How to Field Judge a Pronghorn

America's pronghorn antelope aren't just cowboy country's ultimate starter species. They're tremendously fun to hunt and present certain unique challenges.

According to an excerpt from Boone & Crockett's Field Guide to Measuring and Judging Big Game, 2nd Edition, pronghorn antelope are currently the second most populous big-game animal west of the Mississippi. Almost every state in the West now offers a pronghorn season. Wily, fleet, and possessed of extraordinary eyesight, they're easy to find and difficult to shoot. And before you shoot, you must overcome the trickiest of all the pronghorn-hunting hurdles: field judging your trophy.

By my book, only bears are more difficult to accurately field judge. Estimating size must be done via somewhat subjective comparisons to eye diameter and ear and head length. To quote B&C's Eldon L. "Buck" Buckner, who writes the field-judging guides for B&C's site and scoring books, "Nearly always, the first-time successful pronghorn hunter finds the horns of his buck to be much smaller than they appeared to be when he made the shot."

Made up of fibrous growth around a bone core, a pronghorn's headgear sheds each year, much like their antlered cousins. Sheaths drop around mid to late November, leaving a spike-like black stump that quickly grows back into full-size horns. Animal health and habitat conditions play major roles in determining growth, so even though antelope are a properly horned species, their horn size varies from year to year.

What's a Trophy?

Currently, an 80-inch antelope makes B&C's four-year book, and an 82-inch buck earns a spot in the all-time book. However, like all B&C trophies, such animals are hard to find. When B&C first listed pronghorn in the 1952 record book, the minimum score for entry was 70 inches. Today, a 70-inch buck is still a very nice trophy, and if you're selective and hunt hard, a 70-incher is well within the realm of possibility.

Unless you're hunting one of the legendary units in New Mexico or Arizona, think really hard before passing up any buck over 75 inches. Such pronghorns are typically fully mature, heavy-horned animals and make a really impressive mount.

Mass, Prong, Height

Of the professional antelope guides I've hunted with, none remotely equal the level of expertise of Dr. Pepper Murray, an orthopedic surgeon with a fascination with pronghorns. "MPH applies to pronghorns," he says. "Easy to remember. They're America's fastest mammal, so apply MPH: mass, prong, height…in that order of priority."

"If you're looking for a book buck, remember the 'rule of sixes,'" Murray says. "Six-inch base, six-inch prong, sixteen-inch height. That's the foundation for an 82-inch buck."

Horn length (38 percent of total score*)

Historically, horn length has been valued more than any other characteristic. Saying "I shot a 16-inch antelope" was like saying you'd shot a 30-inch mule deer.

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Use ear length and head length as references. Ears are typically around six inches, and head length is usually about 13 inches. Ideally, horn height should appear two-and-a-half to three times as long as the ear.

Murray suggests that when the buck is looking at you, the ear tip would appear to be about seven inches up the horn. You can use that to estimate horn height. However, a side view is necessary to estimate length past the turnover.

Be aware that even though they appear quite tall, nearly straight horns with little hook up top will measure much shorter than lesser-height horns with long curved points that hook in and downward.

Mass (49 percent of total score*)

Although horn length is the traditional benchmark of choice, note that around 50 percent of the total score is derived from mass measurements alone.

Because such a large percentage of score is drawn from mass measurements, heavy horns are critical to "making book." Four circumferences are measured. Take the first measurement right at the base, then divide the horn into quarters and measure the circumference at the dividing lines.

Mass is best judged from the side. According to the B&C Field Guide, a pronghorn buck's eye averages just over two inches, measured front to back. You want the horn base visibly bigger than the eye. "Also, round mass will give you a lot more inches than flat mass," Murray adds. "So you want to get a good look from the front to see if his horns are wide and flat or wide and round."

Beware of prongs that fork from the horn below the height of the ears, which will likely result in only one mass measurement below the prong, and watch out for horns that don't carry mass above the prong. Willowy tops result in a score that is several inches less than ideal.

Prongs (13 percent of total score*)

Prongs, also known as "cutters," can be the joker in the deck. Sometimes a tall, massive buck will have short, insignificant prongs. If you like his look, shoot him anyway — he'll still be a big, mature buck with plenty of eye appeal. However, if you're looking for a really high scorer, you need a buck with big prongs.

Average prongs run three to four inches when measured from the rear edge of the horn to the tip of the prong, around the curve. A great prong will measure six inches and will fork from the horn above the tip of the ears.

Prong length is perhaps the easiest of the various elements to judge. A mature buck's main horn is roughly two inches from back edge to front edge just below the prong.

Tools and Time

Buy good optics, get into the field, and spend lots of time observing antelope. "Bottom line," Murray says, "is you've got to look at a bunch of bucks. Take video. Study it. Compare. When you finally see a really big one, you'll know it."