Ethical hunting is a difficult issue, for one man's hunting endeavor is another's immoral act. We make no attempt justify hunting or philosophize on the subject. Instead, the physics of the process is covered, distilling down to just two numbers that FlyingSticks calculates: the Probability of an Ethical Kill and the Maximum Ethical Range for various game types.
The ethical hunter aims to achieve a quick and clean kill. This usually involves causing catastrophic bleeding to vital organs, namely the lungs and heart, so that the animal quickly loses consciousness due to the lack of blood flow to the brain. It is possible to cause a quicker death by head shots, however the target area is significantly smaller and sometimes encased in thick bone.
Wounding is to be avoid at all cost - it is cruel, traumatizing and simply poor sportsmanship. Further the hunter should feel and show respect for the quarry before and after the shot.
To achieve this level of sportsmanship, the hunter needs to develop appropriate skills and a strong awareness of his or her shooting and equipment capabilities. To assist in this regard, FlyingSticks makes a technical calculation of the probability of an ethical kill. This is a statistical assessment based on many factors.
archer's grouping form
range estimation error
wind drift and wind gust or uncertainty
game type, size and legality
arrow penetration
broadhead blade cut width
Each of these is covered briefly below. Essentially a probability associated with each factor is calculated and these are weighted and combined to achieve a probability of an ethical kill. From this the maximum ethical range can be calculated for the current setup.
Obviously, the archer requires the skill to reliably hit the target's kill zone at the proposed distance. This is fundamental and one should be very aware of one's capabilities as it determines what can be achieve in ideal conditions.
FlyingSticks endeavors to keep track of your skill as an archer by assuming you continue to enter your groups size at some range or even a round score. You can easily fool FlyingSticks, but that is not in anyone's interest.
An error is estimating the distance to the target has a significant impact on arrow placement, no matter how good the archer's form. The result is a ranging error that significantly enlarges the vertical grouping. Faster arrows have less time to drop so are less sensitive to range estimation errors.
FlyingSticks allows you to enter a range estimation error as a percentage and shows the result as an elongated grouping oval. The effect is most significant at longer ranges.
The ethical hunter will stalk or range-find the target, reducing the range until the range estimation error will have minimal effect on the kill probability.
Most laser rangefinders have only 1 m range resolution when carefully used. Even a 1 m range estimation error on smaller game at longer ranges can be seen as problematic.
Wind, and particularly the uncertainty in the wind has a significant impact on the horizontal grouping. The wind effect become more apparent at longer ranges and is proportional to an arrow's aerodynamic drag. This is why keeping broadhead and fletching drag to the minimum consistent with arrow stability is so important.
One could add other uncertain meteorological conditions such as rain and snow. Both these will slow an arrow more quickly, causing extra (and difficult to estimate) drop.
The game's kill zone size and penetration requirements dictate the accuracy and bow power needed.
Deep penetration is required to compromise vital organs. "Deep" is a relative term and should usually be regarded as at least 3/4 of the game's chest width. It assumes rib and soft tissue penetration. The cut width should exceed the arrow diameter so that bleeding can pass the arrow's shaft for quicker blood loss and to leave a good blood trail.
The ideal shot is generally side-on. This give the least likelihood of heavy bone or deflection caused by a bone glance. A quick kill double lung shot is also possible.
Front or front quarter shots have a smaller kill zone and are more likely to strike heavier bone.
A rear shot is totally unethical and cruel except for small game where vital organs can still be reached due to good relative penetration. A quarter rear shot is more likely to be deflected by ribs, so is not recommended.
Despite what some may think, the reasons most government wild-life departments declare some species protected are generally sound. Its all about conservation and sustainability for the longer term.
A game animal hearing or seeing the archer's release, may lead to a fast, instinctive flight response that can cause a miss or a wounding. The probability of this occurring is dependent on multiple factors:
In general, large animals respond more slowly than small. Also, predator animals tend to respond more slowly than their prey. Rabbits may respond in less than 200 ms while a buffalo over 500 ms. For our purposes we define the response time as the time between the beginning of the stimuli and the movement of animal sufficient to compromise the shot.
A low signal to noise ratio of a stimuli is likely to take a little longer to be recognized, hence in acoustically or visually noisy environments, the stimuli may not be detected or the response may be slower.
Sound travels through still air at about 330 m/s (1100 ft/s). This is significant compared to game response times, so needs to be accounted for in any probability estimate.
Wind impacts the speed of sound over the ground. Thus, a head wind is preferred as it will take longer for the stimuli to reach the target (not to mention the value of the archer's sent not being detected).
Obviously, a shorter flight time (i.e. a lighter and faster arrow) is better as less warning time is available. Note that this tends to be in conflict with the fact that heavy arrows have better penetration and less susceptibility to cross winds.
FlyingSticks calculates and presents a time margin which is the response time plus the sound travel time (allowing for wind) minus the flight time. A negative value indicates the probability of a startled game moving has become significant.
Grazing game will often be in a stop-graze-move-stop-graze cycle. Presently, FlyingSticks makes no attempt to model this animal behavior. Part of the hunter's skill is to judge this cycle and time a shot accordingly.
Arrow penetration is an involved and at times a controversial topic. This subject is covered in more detail here.
It is obvious that a more powerful bow will impart more energy to an arrow. A faster arrow will travel the distance with less drop, meaning it will be more tolerant to range estimation errors. An arrow with more energy is also likely to penetrate the target deeper.
Penetration is a function of an arrow's speed, mass, broadhead characteristics, and the target's characteristics at the point of impact. It is the uncertainty in the latter that tends to define the marginality of a shot.
Penetration is very dependent on the broadhead characteristics. An aerodynamically clean, mechanically strong, swept-back design with razor sharp edges is needed for large game.
The aim of a broadhead is to cause catastrophic bleeding by penetrating vital organs and cutting arteries. This is a relative requirement - large animals will need to loose blood at a higher rate, so will require a larger cut area. With small game the massive trauma is likely to cause a quick death.
Apart from assisting in penetration, the blades of a broadhead are there to cut a wide path to maximize the probability of severing an artery. An arrow without extended blades is likely to leave the wound plugged by the arrow. An arrow with oversized blades is likely to be obstructed by bone and not penetrate adequately. Some jurisdictions regulate the minimum blade width, although the rational is sometimes dubious.
A point without blades is simply unethical. The flesh is likely to stretch around the arrow with minimal cutting, and then the arrow seals by a septum action, greatly reducing blood loss and blood trail. While death may occur, it will be slower and without a blood trail the game is likely to be lost.
It is clear that a considerable level of skill and knowledge is required to achieve a high probability of an ethical kill. Sadly, many bow hunters are below the minimum with the result that in some regions the reported wounding rates are unacceptably high.
Bow hunters must actively seek to understand their limitations, work on their short-comings or shoot within their limitations.
FlyingSticks provides a tool to judge your limits. For many, a better understanding of the impact of range estimation errors will service. For others grouping will need to be improved - and this is the hard part.