When people encounter snakes, a common question is “how many snakes are poisonous?” This highlights a widespread misunderstanding about how these reptiles can cause harm. Understanding their actual harmful capabilities can clarify these misconceptions.
Understanding Venomous and Poisonous
The terms “venomous” and “poisonous” are often used interchangeably, but they describe fundamentally different mechanisms of harm. A creature is venomous if it injects toxins into another organism, typically through a bite or a sting. Snakes deliver venom using specialized fangs to inject it into prey or a perceived threat. Conversely, an organism is poisonous if it contains toxins harmful when absorbed, ingested, or touched. Toxins must enter the body passively, such as by eating the organism or through direct skin contact. Most snakes that pose a threat to humans are venomous, not poisonous.
Global Diversity of Venomous Snakes
Globally, approximately 3,900 to 4,000 snake species inhabit various environments across all continents except Antarctica. Of these, 600 to 700 species are venomous. However, only 200 to 250 species possess venom potent enough to be medically significant to humans. Most snake encounters involve species not equipped to deliver a dangerous dose of venom.
The Rarity of Truly Poisonous Snakes
Truly poisonous snakes, which cause harm upon touch or ingestion rather than through a bite, are exceptionally rare in the natural world. This distinction reinforces the difference between venom and poison, as these few species do not actively inject toxins. A notable example is the Rhabdophis genus, commonly known as keelback snakes, primarily found in Asia. These snakes possess a unique defense mechanism where they sequester toxins, specifically cardiotonic steroids, from poisonous toads and firefly larvae they consume. These acquired toxins are stored in specialized glands located on the back of their necks, making their skin poisonous if touched or ingested. Similarly, certain garter snakes (Thamnophis) from regions like Oregon can retain toxins in their livers after eating rough-skinned newts. Such instances represent an unusual adaptation and are significant exceptions to the general rule that snakes are venomous.
Where Venomous Snakes Live and Key Families
Venomous snakes inhabit diverse ecosystems across the globe, with higher concentrations typically found in tropical and subtropical regions. The two primary families responsible for most medically significant snakebites worldwide are Elapidae and Viperidae. The Elapidae family includes species such as cobras, mambas, kraits, coral snakes, and sea snakes. Their venom is predominantly neurotoxic, meaning it primarily affects the nervous system, leading to symptoms like paralysis.
The Viperidae family, encompassing vipers, rattlesnakes, and adders, utilizes a different type of venom. Their venom is largely hemotoxic, causing damage to blood cells and tissues, which can result in severe pain, local swelling, tissue necrosis, and disruptions to the blood clotting system. While venomous snakes are found globally, countries like Australia are particularly known for their high number of venomous species.
Staying Safe Around Snakes
Being aware of your surroundings is the first step in preventing snake encounters, particularly in areas where snakes are known to live, such as tall grass, rocky outcrops, or under logs. Wearing appropriate footwear, like closed-toe shoes and long pants, can offer a layer of protection when venturing into snake habitats. Using a flashlight when walking at night can also help illuminate paths and potential hidden snakes.
It is important to remember that most snakes are not aggressive and typically bite only when they feel threatened, often when people try to handle them or accidentally step on them. Therefore, never attempt to handle, provoke, or approach a snake, even if it appears to be dead, as reflexes can persist.
In the event of a snakebite, remain calm and immediately seek emergency medical attention by calling local emergency services. Remove any jewelry or tight clothing near the bite area, gently wash the wound with soap and water, and try to keep the affected limb immobilized below the level of the heart. Do not attempt to cut the wound, suck out the venom, apply a tourniquet, or use ice, as these actions can cause more harm.