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Is That Snake Poisonous?
By Randy Liles, Area Biologist, Division of Wildlife and Freshwater Fisheries
Author's note: The correct terms are actually venomous and non-venomous, but since this article is for the layperson who is more familiar with the terms poisonous and non-poisonous, we've chosen to use those terms.
How many times have your encountered a snake and wondered if it was poisonous or non-poisonous? Unfortunately, there is no one simple, quick and unmistakable characteristic to tell a poisonous snake from a non-poisonous one. However, there are several general rules that can be used when identifying snakes in the field.
Poisonous snakes usually have a triangular or arrowhead-shaped head (except the coral snake). You must also be aware that several non-poisonous snakes, the Eastern hognose snake, for example, may flatten their heads when threatened. This defensive behavior may give the appearance of being a poisonous snake. The pupil of non-poisonous snakes will be round and located in the center of the eye. Most poisonous snakes have a vertical, elliptical (catlike) pupil. Another distinguishing characteristic of most poisonous snakes is the single row of scales on the underside of the tail, except for the poisonous coral snake, which has a double row. A double row is common in most non-poisonous snakes. Of course, this method of identification is not recommended on live specimens, but is very useful when looking at a shed skin.
A third way to help identify a poisonous snake is by the presence of a pit, or hole, between the snake’s eyes and nostrils (hence the name “pit viper”). This pit is heat-sensitive and enables the snake to locate warm-blooded prey, even in the dark. Non-poisonous snakes lack these specialized sensory pits.
Field guides are a great source of information and pictures to help identify snakes. They are available at most books stores and libraries. Another valuable source of information is the Internet.
In Alabama, there are numerous non-poisonous snakes, but only six species of poisonous snakes. Five of the six belong to the pit viper group and include the Eastern diamondback rattlesnake, timber rattlesnake, pigmy rattlesnake, cottonmouth (water moccasin) and copperhead. Snakes in this group are also characterized by having retractable, hollow fangs near the front of the mouth. These are used to inject venom into prey. The sixth poisonous snake found in Alabama is the coral snake, which belongs to a non-viper group. The coral snake does not have retractable, hollow fangs, but rather a pair of short, erect, grooved fangs near the front of the upper jaw.
Three non-poisonous snakes that look similar to the coral snake are the scarlet snake, scarlet kingsnake and the red milk snake. All these colorful snakes have different combinations of red and yellow-colored bands that prompted this rhyme: “Red on yellow will kill a fellow, but red on black won’t hurt Jack,” meaning the coral snake’s red touching yellow is an absolute identifying characteristic.
Before deciding to kill a snake you may encounter in your yard, garden, or while hiking through the woods, please remember the many benefits that snakes provide. Snakes kill and eat a variety of rodents and other pests. Some of the pests could transmit diseases to humans. Although snakes cannot eliminate these pests, they do help control their numbers. Many other species of animals as well as raptors utilize snakes as a source of food. Snakes--poisonous and non-poisonous--are helpful in many ways to humans and are an important part of our natural environment.
The Alabama Department of Conservation and Natural Resources (ADCNR) promotes wise stewardship, management and enjoyment of