Rattlesnakes are a group of venomous snakes found throughout North and South America. They are known for the iconic rattle at the end of their tails, which makes a loud buzzing noise when the snake feels threatened. Rattlesnakes use their venomous bite both for hunting and self-defense. When they bite humans, it is almost always in self-defense. But what part of the human body do they most commonly target?
The Main Target – the Lower Leg
Research has shown that rattlesnakes most often strike at the lower leg and foot area on human victims. One study that looked at 172 rattlesnake bites found that over half of the bites were to the feet and ankles. Less than 15% were to the hands and arms.
There are a few key reasons why rattlesnakes tend to aim for the lower limb:
– It’s the closest target. When threatened, rattlesnakes will typically be coiled low to the ground. The legs and feet of an approaching human are the nearest fleshy area to bite.
– Less range of motion. The legs and feet have a more limited range of motion compared to the arms and hands. It’s harder for a victim to quickly jerk their foot away compared to their arm or hand. This makes the lower limb an easier target.
– Less dexterity. Hands have more dexterity and sensitivity. They can be used to deflect or grab an attacking snake. Feet lack this level of dexterity, making them more vulnerable.
– Abundant blood flow. The feet and ankles contain lots of blood vessels close to the surface, which maximizes circulation of the venom when bitten.
– Thinner skin. The skin on the feet and ankles is relatively thin compared to other parts of the body. This allows the venom to penetrate more readily.
So in summary, when rattlesnakes bite defensively, they aim for the lower legs and feet more than 70% of the time because it’s the closest, least mobile, and most vulnerable part of an approaching predator or threat.
Other Targets
While the lower leg might be the number one target, rattlesnakes won’t hesitate to bite other parts of the body when threatened. Here are some of the other areas they may strike:
– Hands and arms. If a person reaches down to grab or provoke a rattlesnake, their hands and arms become prime targets. Around 15-25% of bites occur in this area.
– Torso. If a rattlesnake is stepped on or pinned down, they may lunge upwards and bite the torso or hips. Around 10-15% of bites occur in this region.
– Head and neck. Rarer targets but potentially more dangerous. The head contains lots of blood vessels and highly vascularized tissue. Only around 5% of bites occur on the head or neck.
So while the lower limbs see the majority of rattlesnake bites, no part of the body is completely safe. The snakes will bite anywhere they can reach to defend themselves.
Fatality Rate by Body Part
Are rattlesnake bites to certain body parts more deadly than others? Unfortunately, there is limited in-depth research on mortality rates correlated to bite location. But we can make some general conclusions:
– Head and neck bites are particularly dangerous due to the presence of major blood vessels and nerves. Even a small amount of venom in this area can be rapidly fatal.
– Torso bites can be extremely dangerous as well, putting major organs at risk. Venom reaching the heart can cause rapid collapse.
– Lower limb bites have a lower mortality rate simply due to distance from the core. But they still involve major risks like severe tissue damage, blood loss, and infection.
– Arm and hand bites are the least likely to be fatal. But they still warrant urgent medical treatment.
Overall fatality rates from rattlesnake bites are thankfully low, with only about 0.5-3% resulting in death when proper antivenom treatment is given. But bites to the head, neck, and torso have the highest risk of being life-threatening. All rattlesnake bites should be treated as a serious medical emergency.
Fatal Rattlesnake Bite Case Studies
To get a better sense of the danger of rattlesnake bites to different body parts, let’s take a look at two real-world fatalities:
Case 1 – Neck Bite
A 63-year old man was bitten in the neck by an Eastern diamondback rattlesnake while hunting in Florida. Within minutes he collapsed with nausea, vomiting, and sweating as the highly potent venom entered his vascularized neck tissue and circulated rapidly. By the time antivenom was administered, he had already suffered cardiac arrest and could not be revived. Autopsy showed generalized hemorrhaging and necrosis throughout the body from the rapid neurotoxic and hemotoxic effects.
Case 2 – Foot Bite
A 38-year old woman received what appeared to be a minor bite to the foot from a Southern Pacific rattlesnake while hiking in California. She washed the bite and continued hiking for over 2 more hours before seeking medical care. In that time, the venom caused severe tissue destruction at the bite site, broke down blood cells, blocked circulation, and sent her into hypovolemic shock. Despite antivenom, the damage was too severe and she died 28 hours later.
These cases illustrate how rapidly fatal a rattlesnake bite to a sensitive area like the neck can be. But they also demonstrate the potential danger of lower limb bites that aren’t treated promptly. Both scenarios can prove deadly in a matter of hours.
Venom Composition and Effects
To fully understand why rattlesnake bites to different body areas can become so dangerous, it helps to know what exactly is in their potent venom. There are four main components that work synergistically to attack tissues and blood cells:
Hemotoxins – Break down red blood cells, disrupt blood clotting, and cause hemorrhaging and tissue damage.
Neurotoxins – Disrupt nerve impulses and cause muscle paralysis.
Myotoxins – Break down muscle tissue.
Necrotizing agents – Cause cell death and dissolve flesh.
This toxic cocktail of enzymatic and polypeptide compounds attacks the body on multiple levels. Even a small amount rapidly circulating through vascularized areas like the head or neck can overwhelm the body’s systems and become deadly. A larger dose in the limbs causes extensive local tissue damage that can lead to secondary medical complications.
Snake Size and Venom Yield
Larger rattlesnakes can potentially deliver a more dangerous bite than smaller ones for two reasons:
1. They tend to have larger, more deeply penetrating fangs that inject venom deeper into tissue.
2. They physically have larger venom glands and can inject more venom with a single bite. A large adult rattlesnake may yield over 150-200mg of venom in a single bite – over 10 times that of a smaller juvenile.
However, all rattlesnake bites should be treated with equal caution, regardless of the size of the snake. Even a small amount of rapidly circulating venom can prove deadly. And the bite of a small rattlesnake is capable of delivering a lethal dose to a human. Their venom is just that potent.
Volume of Venom Injected
Not all rattlesnake bites involve injection of venom – some are “dry bites”. But when they do envenomate a bite, how much venom is typically injected?
Estimates vary, but an average venom yield is in the range of 30-150mg. The volume depends on factors like the size of the snake, how threatened it feels, and mechanical dynamics of the bite. Some key points:
– Juvenile snakes often don’t control venom release well and may empty their glands completely.
– Multiple rapid strikes generally inject more total venom than a single prolonged bite.
– A longer bite duration results in more venom being introduced. Rattlesnakes can bite and hold for many seconds.
– Pressure on the venom glands, as occurs when the snake is pinned, forces more venom out.
– Around 25% is thought to be left in the tissue, 75% actually enters circulation.
So in summary, a typical full envenomating bite may involve 50-150mg, but amounts over 400mg have been measured. This is far more than enough to rapidly overwhelm the body.
How Much Venom is Lethal?
Exact lethal doses are not ethically measured in humans, but estimates suggest as little as 2-4mg of some rattlesnake venoms introduced intravenously could potentially kill an adult human. Other estimates of the mouse-tested LD50 (lethal dose for 50% of subjects) for rattlesnake venom indicate:
– Western diamondback: 2-4 mg/kg
– Eastern diamondback: 0.4-2 mg/kg
– Southern Pacific: 1-2 mg/kg
At these levels, an intravenous dose of less than 100mg and potentially as little as 10-20mg could be fatal to an adult human. This demonstrates how toxic just a small amount of rapidly circulating rattlesnake venom can be.
However, the actual amount causing death depends on many factors like site of injection, health of the individual, and timeliness of treatment. With prompt medical care, severe envenomations are survivable in most cases.
Rattlesnake Bite Treatment and First Aid
If you or someone else suffers a rattlesnake bite, here are some key first aid steps while awaiting emergency medical care:
– Remain calm but act swiftly – venom spreads rapidly from injection site.
– Wash the bite area with soap and water if possible.
– Immobilize the bitten limb but avoid constricting.
– Apply cool pack to help slow venom absorption.
– Do NOT cut, slice, or suction the bite. This can spread venom.
– Remove any rings or constricting jewelry to prevent circulatory issues.
– Monitor vital signs carefully for hypotension, tachycardia, etc.
– Seek emergency medical help immediately. Antivenom can be life-saving.
– Take note of snake characteristics if possible for identification.
– Keep the bite area below heart level if possible.
The key is to remain still and calm, avoid spreading venom, and get antivenom fast. With proper modern treatment, almost all rattlesnake bites are survivable if acted upon quickly. Don’t take chances with this extremely dangerous venom.
Conclusion
In summary, rattlesnakes most frequently target the lower limbs when biting defensively, striking feet and ankles in over 70% of bites. This allows them to inject their potent hemotoxic, neurotoxic, and necrotizing venom rapidly and debilitatingly into their victim’s body. While bites to the lower extremities are less immediately fatal, they still lead to severe localized tissue damage and major medical complications.
More proximal areas like the torso, neck, and head are less frequent targets, but are far more likely to rapidly lead to death due to the presence of critical organs and vessels in those regions. Regardless of the location, all rattlesnake bites warrant immediate and intensive medical therapy. By understanding where rattlesnakes are most likely to strike and the severe consequences of their powerful venom, we can be better prepared to avoid attacks and provide appropriate treatment. Respect for these dangerous reptiles in their native habitat is vital.