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Of
the tigers that survive in the wild, as few as twenty or less represent
the subspecies we currently call the South China tiger. But as many as
an estimated three or four thousand represent the subspecies we call the
Bengal tiger. Should we be as concerned about conserving one of these
two subspecies as we are about conserving the other? If so, why? If not,
which of the two deserves the greater consideration in terms of conservation
effort?
Should
we pursue the conservation of the South China tiger more aggressively
specifically because there are fewer of them? Such a strategy in fact
contradicts the reality believed to be true by most felid conservation
biologists that so small a population is profoundly less likely to survive
in the wild than its less-endangered cousins. However, other conservation
beliefs dictate that the very criticality of the endangerment of the South
China tiger is the feature that entitles it to more attention than less-endangered
subspecies. The Bengal tiger, after all (such a strategy dictates), is
apparently doing much better under current circumstances than the South
China tiger, so let's devote efforts where they are "most" needed
.
Taken to its extreme, and thanks to the extraordinary advances in the
field of cloning, this argument can even be extended to include tiger
subspecies that already have gone extinct. The Bali, Javan, and Caspian
tigers are, technically, even more "endangered" than the South
China tiger. There are none left, either in the wild or in zoos. But there
are pelts
from which genetic material can be harvested
. Should
we not devote a portion of our conservation efforts to producing "Jurassic"
tigers?
What
differentiates tiger subspecies?
Even
before any consideration is given to the foregoing questions, however,
the very nature of genetic classification needs to be carefully re-evaluated.
While many sophisticated genetic researchers consider classifications
of life forms valid down to the species level, far fewer experts consider
designations below that level - i.e. down to the subspecies level - to
be either crucial or useful.
Just what is it that makes a South China different from a Bengal tiger?
Physically, while the animals are very similar in appearance, there are
subtle differences in terms of size and color that can be used in the
most general of terms to distinguish between members of the two subspecies.
Genetically, there are-it has recently been determined-also characteristics
that can be used to distinguish between the two. However, the members
of the two subspecies can interbreed readily and produce fertile offspring.
So just how much attention should we pay to the "difference"
between these two animals for the sake of conservation?
Resources in terms of funding and manpower are severely limited when it
comes to conservation. We therefore need to be supremely careful in allotting
those resources based on anything that has to do with and index as arbitrary-even
though it may not seem so-as subspeciation. The fact that we-human beings-have
chosen at this point in time to establish discrete names for each of the
tiger subspecies is more indicative of the needs of humans than the needs
of tigers. The fact of the matter is that tigers have been slowly but
steadily differentiating themselves for millions of years, one generation
at a time. Furthermore, with the exception of the tigers on the islands
of Sumatra, Java, and Bali, the geographic separation among the subspecies
is extremely flexible, uncertain, and at least partly reliant upon man-made
designations - for example the line dividing Bengal and Indochinese tigers
is the Irrawaddy River in Myanmar.
With captive tigers, these complication are equally vexing. Should we
keep representatives of the subspecies separate (a technique known within
the science of conservation breeding as "splitting"), or should
we interbreed them ("lumping")? Lumping will certainly lead
to offspring that are more genetically robust, but they will also be hybrids.
To many conservation strategists, that is the consequence that must be
avoided at all costs; not only do hybrid tigers represent neither subspecies
purely, they can only and forever give birth to other hybrids. Other strategists,
however, point to the fact that many animals will hybridize naturally
among their subspecies in certain cases-including tigers. Indeed, as the
geographic boundaries between tiger populations merge and the animals
wander to and from regions, their genetic differentiation smoothes into
near nonexistence.
Then there's the white tiger. Not only are these animals not albinos,
they're also not a distinct subspecies. White tigers were originally just
a "type" of tiger within the Bengal subspecies. Now, however,
in captivity, cross breeding has rendered nearly all the surviving white
tigers as hybrids. At the same time, the process of selective breeding
of white tigers for the sake of propagating their unique physical type
has ironically given rise to another, functionally opposite, aspect of
genetics known as "inbreeding depression," which manifests itself
through such physical deformities as crossed eyes, swayed backs, pinched
pelvises, and knocked knees. As a result, most conservation biologists
consider almost every white tiger now in captivity to be "worthless"
in terms of genetic viability. Nevertheless, many zoos like to exhibit
the animals because the public is especially enthusiastic about viewing
these undeniably beautiful creatures.
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