3–4 years, whereas males reach sexual maturity at 4–5 years.[72]
Over the course of her life, a female tiger will give birth to an approximately equal number of male and female cubs. Tigers breed well in captivity, and the captive population in the United States may rival the wild population of the world.[73]
Interspecific predatory relationships
Tigers may kill such formidable predators as leopards, pythons and even crocodiles on occasion,[74][75][76] although predators typically avoid one another. When seized by a crocodile, a tiger will strike at the reptile's eyes with its paws.[64] Eighteenth century Physician Oliver Goldsmith described the frequent conflicts between mugger crocodiles and tigers that occurred during that time. Thirsty tigers would frequently descend to the rivers to drink and on occasion were seized and killed by the muggers, though more often the tiger escaped and the reptile was disabled.[77] Leopards dodge competition from tigers by hunting in different times of the day and hunting different prey.[78] With relatively abundant prey, tigers and leopards were seen to successfully coexist without competitive exclusion or inter-species dominance hierarchies that may be more common to the savanna.[79] Tigers have been known to suppress wolf populations in areas where the two species coexist.[80][81] Dhole packs have been observed to attack and kill tigers in disputes over food, though not usually without heavy losses.[70]Lone golden jackals expelled from their pack have been known to form commensal relationships with tigers. These solitary jackals, known askol-bahl, will attach themselves to a particular tiger, trailing it at a safe distance in order to feed on the big cat's kills. A kol-bahl will even alert a tiger to a kill with a loud pheal. Tigers have been known to tolerate these jackals: one report describes how a jackal confidently walked in and out between three tigers walking together a few feet away from each other.[82] Siberian tigers and brown bears can be competitors and usually avoid confrontation; however, tigers will kill bear cubs and even some adults on occasion. Bears (Asiatic black bears and brown bears) make up 5–8% of the tiger's diet in the Russian Far East.[5] There are also a few records of brown bears killing tigers, either in self defense or in disputes over kills.[19] Some bears emerging from hibernation will try to steal tigers' kills, although the tiger will sometimes defend its kill. Sloth bears are quite aggressive and will sometimes drive young tigers away from their kills, although it is more common for Bengal tigers to prey on sloth bears.[5]
Conservation efforts
For more details on this topic, see Tiger hunting.
Poaching for fur and destruction of habitat have greatly reduced tiger populations in the wild. At the start of the 20th century, it is estimated there were over 100,000 tigers in the world but the population has dwindled to between 1,500 and 3,500 in the wild.[83] Some estimates suggest that there are less than 2,500 mature breeding individuals, with no subpopulation containing more than 250 mature breeding individuals.[1]
India
Main article: Project Tiger
India is home to the world's largest population of tigers in the wild.[85] According to the World Wildlife Fund, of the 3,500 tigers around the world, 1,400 are found in India. Only 11% of original Indian tiger habitat remains, and it is becoming significantly fragmented and often degraded.[86][87]
A major concerted conservation effort, known as Project Tiger, has been underway since 1973, initially spearheaded by Indira Gandhi. The fundamental accomplishment has been the establishment of over 25 well-monitored tiger reserves in reclaimed land where human development is categorically forbidden. The program has been credited with tripling the number of wild Bengal tigers from roughly 1,200 in 1973 to over 3,500 in the 1990s. However, a tiger census carried out in 2007, whose report was published on February 12, 2008, stated that the wild tiger population in India declined by 60% to approximately 1,411.[88] It is noted in the report that the decrease of tiger population can be attributed directly to poaching.[89]
Following the release of the report, the Indian government pledged $153 million to further fund the Project Tiger initiative, set up a Tiger Protection Force to combat poachers, and fund the relocation of up to 200,000 villagers to minimise human-tiger interaction.[90] Additionally, eight new tiger reserves in India were set up.[91] Indian officials successfully started a project to reintroduce the tigers into the Sariska Tiger Reserve.[92] The Ranthambore National Parkis often cited as a major success by Indian officials against poaching.[93]
Tigers Forever is a collaboration between the Wildlife Conservation Society and Panthera Corporation to serve as both a science-based action plan and a business model to ensure that tigers live in the wild forever. Initial field sites of Tigers Forever include the world's largest tiger reserve, the 21,756 km2 (8,400 sq mi) Hukaung Valley in Myanmar, the Western Ghats in India, Thailand's Huai Khai Khaeng-Thung Yai protected areas, and other sites in Laos PDR, Cambodia, the Russian Far East and China covering approximately 260,000 km2 (100,000 sq mi) of critical tiger habitat.[94]
Russia
The Siberian tiger was on the brink of extinction with only about 40 animals in the wild in the 1940s. Under the Soviet Union, anti-poaching controls were strict and a network of protected zones (zapovedniks) were instituted, leading to a rise in the population to several hundred. Poaching again became a problem in the 1990s, when the economy of Russia collapsed, local hunters had access to a formerly sealed off lucrative Chinese market, and logging in the region increased. While an improvement in the local economy has led to greater resources being invested in conservation efforts, an increase of economic activity has led to an increased rate of development and deforestation. The major obstacle in preserving the species is the enormous territory individual tigers require (up to 450 km2 needed by a single female and more for a single male).[95] Current conservation efforts are led by local governments and NGO's in consort with international organisations, such as the World Wide Fund and the Wildlife Conservation Society.[96]The competitive exclusion of wolves by tigers has been used by Russian conservationists to convince hunters in the Far East to tolerate the big cats, as they limit ungulate populations less than wolves, and are effective in controlling the latter's numbers.[97]Currently, there are about 400–550 animals in the wild.
Tibet
The trade in tiger skins is illegal in the People's Republic of China, of which Tibet is a part. However, the law banning the trade in endangered animal parts is not enforced in Tibet. An undercover investigation in 2000 by the Wildlife Protection Society of Indiaproduced much news about the tiger skin trade and pictures of Tibetans wearing tiger skins. The tigers poached for their skins, subsequent investigations found, originated in India, in a "highly sophisticated" smuggling operation that crossed through Nepal, that "had less to do with old customs than new money" and even attracted European tourists for the tiger skin products of Lhasa. When in 2005, officials in Tibet intercepted "32 tiger, 579 leopard and 665 otter skins", the 14th Dalai Lama called on exiled Tibetans, who are involved in the trade, to cease their activity.[98] The 14th Dalai Lama had spoken out about wearing furs before, but he repeated his condemnation during the 2006 Kalachakra festival in India toexpatriate Tibetans.[99] Afterwards, the Dalai Lama issued a press release claiming to have received video of Tibetans burning their animal skin coats, and reports of arrests of eight Tibetans involved for conspiring with the Dalai Lama's government.[100]
Population estimate
The global wild tiger population is estimated at anywhere between 3,062 and 3,948 individuals. The World Wide Fund for Nature estimates the tiger population at 3,200.[101] The exact number of wild tigers is unknown, as many estimates are outdated or come from educated guesses. Few estimates are considered reliable, coming from comprehensive scientific censuses. The table shows estimates per country according to IUCN and range country governments.[102]
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