The Bay State’s Most Common Snake

My ViewDon LymanThe Salem NewsTue May 31, 2011, 05:01 AM EDT

A sure sign of spring in New England is the appearance of garter snakes.

Having spent the winter lying dormant safely below the frost line, the ubiquitous striped serpents usually emerge from their underground hiding places when the weather starts to warm in April and May.

Named for their resemblance to the colorful striped garter belts men used to wear to hold their stockings up, garter snakes are found from Canada to Costa Rica, and from coast to coast in the United States, including southeastern Alaska. There are 30 species of garter snakes, ranging in size from the 18-inch-long exiled garter snake of Mexico to the aptly named 51/2-foot-giant garter snake of California.

The eastern garter snake, the species native to Massachusetts, is typically 2 feet or so in length, but the record is slightly over 4 feet. Declared the state reptile in 2007 by then Gov. Mitt Romney, it is also the commonwealth’s most common snake, being found in a variety of habitats from fields to forests, as well as wetlands, yards and gardens. Occasionally garter snakes even show up in people’s basements, usually in spring or fall.

Garter snakes typically mate in the early spring after emerging from hibernation, and give birth to anywhere from a dozen to 40 live young from July to October. The cold-blooded reptiles remain active as long as the weather is warm, and can even be observed basking on sunny days in late October and early November, before they disappear underground again for the winter.

While most species of garter snakes are adorned with the familiar yellow stripes, some species sport fancier colors, such as the red-sided garter snake of the West Coast, and the bluestripe garter snake, which is native to the Florida panhandle. The eastern garter snakes we see in Massachusetts generally have a brownish body color with three yellow stripes — one down the middle of the back and one on either side of the snake’s body; but some eastern garters have a checkered pattern with faint or even no stripes.

Butch Brodie III, an evolutionary biologist from the University of Virginia who studies garter snakes, says it was the garter snakes’ color patterns that initially sparked his interest in them.

“I began working on garter snakes because I was fascinated with the color pattern variation in some species, especially in western North America,” says Brodie. “The problem of how variation is maintained in the face of natural selection is an old puzzle for biologists, and garter snakes seemed like a group that might offer some new answers.”

Brodie and his colleagues discovered that different color patterns are inherited along with different kinds of escape behavior.

“Snakes with stripes tend to flee from predators, because striped patterns work well with flight (the stripes create an optical illusion of the snake moving faster than he actually is),” says Brodie. “Spotted patterns don’t appear to move as fast, so snakes with those patterns have better success by hiding or fighting.”

The closely related eastern ribbon snake, also a resident of the commonwealth, is frequently confused with the garter snake. Ribbon snakes are more slender than garters, with brighter, more clearly defined yellow stripes, and are more aquatic in their behavior, often being found in the weedy habitat along the edges of ponds, streams, marshes and vernal pools, where they hunt for frogs, fish and tadpoles.

Eastern garter snakes feed on small animals like earthworms, frogs, toads, and salamanders. They will strike vigorously if threatened and may bite if handled. Like many snake species, garters also have another weapon in their self-defense arsenal — they can emit musk from glands at the base of their tail which has a strong, unpleasant odor.

The Massachusetts Division of Fisheries and Wildlife website states that the saliva of the garter snake may actually be toxic to amphibians like frogs and salamanders; and, while harmless to humans, may occasionally produce a rash.

Patrick Gregory, a biology professor who studies garter snakes at the University of Victoria in British Columbia, Canada, published an article in 2008 in the Canadian Association of Herpetologists Bulletin where he described a bite he received from a western terrestrial garter snake that produced pain, itching and swelling of his hand. The adverse effects of the bite resolved completely after a couple of days. Gregory says he’s had many bites from garter snakes that produced no ill effects.

“I think that a big part of the reaction here was due to the fact that I let the snake hang on (for about two minutes) because I wanted a picture of it biting,” says Gregory. “Ordinarily I would have separated it from my hand earlier.”

In an email interview, Professor Brodie also weighed in on the garter snake venom issue.

“There is considerable controversy over what people refer to as ‘toxic,’ and what constitutes a venom in snakes,” says Brodie. “A variety of snakes have modified glands in the mouth (known as Duvernoy’s glands) that produce secretions like saliva, some of which have effects on prey. Garter snakes have these glands, but only a few western species have been identified as having potentially toxic secretions. Eastern garter snakes are not among these.”

He added, “These secretions have not been tested on humans. The more likely explanation for a ‘rash’ after a bite is minor infection due to the bacteria that live in most animals’ mouths.”

Gregory felt that in the case of his garter snake bite the symptoms appeared too quickly (right after the bite) to be due to infection.

Another interesting phenomenon pertaining to garter snakes and toxins involves an evolutionary “arms race” between some western garter snake species and newts, a type of salamander that produces toxic skin secretions. According to Brodie, newts, including the eastern red-spotted newt, a species native to Massachusetts, possess this toxin in the skin as a protection from predators.

“The common garter snake has evolved resistance to one of the most poisonous natural toxins known, tetrodotoxin,” says Brodie. “Garter snakes, through an arms race with newts, have evolved a different form of nerve channel that resists the effects of this poison. A garter snake from some parts of the western U.S. can safely ingest an amount of toxin that would kill more than 20 humans. We’re just now learning about eastern garter snakes, but they appear to have the same kind of resistance in some places.”

It should also be noted that newts are not toxic to people or animals unless their toxins are ingested or if their skin secretions come into contact with cuts or mucous membranes. Hand-washing after handling a newt should be sufficient to remove any toxins from the skin.

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Biologist Tim Beaulieu with a very large eastern garter snake he found in the suburban Boston area.

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Don Lyman is a biologist and an adjunct instructor in the biology department at Merrimack College in North Andover. He also works part time as a pharmacist at Beverly Hospital. He can be reached at Donald.Lyman@merrimack.edu.

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