Are Garter Snakes Venomous? Mild Saliva and Harmless Bites

The short answer: mild secretions, not dangerous venom

For a long time garter snakes were simply called nonvenomous, and in everyday terms that is still fair. Research in the late 20th and early 21st centuries showed that garter snakes, like many snakes in the family Colubridae, produce mildly toxic secretions in a gland in the upper jaw called the Duvernoy’s gland. These secretions flow into the mouth near the back teeth while the snake chews on its prey.

The key point is the difference between having a toxic secretion and being medically dangerous. Garter snakes make very small amounts, the secretion is weak, and it is not pushed in under pressure. That is why biologists sometimes describe them as “mildly venomous” while also stressing that the common garter snake poses no real threat to humans.

How garter snakes deliver their saliva

Truly dangerous venomous snakes, such as rattlesnakes or cobras, have a venom gland surrounded by muscles and long fangs that work like hypodermic needles. A single fast strike can deliver a large dose deep into tissue.

Garter snakes work very differently:

• No fangs. They have rows of small, solid, backward-curving teeth. The teeth at the back of the upper jaw are slightly larger, but they are not grooved or hollow.
• No pressure system. The Duvernoy’s gland lacks the strong muscles that squeeze venom out in vipers and cobras, so the secretion seeps into the mouth slowly.
• Chewing, not striking. To use it, a garter snake has to hold on and chew for some time. With a frog or worm that happens naturally while swallowing; with a person it rarely does.

For small, slippery prey, the secretion may help calm or weaken the animal and make it easier to swallow. Garter snakes do not constrict, so anything that helps hold struggling prey is useful.

What happens if a garter snake bites you?

Most garter snakes would rather freeze, flee or musk than bite. If someone grabs or pins one, it may strike and bite in defense. Because the snake is small and its teeth are tiny, the bite usually feels like a pinch or a scratch from a rough plant, and it often does not break the skin.

When the skin is broken, people sometimes report mild itching, burning, redness or a little swelling around the bite. A small number of published case reports, mostly involving snakes that were allowed to chew for a long time, describe more noticeable local swelling or bruising that faded on its own. Serious reactions are not a recognized risk. As with any bite or scratch from a wild animal, anyone who develops an unusual or severe reaction should seek medical help.

The simplest way to avoid bites altogether is to watch garter snakes without handling them. Left alone, they almost always move away.

Musk: the defense most people actually meet

Far more people encounter a garter snake’s musk than its bite. When it feels threatened, a garter snake releases a pungent fluid from scent glands at the base of its tail and thrashes so that the musk, often mixed with droppings, is smeared over whatever is holding it. The smell is strong and lingers, which is exactly the point: many predators let go of a snake that suddenly smells and tastes terrible.

The musk is not venom and is not toxic to people. It is simply unpleasant.

Venomous or poisonous? Garter snakes can be both

Biologists use “venomous” for animals that inject a toxin, usually by bite or sting, and “poisonous” for animals that are toxic to touch or eat. Garter snakes are unusual because some can fit both labels.

In parts of the Pacific Northwest and California, common garter snakes eat rough-skinned newts, which carry tetrodotoxin, one of the most powerful nerve poisons known. Resistant snakes survive the meal and can keep the newt toxin in their liver for several weeks afterward. During that time the snake itself is poisonous to a predator that eats it. This is a different issue from its own mild saliva and has nothing to do with the danger of a bite.

Garter snakes compared with truly venomous snakes

In most of the United States and Canada, garter snakes share their range with only a handful of medically important species, such as rattlesnakes, copperheads, cottonmouths and coral snakes. The comparison helps put the garter snake’s “venom” in perspective.

Garter snakes are also easy to tell apart from North American pit vipers: they are slender, have round pupils, a narrow head that is only a little wider than the neck, and usually long, bold stripes. Anyone bitten by a snake they cannot identify should treat it as a possible venomous bite and call 911 (US) or 112 (EU) immediately.

Why the “nonvenomous” label is changing

Many snakes once grouped as harmless colubrids turned out to have Duvernoy’s glands and mild secretions when scientists studied them closely. As a result, field guides increasingly avoid a simple venomous-or-not split and instead describe snakes by how dangerous they are to people. On that scale, garter snakes sit firmly at the harmless end. For a broader look at the terms, see Is a snake venomous or poisonous? and How does snake venom work?.