• Chuck Adams

The Shocking Science About String Jumping


Animal reaction time, arrow speed, and shot distance can be combined to predict how likely you are to bag a critter that hears your bow. The following facts might blow your mind. (My ground breaking article from Bowhunting World Magazine reprinted by popular demand.)




If you haven’t experienced string jumping, you haven’t bowhunted very long.


I tasted this bitter pill during my first bowhunt for blacktail deer in my native state of California. I was an inexperienced teenager, but I practiced hard with my Ben Pearson Hunter recurve bow and Herter’s aluminum arrows. Within 30 yards, I naively believed that bucks would be in serious trouble.


I got my first dose of reality on the second day of deer season. I tiptoed close to a handsome forked horn buck as he chewed on a bush. I was hyped up, but the arrow came back smoothly and the shot felt good. To my horror, the shaft smacked empty dirt at least two feet behind the deer. That animal crouched and leaped ahead so fast I did not even see the move.


At first I thought I had blown the shot. Then I realized my arrow was buried in about the right place. It was the first of many sad lessons learned about shooting a bow at quick-footed critters.


The late, great Fred Bear told me many years ago that it took him three years to bow-bag his first deer. At the tender age of 16, after three years of trying, I also shot my first archery buck. I felt honored to follow in the footsteps of my boyhood hero.


Those three years included dozens of mistakes, but my single biggest frustration was string jumping. Even with a new, faster and quieter Wing Thunderbird recurve bow and lighter Easton aluminum shafts, it seemed that every close-range buck ducked my arrow. Unlike blacktails in most places, California deer were small, quick, and scared to death by large populations of mountain lions, coyotes, and human hunters. My arrows were flying less than 200 fps, and deer easily hopped out of the way.


The last straw came when I decided to aim two feet in front of a 30-yard buck. The deer had me nailed, with ears cupped ahead and eyeballs boring right through me. Yet when I released, the rascal stood like a statue and watched the Bear Razorhead broadhead hit in front of his chest. Only then did he swap ends and flee.


Sweet success finally happened a few days later. A small two-point fed from a thicket at sundown. I guessed the distance at 40 yards and let fly. The deer did not move, and the arrow smashed home with a satisfying plunk. Until that instant, I had begun to doubt I would ever see my arrow hit a deer.


Contrary to common belief, a target animal almost never “ducks the arrow”. In rare cases, on ground-level hunts, a deer, antelope, elk, or other fast critter might see your hand move as you release the bowstring or catch the glint of an arrow arching through the air. This was more likely 100 years ago when Pope, Young, Compton, and other bowhunting pioneers sneaked around and shot arrows under 150 fps. Even half a century ago, bowhunters like Fred Bear almost exclusively hunted on foot and shot arrows below 200 fps. Stalking at eye level with game and shooting slow arrows increased the odds of animals seeing the shot. But today, with fast arrows and most hunting accomplished from tree stands or enclosed ground blinds, the reason animals jump is almost always sound—not sight.


I am surprised that myths and confusion still abound among bowhunters about string-jumping. Today’s age of hunts on film and precise electronic calculations should remove a lot of random speculation about the ins and outs of shooting at fast-footed game. Yet arguments still rage at archery shops and hunting camps. Can deer duck a fast arrow? How much do deer crouch to load their leg muscles? Can an arrow ever beat the sound of the bow?


The following, mind-blowing facts should help to settle questions about how and why animals manage to evade even fast-flying shafts.


First, let me tell you there is no such thing as a silent bow. Unless the wind is blowing and nearby cornstalks are rustling, a low-flying airplane is passing overhead, or rain is pounding the countryside, critters like whitetail deer WILL hear you shoot. In today’s age of aggressive cam-bows, super-light arrows, and metal-jawed release aids, even moderately hushing a shooting setup is difficult.


With rubber string silencers, brush buttons against the limbs, an arrow weighing nearly 600 grains, and a finger release, the recurves and longbows of yesteryear shot with a muted swish and thump. Yet deer inside 30 yards still registered the sound. The solid crack of a modern compound bow—even one dampened with limb cushions, string and cable silencers, and a flex-stabilizer—will be heard by every nearby animal.


In my experience and that of several deer-hunting buddies, a close-range whitetail deer will jump the bowstring at least 75-percent of the time. Pronghorn antelope hunted on foot are almost as bad, and even innately calmer species like mule deer can also come unglued if intimately threatened by the close-range sound of a bow.


All things considered, whitetails are the string-jumpiest critters on our continent. Lucky us. More archers hunt whitetails in more places than all the other 28 varieties of North American big game combined.


A deer’s string-jumping movement happens so fast that most bowhunters never see it. In many cases, archers believe they have muffed the shot when they miss or score a poor hit. Fact is, a high percentage of “bad” shots would have been perfect if the animal had simply stayed put.


Thanks to modern filmography, we now know that string-jumping animals follow a surprisingly predictable pattern. A critter hears the bow, crouches in the front end, and jumps away to avoid danger. Deer and other species often lean away from threatening sounds as they drop to load their leg muscles before they spring away. Which direction they run is anybody’s guess.


Some animal reactions to noise are mind-blowing. African impala antelope are similar in size and temperament to Texas whitetail deer, and they are chased by predators every day of their lives. It should be no surprise that they are world-class string jumpers. However, one nice impala did surprise me with his stunning attempt to dodge an arrow.


I shot the animal at 20 yards from a 20-foot tree platform, and as usual I aimed at the bottom edge of his brisket to compensate for the expected duck. The arrow sliced both lungs and lodged in the far shoulder, and the impala dropped after running 50 yards. Something seemed odd as he ran, and I realized my arrow had angled UPWARD through the antelope despite the downward shot. A quick inspection of the carcass confirmed it.


Back at the water’s edge, I found a deep dent where the antelope had dropped completely to the ground and driven his shoulder into the mud in a frantic attempt to get away. When my arrow arrived, the impala was on his side with his left ribcage toward the sky. The arrow entered low and angled upward through the chest. If I had not aimed below the chest cavity, that impala would have completely avoided my arrow.


The basic dropping, leg-loading, and lunging away of an impala, whitetail deer, and other speedsters might be predictable, but variables can cause bow-shooting trouble. An abundance of slow-motion videos of string-jumping deer are available on the Internet, and I would encourage you to watch a few so you understand what you might be up against. Some even completely relaxed deer drop their bodies all the way to the ground before the arrow arrives, and a few flop on their sides like my African impala did. Others respond with a half-crouch before running away. As mentioned before, a handful of deer do not react at all.


It seems that regional and gender variations in deer can affect string-jumping too, along with more obvious things like rutting preoccupation, bow-masking wind noise or rainfall, etc.


Here’s one example. It has been my experience that southern whitetails are jumpier then northern deer. Why this is remains a mystery, except that animals in states like Alabama and Texas are smaller and seem to be naturally more agile. Deer in the South might also be hunted harder and more tightly wired than animals in more remote places like Montana and Saskatchewan.


Similarly, a number of bowhunters I know have confirmed my belief that does are more prone to jump the string than bucks. During the rut, this makes perfect sense. Females tend to keep their wits about them while males strut around in a hormone-triggered daze. But even non-rutting whitetail bucks seem a bit less string-jumpy than females.


A seasoned bowhunter does not need slow-motion videotape to know the legendary speed with which a deer can evade an arrow. For example, western Montana offers a late-season archery bowhunt for whitetail does. I lived in the Big Sky State for several years, and took full advantage of this chance to fill the freezer with venison.


One morning, a fat doe fed toward my brush blind and quartered away at 30 yards. I scored a perfect double-lung hit. She whirled, ran the opposite direction, and collapsed. Amazingly, I shot at her right side, but the nock and fletching was sticking out the LEFT side with the broadhead buried in the right shoulder. In a few milliseconds, that deer had crouched and whirled 180 degrees before the arrow arrived! I never saw it happen.


Back then, my bow-and-arrow was slow—a touch over 200 fps—and as I’m about to discuss, that left plenty of time for the Montana doe to perform her Olympic-level evasion move.


String-jumping is a five-part process. First, the bow makes noise. Second, the noise travels to the animal. Third, the animal’s ears register the noise. Fourth, the brain processes the noise and sends a signal to the muscles. Fifth, the muscles receive the signal and react. Thanks to modern technology, the approximate timing of this process is no longer a mystery.


To understand animal reaction times, it is instructive to first consider world