Monday, May 5, 2014

A Triangular Shaped Head Does Not Mean A Snake is Venomous (or Poisonous)


This is the head of a venomous Cottonmouth.
Compare it to the Cornsnake below.
    We’ve all heard it. If a snake has a triangle or diamond-shaped head, it is venomous (or poisonous), right? Wrong. This trick just doesn’t work and we should stop using it.

    Environmental educators: don't tell people this is a good way to tell whether a snake is venomous or not.

   Everybody else who isn’t already good at identifying snakes: just because a snake has a triangle-shaped head doesn’t mean it is venomous.

    Here’s the thing. If you have seen a lot of snakes and are really good at identifying them, you probably have no problem recognizing that vipers do have a characteristic and relatively triangular head shape. But let’s admit it-that’s not how you identified the snake in the first place. You probably used your overall impression of the animal to determine the species and only even considered the head shape if you weren't confident in your identification. For example, maybe you were looking at a poor quality photograph and had trouble recognizing the snake. 


This harmless Corn Snake's head is 
about as non-triangular as they come. 

    If those of us that are snake experts don’t use head shape to help with our identifications, why should we tell other people to do it?

    There are a number of problems with using head shape to determine if a snake is dangerous. Most snakes have a head and jaw structure that is at least vaguely triangular and that’s just because of basic snake morphology. Snakes have vertebrae, ribs, and a skull, and they give the animal its shape. Even though a snake doesn’t have legs doesn’t mean it’s just a tube with a mouth! Many people that encounter an unidentified snake in their yard haven’t spent a lot of time looking at snakes and without that experience it is very easy to imagine any snake’s head as one that is triangle-shaped.

    Cornsnakes and Racers have some of the least triangle-shaped heads that a snake could possibly have. Yet, people frequently kill these animals because they think their heads look triangular. If people consider these species to have triangle-shaped heads, they could do the same for any snake in the world. And that means using head shape to determine if a snake is venomous is a trick that is no good.

Non-venomous Water Snake (from Comments thread below).
    As if identifying snakes based on their head shape wasn’t hard enough, many completely harmless snakes actually make their head appear more triangle-shaped when they are feeling threatened! One reason they might do that is so that potential predators think the snake is venomous and leave it alone. Hognosed Snakes and Watersnakes are notorious for this defensive strategy. I have seen some snakes perfect the behavior to the point that I feel I could have taken out a protractor and confirmed that their head was a perfect isosceles triangle. This doesn’t make them dangerous.

Non-venomous Corn Snake (from Comments thread below). 
Compare this defensive Corn Snake to the relaxed one above.
    Another problem is that by stressing that snakes with triangular shaped heads are venomous, it is possible for people to forget that this “rule” applies only to vipers. Snakes within the Elapidae family (e.g., cobras and coral snakes) are also venomous but don’t have a triangular shaped head at all! 

    Many harmless snakes are being killed because their heads appear triangle-shaped. This is bad for snakes, obviously, but it also leads people to exaggerate the danger that snakes pose to them. This doesn’t help reduce conflicts between humans and wildlife, it exaggerates it. Unfortunately I don’t think the solution is necessarily easy. But, I think we need to move away from emphasizing tips and tricks and encourage a more comprehensive understanding of the wildlife around us. 

   Check out the comments below for a few more great pictures of non-venomous snakes with triangular-shaped heads.

    What do you think? If you agree, please use the icons below to share this post on Facebook, Twitter, etc. Disagree? Let me know why below.

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