Wednesday, September 18, 2013

Readers Write In: Of Decapitated Copperheads Biting Themselves

Hey Dave,

Have you seen this video yet? It's getting a bit of attention online and might be worth posting about on your blog.

It shows an unfortunately decapitated Copperhead still wiggling and around 28 seconds the head bites the tail. If you do make a post, I had a couple of questions! I was wondering, can the decapitated head still inject venom? Also, one of the comments I've seen was along the lines of, "If it wasn't dead yet, it is now." So could this bite (assuming venom was injected) have affected the lingering nerve action in the body? Thanks!

Stephanie C.
Williamsburg, VA

Caution: Graphic Video

    A lot of attention is right, various iterations of this video have been viewed millions of times and Twitter is alive with people sharing the link. I'd generally avoided this clip and hadn't watched it because I think pictures and videos of people killing snakes is boring and I don't want to feed the publicity. More attention only encourages even more people to kill snakes and videotape the act, but, Stephanie brings up some interesting biological questions (National Geographic has also briefly touched on some of them).

    First off, can the decapitated head still inject venom? Yes. A pit viper's venom glands (there are two) are located on each side of the head just behind their eyes. Venom travels from the glands to the fangs during a bite, so a decapitated pit viper head has everything it needs to deliver venom. It is generally thought that an animal will die nearly immediately after being decapitated, but reflexive movements may still happen. That could be what this bite was. Stick something in front of a pit viper head and it might reflexively bite (let's not test this).

   Secondly, can a snake's own venom harm it? Yes. This isn't an area where there has been a lot of research and experimentation (just imagine the required permits!), but snakes do not have special immunity from their own venom. When venom is stored in a snake's body, it is located within specially-evolved glands that can safely contain it. This is the same basic idea that allows us to hold potentially harmful stuff in our appendix or gall bladder. If chemicals escaped from a snake's venom gland (or our appendix or gall bladder), it would be bad news.

    Also, regardless of whether venom was injected, two large fangs can cause some serious physical damage. So, it's probably an all-around good idea to avoid bites from venomous snakes.

   There are some snakes, like Kingsnakes or Indigo Snakes, that have developed resistance to pit viper venom. These two snakes are well-known for eating things like Copperheads and rattlesnakes, so it's not surprising they've developed some resistance. A few other snake-eating animals also have some degree of immunity from venom, but again, this isn't an area that has enjoyed much research.

    But, we do know that humans aren't immune from pit viper venom, so I'll have to continue to warn potential future snake-killers that harassing venomous snakes is dangerous. Compared to when you just let a snake go on its way, you are much more likely to get bitten by a snake when you mess with it. That may be especially true when you stick around to record what happens afterwards.

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