How an Arrow Kills?

How Arrows Kill

By Chris Eberhart:

It was quiet and there wasn’t the slightest breeze. Chipmunks scurried about acoustic in their movements informing my ears of every step. A moose passed by, probably a kilometer away, and I could hear every step. The steps were accompanied with the guttural music of an amorous bull. For over three hours I sat as still as possible in my stand, listening, enjoying the sounds of autumn, and waiting patiently for a bear to show up.

A subtle movement among the shadows caught my attention and suddenly there it was. A bear, or rather the head of a bear, peered out from the wall of spruce a mere eight meters away. The black bear looked right up at me in my treestand, three times, each time glancing towards the bait and then up the hill and back again. Seeming unsure of the situation the bear cautiously stepped forward out of the shadows and turned up the hill, revealing a white scar on its shoulder.  It quickly turned back into the spruce, never offering a shot. Listening intently I tried to pick up the sound of footsteps, unsuccessfully.

My stand was positioned along an old logging road which enabled me virtually an unlimited view in either direction. In order to get to the bait the bear must invariably cross that road. For fifty minutes I watched closely. Just as I was beginning to think the bear must have decided otherwise and departed that black head once again emerged from the shadows, this time staring at the bait from the other side.  Initially I thought it must be a different bear, but a few steps later that scar on its shoulder proved it the same Ursidae as before. The black bear’s ability to move through the forest silently is uncanny. A friend of mine, and experienced bear hunter, once described it to me as “quieter than a mouse wearing slippers walking across a shag rug.” Though this may be a mild exaggeration, black bears are indeed very quiet animals. The bear edged towards the bait, eased around the end of the barrel and looked inside, now quartering slightly away at twenty meters.

At full draw I anchored, and aimed carefully at the middle of the middle slightly back off the shoulder to compensate for the angle, and released. My arrow hit where I aimed and buried to the fletching with a loud crack. In a blur the bear jumped sharply forward, slammed into the barrel, spun a circle, and bolted away, attempting to circle back. A second or two later an unforgettable death moan echoed through the Maine forest. The bear had fallen a mere forty meters from where it stood at the shot. My arrow downed that bear in about three seconds.  Impossible you say? Lucky shot? Or, is this a typical situation for a bowhunter?

One of the first questions that hunters unfamiliar with bowhunting ask is how an arrow kills? This is usually followed by some comparison to more familiar hunting rifles?  And the final question asked is often regarding the effectiveness of the bow and arrow as a hunting weapon? These are very legitimate questions and vitally important to anyone considering bowhunting, or simply considering bowhunting as a viable and ethical hunting form.

How an Arrow Kills

Generally speaking arrows tipped with razor sharp broadheads kill by cutting major blood vessels, both arteries and veins. This causes massive blood loss, reduced blood pressure, and loss of oxygen to the brain. This process is known as hemorrhagic shock.  An animal needs to lose about one third of its blood volume for this to happen. This process can take from seconds to several hours depending on where an animal is hit. Another way in which an arrow kills is by puncturing the lungs. Lungs are contained within a pneumatic lining that is airtight and functions like a vacuum allowing the animal to breath. When the lungs are punctured this function is disrupted and the lungs collapse. The collapse of the lungs is known as a pneumo-thorax, and interrupts the exchange of oxygen in blood. When this happens the supply of oxygen to the brain is immediately interrupted and death comes within seconds.  A third way that an arrow kills an animal is by cutting through the heart. Hitting the heart also causes death within seconds by stopping blood circulation, and again transport of oxygen to the brain. Since the aiming point on all big game animals is the lung area, most good shots result in a combination of these three factors. If you hit the lungs you will automatically slice through numerous veins and arteries, causing death within seconds. The same goes for a heart shot. 

The expedient expiration may sound like exaggeration until you see the wound channels caused by modern broadheads.  Typical modern broadheads have between two and four razor sharp blades with a cutting diameter mostly between 2.5 and 4 centimeters, depending on design. A typical three bladed broadhead creates a wound channel that has a circumference of almost 12 centimeters.  Any wound channel of this size through major organs such as lungs, heart, or liver causes excessive blood loss. A good solid sharp broadhead is critical for a hunting arrow to do its job effectively.

Shots outside of the chest cavity are equally deadly with bow and arrow. These shots sometimes happen but should never be purposely attempted. Depending on the shot the chances of an expedient recovery vary. Any arrow that errantly hits the abdominal cavity is without exception deadly.  These animals die by a combination of hemorrhagic shock and peritonitis.  However, just like with a rifle, the time until exitus takes far longer with stomach and intestinal shots, and recovery of such a wounded animal can prove difficult.  Other possible shots, albeit poor ones, are shots to large muscles, such the back legs or neck. These shots can sometimes prove as fatal as quickly as a lung hit, if large arteries, such as the femoral artery, are hit. In cases where large arteries are not hit recovering these animals is nearly impossible, because unlike bullet holes that blast a hole through muscle and tend to get infected, causing unavoidable slow death, clean slices of a razor sharp broadhead are far more likely to heal. Most big game animals will survive such hits without notable hindrance. Spine shots are basically the last possibility. Again, these should never be purposefully attempted, but if a game animal’s spinal column is severed it will fall to the ground. Another arrow to the lung area is always necessary to dispatch such an animal. Whether shooting bow and arrow or rifle a bad shot is a bad shot and I don’t want to dwell on this. Every hunter has a responsibility to take shots only within his effective range and ability regardless of which weapon at hand.

Arrow Bullet Comparison (Penetration)

For readers who are unfamiliar with bowhunting arrows and equipment it is helpful to describe how bullets and arrows differ in the way they impact and kill an animal.  Bullets kill by high energy impact that crushes both bone and tissue. They often immobilize animals by breaking major bones, and shocking the complete neural system.  The common measure of this capacity is kinetic energy, measured in joules. Most hunters are quite familiar with minimum joule requirements for hunting certain species in some countries. Broadhead tipped arrows, on the other hand, kill by cutting vital tissue, and because of their form and physics of arrow flight do not need the excessive energy found in bullets to penetrate and kill effectively.  Arrows will often times penetrate far deeper than a bullet through more economical use of far lower energy.  

Let me explain: Bullets are dull projectiles that rely fully on energy to penetrate. The energy an arrow uses to penetrate an object is directed to a very sharp tip. The difference can be demonstrated through a simple experiment. Strap a hide, or thick cloth, of any game animal to a solid frame. Pick up some rocks and try to throw the rocks through the hide from close range. You will find this nearly impossible, sort of like digging a hole with a baseball bat. Now walk up to the hide with a sharp knife, or even just a pointed stick, and with a short thrust of your forearm poke a hole in the hide. With far less effort (energy) than throwing rocks you will be able to puncture the hide.  The point here isn’t to infer that bullets are not effective hunting implements. The point is that bullets and arrows work differently, and the energy required for arrow penetration is for less than that of bullets.

Kinetic energy is mass multiplied by velocity squared divided by two.  The kinetic energy of a common caliber (30.06 with a normal load and 9g bullet and a muzzle velocity of 800meters per second) is 2880 joules. An arrow (35g) shot from a 70 lb hunting bow  at 90 m/s comes in at 141 joules. By this calculation the bullet has 20.4 times the energy as the arrow.  This however means very little in the realm of penetration, since the arrow cuts cleanly through tissue that the bullet must rip and tear. Since mass is more important to penetration than velocity a far better way to measure and compare the penetration power of bullets to arrows is momentum. Momentum is simply mass multiplied by velocity. If we do the calculation with the same bullet and arrow we come up with the sum of 7.2 Newton for the bullet and 3.15 Newton for the arrow. This is a factor of only 2.28 times.  Arrows with their far more direct impulse will have often times more penetration than a bullet. Considering the maximum effective range of most archers is around thirty meters, the energy for good penetration is readily available for a bowhunter within that range.  What this means to the bowhunter is simply that a normal modern hunting bow has enough penetrating power to shoot through most common big game animals within normal range. And as long as this range is strictly observed arrows are as effective as rifles within their respective range (up to 300 meters). 

Comparisons have been made between the time of immobilization between arrow shot and rifle shot African big game (1). The time difference between the rifle and bow shot animals was mere seconds. The principle difference being the distance covered after the shot. Almost all animals covered some distance after being shot with an arrow, whereas a portion of the rifle shot animals fell where they stood.  It must however, be understood that a rifle shot animal that falls where it stood often takes the same amount of time to expire as one that flees, it is simply unable to flee due to massive skeletal and neural disruption.  A paradox to this situation is the fact that many game animals shot with arrows do not actually run away at all. A well placed arrow shot at an animal that is completely unaware of the lurking bowhunter often passes through the chest cavity seemingly without the animal fleeing. In this case these animals do not sprint away, rather they continue walking or feeding until they simply fall over, unaware of impending death or even the danger they were in. Those who consider bowhunting unethical due the fact that animals doe not die “in the fire” should definitely consider this. The key to short blood trails is taking good shots, a truism no matter what weapon you choose.

Range, Shot Placement, and Self Control

The effective bow range of most hunters is within thirty meters.  Of course, this varies by hunter. I consider effective range whatever distance an archer can put 9 out of 10 arrows inside a 10 centimeter diameter circle. Some hunters have to limit themselves to shots less than twenty meters, and I have met hunters who were effective at up to seventy meters.  In my own hunting experience most of my actual shots are less than twenty meters, with my average around fifteen.  The closest shot I ever took was five meters, and the farthest forty.  Hunting so that game animals are so close you can even smell them is one of the main attractions and challenges of bowhunting.

Even when game animals are at such close range the deal isn’t yet done. A bowhunter must wait for the correct angle before shooting.  The most common shot position is having game standing broadside. This gives the archer a clear shot to the lung area. The most effective shot angle, however, is quartering slightly away.  An arrow shot from this angle almost always enters the heart lung area causing a quick death.  A well placed arrow in either of these positions will generally pass completely through the animal leaving a copious blood trail to follow. Most other shot angles generally speaking shouldn’t be taken with bow and arrow, or at least not without a great deal of experience. It is also important that bowhunters take shots that enter just behind the shoulder on most large animals. The heavy shoulder bones of big heavy animals can sometimes stop arrows, so it is simply best to avoid them. This is a little different than rifle hunting where the shoulder is the optimal target for massive skeletal disruption. I have often had large mature animals well within shot range only to let them pass without firing an arrow because a good shot angle never presented itself.  Being patient, knowing your limitations as an archer, and waiting for good shots, is a major part of bowhunting.  

Effectiveness of Bow and Arrow as a hunting weapon

Hunting with bow and arrow is a common practice in much of the world (more about that in the next issue). In many places hunters never stopped hunting with bows and arrows, and have been doing so for the last few millennium.  That pre-history time span speaks for itself.

Though not as widespread in Europe as in North America bowhunting is allowed in numerous countries, some notable ones are France, Spain, Hungary and Denmark. These countries all considered the effectiveness of archery equipment and determined it appropriate for hunting. For example, in Denmark, during the process of considering legalizing modern bowhunting, a thorough study of the effectiveness of the bow and arrow as a hunting weapon was conducted over the course of five years.  The results confirmed killing effectiveness of the bow and arrow rivals other forms for firearm hunting, both stand hunting and driven hunts, while hunting roe deer. The results of this study led to the legalization of bowhunting in Denmark (2). There have also been many other studies of the effectiveness of bowhunting in the United States and Africa (3)(4).

In the United States alone there are over three million licensed bowhunters, who harvest millions of game animals each year. In some states the annual harvest by bowhunters of whitetails makes up between 25 and 35 percent of the total harvest (5). And many suburban areas, urban areas, parks, and military bases bowhunting is the only form of hunting allowed. (This is something that could perhaps be a reasonable consideration for some urban European areas with wild boar problems.) The numbers alone are a good testimony that bowhunting is certainly an effective form of hunting.

There isn’t a land animal on this planet that cannot be hunted and killed with a bow and arrow. In fact, very animal on this planet has at some point been killed by bow and arrow, from rabbit to roe deer, from boar to buffalo, from grey fox to grizzly, and even the big five, all as recently as this year.  The key to successful harvesting of game animals is hunting well enough to get within bow range, and being patient and careful enough to make a good shot. For those of you who would like to consider taking up the path of the bow I will cover where and how to get started in the next issue.

 

Authors Note:  The topics mentioned above are all highly complex, and this article is meant merely as an introduction to a few important topics related to bowhunting.  For further information on the physics of shooting, the energy involved, and the effects of both bullets and arrows this is a list of resources available on the internet:

European Bowhunting Association:  www.europeanbowhunting.org

National Bowhunter Education Foundation: www.nbef.org

CIC:  www.cic-wildlife.org (search+ bow hunting)

 

Sources:

1. Ludbrook JV, and Tomkinson AJ, Game and Fish Preservation Board Natal South Africa, “Evaluation of Bow Hunting as a form of Recreational Hunting in Natal Parks” 1985

2. Evaluation of The Danish Bowhunters Association & The Danish National Forest and Nature Agency´s  Statistics on Roedeer (Capreolus Capreolus)shot with bow and arrow in Denmark Between 1 October 1999 –15 January 2004

3.Mayer, Kenneth E. and Samuel, David E., California Department of Fish and Game,  „A Review of Bow Wounding Literature” 1992.

4. Ashby, Ed Dr., “Momentum, Kinetic Energy, and Arrow Penetration” 2005; “Arrow Lethality Study Update” 2006.

5. Michigan Department of Natural Resources, “Deer Hunting Harvest Statistics” 2004: New Jersey Division of Fish and Wildlife, “Deer Hunting Harvest Statistics” 2004.

3 Responses to How an Arrow Kills?

  • [...] How An Arrow Kills – Bowhunting Wild Food: A detailed and well explained analysis of how an arrow kills big game and a discussion of the bow & arrows merits as a hunting device. Very interesting stuff! [...]

  • C
    June 16, 2012

    GREAT article! I’m new to bowhunting, and most of my friends are “gun guys.Now I’ve got some information ammo for the next gun vs. bow conversation. Please keep these great articles coming!

    • admin
      June 16, 2012

      Thank you for the kind words of encouragement. I’ve got some more stuff like this coming up soon. C

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