Komodo Dragons Kill by Combining Tearing Teeth With Vile Venom

By Eliza Strickland | May 19, 2009 10:34 am

Komodo dragonThe Komodo dragon has unusual hunting methods, but it generally gets its meal: The monstrous lizard, which can reach 10 feet in length, lies in wait for prey and then lunges out to deliver a single deep bite, often to the leg or the belly. Sometimes the victim immediately falls, and the lizards can finish it off. But sometimes a bitten animal escapes. Biologists have noted that the lizard’s victims may collapse later, becoming still and quiet, and even die [The New York Times].

This delayed reaction had caused previous researchers to suggest that the dragon kills via blood poisoning caused by the multiple strains of bacteria in the dragon’s saliva. But “that whole bacteria stuff has been a scientific fairy tale,” said Bryan Fry [National Geographic News], lead researcher in a new study. Instead, the dragon uses its sharp, serrated teeth to rend its victim’s flesh while it simultaneously injects a venom that lowers the animal’s blood pressure and prevents blood clotting. Says Fry: “If you keep it bleeding and lower its blood pressure, it’s going to lose consciousness, and then you can tear its guts out at your leisure” [The New York Times].

For the new study, published in the Proceedings of the National Academy of Sciences, researchers dissected a Komodo dragon that died of natural causes at a zoo in Singapore. They found a set of six venom glands and ducts that led to the spaces between the lizard’s teeth, and detected proteins known to be in snake venom. In particular, compounds known to widen blood vessels and thin the blood — which induces shock — were present. Fry and his colleagues injected the venom into rats and confirmed that their blood pressure and aortic tension decreased. After the injection, the rats also became still, an outward sign of shock [Science News].

The venom is relatively weak, and the delivery system isn’t the most efficient, comments Christofer Clement, a comparative physiologist–but it’s enough to do the trick, he says. “These lizards make a huge wound using their teeth; that’s good enough to get the venom in…. They are robust enough that they can hang onto prey. Other groups like snakes are much more fragile – they have to bite something and let it go. So they have these hollow fangs and more deadly venom” [BBC News].

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DISCOVER: The Evolution of the Dragon

Image: Chris Kegelman

CATEGORIZED UNDER: Living World
MORE ABOUT: reptiles
  • http://clubneko.net Nick

    Did they also inject the bacteria and see what effect that had on the rats, and/or a combination of venom and bacteria? The dragon’s blood has been studied for it’s antibacterial properties, though if they harbor no more dangerous mouth bacteria than any other predator (presumably including us humans as we are the ultimate predators, but they don’t specifically say) I guess those scientists studying the blood are just wasting their time (and Discovery Networks).

    Also, they mention there is only 1.2 ml of venom in the dragon’s huge head. Enough to paralyze a rat, sure… but adult komodo dragons generally eat larger things – only the juveniles eat small mammals regularly. http://en.wikipedia.org/wiki/Komodo_dragon#Diet

    They also have the ability to smell dead/rotting flesh from up to 9 kilometers away – so the bacteria killing a mammal days later, the dragon would be able to track that.

    When they test the venom out on something the size of a goat and it has the same immediate effects that happened on the rat, then the toxic ability of the dragon’s venom will be proven, but if it only paralyzes a rat, that’s not gonna be much good to an adult dragon, which can survive on as little as one meal a month. Further evidence that, yeah, the dragon does have 3 days to track down something it bit and wait for the sepsis to disable it.

    If I had to guess, I’d say that it’s a combination of venom and bacteria – the bites locally paralyzes larger animals limbs (but not the whole body), according to wikipedia – but a goat with one down limb can get away. However, if the limb is paraylzed and bleeding, that will allow the bacteria to get in, which wouldn’t have as great a foothold if the wound bled and clotted normally. Bacterial infections can also cause fever and disorientation, further disabling the animal for the dragon’s eventual arrival.

    Still, up until about 4 years ago, no one believed the dragon had any venom at all, so this is still important work on the largest of all lizards, unfortunately endangered and probably not going to make it to the 22nd century.

    Hey, we should sequence some komodo DNA. I bet their DNA holds secrets.

  • frogboy

    i think this sucks balls!!!!!

  • Ryan

    Presenting the bacterial payload, and the blood thining hypotheses as somehow mutually exclusive makes no sense. Neither of those processes has any chance of inhibiting the other process from disabling prey (that I can see at least). Fry’s work clearly goes a long way in showing that some sort of anti-clotting venom is used by Komodo Dragons. However, his work does not appear to support statements like, “that whole bacteria stuff has been a scientific fairy tale.”

  • landshark

    Every good landshark knows that if you want a
    Kimodo to open the door, you’ve got to tell em
    that you’ve got a hawaaiian pizza. Maybe its the pineapple, I don’t know.

  • Lemur

    Nick, youre correct in thinking that nobody would have concieved the idea of a Komodo dragon having venom, but thats because of how the teeth are shaped. The Komodo dragon has the most complex venom delivering system in the world (for reptiles). and shows no sign of venom if just glanced over as it had been four years ago. Another reason is because of how the monster kills, a snake quickly bites and then lets go so we wonder “how does it efficiently kill its prey?” A komodo dragon is different since all it does is bite down and keep holding it, keeping a forcefull grip on its pray making us believe that it kills its prey like that and only like that. Then we figured out when it bites something and it escapes it later dies, so we wondered “how does this animal die when bitten by a Komodo dragon?” and after seeing how much bacteria is in a Komodo dragon’s mouth, we jumped to the conclusion that its the bacteria causing it. Now that we are going deeper into the anatomy of a Komodo dragon youre scorning this science? you can have your opinion and i respect that, but do more research then one 387 word article

  • Lemur

    furthermore, I would like to recommend you to a site that is more descriptive and is not a website that a 12 year old can change in less than 5 minutes (refering to Nick’s use of wikipedia) :

    http://scienceblogs.com/notrocketscience/2009/05/venomous_komodo_dragons_kill_prey_with_wound-and-poison_tact.php

  • Timothy Earl Gough

    I am so pleased to read that my dream of Komoto Dragon saliva, is being realised for potential use in heart & cancer-tumor patients. I have so many scientific theories on the uses for this saliva. My further dream is to see private corporations developing this saliva to be genetically synthesized into nano-technology; with hope of seeing it applied to computer processors, robotics & batteries.
    Best regards to the scientific community!

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