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.
Late one afternoon as I drove down a dirt road at Carrizo Plain National Monument in California, where a small herd of once-native pronghorn has been reintroduced, I saw a plume of dust in the distance and something moving incredibly quickly -- so fast and steady I thought it was someone on a dirt bike. But no off-roading is allowed out here. What on earth would be moving like that? The single shape seemed to be flying along the base of the hills.
And then I realized, it was a pronghorn -- and the reason it seemed to be zooming along so effortlessly is because 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 without breaking a sweat.
Now That's Fast!
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.
"If I'm in reasonable physical condition, I can usually run down a 5-day-old fawn," says John A. Byers, a scientist who has studied pronghorn for over 20 years and has had to test out these speeds while trying to tag fawns for long-term study. "A contest against a 7-day-old fawn is a toss-up, and a 10-day-old fawn can in effect thumb its nose at me with impunity."
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. Aahhh... now we see 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.
And now we have a marvel of speed still roaming the prairies, perhaps a relic but still fascinating.
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, their main food source.
Here is more about fence-removal and modification efforts around Yellowstone: