Bengal tiger
The Bengal tiger, or Royal Bengal tiger (Panthera tigris tigris), is a tiger subspecies native to India, Bangladesh, Nepal and Bhutan, and has been classified as endangered by IUCN as the population is estimated at fewer than 2,500 individuals with a decreasing trend. None of the Tiger Conservation Landscapes within the Bengal's tiger range is large enough to support an effective population size of 250.
The Bengal tiger is the most numerous of the tiger subspecies — with populations estimated at 1,706 in India, 200 in Bangladesh, 155 in Nepal and 67–81 in Bhutan.
Physical characteristics
Its coat is a yellow to light orange, and the stripes range from dark brown to black; the belly is white, and the tail is white with black rings. A mutation of the Bengal subspecies, the white tiger, has dark brown or reddish brown stripes on a white background, and some are entirely white. Black tigers have tawny, yellow or white stripes on a black background color. The skin of a black tiger, recovered from smugglers, measured 259 cm (102 in) and was displayed at the National Museum of Natural History, in New Delhi. The existence of black tigers without stripes has been reported but not substantiated.
The total body length, including the tail, of males is 270 to 310 cm (110 to 120 in), while females are 240 to 265 cm (94 to 104 in). The tail measures 85 to 110 cm (33 to 43 in), and the height at the shoulder is 90 to 110 cm (35 to 43 in). The average weight of males is 221.2 kg (488 lb), while that of females is 139.7 kg (308 lb).
Male Bengal tigers from the northern Indian subcontinent are as large as Siberian tigers with a greatest length of skulls of 332 to 376 mm (13.1 to 14.8 in). In northern India and Nepal, males have an average weight of 235 kg (520 lb), and females 140 kg (310 lb). Recent studies of body weights of the different tiger subspecies have shown that Bengal tigers are on average larger than Siberian tigers.
Tiger records
A heavy male Bengal tiger weighing 258.6 kg (570 lb) was shot in Northern India in 1938. In 1980 and 1984, scientists captured and tagged two male tigers (M105 and M026) in Nepal that weighed more than 270 kg (600 lb). The largest known Bengal tiger was a male with a head and body length of 221 cm (87 in) measured between pegs, 150 cm (59 in) of chest girth, a shoulder height of 109 cm (43 in) and a tail of just 81 cm (32 in), perhaps bitten off by a rival male. This specimen could not be weighed, but it was calculated to weigh no less than 272 kg (600 lb). Finally, according to the Guinness Book of Records, the heaviest tiger known was a huge male hunted in 1967, that measured 322 cm (127 in) in total length between pegs, 338 cm (133 in) over curves and weighed 388.7 kg (857 lb). This specimen was hunted in northern India by David Hasinger and is on exhibition in the Mammals Hall of the Smithsonian Institution.
In the beginning of the 20th century, there were reports of big males measuring about 12 ft (3.7 m) in total length; however, there was not scientific corroboration in the field, and it is probable that this measurement was taken over the curves of the body.
Genetic ancestry
Bengal tigers are defined by three distinct mitochondrial nucleotide sites and 12 unique microsatellite alleles. The pattern of genetic variation in the Bengal tiger corresponds to the premise that these tigers arrived in India approximately 12,000 years ago. This recent history of tigers in the Indian subcontinent is consistent with the lack of tiger fossils from India prior to the late Pleistocene and the absence of tigers from Sri Lanka, which was separated from the subcontinent by rising sea levels in the early Holocene. However, a recent study of two independent fossil finds from Sri Lanka, one dated to approximately 16,500 years ago, tentatively classifies them as being a tiger.
Behaviour and ecology
Tigers do not live in prides as lions do. They do not live as family units because the male plays no part in raising his offspring. Tigers mark their territory by spraying urine on a branch or leaves or bark of a tree, which leaves a particular scent behind. Tigers also spray urine to attract the opposite sex. When an outside individual comes into contact with the scent, it learns that the territory is occupied by another tiger. Hence, every tiger lives independently in its own territory.
Male Bengal tigers fiercely defend their territory from other tigers, often engaging in serious fighting. Female tigers are less territorial: occasionally a female will share her territory with other females. If a male happens to enter a female's territory, he will probably mate with her, if she is not already pregnant or has a litter. If she is pregnant or has a litter, he has no choice but to find himself a new territory and another potential mate. Similarly, females entering a male's territory are known to mate with him. Both males and females become independent of their mother around 18 months old, whereupon the cubs have to establish their own territories and fend for themselves. A male's territory is larger than a female's territory.
Reproduction and lifecycle
Males reach maturity at 4–5 years of age, and females at 3–4 years. Mating can occur at any time, but is most prevalent between November and April. A tigress comes into heat at intervals of about 3–9 weeks, and is receptive for 3–6 days. After a gestation period of 104–106 days, 1–4 cubs are born in a shelter situated in tall grass, thick bush or in caves. Newborn cubs weigh 780–1600 g (2 lb) and they have a thick wooly fur that is shed after 3.5–5 months. Their eyes and ears are closed. Their milk teeth start to erupt at about 2–3 weeks after birth, and are slowly replaced by permanent dentition from 8.5–9.5 weeks of age onwards. They suckle for 3–6 months, and begin to eat small amounts of solid food at about 2 months of age. At this time, they follow their mother on her hunting expeditions and begin to take part in hunting at 5–6 months of age. At the age of 2–3 years, they slowly start to separate from the family group and become transient — looking out for an area, where they can establish their own territory. Young males move further away from their mother's territory than young females. Once the family group has split, the mother comes into heat again.
Hunting and diet
Tigers are obligate carnivores. They prefer hunting large ungulates such as chital, sambar, gaur, and to a lesser extent also barasingha, water buffalo, nilgai, serow and takin. Among the medium-sized prey species they frequently kill wild boar, and occasionally hog deer, muntjac and Gray langur. Small prey species such as porcupines, hares and peafowl form a very small part in their diet. Due to the encroachment of humans onto their habitat, they also prey on domestic livestock.
Bengal tigers have also been known to take other predators, such as leopards, wolves, jackals, foxes, crocodiles, Asiatic black bears, sloth bears, and dholes as prey, although these predators are not typically a part of the tiger's diet. Adult elephants and rhinoceroses are too large to be successfully tackled by tigers, but such extraordinarily rare events have been recorded. The Indian hunter and naturalist Jim Corbett described an incident in which two tigers fought and killed a large bull elephant. If injured, old or weak, or their normal prey is becoming scarce, they may even attack humans and become man-eaters.
In most cases, tigers approach their victim from the side or behind from as close a distance as possible and grasp the prey's throat to kill it. Then they drag the carcass into cover, occasionally over several hundred meters, to consume it. The nature of the tiger's hunting method and prey availability results in a "feast or famine" feeding style: they often consume 18–40 kilograms (40–88 lb) of meat at one time.
Population and distribution
In 2010, the population of wild Bengal tigers in the Indian subcontinent is estimated to be fewer than 2,500. Of these, 1,165–1,657 are found in India, 200–419 in Bangladesh, mostly in the Sunderbans, 100–194 in Nepal and 67–81 in Bhutan. Over the past century tiger numbers have fallen dramatically, with a decreasing population trend. None of the Tiger Conservation Landscapes within the Bengal tiger range is large enough to support an effective population size of 250. Habitat losses and the extremely large-scale incidences of poaching are serious threats to the species' survival. The extent of area occupied by tigers is estimated at less than 1,184,911 square kilometres (457,497 sq mi), a 41% decline from the area estimated in the mid-1990s.
Threats
The most significant immediate threat to the existence of wild tiger populations is the illegal trade in poached skins and body parts between India, Nepal and China. The governments of these countries have failed to implement adequate enforcement response, and wildlife crime remained a low priority in terms of political commitment and investment for years. There are well-organised gangs of professional poachers, who move from place to place and set up camp in vulnerable areas. Skins are rough-cured in the field and handed over to dealers, who send them for further treatment to Indian tanning centres. Buyers choose the skins from dealers or tanneries and smuggle them through a complex interlinking network to markets outside India, mainly in China.
The illicit demand for bones and body parts from wild tigers for use in Traditional Chinese medicine is another reason for the unrelenting poaching pressure on tigers on the Indian subcontinent. For at least a thousand years, tiger bones have been an ingredient in traditional medicines that are prescribed as a muscle strengthener and treatment for rheumatism and body pain.
Other factors contributing to their loss are urbanization and revenge killing. Farmers blame tigers for killing cattle and shoot them. Their skins and body parts may however become a part of the illegal trade.
The Wildlife Protection Society of India (WPSI) works with law enforcement agencies in India to apprehend tiger poachers and wildlife traders throughout India. WPSI investigates and verifies any seizure of tiger parts and unnatural tiger deaths that are brought to their notice. Between 1994 and 2009, WPSI has documented 893 cases of tigers killed in India, which is just a fraction of the actual poaching and trade in tiger parts during those years. In 2007, police in Allahabad raided a meeting of suspected poachers, traders and couriers. One of the arrested persons was the biggest buyer of tiger parts in India who used to sell them off to the Chinese traditional medicinal market, using women from a nomadic tribe as couriers.
In 2006, India's Sariska Tiger Reserve lost all of its 26 tigers, mostly to poaching. In 2009, none of the 24 tigers residing in the Panna Tiger Reserve were left due to excessive poaching.
Conservation efforts
A Bengal Tiger in a natural reserve in Karnataka, India. Following the revelation that only 1,411 Bengal tigers exist in the wild in India, down from 3,600 in 2003, the Indian government has decided to set up eight new tiger reserves.
An area of special interest lies in the Terai Arc Landscape in the Himalayan foothills in northern India and southern Nepal, where 11 protected 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. Nepal has developed a community-based tourism model, with a strong emphasis on sharing benefits with locals and on the regeneration of degraded forests. The approach has been successful in reducing poaching, restoring habitats, and creating a local constituency for conservation.
In Bangladesh
The Sundarbans tiger project is a Bangladesh Forest Department initiative that started its field activities in February 2005. The idea for creating such a project was first developed during a field survey in 2001, conducted by Md. Osman Gani, Ishtiaq U. Ahmad, James L. D. Smith and K. Ullas Karanth. They realized that the Sundarbans mangrove forest at the mouth of the Ganges River contained probably one of the largest populations of wild tigers left in the world. As such, there was an urgent need to start measures that would ensure the protection of this precious area. The Save the Tiger Fund and the United States Fish and Wildlife Service generously donated funds to support the initial phase of research that aimed to collect data on tiger ecology using telemetry, and study the tiger’s environment by assessing its habitat and prey. But management of a wilderness area needs more than just information on the species to be protected. Personnel with skills and resources to implement conservation strategies, and the general support of the country are also required. So from the research base, the project is evolving rapidly to also encompass capacity building and conservation awareness activities. It has been able to do so through the forward thinking approach to management taken by the Forest Department, and the incredible support of the Bangladeshi people. The project is administered by the Forest Department. At the field level, there is a team of 8 persons, made up of Forest Department personnel and one wildlife consultant from the University of Minnesota who advises on research strategies and trains staff.
Relationship with humans
Genetic pollution
Tara, a hand-reared supposedly Bengal tigress acquired from Twycross Zoo in England in July 1976, was trained by Billy Arjan Singh and reintroduced to the wild in Dudhwa National Park, India, with the permission of India's then-Prime Minister Indira Gandhi, in an attempt to prove that zoo-bred, hand-reared tigers can be released in the wild with success. In the 1990s, some tigers from Dudhwa were observed which had the typical appearance of Siberian tigers: white complexion, pale fur, large head and wide stripes. With recent advances in science, it was subsequently found that Siberian tigers' genes have polluted the otherwise pure Bengal tiger gene pool of Dudhwa National Park. It was proved later that Twycross Zoo had been irresponsible and maintained no breeding records and had given India a hybrid Siberian-Bengal tigress instead. Dudhwa tigers constitute about 1% of India's total wild population, but the possibility exists of this genetic pollution spreading to other tiger groups; at its worst, this could jeopardize the Bengal tiger as a distinct subspecies.
Attack on humans
Tigers are known to not like the presence of humans in their territory, since they like to be alone. Any human interference in tiger hunting or whilst nursing are met by the tiger unwelcomingly. There have been incidences where mother tigers have been separated from their cubs due to human interference. A well-known incident occurred in Bandhavgarh National Park, where a tigress known as Mohini was separated from her cubs while crossing the road, since some tourists blocked her road to the other side, resulting in losing her contact with her cubs, who had already crossed the road. Usually, tigers become man eaters when they grow old and have no strength to hunt. At such times, if a human comes in contact with the tiger, he/she may be killed. But that is not the only reason why tigers become man eaters. If tigers do not have enough prey to feed upon, due to an imbalance in the food chain, they will often try to hunt humans. If a young tiger has injured teeth or paws, then it becomes difficult for him to tear apart his prey, which is also another reason for him to eat man.
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