Are Copperheads Venomous? How Dangerous Copperheads Really Are

How venomous is a copperhead?

The copperhead (Agkistrodon contortrix) delivers its venom through two long, hollow fangs at the front of the upper jaw. The fangs fold back against the roof of the mouth when the mouth is closed and swing forward when the snake strikes. Fang, venom gland and bite work exactly as they do in rattlesnakes.

Copperhead venom is mainly hemotoxic and cytotoxic. In plain terms, it attacks blood vessels, blood clotting and the tissue around the bite, causing pain, swelling and bruising. It does not mainly attack the nervous system the way coral snake or cobra venom does. You can read about the different venom types in how does snake venom work?

In laboratory tests on mice, copperhead venom is among the least potent of all pit vipers and slightly weaker than that of its close relative, the cottonmouth. Copperheads are also medium-sized snakes, usually 50 to 95 cm (20 to 37 in) long, so they have smaller venom glands than big rattlesnakes.

How dangerous are copperhead bites?

Copperheads are responsible for more venomous snakebites than any other snake in the United States. That is not because they are especially aggressive, but because they are common, live in the most densely populated part of the country and often share wooded suburbs and yards with people.

The CDC estimates that 7,000 to 8,000 people are bitten by venomous snakes in the US each year and that about five of them die. Most of those deaths are caused by large rattlesnakes. Deaths from copperhead bites are extremely rare, and healthy adults who reach medical care almost always recover.

That does not make a bite harmless. A copperhead bite is usually very painful, and swelling can spread up an arm or leg over the following hours. Bites to the fingers, hands and feet, where there is little muscle to absorb the venom, can damage tissue, and recovery can take weeks. Children, older people and anyone with an allergy to the venom face a greater risk. An allergic reaction or an infection is always possible.

Dry bites and warning bites

Many copperhead bites deliver little or no venom. A “dry bite” is one in which the snake strikes without injecting venom at all, and dry bites seem to be particularly common in copperheads. When stepped on or cornered, a copperhead often gives a quick defensive bite rather than the full envenomation it would use on prey.

Because there is no way to tell at first whether venom was injected, every bite must still be treated as an emergency. Symptoms can take some time to develop.

Why copperhead bites happen

The copperhead’s main defense is camouflage. Its tan body with dark hourglass crossbands blends almost perfectly into dead leaves, pine needles and red clay. Instead of fleeing when a person approaches, a copperhead often freezes and trusts that it will not be seen. When a foot lands on it or a hand reaches into the leaf pile where it lies, it bites.

Typical situations include:

• Walking barefoot or in sandals in the yard, especially on warm summer evenings when copperheads are most active.
• Gardening, raking leaves, clearing brush or picking up firewood, boards and stones by hand.
• Stepping over logs or rocks without looking where the foot lands.
• Trying to catch, move or kill the snake. Many bites to the hands happen this way.

Copperheads are mostly active by day in spring and fall but largely nocturnal in the heat of summer. That is why so many encounters happen at dusk and after dark in July and August.

Are copperheads aggressive?

No. Studies of copperhead behavior show that, when approached, they are far more likely to stay still or crawl away than to strike. Before biting, a disturbed copperhead may vibrate the tip of its tail, which can sound like a buzz in dry leaves, raise its head in an S-shaped coil or release a strong musk from glands near the tail.

A copperhead that appears to be “coming at” a person is usually heading for the nearest cover, which may simply lie in the person’s direction. Copperheads do not chase people.

How to avoid copperhead bites

The safest approach is simply to give copperheads space:

• Watch where you put your hands and feet in leafy, rocky or overgrown places, and use a flashlight at night.
• Wear closed shoes outdoors where copperheads live.
• Never try to handle, catch or kill a copperhead. Leave it alone; it will usually move on.
• Never pick up a dead copperhead. Even a dead snake or a severed head can bite by reflex.
• Teach children to stay away from any snake they find and tell an adult.

If someone is bitten, move away from the snake, keep the person calm and seek emergency medical help immediately: call 911 in the US. Do not waste time trying to catch or photograph the snake.

Copperheads compared with other US venomous snakes

The United States has four groups of venomous snakes: rattlesnakes, copperheads, cottonmouths and coral snakes. Among them, the copperhead causes the most bites but has some of the weakest venom. Large rattlesnakes such as the eastern and western diamondbacks cause most of the serious bites and deaths. See the full picture in venomous snakes in the US.

A related point of confusion is the word “poisonous.” Copperheads are venomous, meaning they inject a toxin through a bite; they are not poisonous to touch. Learn the difference in is a snake venomous or poisonous?

Why copperhead venom interests scientists

Copperhead venom contains a protein called contortrostatin that, in laboratory studies on mice, slowed the growth and spread of tumors. This is early research in animals, not a human treatment, but it shows how venoms that cause harm in a bite can also be valuable to medicine.