Archives of The Cold Blooded News

The Newsletter of the Colorado Herpetological Society

Volume 33, Number 4;   April, 2006

What is a Venomous Snake Anyway?

By J. DeRyke

Venom, venomous, and non-venomous snakes and the problems associated with keeping such creatures are somewhat magnified by the venomous variety's reputation. But what is a "venomous" snake anyway? The dictionary's definition is 'a creature having a poison-producing gland and able to inflict a poisoned wound.' That, as we shall see, covers a very broad area.

Snakes have rather slow metabolisms as befitting their slow life-style. They don't eat very often, and when they do, the meal is likely to be relatively huge. This is abetted by not having any limbs with which to tear chunks off, so all meals will be whole animals. Chewing is not effective either, so the digestive juices are not forced into the prey and its surface area is not increased by chewing or tearing.

Once swallowed, a prey animal being large will slow the maneuverability and speed of a successful snake. This makes just fed snakes vulnerable to attack by their own predators. Prey animals such as rodents often have tough skins, further slowing digestion and prolonging the vulnerability of a just-fed snake. Nature, in her attempts to help the situation, equipped the snake with powerful digestive juices to speed up digestion. And in many species, the saliva not only lubricates the prey so it goes down the snakes throat easier, but the saliva itself is a powerful digestive fluid.

Research has shown that 'venom' is primarily a digestive medium from highly modified saliva glands. It immediately starts cell breakdown and in some types, actual liquefaction of tissue. The fact that venom also kills the animal it’s applied to seems almost a byproduct, even though some snakes (vipers for instance) have evolved to take full advantage of it more than others. The kicker is, most animals have pre-digestive juices in their mouths, humans included. Some secretions are more powerful than others, and some are quicker acting than others.

For instance, all colubrid snakes including garters, racers, and corn snakes have a Dunevoy's gland that feeds its secretions into the snake's mouth during feeding. Some, such as the hognose snake, have specialized, enlarged rear teeth used to deflate puffed-up toads or frogs and deliver these secretions into the animals body. This 'enlargement' produces a pair of back teeth around 0.050" long. And while the hognose oral secretions do not kills its prey, it does seem to quiet them almost like a sedative, making swallowing less of a battle.

So, are Colubrids venomous? Almost all authorities say no, but a few say, "Well.…it depends…" A humans reaction to venom seems critical to the definition as it now exists. And we all know that, somewhere, someone will react allergically to almost anything including milk and peanuts -- two things not normally thought of as poisons. It turns out to be quite difficult for medical technicians to separate 'anaphylactic' shock from a sensitized material and a true venom reaction.

Again, the dictionary waffles a bit: 'anaphylaxis:hypersensitivity (as to foreign proteins or drugs) resulting from sensitization due to prior contact with the causative agent.'

Indeed, this has caused problems with venomous snake-wranglers that have already been bitten and received antivenin. Anaphylactic shock occurs when a once-bitten and treated human reacts more strongly to anti-venom proteins than to the snake venom itself. Nowadays, people who are snake-bitten and rushed to a hospital do not automatically receive antivenin shots, especially if the snake that caused the problem is not present for examination.

Rather than sensitize you needlessly, injecting you with unneeded anti-venin, then risking throwing you into cardiac arrest from anaphylactic shock, they wait to see what happens. It is not much fun. Ok, back to the subject, what is a venomous snake?

My definition is, "any one that can kill you." It would be foolish to exclude known killers such as rattlesnakes, copperheads, moccasins, and the coral snake. However, if you happen to be sensitive to bee or wasp stings, spider bites, or maybe mosquitoes, it may pay to steer clear of big snakes known to possess a Dunevoy's gland. This will include False Water Cobras, Giant Garter snakes, Madagascar Giant Hognoses, and Jewelled Ratsnakes.

Large examples of the foregoing species simply carry more volume of their secretions than small ones. Also, their teeth are longer, making it more likely you will get some of the secretions in a wound.