Snake Field Guide

Snake Field Guide
Despite all of their legend and infamy, snakes are actually rarely seen in the field, at least compared to other small animals. But if you're in a likely habitat at the right time of day---such as dusk---you may catch a glimpse of a fast-retreating serpent. Although there are hundreds of snake species in the United States, honing your eye to a few general characteristics and utilizing some of the many available field-guide resources can help you make an educated guess at identifying the snakes you see on the trail.

Snake ID

When you see an unfamiliar snake, try to estimate its length, which in North America will range from less than a foot to more than 8 feet. Consider whether the animal's head is broader than the "neck" leading to it, and the general girth of its body. Is the snake glossy or dull (which relate to smooth or keeled scales, respectively)? What is the skin pattern: uniformly colored, banded, blotchy, striped? Note the snake's behavior; does it coil up to defend its turf, lie perfectly still, or attempt to flee? Also make note of its location, both specifically in terms of habitat and broadly in terms of geography. All of that information will help you identify the snake using field guides and other references.


There are many fine field guides dedicated to North American snakes, including the Peterson series on reptiles and amphibians (split into Eastern/Central and Western North America). Although smaller books are ideal for keeping in your backpack or glove compartment, larger reference editions, such as Carl and Evelyn Ernst's "Snakes of the United States and Canada" (2003), are useful for perusing at home for more thorough information, and may be more likely to contain taxonomic keys. Check your local library or bookstore to see whether there are any field guides specially dedicated to snakes in your particular state or region.

Taxonomic Keys and the Internet

For serious snake ID, you'll want to seek out a taxonomic key, which is usually a series of paired questions about detailed physical characteristics. The key can help you identify a single species that matches the description of your snake. Such keys are no longer confined to expensive technical manuals; there are Web resources of varying complexity that can be of use. The most reliable are often productions of universities, museums, extension offices, or government agencies. See the "Resources" section for some examples.

Agency Resources

Many wildlife, natural resource, and extension agencies provide information about regional snakes. The Wisconsin Department of Natural Resources, for example, offers a richly photographed guide to that state's species, complete with Wisconsin-specific details, such as county range maps, that often are unavailable in broader-focused field guide.

Keep in Mind

While a comparative few North American snakes are venemous, you should err on the side of caution in all cases. Don't heedlessly approach an unfamiliar snake. If possible, make your observations without unduly stressing the animal. For novice snake enthusiasts, it's a good idea to learn the potentially dangerous species---rattlesnakes, copperheads, cottonmouths, and coral snakes---so you can quickly identify them in the field and give them wide berths.

Article Written By Ethan Schowalter-Hay

Ethan Schowalter-Hay is a writer and naturalist living in Oregon. He has written for the "Observer," the Bureau of Land Management and various online publishers. He holds a Bachelor of Science in wildlife ecology and a graduate certificate in geographic information systems from the University of Wisconsin.

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