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Front- versus Rear-fanged Snakes

Updated on August 23, 2013

Front-fanged Snake Dentition

An average (~3' long) adult Southern Pacific Rattlesnake (Crotalus oreganus helleri) with its mouth opened to emphasize the outer/inner rows of teeth, the front-fangs, and some leaked venom in the floor of the mouth.
An average (~3' long) adult Southern Pacific Rattlesnake (Crotalus oreganus helleri) with its mouth opened to emphasize the outer/inner rows of teeth, the front-fangs, and some leaked venom in the floor of the mouth.

Rear-fanged Snake Dentition

An average (~6' long) adult Brown Treesnake (Boiga irregularis) with its mouth opened to emphasize the outer/inner rows of teeth and the rear-fangs.
An average (~6' long) adult Brown Treesnake (Boiga irregularis) with its mouth opened to emphasize the outer/inner rows of teeth and the rear-fangs.

What does front- or rear-fanged mean?

Not surprisingly, it refers to exactly what you think it would mean: the placement of the pair of fangs in the outer row of teeth on the upper jaw of the snake's mouth. Generally speaking, front-fanged snakes have fangs at the front of the mouth, whereas rear-fanged snakes have fangs near the rear or back of the mouth. If it was just that easy and the differences stopped there, however, you wouldn't be seeing two hubs dedicated to this topic.

They are actually classified in different taxonomic families within the superfamily Colubroidea (advanced snakes). Front-fanged snakes belong to the families Atractaspididae (although some species possess fangs towards the rear of the mouth, and some other species are nonvenomous), Elapidae, and Viperidae, while rear-fanged snakes are members of family Colubridae (many nonvenomous species also reside within this family). Examples of snakes from each family are as follows: Burrowing Asps and the side-stabbing Stiletto Snakes (Atractaspididae); Cobras, Coral Snakes, and Sea Snakes (Elapidae); Rattlesnakes and Vipers (Viperidae); Boomslangs, Garter Snakes, Hognose Snakes, and many other "common/typical" snakes (Colubridae).

Handbook of Venoms and Toxins of Reptiles
Handbook of Venoms and Toxins of Reptiles

This book provides great coverage on distinguishing front- and rear-fanged snakes.

 

Dentition of Front- and Rear-fanged Snakes

Whereas rear-fanged snakes tend to possess a similar tooth number and layout (placement) to nonvenomous snakes, front-fanged snakes have significantly fewer teeth in a condensed layout. Why would the "normal" teeth (non-fangs) be different between front- and rear-fanged snakes? This partially comes down to the venom transport efficiency problem we mentioned before, which we will elaborate upon a bit more in the next hub. Since rear-fanged snakes are significantly less efficient at transferring venom, they must bite and hold onto their prey (and, in some cases, actually "chew") in order to effectively envenomate them. Therefore, they still need the rest of their "normal" teeth for grasping and holding struggling prey. Front-fanged snakes, on the other hand, possess a very efficient venom-transport system that permits them to bite prey and release them shortly thereafter (allowing the prey to succumb to the venom before attempting to ingest them). Since they don't often deal with struggling prey being held in their mouths, they don't need many teeth to grasp with (although they still need to be able to effectively hold prey for ingestion since they have no limbs). Generally speaking (see diagram below), front-fanged snakes possess less than half the number of teeth on their lower jaw (keeping in mind that no snake has any inner row teeth on the lower jaw) and completely lack any outer row teeth on their upper jaw (with the exception of the pair of front-fangs). Virtually all snakes possess a gap in the center of their tooth rows in order to accommodate the forked tongue and trachea, which protrudes to permit uninterrupted breathing during ingestion.

We will continue discussing this front- and rear-fanged snake dichotomy in the next hub that compares their envenomation systems, which you may explore after testing your basic knowledge of front- and rear-fanged snake dentition. You can also check out the video below, which shows a rear-fanged snake grabbing and holding onto its prey in order to effectively envenomate it. If you would like to learn more about the envenomation symptoms elicited by front-fanged snakes, please see the Amazon links below for some useful book resources. If you have further questions about snakes that are not addressed by this article on front- versus rear-fanged snakes (or any other articles in this Snake Venom hub series), please see my hub on FAQs About Snakes.

Rear- versus Front-fanged Snake Dentition

Simplified diagram illustrating the relative differences between most rear-fanged snake skulls (left) and front-fanged snake skulls (right). The diagrams are oriented as if you are peering into the open mouths of the snakes, just as the above photos.
Simplified diagram illustrating the relative differences between most rear-fanged snake skulls (left) and front-fanged snake skulls (right). The diagrams are oriented as if you are peering into the open mouths of the snakes, just as the above photos.
Snake Venoms and Envenomations
Snake Venoms and Envenomations

This book analyzes some of the basic differences between front- and rear-fanged snakes.

 

Can you tell the difference between front- and rear-fanged snakes?


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Rear-fanged Snakes are Much Less Efficient at Injecting Venom and Often Hold onto Prey

Disclaimer

This hub is intended to educate people ranging from snake experts to laymen about the particulars of distinguishing front-fanged snakes from rear-fanged snakes. This information contains generalizations and by no means encompasses all exceptions to the most common "rules" presented here. This information comes from my personal experience/knowledge as well as various primary (journal articles) and secondary (books) literature sources (and can be made available upon request). All pictures and videos, unless specifically noted otherwise, are my property and may not be used in any form, to any degree, without my express permission (please send email inquiries to christopher.j.rex@gmail.com).

I wholly believe feedback can be a useful tool for helping make the world a better place, so I welcome any (positive or negative) that you might feel compelled to offer. But, before actually leaving feedback, please consider the following two points: 1. Please mention in your positive comments what you thought was done well, and mention in your negative comments how the article can be altered to better suit your needs/expectations; 2. If you intend on criticizing "missing" information that you feel would be relevant to this hub, please be sure you read through all of the other hubs in this Snake Venom series first in order to see if your concerns are addressed elsewhere.

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Handbook of Clinical Toxicology of Animal Venoms and Poisons
Handbook of Clinical Toxicology of Animal Venoms and Poisons

This book discusses some basic differences between front- and rear-fanged snakes.

 

© 2012 ChristopherJRex

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