The pronghorn is one of the often overlooked mammals on the North
American continent. Usually mislabeled as antelope, this species of
grazer is actually more closely related to goats and vast herds once
roamed throughout the plains.
At
Carrizo Plain National Monument
in California, a small herd of once-native pronghorn has been
reintroduced.
Pronghorn are the fastest land animal on North America. In fact, it is
the second fastest land animal in the world with only the cheetah
clocking faster speeds.
The difference, though, is that while
cheetahs can reach a faster top speed, they can only hold that speed for
a few hundred yards. Pronghorn can sustain blazing speeds for miles,
and in a distance run would easily beat a cheetah.
Pronghorn
can reach top speeds of around 55 mph and can run at a steady clip of
30 mph for over 20 miles. For comparison with the other fastest land
animal, cheetahs can reach speeds of over 60 mph but only for sprints of
about 700 yards.
Pronghorn could finish a marathon in about 45 minutes,
while a human would be working hard to finish a marathon in over two
hours.
This speed starts at a very young age. Females give birth
in the spring to one or two fawns, which stay hidden in the grass until
they are old enough to outrun their primary (non-human) predators of
coyotes, bobcats and golden eagles. This happens in just a couple weeks.
In fact, a fawn can outrun a human in just a matter of days after being
born.
But if a pronghorn can so easily leave every
predator on North America in the dust, even at a very young age, just
how and why did it get to be
this fast?
A Speed Machine
According
to Stan Lindstedt, a comparative physiologist at Northern Arizona
University, there is no secret trick to pronghorn reaching such
incredible speeds. "It has simply perfected the same equipment that all
mammals have," he told
Discover Magazine.
"We
found that pronghorn have an extraordinary capacity to process oxygen.
Each antelope consumed between six and ten liters of oxygen a minute,
which is five times as much as a typical mammal of similar size would
burn--a 70-pound goat, say--and more than four times as much as Carl
Lewis would consume if he were shrunk to the size of a pronghorn
antelope. (A pronghorn stands about three feet at the shoulder.)
Compared with the goat, it has bigger lungs with which to absorb oxygen,
slightly more blood hemoglobin with which to transport the oxygen from
the lungs to the muscles, and slightly bigger and leaner muscles
containing a higher concentration of mitochondria--the cellular
organelles that burn oxygen to provide power for muscle contraction. In
other words, there are no tricks to the pronghorn antelope."
So
why are they so amazing at running?
Outrunning Ancient Predators
After 20-some years of wondering about pronghorn in his researches, Dr. Byers has come up with a compelling theory.
Though there is no predator
today who
can catch a pronghorn at a sprint, this wasn't always the case. Dr.
Byers says the pronghorn runs this fast because it is chased by the
"ghosts of predators past" -- including American cheetahs. This is why pronghorn can only be beaten by cheetahs in a sprint.
In American Pronghorn: Social Adaptations and the Ghosts of Predators Past,
Dr. Byers argues that the pronghorn perfected its running prowess well
over 10,000 years ago when the North American continent was still home
to swift-footed predators like cheetahs, long-legged hyenas, the giant
short-faced bear, huge jaguars and saber-toothed cats, along with the
more familiar, albeit slower, coyotes and wolves.
Predators were
much bigger and much faster back then, and thus forced the pronghorn --
and some similarly built and now extinct cousins -- to evolve to be
incredibly fast. Though the predators disappeared, the pronghorns'
ability to outrun them has persisted.
So now we have a marvel of speed still roaming the prairies, perhaps a relic but still fascinating.
Modern Threats
There
are two things, however, that pronghorn cannot outrun, and these
threats come from humans. The first is habitat loss from urban sprawl,
and the second is miles upon miles of fencing along ranches, roadsides,
farms and developments.
Habitat loss is a rather obvious threat.
Pronghorn need vast spaces to forage for food. The less grassland they
have, the less food they have, and the lower their chances for
successful reproduction and survival. Not as obvious is the threat of
fencing.
Pronghorn
are amazing runners, but they cannot jump fences. We may think that
because they look a little bit like deer, they can spring over a fence
with the same lightness and nonchalance. But that is not the case, and
miles of fencing put up along migration routes is a serious problem by
limiting access to food and blocking off paths to get access to food, as
well as room to outrun remaining predators.
As the
National Parks Conservation Association
states, "These 'new threats' not only restrict their greatest asset to
escape predators but also their ability to migrate over long distances
required to find adequate snow-free habitat and forage. As wildlife move
from one place to another they do not distinguish between state,
federal and private land; they go where there is habitat. Conserving
pronghorn migration on public and private lands outside of the
Yellowstone National Park offers the last best hope for this iconic
species."
Fence removal programs have gone a long way in helping
the pronghorn.
In 2010, the Yellowstone Field Office worked with
landowners and the Gallatin National Forest to remove two miles of
wooden fence and barbed wire, restoring the local pronghorns' migration
route.
Similarly, in and around Carrizo Plain National Monument, miles
upon miles of old barbed wire fencing remained in the area decades after
the last human residents had moved away, creating a somewhat haphazard
maze of barbed wire throughout the area. Volunteers continually help to
remove or modify these fences to provide the newly reintroduced
pronghorn room to escape coyotes and find forbs, like milkweed, which are their main food source.
Link:
http://www.treehugger.com/natural-sciences/nature-blows-mind-north-americas-fastest-land-animal-can-outrun-cheetah.html
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Pronghorn Range
