This female pronghorn was photographed in northwestern Colorado on July 7, 2018, one of a pair of them.
Pronghorns (Antilocapra americana) are two-toed, hoofed ungulates of the American West, with smaller ranges also extending into Canada and Mexico. They are often mistakenly called pronghorn antelope, but the second designation should be dropped since they are not in truth very closely related to African antelopes, despite a superficial similarity in appearance. In fact, the Latin name means “American antelope-goat” and is itself a misnomer because they aren’t all that close to goats either, taxonomically speaking. It might not seem like it, but their closest living relatives are the giraffes and okapis from Africa.
This group of four was part of a larger herd of 13 pronghorns, and were photographed in western Utah on September 30, 2019. Note the distinctive twin-forked horns on the male to the right, a feature which gives the species its name.
Pronghorns shed only the outermost keratinous sheath of their forked horns every year, while retaining a bony core to regenerate them for the next season. This partial shedding pattern is unique to these ungulates – members of the deer family shed and regrow their entire antler rack every year, while antelopes, goats, sheep, and cattle never shed their horns. Their eyes are very large and have a 320-degree field of vision, which is nearly a full circle.
These pronghorns were squirming under the bottom wire of a fence in central Wyoming on July 8, 2018. You can see the very large and protruding eyes, mounted on the sides of their heads, which give them a very wide field of vision. They probably have only very small blind spots directly in front of and directly behind them, which can of course be easily overcome by simple head rotation.
Pronghorns are in their own taxonomic family, and are also the only surviving members of that lineage – three other genera and a total of twelve different other species that used to exist in the North American family Antilocapridae before prehistoric humans arrived were made extinct after we got to this hemisphere. By the late Pleistocene, dozens of large animals were made extinct through a possible combination of climate change and human hunting pressure. We made 93% of the family Antilocapridae extinct within a few thousand years after we showed up. In fact, we almost made it 100%. The population of pronghorns in North America was dropped from tens of millions originally to less than 13,000 animals by the 1920s thanks to unrelenting hunting pressure. Not quite as low as the American bison population dropped (less than 100 animals) but damn close to extinction nonetheless compared to prehistoric levels.
Today, with more strict regulation on hunting, the pronghorn population is healthy at somewhere between 500,000 and 1 million animals, so at least for now the species is secure. (Well this is true aside from the very endangered and distinct Sonoran pronghorn, Antilocapra americana sonoriensis, which has been discussed elsewhere on my blog regarding the border wall. See link above for that discussion of this unique subspecies and the impacts that a border wall could have upon them and their possible extinction, joining their 12 other extended family relations.) At least we still have this species to remind us of the cost of our behaviors, and that we tend to make larger animals extinct whenever and wherever we arrive.
The same female pronghorn as in the lead photo at the top of the post wanders away across the hills, as a smokestack from a power plant west of Craig, Colorado emits gases and pollution into the air.
These interesting animals are the fastest land mammals in North America, capable of sustained running at 35 MPH for 4 miles, and 55 MPH for a half mile. This is far faster than any living North American predator can muster, so why did they develop it? It is believed that they evolved this speed (and the large heart, trachea, and lungs to supply the oxygen required to support it) to avoid a now extinct predator called the American cheetah. I haven’t found information online yet regarding why the cheetahs were made extinct, but I’d be willing to bet that humanity had something to do with it since they were still around as recently as 15,000 years ago….
More individuals of the Utah herd shown earlier escape the road easement by slipping under the fence. Even though I’ve been aware of their propensity to go under fences rather than jumping over for many years, I still find this behavior somewhat surprising for these fairly large animals. If deer can jump over fences with such agility, why don’t pronghorns do the same?
I’ve taken photos of pronghorns slipping underneath fencing in several states. Pronghorns do not really jump and instead prefer to cross fences by wriggling underneath the lowest wires, which they sometimes do at a surprisingly high speed. In recent decades various landowners and land management agencies have been trying to improve the ability of highly mobile, wide-ranging pronghorns to migrate to different grazing areas by changing the lowest wire of fences from barbed to smooth, which causes far less injury to pronghorns. As long as the rest of the upper wires remain barbed the fences will still contain large cattle (which neither jump over nor squirm underneath standard fencing) while permitting pronghorns to go about their lives more readily. The fence shown above in western Utah has indeed got a smooth base wire, which explains perhaps why the 13 pronghorns in this particular herd didn’t hesitate to cross it to get away from me, my car, and my camera.
I have deliberately spent some time trying to get photos of pronghorns crossing fences by going underneath them in the past several years. Here, the central Wyoming band exhibits this behavioral quirk.
Well at least cameras won’t hurt or kill them. 
What are pronghorn’s horns/antlers called? Have some knife handles which were described as hell horns!
They are actually simply called horns, but they are unusual in two regards. First is that they are the only horns on animals that are shed, and second they are also the only horns that are forked as opposed to single. Most creatures with horns retain them permanently (never shedding them) and they are unforked, whereas antlers are annually shed and commonly branched. In the ecological sense, this is what separates members of the deer family from members of the bovine, goat, antelope, and sheep families. Pronghorns are intermediary between those two main groups of ungulates and therefore occupy their own branch on the tree of life in this regard.