Bengal tiger

The tiger is the largest cat species, most recognisable for their pattern of dark vertical stripes on reddish-orange fur with a lighter underside. The species is classified in the genus Panthera with the lion, leopard, jaguar and snow leopard. Tigers are apex predators, primarily preying on ungulates such as deer and bovids. 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 the International Union for Conservation of Nature (IUCN). The global population in the wild is estimated to number between 3,062 and 3,948 individuals, down from around 100,000 at the start of the 20th century, with most remaining populations occurring in small pockets isolated from each other, of which about 2,000 exist on the Indian subcontinent. A 2016 global census estimated the population of wild tigers at approximately 3,890 individuals. Major reasons for population decline include habitat destruction, habitat fragmentation and poaching. 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. In 2016, wildlife conservation group at WWF declared that world's count of wild tigers has risen for the first time in a century.
Tigers are among the most recognisable and popular of the world's charismatic megafauna. They have featured prominently in ancient mythology and folklore, and continue to be depicted in modern films and literature. They appear on many flags, coats of arms, and as mascots for sporting teams. The tiger is the national animal of Bangladesh, India, Malaysia and South Korea. Tigers have muscular bodies with powerful forelimbs, large heads and long tails. The pelage is dense and heavy; colouration varies between shades of orange and brown with white ventral areas and distinctive vertical black stripes, whose patterns are unique to each individual. Their function is likely for camouflage in vegetation such as long grass with strong vertical patterns of light and shade. 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 pattern among felids. The tiger's stripes are also found on the skin, so that if it were to be shaved, its distinctive coat pattern would still be visible. They have a mane-like heavy growth of fur around the neck and jaws and long whiskers, especially in males. The pupils are circular with yellow irises. The small, rounded ears have a prominent white spot on the back, surrounded by black. These false "eyespots", called ocelli, apparently play an important role in intraspecies communication.
The skull is 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 variation in skulls of the two species, the structure of the lower jaw is a more reliable indicator of species. The tiger also has fairly stout teeth; the somewhat curved canines are the longest among living felids with a crown height of up to 90 mm (3.5 in).
The oldest recorded captive tiger lived for 26 years. A wild specimen, having no natural predators, could in theory live to a comparable age. Tigers are the most variable in size of all big cats, much more so than lions. The Bengal and Siberian subspecies are the tallest at the shoulder and thus considered the largest living felids, ranking with the extinct Caspian tiger among the biggest that ever existed.[64] An average adult male tiger from Northern India or Siberia outweighs an average adult male lion by around 45.5 kg (100 lb). Males vary in total length from 250 to 390 cm (98 to 154 in) and weigh between 90 to 306 kg (198 to 675 lb) with skull length ranging from 316 to 383 mm (12.4 to 15.1 in). Females vary in total length from 200 to 275 cm (79 to 108 in), weigh 65 to 167 kg (143 to 368 lb) with skull length ranging from 268 to 318 mm (10.6 to 12.5 in). The largest wild tiger ever reported had a total body length of 3.38 m (11.1 ft) over curves and weighed 388.7 kg (857 lb). In either sex, the tail represents about 0.6 to 1.1 m (24 to 43 in) of total length.
Body size of different populations seems to be correlated with climate-Bergmann's rule-and can be explained by thermoregulation. Large male Siberian tigers can reach a total length of more than 3.5 m (11.5 ft) over curves and 3.3 m (10.8 ft) between pegs, and can weigh up to 306 kg (675 lb). This is considerably larger than the weight of 75 to 140 kg (165 to 309 lb) reached by the smallest living subspecies, the Sumatran tiger. At the shoulder, tigers may variously stand 0.7 to 1.22 m (2.3 to 4.0 ft) tall. The current record weight in the wild was 389 kg (858 lb) for a Bengal tiger shot in 1967.
They are a notably sexually dimorphic species, females being consistently smaller than males. The size difference between males and females is proportionally greater in the larger tiger subspecies, with males weighing up to 1.7 times more than females. Males also have wider forepaw pads than females, enabling gender to be told from tracks. A well-known allele found only in the Bengal subspecies produces the white tiger, a colour variant first recorded in the early 19th century and found in an estimated one in 10,000 natural births. Genetically, whiteness is recessive: a cub is white only when both parents carry the allele for whiteness. It is not albinism, pigment being evident in the white tiger's stripes and in their blue eyes. The causative mutation changes a single amino acid in the transporter protein SLC45A2.
White tigers are more frequently bred in captivity, where the comparatively small gene pool can lead to inbreeding. This has given white tigers a greater likelihood of being born with physical defects, such as cleft palate, scoliosis (curvature of the spine), and strabismus (squint). Even apparently healthy white tigers generally do not live as long as their orange counterparts. Attempts have been made to cross white and orange tigers to remedy this, often mixing with other subspecies in the process.
Another recessive gene creates the "golden" or "golden tabby" colour variation, sometimes known as "strawberry". Golden tigers have thicker than usual light-gold fur, pale legs, and faint orange stripes. Few golden tigers are kept in captivity; they are invariably at least part Bengal. Some golden tigers carry the white tiger gene, and when two such tigers are mated, they can produce some stripeless white offspring. Although a "pseudo-melanistic" effect-wide stripes that partially obscure the orange background has been seen in some pelts, no true black tigers have been authenticated, with the possible exception of one dead specimen examined in Chittagong in 1846. These wholly or partially melanistic tigers, if they exist, are assumed to be intermittent mutations rather than a distinct species. There are further unconfirmed reports of a "blue" or slate-coloured variant, the Maltese tiger. However, while some felids do exhibit this colouration as a solid coat, there is no known genetic configuration that would result in black stripes on a blue-gray background. In the past, tigers were found throughout Asia, from the Caucasus and the Caspian Sea to Siberia and the Indonesian islands of Java, Bali and Sumatra. Fossil remains indicate tigers were also present in Borneo and Palawan in the Philippines during the late Pleistocene and Holocene.
During the 20th century, tigers became extinct in western Asia and were restricted to isolated pockets in the remaining parts of their range. They were extirpated on the island of Bali in the 1940s, around the Caspian Sea in the 1970s, and on Java in the 1980s. This was the result of habitat loss and the ongoing killing of tigers and tiger prey. 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 southeastern Siberia. The only large island they still inhabit is Sumatra. Since the beginning of the 20th century, tigers' 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%.
Tigers can occupy a wide range of habitat types, but will usually require sufficient cover, proximity to water, and an abundance of prey. 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. A further habitat requirement is the placement of suitably secluded den locations, which may consist of caves, large hollow trees, or dense vegetation. Bengal tigers in particular live in many types of forests, including wet, evergreen, and the semievergreen of Assam and eastern Bengal; the swampy mangrove forest of the Ganges Delta; the deciduous forest of Nepal, and the thorn forests of the Western Ghats. In various parts of their range they inhabit or have inhabited additionally partially open grassland and savanna as well as taiga forests and rocky habitats. Adult tigers lead largely solitary lives. They establish and maintain territories but have much wider home ranges within which they roam. Resident adults of either sex generally confine their movements to their home ranges, within which they satisfy their needs and those of their growing cubs. Individuals sharing the same area are aware of each other's movements and activities. The size of the home range mainly depends on prey abundance, and, in the case of males, 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, providing him with a large field of prospective mating partners.
Unlike many felids, tigers are strong swimmers and often deliberately bathe in ponds, lakes and rivers as a means of keeping cool in the heat of the day. Among the big cats, only the jaguar shares a similar fondness for water. They may cross rivers up to 7 km (4.3 mi) across and can swim up to 29 km (18 mi) in a day. They are able to carry prey through or capture it in the water.
Young female tigers establish their first territories close to their mother's. The overlap between the female and her mother's territory reduces with time. Males, however, migrate further than their female counterparts and set out at a younger age to mark out their own area. A young male acquires territory either by seeking out an area devoid of other male tigers, or by living as a transient in another male's territory until he is older and strong enough to challenge the resident male. Young males seeking to establish themselves thereby comprise the highest mortality rate (30-35% per year) amongst adult tigers.
To identify his territory, the male marks trees by spraying urine and anal gland secretions, as well as marking trails with scat and marking trees or the ground with their claws. Females also use these "scrapes", as well as urine and scat markings. Scent markings of this type allow an individual to pick up information on another's identity, sex and reproductive status. Females in oestrus will signal their availability by scent marking more frequently and increasing their vocalisations.
Although for the most part avoiding each other, tigers are not always territorial and relationships between individuals can be complex. An adult of either sex will sometimes share its kill with others, even those who may not be related to them. George Schaller observed a male share a kill with two females and four cubs. Unlike male lions, male tigers allow females and cubs to feed on the kill before the male is finished with it; all involved generally seem to behave amicably, in contrast to the competitive behaviour shown by a lion pride. This quotation is from Stephen Mills' book Tiger, describing an event witnessed by Valmik Thapar and Fateh Singh Rathore in Ranthambhore National Park.
Occasionally, male tigers participate in raising cubs, usually their own, but this is extremely rare and not always well understood. In May 2015, Amur tigers were photographed by camera traps in the Sikhote-Alin Bioshpere Reserve. The photos show a male Amur tiger pass by, followed by a female and three cubs within the span of about two minutes. In Ranthambore, a male Bengal tiger raised and defended two orphaned female cubs after their mother had died of illness. The cubs remained under his care, he supplied them with food, protected them from his rival and sister, and apparently also trained them.
Male tigers are generally more intolerant of other males within their territories than females are of other females. Territory 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 and showing its belly in a submissive posture. Once dominance has been established, a male may tolerate a subordinate within his range, as long as they do not live in too close quarters. The most aggressive disputes tend to occur between two males when a female is in oestrus, and may rarely result in the death of one of the males.
Facial expressions include the "defense threat", where an individual bares its teeth, flattens its ears and its pupils enlarge. Both males and females show a flehmen response, a characteristic grimace, when sniffing urine markings but flehmen is more often associated with males detecting the markings made by tigresses in oestrus. Like other Panthera, tigers roar, particularly in aggressive situations, during the mating season or when making a kill. There are two different roars: the "true" roar is made using the hyoid apparatus and forced through an open mouth as it progressively closes, and the shorter, harsher "coughing" roar is made with the mouth open and teeth exposed. The "true" roar can be heard at up to 3 km (1.9 mi) away and is sometimes emitted three or four times in succession. When tense, tigers will moan, a sound similar to a roar but more subdued and made when the mouth is partially or completely closed. Moaning can be heard 400 m (1,300 ft) away. Chuffing, soft, low-frequency snorting similar to purring in smaller cats, is heard in more friendly situations. Other vocal communications include grunts, woofs, snarls, miaows, hisses and growls.
Tigers have been studied in the wild using a variety of techniques. The populations of tigers have been estimated using plaster casts of their pugmarks, although this method was criticised as being inaccurate. More recent attempts have been made using camera trapping and studies on DNA from their scat, while radio collaring has been used to track tigers in the wild. Tiger spray has been found to be just as good, or better, as a source of DNA as scat. In the wild, tigers mostly feed on large and medium-sized animals, preferring native ungulates weighing at least 90 kg (200 lb). They typically have little or no deleterious effect on their prey populations. Sambar deer, chital, barasingha, wild boar, gaur, nilgai and both water buffalo and domestic buffalo, in descending order of preference, are the tiger's favoured prey in Tamil Nadu, India, while gaur and sambar are the preferred prey and constitute the main diet of tigers in other parts of India. They also prey on other predators, including dogs, leopards, pythons, sloth bears, and crocodiles. In Siberia, the main prey species are Manchurian wapiti and wild boar (the two species comprising nearly 80% of the prey selected) followed by sika deer, moose, roe deer, and musk deer. Asiatic black bears and Ussuri brown bears may also fall prey to tigers, and they constitute up to 40.7% of the diet of Siberian tigers depending on local conditions and the bear populations. In Sumatra, prey include sambar deer, muntjac, wild boar, Malayan tapir and orangutan. In the former Caspian tiger's range, prey included saiga antelope, camels, Caucasian wisent, yak, and wild horses. Like many predators, tigers are opportunistic and may eat much smaller prey, such as monkeys, peafowl and other ground-based birds, hares, porcupines, and fish.
Tigers generally do not prey on fully grown adult Asian elephants and Indian rhinoceros but incidents have been reported. More often, it is the more vulnerable small calves that are taken. Tigers have been reported attacking and killing elephants ridden by humans during tiger hunts in the 19th century. When in close proximity to humans, tigers will also sometimes prey on such domestic livestock as cattle, horses, and donkeys. Old or wounded tigers, unable to catch wild prey, can become man-eaters; this pattern has recurred frequently across India. An exception is in 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. Although almost exclusively carnivorous, tigers will occasionally eat vegetation for dietary fibre such as fruit of the slow match tree.
Tigers are thought to be mainly nocturnal predators, but in areas where humans are typically absent, they have been observed via remote-controlled, hidden cameras, hunting in daylight. 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 the prey off balance. Successful hunts usually require the tiger to almost simultaneously leap onto its quarry, knock it over, and grab the throat or nape with its teeth. Despite their large size, tigers can reach speeds of about 49-65 km/h (30-40 mph) but only in short bursts; consequently, tigers must be close to their prey before they break cover. If the prey catches wind of the tiger's presence before this, the tiger usually abandons the hunt rather than chase prey or battle it head-on. Horizontal leaps of up to 10 m (33 ft) have been reported, although leaps of around half this distance are more typical. One in 2 to 20 hunts, including stalking near potential prey, ends in a successful kill.
When hunting larger animals, tigers prefer to bite the throat and use their powerful forelimbs to hold onto the prey, often simultaneously wrestling it to the ground. The tiger remains latched onto the neck until its target dies of strangulation. By this method, gaurs and water buffaloes weighing over a ton have been killed by tigers weighing about a sixth as much. Although they can kill healthy adults, tigers often select the calves or infirm of very large species. Healthy adult prey of this type can be dangerous to tackle, as long, strong horns, legs and tusks are all potentially fatal to the tiger. No other extant land predator routinely takes on prey this large on their own. Whilst hunting sambars, which comprise up to 60% of their prey in India, tigers have reportedly made a passable impersonation of the male sambar's rutting call to attract them. With smaller prey, such as monkeys and hares, the tiger bites the nape, often breaking the spinal cord, piercing the windpipe, or severing the jugular vein or common carotid artery. 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, and break the backs of sloth bears.
During the 1980s, a tiger named "Genghis" in Ranthambhore National Park was observed frequently hunting prey through deep lake water, a pattern of behaviour that had not previously been witnessed in over 200 years of observations. Moreover, he appeared to be unusually successful, with 20% of hunts ending in a kill.
After killing their prey, tigers sometimes drag it to conceal it in vegetative cover, usually pulling it by grasping with their mouths at the site of the killing bite. This, too, can require great physical strength. In one case, after it had killed an adult gaur, a tiger was observed to drag the massive carcass over a distance of 12 m (39 ft). When 13 men simultaneously tried to drag the same carcass later, they were unable to move it. An adult tiger can go for up to two weeks without eating, then gorge on 34 kg (75 lb) of flesh at one time. In captivity, adult tigers are fed 3 to 6 kg (6.6 to 13.2 lb) of meat a day. Mating can occur all year round, but is more common between November and April. A female is only receptive for three to six days. Mating is frequent and noisy during that time. Gestation can range from 93 to 112 days, the average being 105 days. The litter is usually two or three cubs, occasionally as few as one or as many as six. Cubs weigh from 680 to 1,400 g (1.50 to 3.09 lb) each at birth, and are born blind and helpless. The females rear them alone, with the birth site and maternal den in a sheltered location such as a thicket, cave or rocky crevice. The father generally takes no part in rearing them. Unrelated wandering male tigers may kill cubs to make the female receptive, since the tigress may give birth to another litter within five months if the cubs of the previous litter are lost. The mortality rate of tiger cubs is about 50% in the first two years. Few other predators attack tiger cubs due to the diligence and ferocity of the mother tiger. Apart from humans and other tigers, common causes of cub mortality are starvation, freezing, and accidents.
A dominant cub emerges in most litters, usually a male. This cub is more active than its siblings and takes the lead in their play, eventually leaving its mother and becoming independent earlier. The cubs open their eyes at six to fourteen days old. By eight weeks, the cubs make short ventures outside the den with their mother, although they do not travel with her as she roams her territory until they are older. The cubs are nursed for three to six months. Around the time they are weaned, they start to accompany their mother on territorial walks and they are taught how to hunt. The cubs often become capable (and nearly adult size) hunters at eleven months old. The cubs become independent around eighteen months of age, but it is not until they are around two to two and a half years old that they fully separate from their mother. Females reach sexual maturity at three to four years, whereas males do so at four to five years.