|Bengal tiger in Bannerghatta National Park|
|Panthera tigris tigris
The Bengal tiger (Panthera tigris tigris) is a tiger subspecies native to the Indian subcontinent. It lives in Bhutan, Nepal, Bangladesh and northern India. It is the National animal of both India and Bangladesh.
The tiger's habitat includes tropical moist evergreen forests, tropical dry forests, tropical and subtropical moist deciduous forests, mangroves, subtropical and temperate upland forests, and alluvial grasslands.
The Bengal tiger's coat is yellow to light orange, with stripes ranging from dark brown to black; the belly and the interior parts of the limbs are white, and the tail is orange with black rings. The white tiger is a recessive mutant of the Bengal tiger, which is reported in the wild from time to time in Assam, Bengal, Bihar, and especially from the former State of Rewa. However, it is not to be mistaken as an occurrence of albinism. In fact, there is only one fully authenticated case of a true albino tiger, and none of black tigers, with the possible exception of one dead specimen examined in Chittagong in 1846.
Male Bengal tigers have an average total length of 270 to 310 cm (110 to 120 in) including the tail, while females measure 240 to 265 cm (94 to 104 in) on average. The tail is typically 85 to 110 cm (33 to 43 in) long, and on average, tigers are 90 to 110 cm (35 to 43 in) in height at the shoulders. The weight of males ranges from 180 to 258 kg (397 to 569 lb), while that of the females ranges from 100 to 160 kg (220 to 350 lb). The smallest recorded weights for Bengal tigers are from the Bangladesh Sundarbans, where adult females are 75 to 80 kg (165 to 176 lb). Bengal tigers have exceptionally stout teeth, and the canines are the longest among all living felids; measuring from 7.5 to 10 cm (3.0 to 3.9 in) in length.
Distribution and habitat
In 1982, a sub-fossil right middle phalanx was found in a prehistoric midden near Kuruwita in Sri Lanka, which is dated to about 16,500 ybp and tentatively considered to be of a tiger. Tigers appear to have arrived in Sri Lanka during a pluvial period, during which sea levels were depressed, evidently prior to the last glacial maximum about 20,000 years ago. In 1929, the British taxonomist Pocock assumed that tigers arrived in southern India too late to colonize Sri Lanka, which earlier had been connected to India by a land bridge.
Results of a phylogeographic study using 134 samples from tigers across the global range suggest that the historical northeastern distribution limit of the Bengal tiger is the region in the Chittagong Hills and Brahmaputra River basin, bordering the historical range of the Indochinese tiger.
In the Indian subcontinent, tigers inhabit tropical moist evergreen forests, tropical dry forests, tropical and subtropical moist deciduous forests, mangroves, subtropical and temperate upland forests, and alluvial grasslands. Latter habitat once covered a huge swath of grassland, riverine and moist semi-deciduous forests along the major river system of the Gangetic and Brahmaputra plains, but has now been largely converted to agricultural land or severely degraded. Today, the best examples of this habitat type are limited to a few blocks at the base of the outer foothills of the Himalayas including the Tiger Conservation Units (TCUs) Rajaji-Corbett, Bardia-Banke, and the transboundary TCUs Chitwan-Parsa-Valmiki, Dudhwa-Kailali and Shuklaphanta-Kishanpur. Tiger densities in these TCUs are high, in part because of the extraordinary biomass of ungulate prey.
In the past, Indian censuses of wild tigers relied on the individual identification of footprints known as pug marks — a method that has been criticised as deficient and inaccurate, though now camera traps are being used in many places.
Good tiger habitats in subtropical and temperate upland forests include the Tiger Conservation Units (TCUs) Manas-Namdapha. TCUs in tropical dry forest include Hazaribagh National Park, Nagarjunsagar-Srisailam Tiger Reserve, Kanha-Indravati corridor, Orissa dry forests, Panna National Park, Melghat Tiger Reserve and Ratapani Tiger Reserve. The TCUs in tropical moist deciduous forest are probably some of the most productive habitats for tigers and their prey, and include Kaziranga-Meghalaya, Kanha-Pench, Simlipal and Indravati Tiger Reserves. The TCUs in tropical moist evergreen forests represent the less common tiger habitats, being largely limited to the upland areas and wetter parts of the Western Ghats, and include the tiger reserves of Periyar, Kalakad-Mundathurai, Bandipur and Parambikulam Wildlife Sanctuary.
During the tiger census of 2008, camera trap and sign surveys using GIS were employed to project site-specific densities of tigers, their co-predators and prey. Based on the result of these surveys, the total tiger population was estimated at 1,411 individuals ranging from 1,165 to 1,657 adult and sub-adult tigers of more than 1.5 years of age. Across India, six landscape complexes were surveyed that host tigers and have the potential to be connected. These landscapes comprise the following:
- in the Shivaliks–Gangetic flood plain landscape there are six populations with an estimated population size of 259 to 335 individuals occupying 5,080 km2 (1,960 sq mi) of forested habitats, which are located in Rajaji and Corbett national parks, in the connected habitats of Dudhwa-Kheri-Pilibhit, in Suhelwa Tiger Reserve, in Sohagi Barwa Sanctuary and in Valmiki National Park;
- in the Central Indian highlands there are 17 populations with an estimated population size of 437 to 661 individuals occupying 48,610 km2 (18,770 sq mi) of forested habitats, which are located in the landscapes of Kanha-Pench, Satpura-Melghat, Sanjay-Palamau, Navegaon-Indravati; isolated populations are supported in the tiger reserves of Bandhavgarh, Tadoba, Simlipal and the national parks of Panna, Ranthambore–Kuno–Palpur–Madhav and Saranda;
- in the Eastern Ghats landscape there is a single population with an estimated population size of 49 to 57 individuals occupying 7,772 km2 (3,001 sq mi) of habitat in three separate forest blocks located in the Srivenkateshwara National Park, Nagarjunasagar Tiger Reserve and the adjacent proposed Gundla Brahmeshwara National Park, and forest patches in the tehsils of Kanigiri, Baduel, Udayagiri and Giddalur;
- in the Western Ghats landscape there are seven populations with an estimated population size of 336 to 487 individuals occupying 21,435 km2 (8,276 sq mi) forest in three major landscape units Periyar-Kalakad-Mundathurai, Bandipur-Parambikulam-Sathyamangalam-Mudumalai-Anamalai-Mukurthi and Anshi-Kudremukh-Dandeli;
- in the Brahmaputra flood plains and north-eastern hills tigers occupy 4,230 km2 (1,630 sq mi) in several patchy and fragmented forests;
- in the Sundarbans National Park tigers occupy about 1,586 km2 (612 sq mi) of mangrove forest.
In May 2008, forest officials spotted 14 tiger cubs in Rajasthan's Ranthambore National Park. In June 2008, a tiger from Ranthambore was relocated to Sariska Tiger Reserve, where all tigers had fallen victim to poachers and human encroachments since 2005.
As of 2014, adult and subadult tigers at 1.5 years or older are estimated to number 408 in Karnataka, 340 in Uttarakhand, 308 in Madhya Pradesh, 229 in Tamil Nadu, 190 in Maharashtra, 167 in Assam, 136 in Kerala, and 117 in Uttar Pradesh.
Tigers in Bangladesh are now relegated to the forests of the Sundarbans and the Chittagong Hill Tracts. The Chittagong forest is contiguous with tiger habitat in India and Myanmar, but the tiger population is of unknown status.
As of 2004, population estimates in Bangladesh ranged from 200 to 419, mostly in the Sundarbans. This region is the only mangrove habitat in this bioregion, where tigers survive, swimming between islands in the delta to hunt prey. Bangladesh's Forest Department is raising mangrove plantations supplying forage for spotted deer. Since 2001, afforestation has continued on a small scale in newly accreted lands and islands of the Sundarbans. From October 2005 to January 2007, the first camera-trap survey was conducted across six sites in the Bangladesh Sundarbans to estimate tiger population density. The average of these six sites provided an estimate of 3.7 tigers per 100 km2 (39 sq mi). Since the Bangladesh Sundarbans is an area of 5,770 km2 (2,230 sq mi) it was inferred that the total tiger population comprised approximately 200 individuals. In another study, home ranges of adult female tigers were recorded comprising between 12 and 14 km2 (4.6 and 5.4 sq mi)., which would indicate an approximate carrying capacity of 150 adult females. The small home range of adult female tigers (and consequent high density of tigers) in this habitat type relative to other areas may be related to both the high density of prey and the small size of the Sundarbans tigers.
Since 2007 tiger monitoring surveys have been carried out every year by WildTeam in the Bangladesh Sundarbans to monitor changes in the Bangladesh tiger population and assess the effectiveness of conservation actions. This survey measures changes in the frequency of tiger track sets along the sides of tidal waterways as an index of relative tiger abundance across the Sundarbans landscape.
The population size for the Bangladesh Sundarbans was estimated as 100–150 adult females or 335–500 tigers overall. Female home ranges, recorded using Global Positioning System collars, were some of the smallest recorded for tigers, indicating that the Bangladesh Sundarbans could have one of the highest densities and largest populations of tigers anywhere in the world. They are isolated from the next tiger population by a distance of up to 300 km (190 mi). Information is lacking on many aspects of Sundarbans tiger ecology, including relative abundance, population status, spatial dynamics, habitat selection, life history characteristics, taxonomy, genetics, and disease. There is also no monitoring program in place to track changes in the tiger population over time, and therefore no way of measuring the response of the population to conservation activities or threats. Most studies have focused on the tiger-human conflict in the area, but two studies in the Sundarbans East Wildlife sanctuary documented habitat-use patterns of tigers, and abundances of tiger prey, and another study investigated tiger parasite load. Some major threats to tigers have been identified. The tigers living in the Sundarbans are threatened by habitat destruction, prey depletion, highly aggressive and rampant intraspecific competition, tiger-human conflict, and direct tiger loss.
The tiger population in the Terai of Nepal is split into three isolated subpopulations that are separated by cultivation and densely settled habitat. The largest population lives in Chitwan National Park and in the adjacent Parsa Wildlife Reserve encompassing an area of 2,543 km2 (982 sq mi) of prime lowland forest. To the west, the Chitwan population is isolated from the one in Bardia National Park and adjacent unprotected habitat farther west, extending to within 15 km (9.3 mi) of the Shuklaphanta Wildlife Reserve, which harbours the smallest population. The bottleneck between the Chitwan-Parsa and Bardia-Sukla Phanta metapopulations is situated just north of the town of Butwal.
As of 2009, an estimated 121 breeding tigers lived in Nepal. By 2010, the number of adult tigers had reached 155. A survey conducted from December 2009 to March 2010 indicates that 125 adult tigers live in Chitwan National Park and its border areas covering 1,261 km2 (487 sq mi). From February to June 2013, a camera trapping survey was carried out in the Terai Arc Landscape, covering an area of 4,841 km2 (1,869 sq mi) in 14 districts. The country's tiger population was estimated at 163–235 breeding adults comprising 102–152 tigers in the Chitwan-Parsa protected areas, 48–62 in the Bardia-Banke National Parks and 13–21 in the Shuklaphanta Wildlife Reserve.
As of 2015, the population in Bhutan is estimated at 103 individuals. Tigers occur from an altitude of 200 m (660 ft) in the subtropical Himalayan foothills in the south along the border with India to over 3,000 m (9,800 ft) in the temperate forests in the north, and are known from 17 of 18 districts. Their stronghold appears to be the central belt of the country ranging in altitude between 2,000 and 3,500 m (6,600 and 11,500 ft), between the Mo River in the west and the Kulong River in the east. In 2010, camera traps recorded a pair of tigers at altitudes of 3,000 to 4,100 m (9,800 to 13,500 ft). The male was recorded scent-marking, and the female can also be seen to be lactating, confirming that the pair are living within their own territory, and strongly suggesting they are breeding at that altitude.
Ecology and behavior
The basic social unit of the tiger is the elemental one of mother and offspring. Adult animals congregate only on an ad hoc and transitory basis when special conditions permit, such as plentiful supply of food. Otherwise they lead solitary lives, hunting individually for the dispersed forest and tall grassland animals, upon which they prey. They establish and maintain home ranges. Resident adults of either sex tend to confine their movements to a definite area of habitat within which they satisfy their needs, and in the case of tigresses, those of their growing cubs. Besides providing the requirements of an adequate food supply, sufficient water and shelter, and a modicum of peace and seclusion, this location must make it possible for the resident to maintain contact with other tigers, especially those of the opposite sex. Those sharing the same ground are well aware of each other's movements and activities.
In the Panna Tiger Reserve an adult radio-collared male tiger moved 1.7 to 10.5 km (1.1 to 6.5 mi) between locations on successive days in winter, and 1 to 13.9 km (0.62 to 8.64 mi) in summer. His home range was about 200 km2 (77 sq mi) in summer and 110 km2 (42 sq mi) in winter. Included in his home range were the much smaller home ranges of two females, a tigress with cubs and a sub-adult tigress. They occupied home ranges of 16 to 31 km2 (6.2 to 12.0 sq mi).
The home ranges occupied by adult male residents tend to be mutually exclusive, even though one of these residents may tolerate a transient or sub-adult male at least for a time. A male tiger keeps a large territory in order to include the home ranges of several females within its bounds, so that he may maintain mating rights with them. Spacing among females is less complete. Typically there is partial overlap with neighboring female residents. They tend to have core areas, which are more exclusive, at least for most of the time. Home ranges of both males and females are not stable. The shift or alteration of a home range by one animal is correlated with a shift of another. Shifts from less suitable habitat to better ones are made by animals that are already resident. New animals become residents only as vacancies occur when a former resident moves out or dies. There are more places for resident females than for resident males.
During seven years of camera trapping, tracking, and observational data in Chitwan National Park, 6 to 9 breeding tigers, 2 to 16 non-breeding tigers, and 6 to 20 young tigers of less than one year of age were detected in the study area of 100 km2 (39 sq mi). One of the resident females left her territory to one of her female offspring and took over an adjoining area by displacing another female; and a displaced female managed to re-establish herself in a neighboring territory made vacant by the death of the resident. Of 11 resident females, 7 were still alive at the end of the study period, 2 disappeared after losing their territories to rivals, and 2 died. The initial loss of two resident males and subsequent take over of their home ranges by new males caused social instability for two years. Of 4 resident males, 1 was still alive and 3 were displaced by rivals. Five litters of cubs were killed by infanticide, 2 litters died because they were too young to fend for themselves when their mothers died. One juvenile tiger was presumed dead after being photographed with severe injuries from a deer snare. The remaining young lived long enough to reach dispersal age, 2 of them becoming residents in the study area.
Hunting and diet
Tigers are 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 grey langur. Small prey species such as porcupines, hares and peafowl form a very small part in their diet. Because of the encroachment of humans into their habitat, they also prey on domestic livestock.
In Nagarahole National Park, the average weight of 83 tiger kills was 401 kg (884 lb). This sample included several gaurs weighing upwards of 1,000 kg (2,200 lb). Gaurs were the most preferred choice of prey by tigers in Nagarahole, making up 44.8% of all tiger kills. Sambar deer were the second most preferred and made up 28.6% of all tiger kills. In Bandipur National Park, gaur and sambar together also constituted 73% of their diet.
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.
Bengal tigers have 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 their diet. They rarely attack adult elephants and rhinoceroses but such extraordinarily rare events have been recorded. The British-Indian hunter and naturalist Jim Corbett also described an incident of two tigers fighting and killing 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.
Reproduction and lifecycle
The tiger in India has no definite mating and birth seasons. Most young are born in December and April. Young have also been found in March, May, October and November. In the 1960s, certain aspects of tiger behaviour at Kanha National Park indicated that the peak of sexual activity was from November to about February, with some mating probably occurring throughout the year.
Males reach maturity at 4–5 years of age, and females at 3–4 years. A Bengal 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 to 1,600 g (1.72 to 3.53 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.
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 individuals. Habitat losses and the extremely large-scale incidences of poaching are serious threats to the species' survival.
The challenge in the Western Ghats forest complex in western South India, an area of 14,400 square miles (37,000 km2) stretching across several protected areas is that people live within its borders. The Save the Tiger Fund Council estimates that 7,500 landless people live illegally inside the boundaries of the 386-square-mile (1,000 km2) Nagarhole National Park in southwestern India. A voluntary if controversial resettlement is underway with the aid of the Karnataka Tiger Conservation Project led by K. Ullas Karanth of the Wildlife Conservation Society.
A 2007 report by UNESCO, "Case Studies on Climate Change and World Heritage" has stated that an anthropogenic 45-cm rise in sea level, likely by the end of the 21st century, according to the Intergovernmental Panel on Climate Change, combined with other forms of anthropogenic stress on the Sundarbans, could lead to the destruction of 75% of the Sundarbans mangroves. The Forest Rights Act passed by the Indian government in 2006 grants some of India's most impoverished communities the right to own and live in the forests, which likely brings them into conflict with wildlife and under-resourced, under-trained, ill-equipped forest department staff. In the past, evidence showed that humans and tigers cannot co-exist.
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. 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. In Bangladesh, tigers are killed by professional poachers, local hunters, trappers, pirates and villagers. Each group of people has different motives for killing tigers, ranging from profit, excitement to safety concerns. All groups have access to the commercial trade in body parts.
The illicit demand for bones and body parts from wild tigers for use in Traditional Chinese medicine is the 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.
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 trade in tiger parts during those years.
In 2006, India's Sariska Tiger Reserve lost all of its 26 tigers, mostly to poaching. 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 2009, none of the 24 tigers residing in the Panna Tiger Reserve were left because of excessive poaching. In November 2011, two tigers were found dead in Maharashtra: a male tiger was trapped and killed in a wire snare; a tigress died of electrocution after chewing at an electric cable supplying power to a water pump; another tigress was found dead in Kanha Tiger Reserve landscape — poisoning is suspected to be the cause of her death.
An area of special interest lies in the Terai Arc Landscape in the Himalayan foothills of northern India and southern Nepal, where 11 protected areas composed of 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.
WWF partnered with Leonardo DiCaprio to form a global campaign, Save Tigers Now, with the ambitious goal of building political, financial and public support to double the wild tiger population by 2022. Save Tigers Now started its campaign in 12 different WWF Tiger priority landscapes, since May 2010.
Bengal tigers have been captive bred since 1880 and widely crossed with other tiger subspecies. Indian zoos have bred tigers for the first time at the Alipore Zoo in Kolkata. The 1997 International Tiger Studbook lists the global captive population of Bengal tigers at 210 individuals that are all kept in Indian zoos, except for one female in North America. Completion of the Indian Bengal Tiger Studbook is a necessary prerequisite to establishing a captive management program for tigers in India.
"Re-wilding" project in South Africa
In 2000, the Bengal tiger re-wilding project Tiger Canyons was started by John Varty, who together with the zoologist Dave Salmoni trained captive-bred tiger cubs how to stalk, hunt, associate hunting with food and regain their predatory instincts. They claimed that once the tigers proved that they can sustain themselves in the wild, they would be released into a free-range sanctuary of South Africa to fend for themselves.
The project has received controversy after accusations by their investors and conservationists of manipulating the behaviour of the tigers for the purpose of a film production, Living with Tigers, with the tigers believed to be unable to hunt. Stuart Bray, who had originally invested a large sum of money in the project, claimed that he and his wife, Li Quan, watched the film crew "[chase] the prey up against the fence and into the path of the tigers just for the sake of dramatic footage."
The four tigers involved in this project have been confirmed to be crossbred Siberian–Bengal tigers, which should neither be used for breeding nor being released into the Karoo. Tigers that are not genetically pure will not be able to participate in the tiger Species Survival Plan, as they are not used for breeding, and are not allowed to be released into the wild.
In the USA
In October 2011, 18 Bengal tigers were among the exotic animals shot by the local sheriff's department after the 2011 Ohio exotic animal release.
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