All About Pronghorns
By Chuck Graham
I heard them before I saw them, thundering hooves kicking up shards of grass as a herd of 32 pronghorn antelope ran across a sweeping meadow in Grand Teton National Park in Wyoming. A marauding coyote was loping toward the flustered pronghorn, their white rumps standing out against their powerful, tan-colored hindquarters.
The fastest land mammal in the Western Hemisphere, and the second fastest land mammal in the world only behind the cheetah of the African Savannah, the pronghorn antelope (Antilocapra americana) isn’t actually an antelope after all. Its closest living relatives are also in Africa, the unique-looking okapi and the giraffe. Its distant relatives happen to be cattle and goats.
Sight and flight
The next time you look through a pair of binoculars and scan the horizon, that’s the equivalent of the pronghorn’s vision. Their eyesight is legendary. They can pick up movement three miles away, and with their huge eyes set far back on their heads, they can keep watch while their heads are down during feeding.
Running is actually their final line of defense. No other land mammal on the planet can keep pace with the pronghorn. Even the fastest animal in the world, the cheetah, flames out after a few hundred yards. Pronghorn can run 35 mph for four miles, 42 mph for one mile, and 55 mph for a half mile.
How are pronghorns able to sustain such speeds for those distances? They’re built for speed. They possess a large windpipe that enables them to take in a large amount of air. They also have large hearts and lungs, hollow hairs, and an extremely light bone structure. Their hooves have two long, cushioned, pointed toes which help them absorb shock while they are on the run, fleet of hoof.
The teary-eyed, cud-chewing pronghorns are still running from their distant past more than 10,000 years ago and are the living heritage of the Great Plains. Ghost predators like the giant short-faced bear, American (“false”) cheetahs, and long-legged hyena preyed upon pronghorns during the Pleistocene Era, but today they easily outrun predators like coyotes. However, pronghorns have been forced to deal with other obstacles such as fencing, and especially barbed wire.
Pronghorns flare out the white hairs of their rump when alarmed. It’s a warning to other members of the herd. Herds run in perfect unison in a tight oval-shaped formation — much like a flock of birds — meaning more eyes to see oncoming predators, but easily seen by predators too.
Running from extinction
The pronghorn’s range extends from the Canadian plains of Saskatchewan and Alberta, descending southwest into Minnesota and South Dakota, all the way down to central Texas, and west to central southern California. Subspecies of pronghorn include the Sonoran pronghorn, which occurs in Arizona and Mexico. Other subspecies are found in Oregon and Baja California.
It wasn’t until the Lewis and Clark Expedition in the early 1800s that pronghorns gained scientific notoriety. Unfortunately, by the turn of the 20th century, extinction of the pronghorn was a real possibility. Nearly hunted out, their numbers were a meager 13,000 when conservation efforts began by the 1920s. Conservation groups realized fencing was impeding their propensity to roam and migrate.
On December 31, 1936, then-President Franklin D. Roosevelt signed legislation to preserve 549,000 acres, beginning the recovery of pronghorn in North America. Since that initial conservation boost, pronghorn numbers have swelled between 500,000 and 1 million. Highest concentrations are found in Wyoming and Montana, where annual rainfall averages 9.8 to 15.7 inches per year. Pronghorn even outnumber people in Wyoming and parts of northern Colorado.
Fencing is still an issue for pronghorns, especially with sheep ranches, but pronghorn advocates are pushing to remove the bottom of barbed-wire fences and installing barbless bottom fencing — one thing pronghorns are not is big leapers.
With a perpetual urge to roam over open, expansive terrain from elevations between 3,000 to nearly 6,000 feet, it only makes sense that the pronghorn antelope performs the longest land migration in the continental United States. The only other land mammal to travel farther in North America is the caribou in Alaska.
The pronghorn’s 300-mile round-trip journey extends between Wyoming’s Upper Green River Basin and Grand Teton National Park. Their trip is grueling, requiring them to cross private property and, of course, to negotiate fence lines. The pronghorn’s biggest threats used to be predators and weather, but today they are cars, fences, and encroaching development.
Their migration is initiated when snows start falling in November. They start migrating south to the Grand Tetons across government land, private lands, and ranches. For three days, the herd is on the move until finally arriving at the Upper Green River Valley.
With long legs, short tails, and long snouts, pronghorn antelope have similar body types to deer. The color of their fur fluctuates from reddish to brown, tan or darker brown. Weighing between 75 and 130 pounds, these ungulates (hoofed animals) range from 31 to 40 inches tall at the shoulder.
A buck’s horns, not antlers, reach about 10 to 15 inches long, revealing the distinctive prong. Males have a black patch on their jaw below the eye. The females do not, and only about 40 percent of females have horns, which are smaller, at 1 to 5 inches in length.
The females typically have twins at the end of winter. The young weigh 5 to 7 pounds at birth. Amazingly, they’re up walking in less than an hour after birth. Four days later, they can outrun a man. At this time, coyotes and golden eagles are their biggest threats. To avoid these predators, the young hunker down and lie still. They have no scent at this time. Does visit the young about every five hours or so to check on them and nurse.
The pronghorn’s diet relies heavily on forbs (non-woody flowering plants) and brush. Grasses are only a small portion of their diet. Sagebrush can be critical to them, especially during long, harsh winters when snow levels run too deep and forage is unavailable. Pronghorns seldom drink water, gaining most of their moisture from the plants they eat.
With an average life span of 10 years, pronghorns have proven their hardiness on those wide open spaces crucial to their survival.
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