Venomous Snakes

Relatively few snakes are venomous. Of over 2,500 species of snakes in the world, only about 375 are venomous. Of about 116 species of snakes native to the U.S., only 19 are dangerous. Bites of a few species of the rear-fanged snakes sometimes cause harm, but the effects vary. Basic snake biology, behavior, and control strategies (for those native to the U.S.) are covered in the Fact Sheet on Non-Venomous Snakes. Despite movies and folktales, a venomous snakebite will not always kill, or permanently disable you. Based on reports from the Center for Disease Control and Prevention (CDC), over the past several decades, honeybee stings have killed about twice as many people as have died from snake bites in the U.S. each year.

How to Tell if a Snake is Venomous

As with other animals, the shapes, numbers, and locations of physical structures are important keys used to correctly identify (ID) a species or higher taxonomic group. All venomous snakes do have at least one pair of specialized teeth used to introduce their venom into their prey. These “fangs” are usually distinctly larger or longer than most of that snake’s other teeth. The presence and location of “fangs” is very important to ID a snake as venomous. Other characters may also be important for a geographic area. For example, in the U.S., all pit vipers have only a single row of scales on the underside of their tails; vertically elliptical pupils; and a pair of pits between their nostrils and eyes. Although these characters are common to all pit vipers, there are some very venomous snakes that DO NOT have them. For example, coral and sea snakes have round pupils. Other characters like color patterns or behaviors are often used to ID species or subspecies, and may be important for alerting potential prey, warning away predators, or communicating between members of the same snake species (especially in courtship and mating).

Enemies

Even the most venomous snakes have natural enemies, including: predatory mammals (e.g., foxes, badgers), birds (e.g., hawks, roadrunners), and other snakes (e.g., king snakes, racers). Venomous snakes feed on rodents and other small mammals, but they almost never kill or eat enough to have much effect on even moderate populations of such pests.

Snake Bites

Snakes have very good voluntary control of their strike, whether or not venom is injected, and how much venom is injected. Many strikes and bites, which occur when a snake is disturbed (‘provoked’ bites), are strictly defensive (‘dry’) and very little or no venom is injected. Factors such as the way in which the snake was disturbed, how recently it has fed, and its health can all influence the amount of venom injected during a bite. Unprovoked bites are rare and usually result when a hungry snake mistakes a person’s hand or leg, or a pet, for its normal prey (usually a small animal). Most snakes can only strike for 1/3 to 1/2 of their body length (except for a few “jumping” vipers), so their size is important to note. The longer the snake, the farther it can strike.

First Aid

If bitten by any venomous snake (except a coral or sea snake) a person will usually feel pain and have swelling at
the wound site immediately or within a few minutes.

1. The best first aid for a venomous snakebite is to get the victim to medical aid (such as a hospital emergency room) as soon as possible. Keep the victim reassured, calm and warm until then. If possible without risking another bite, try to kill the snake and take it along with the victim. That could be helpful in case antivenin treatment is needed.
2. Do not cut the wound. That seldom does any good, often causes worse tissue damage, and greatly increases the risk of infection. Applying suction immediately and for the first few minutes may help, but nearly all snake venoms contain chemical factors which cause them to spread quickly (in seconds) and adsorb strongly to the victim’s tissue cells.
3. Do not give the victim alcohol; or use ice, cold packs, or other cooling agents on the wound.
4. If a victim is several hours from the nearest medical care, apply a light-restricting band on the bitten limb 2-4 inches (5-10 cm.) above the bite, between the bite and the heart. This should not be a tourniquet. You should be able to easily insert a finger under the band. Loosen the band if swelling occurs beyond it.

Reprinted from the National Pest Management Association’s NPMA Pest Management Library