Rainforests
stretched for miles. There were no deserts, there was only land
covered in masses of greenery, in thick fields of vegetation. Then
the cooling and drying came, vast tracts of lush life shrinking and
shrinking. On these plains, long-legged, speedy predators stalk their
prey. They race, a blur of gold and black, they jump with muscles
coiled, and they tear with claws outstretched. Survival has won for
them, and lost for their prey.
100,000
years ago, they extended their range. They spread into current-day
Asia, Europe, North America, and Africa, quickly finding themselves
much larger territories. Yet, in this wandering, they suddenly found
themselves almost all alone. The world had grown quieter for them,
their ability to interchange genes becoming vastly limited, to the
point that their populations began to become distinct from one
another. The ones in Africa are not like those in Asia. Those in Asia
are not like those in Europe. Those in Europe are not like those in
North America.
That
was okay, though. They were still surviving.
Until
the end of the ice age came. Those in North America, those in Europe,
they perished. They couldn’t survive the temperatures and the
massive competition for shelter, prey, and other basic needs. It was
only those in Asia and Africa that came through. And even then…
So many of their kin died, starved, frozen, out-competed.
Only
a few exceptionally hardy individuals survived it, and they found
that with so few left, their options of mate were limited.
Interbreeding was rampant, cousins with cousins, sometimes siblings
with siblings. There was no other choice, no other way to survive.
Their genetic variability was reduced on an extreme scale, even more
so than before.
Cheetahs
managed to survive, but their survival is still threatened.
In
the 19th century, cheetah populations were calculated as high as
100,000 individuals. There was a great increase, but it wouldn’t
last. With that low genetic variability stemming from their species'
forerunners being only a handful of individuals, they were
struggling. Their litters shrank, and their reproductive success was
limited. Suddenly their population wasn’t growing anymore, in
fact, it was shrinking, and their ability to adapt to change, whether
it be temperature, disease, or air quality, was limited.
Now,
it’s a population in crisis.
Globally,
there are around 6,500 to 7,100 cheetahs according to the
International Union for Conservation of Nature (IUCN). The
overwhelming majority of these cheetahs are African cheetahs, but a
small pocket of Asiatic cheetahs remain in Iran.
The
cheetahs in captive breeding programs that desperately try to staunch
the bleed out of the species are almost exclusively African cheetahs,
and they face many quality of life-issues. In the wild, they live to
be 7 – 9 on average, although in captivity they may live to the
late teens. But this comes with challenges of its own. At a certain
point, their ability to digest their food becomes limited, with
special enzymes being added to meat to give them their required
nutrition. They face problems with their bones, with their joints,
and generally seem to be held together by a thread of pure will.
Their
quality of life is extensively monitored, with most zoos and
conservation organizations performing consistent wellness checks to
ensure their individuals are comfortable, mobile, alert, bright, and
able to interact with their environments. They ensure that their life
is one worth living.
Yet
even with all of these efforts, even with human intervention, both
subspecies of cheetah are on the brink of extinction, wrought by
their genetics.
This
begs the question: is it worth combining the genetic diversity of the
African and Asiatic cheetah to ensure the continued survival of the
cheetah as a whole?
PubMed
published a study that looked at the DNA of cheetahs. The team
analyzed mitochondrial DNA (passed from mother to offspring) as well
as microsatellite data from 94 cheetah samples. Their global genetic
variation is much higher than what we see in their two species
separately. In that spread of cheetahs, which occurred over 30,000
years ago, they became absolutely separate species.
Molecular
Ecology similarly published a study that found the most significant
differentiation in genetics was between Asiatic and African cheetahs.
Before the Indian cheetah was hunted to extinction, their DNA was
obtained as well. Still, it is the Asiatic and African with the most
variation from one another. Both of these studies are interested in
preserving the distinct species and creating strategies for their
continued wild existence.
It’s
a difficult task, though. With their poor genetic variation stemming
from their narrow escapes from extinction, it’s more likely a
novel disease will wipe out the population than their genetics will
mutate enough to create genetic variation. Perhaps they could outrun
extinction a third time if this happened, but it’s doubtful.
Asiatic
cheetahs are smaller than their African counterparts. Not diminutive,
but even more streamlined. They have smaller and longer necks, with
their legs being even more slender, the envy of ballerinas
everywhere. Arguably, they’re also fluffier, but that’s a
difficult thing to objectively quantify.
The
Asiatic cheetah looks for medium-sized herbivores. Indian gazelle,
goitered gazelle, wild sheep, wild goat, and cape hare. The African
cheetah has over 25 species of herbivores, and the majority of them
are within the cheetah’s diet range. Their sprawling savannas
and grasslands enable them to hunt a variety, while the mountainous
and arid regions of the Asiatic cheetah restrict their choices.
Are
these visible differences so special that we cannot consider the
species’ health as a whole?
Consider
hybridization.
When
most people think of hybridization, they think of a mule, a
horse-donkey hybrid. Mules are cultural idioms, “stubborn as a
mule,” being thrown around quite a bit. The problem with mules
is that they are sterile, unable to create offspring of their own.
However, donkeys and horses are two different species, not a
subspecies attempting to match.
Napoleon
Dynamite also made the idea of the “liger” (lion-tiger
hybrid) popular, and it’s something humans dabbled in. For
example, we know male ligers are sterile, but female ligers are not.
However, one must consider that even though female ligers aren’t
sterile, that doesn’t mean they will be able to produce healthy
or viable offspring themselves (though it has been documented at
least once). Again, these two cats are two very different species.
Hybridization
between two subspecies generally works, which can be seen in certain
tigers and plant species. There’s something called “hybrid
vigor” in which the resulting offspring is not only genetically
different but can be hardier, healthier, and grow bigger than its
parents.
The
National Library of Medicine posted a study that was devoted to
subspecies hybridization as a potential conservation tool for at-risk
species. They used subspecies of the Wild ass and its reintroduction
to Israel as their basis. They found there were no genetic or
behavioral barriers to subspecies hybridizations, that no niche
subpopulations formed, and that it is likely the weak genetic
differentiation between the subspecies that allowed for it. In their
opinion, low levels of divergence between subspecies could make for
good candidates for hybridization as part of genetic management.
Then
comes the ethical questions and concerns. The cheetah would lose the
unique subspecies characteristics. On the other hand, they’d
have increased genetic diversity, and a better chance of bouncing
back in the wild – their populations would be healthier, and
more resilient against potentially extinction level diseases and
climate disturbances.
It’s
a touchy subject, with many voices arguing for and against it.
Instead
of human voices, listen to the voice of the cheetah.
In
South Africa, there’s been significant cheetah population
growth, largely in part due to a conservation project that manages
and rehabilitates cheetahs. Globally, they’ve made a comeback
in the past, at least twice, so why can’t they do it again?
Yet, their genetics remain limited. Their fertility remains stagnant.
Their skulls remain asymmetrical, pointing to inbreeding. Their
genomes often exceed 90 percent homozygosity (genetic similarity).
The
house cat and dog have several inbred groups…and have
significantly lower rates of homozygosity.
Do
you want future generations to be able to see healthy cheetahs, not
only in zoological institutions but even on a safari? Do you want
future generations to be able to see the cheetah, in person, a
currently existing creature, or to never be able to see them, knowing
of them only as a recently extinct beast?
100,000
years ago, they ran across four continents. Today, they run from
extinction.
Cheetahs
have been survivors for over 100,000 years. It’s about time we
stepped up for their preservation and their future because if we do
nothing, we know how the story ends.
