 |
|
|
White Tigers - By Ron Tilson
 All wild white tigers were a color
variation of Bengal tigers. White tigers in the wild were recorded in
India during the Mughal Period from 1556 to 1605 AD. At least 17
instances were recorded in India between 1907 and 1933 in Orissa,
Bilaspur, Sohagpur and Rewa. Wild white tigers were very rare, and none
have been reported in the wild since the 1950s.
White tigers differ from ordinary orange tigers (if a tiger can be
referred to as ordinary) in having ice-blue eyes, a pink nose, and
creamy white fur with chocolate stripes. White tigers are not albinos;
their color is caused by a double recessive allele. A Bengal tiger with
two normal alleles or one normal and one white allele is colored orange.
Only a double dose of the mutant allele results in white tigers.
How frequently do white tigers appear in nature? No one knows. But we
do know that in the last 100 years, only about a dozen such white tigers
have been seen in India (white forms have never been reported for any of
the other subspecies). During this same century, the Bengal tiger
population has dropped from 40,000 to a low of 1,800 tigers, and
approximately 100,000 have lived and died, suggesting that as few as one
in every 10,000 tigers is white.
The white tiger collection in North American zoos traces its ancestry
to a single white male known as Mohan, captured in 1951 in central
India. It did not take long for the Maharajah who captured him to figure
out that the only way to produce additional white tiger cubs was to
breed Mohan back to his daughter, who gave birth to the first generation
of captive-born white tigers in this century. One of these
granddaughters, Mohini, was bred with her uncle and half-brother, an
orange male called Sampson. It was through Mohini that the white tiger
line came to the United States through the National Zoo in Washington
D.C., From there, two of Mohini's offspring, a brother and sister, were
bred at the Cincinnati Zoo and their daughter, Kesari, founded the
Cincinnati white tiger line.
 In Cincinnati, the inbreeding continued. Bhim, a white son of
Kesari, was mated to his sisters Kamala and Sumita, and so on.
Altogether, the average inbreeding coefficient of the white tiger
lineage is much higher that that of either Sumatran of Siberian tigers
managed by the tiger SSP which is methodically working towards
minimizing the average inbreeding coefficient of its captive population.
This translates into a healthier population and decreases the
probability of a number of reproductive and disease problems associated
with inbreeding.
An SSP is a breeding strategy followed by participating zoos that is
designed to maintain small self-sustaining populations of endangered
species in captivity. Every breeding recommendation is designed to
minimize the average inbreeding coefficient of the population and to
equalize the genetic representation of each wild-caught animal
("founders" of the captive population). With some 63 such species
blueprints in hand, zoos are increasingly becoming last-ditch refuges
for endangered species, as a kind of biological (rather than biblical)
Noah's ark. Already on board are several species now extinct in the wild
that survive only in zoos, including Pere David's deer and Asian wild
horses, and three additional species, the California condor, Arabian
oryx, and black-footed ferret, are currently making their way back into
the wild thanks to captive breeding.
The white tiger controversy among zoos is a small part ethics and a
large part economics. For example, the tiger SSP has condemned breeding
white tigers because of their mixed ancestry (most have been hybridized
with other subspecies or are of unknown lineage) and because they serve
no conservation purpose. Owners of white tigers say white tigers are
popular exhibit animals and help increase zoo attendance and, at $60,000
each, revenues as well. The same story can be applied to the selective
propagation of melanistic leopards, white lions, king cheetahs, and
other phenotypic aberrations.
However, there is an unspoken issue that shames the very integrity of
zoos, their conservation programs, and their message to the visiting
public. To produce white tigers or any other phenotypic curiosity,
directors of zoos and facilities must continuously inbreed, father to
daughter, to granddaughter, and so on. At issue is a  contradiction of fundamental genetic
principles upon which all SSPs for endangered species in captivity are
based. White tigers are an aberration artificially bred and proliferated
by a few zoos, private breeders, and circus folks, who do this for
economic rather than conservation reasons.
White Tigers Without Stripes
White tigers showing no stripes have been recorded. A "wholly white
tiger, with the stripe-pattern visible only under reflected light, like
the pattern of a white tabby cat, was exhibited in the Execter Change
Menagerie in the early part of the nineteenth century and described by
Hamilton Smith. Another citing of a "tiger without stripes" was reported
by Sagar and Singh (1989) from Similipal Reserve, Orissa.
|
|
|
