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.
Bangladesh:
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 Sunderbans.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.
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