Bengal Tiger
The Bengal tiger (Panthera tigris tigris) is the most numerous tiger
subspecies. By 2011, the total population was estimated at fewer than 2,500
individuals with a decreasing trend. None of the 'Tiger Conservation
Landscapes' within the Bengal tiger's range is considered large enough to
support an effective population size of 250 adult individuals. Since 2010, it
is listed as Endangered on the IUCN Red List.
As of 2010, Bengal tiger populations in India have been estimated at
1,706–1,909. As of 2014, they had reputedly increased to an estimated 2,226
individuals, but the method used in the census may not be accurate.
Bengal tigers number around 440 in Bangladesh
and 163–253 in Nepal. Prior censuses placed the population of tigers in Bhutan
at around 65-75 individuals, however, the latest census estimated that 103 wild
Bengal tigers are living in the country.
Bengal is traditionally fixed as the typical locality for the binomen
Panthera tigris, to which the British taxonomist Reginald Innes Pocock
subordinated the Bengal tiger in 1929 under the trinomen Panthera tigris
tigris. The Bengal, Caspian and Siberian tigers, and lion rank among the biggest
cats.
It is the national animal of both
India and Bangladesh.
Characteristics:
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.
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 they arrived in India approximately 12,000 years ago. This is consistent
with the lack of tiger fossils from the Indian subcontinent 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.
Body weight:
Bengal tigers may weigh up to 325 kg
(717 lb) and reach a head and body length of 320 cm (130 in). Several
scientists indicated that adult male Bengal tigers from Nepal, Bhutan, and
Assam, Uttarakhand and West Bengal in northern India (collectively, the tigers
of the Terai) consistently attain more than 227 kg (500 lb) of body weight.
Seven adult males captured in Chitwan National Park in the early 1970s had an
average weight of 235 kg (518 lb) ranging from 200 to 261 kg (441 to 575 lb),
and that of the females was 140 kg (310 lb) ranging from 116 to 164 kg (256 to
362 lb). Males from northern India are nearly as large as Siberian tigers with
a greatest length of skull of 332 to 376 mm (13.1 to 14.8 in).
Verifiable Sundarbans tiger weights
are not found in any scientific literature. Forest Department records list
weight measurements for these tigers, but none are verifiable and all are
guesstimates. There are also reports of head and body lengths, some of which
are listed as over 365.7 cm (144.0 in). More recently, researchers from the
University of Minnesota and the Bangladesh Forest Department carried out a
study for the US Fish and Wildlife Service and weighed three Sundarbans
tigresses from Bangladesh. All three tigers were female, two of which were
collared, captured and sedated, but the other one had been killed by local
villagers. The two collared tigresses were weighed using 150 kg (330 lb)
scales, and the tigress killed by villagers was weighed using a balance scale
and weights. The two collared females both showed signs of teeth wear and both
were between 12 and 14 years old. The tigress killed by the villagers was a
young adult, probably between 3 and 4 years old, and she was likely a
pre-territorial transient. The three tigresses had a mean weight of 76.7 kg
(169 lb). One of the two older female's weight 75 kg (165 lb) weighed slightly
less than the mean because of her old age and relatively poor condition at the
time of capture. Skulls and body weights of Sundarbans tigers were found to be
distinct from other subspecies, indicating that they may have adapted to the
unique conditions of the mangrove habitat. Their small sizes are probably due
to a combination of intense intraspecific competition and small size of prey
available to tigers in the Sundarbans, compared to the larger deer and other
prey available to tigers in other parts.
Comparing tiger versus lion, a weight
range of 150 to 189 kg (331 to 417 lb) is considered fairly average for a male
East African lion in the Serengeti.
Records:
Two tigers shot in Kumaon and near
Oude at the end of the 19th century allegedly measured more than 12 ft (370
cm). But at the time, sportsmen had not yet adopted a standard system of
measurement; some would measure between pegs while others would round the
curves.
In the beginning of the 20th century,
a male Bengal tiger was shot in central India with a head and body length of
221 cm (87 in) between pegs, a chest girth of 150 cm (59 in), a shoulder height
of 109 cm (43 in) and a tail length of 81 cm (32 in), which was 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).
A heavy male weighing 570 lb (260 kg)
was shot in northern India in the 1930s. However, the heaviest known tiger was
a huge male killed in 1967 that weighed 388.7 kg (857 lb) and measured 322 cm
(127 in) in total length between pegs, and 338 cm (133 in) over curves. This
specimen is on exhibition in the Mammals Hall of the Smithsonian Institution.
In 1980 and 1984, scientists captured and tagged two male tigers in Chitwan
National Park that weighed more than 270 kg (600 lb).
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.
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 tiger habitat once covered a
huge swath of grassland and 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 Sukla Phanta-Kishanpur. Tiger densities in these TCUs are
high, in part because of the extraordinary biomass of ungulate prey.
The Bengal tigers in the Sundarbans in
India and Bangladesh are the only tigers in the world inhabiting mangrove
forests. The population in the Indian Sundarbans is estimated as 70 tigers in
total.
Reproduction and lifecycle:
A male and female Bengal tiger
interact with each other.
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
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