Features

Ringnecked Snake, a Welcome Neighbor

By JOE EATON Special to the Planet
Tuesday July 01, 2003

Even though gardening for wildlife is a popular trend, some Berkeleyans might be a bit disconcerted to learn that their gardens harbor venomous snakes. There’s no reason to panic, though. These snakes are only kind of venomous, and they’re basically on your side. No, really. 

The serpent in question here is the ring-necked snake, a striking pencil-thin creature with a black head and back and a yellow-orange belly and matching collar. Its size varies geographically, with a maximum length of about 20 inches in our region. Ringnecks are retiring in disposition, most often found under rocks, boards or loose bark, or inside rotting logs. 

The only one I’ve ever seen in Berkeley was a recently deceased specimen, retrieved from a cat. But they can be common in favorable habitat: a study in Kansas found population densities of up to 700 per acre. And they’re sociable as snakes go, 10 or more holing up together. 

When a ringneck feels threatened, it threatens back by coiling its tail (yes, snakes have tails) into a tight corkscrew and presenting the scarlet underside. This warning, like the skunk’s, should not be taken lightly. If picked up, the snake besmears its captor with foul-smelling secretions. Otherwise unemotional herpetologists have used words like “loathsome” to describe the effect. 

Harry W. Greene, author of “Snakes: The Evolution of Mystery in Nature,” speculates that the tail-coiling display may have evolved in response to predation by scrub-jays, sharp-eyed birds that are hell on small vertebrates. Only ringnecks in Florida and the west, where scrub-jays occur, have contrasting red undertails and perform the display. Since birds have color vision, it could be an effective “don’t touch” signal. 

You’re wondering about the other end of the snake, though. Ringnecks are rear-fanged snakes, which means you would have to go out of your way to be bitten by one. Those who have experienced bites report nothing worse than a localized burning sensation. The effect is more powerful on its small prey. Rather than killing its victims outright, the ringneck’s venom just immobilizes them so they can be swallowed without a lot of thrashing around. 

The rear-fanged syndrome appears to have been a first evolutionary step to a venom delivery system, pre-dating the more sophisticated equipment of vipers, cobras and their kin. Most rear-fangers pose no threat to humans. Some, though—the African boomslang, the East Asian yamakagashi—can be deadly. 

Here’s how it works: In the back of its mouth, the ringneck has a pair of enlarged saber-like teeth. Unlike the hypodermic-style fangs of a rattlesnake, they’re not hollow, and there’s no injection mechanism. The teeth channel toxic secretions from a structure called the Duvernoy’s gland—which appears to be a modified salivary gland—into the snake’s prey. Some chewing may be required for the venom to take effect. Snakes that kill by constriction, like kingsnakes and ratsnakes, have Duvernoy’s glands but have either lost or never evolved the ability to produce toxins. 

In addition to its role in prey capture, the ringneck’s venom seems to function as a defense against ophiophagous (snake-eating) snakes. There is no professional courtesy among serpents. A Florida biologist once observed a ringneck being swallowed, alive and tail-first, by a long-nosed snake. When its head came within range, the ringneck bit the longnose in the floor of the mouth. After a few hours, up came the ringneck. The larger snake tried again, and was again bitten by its intended dinner. Following a third iteration the long-nosed snake succumbed, and the ringneck worked its jaws loose and crawled away, apparently none the worse for wear. 

Fine, but why would you want one of these in your garden? Because, in addition to salamanders, lizards, smaller snakes and earthworms, ring-necked snakes eat slugs. Anything that eats slugs is welcome at my place. They don’t do snails, though. There are snail-eating snakes in the New World tropics, but no North American species ever evolved that taste, more’s the pity.