Are Komodo dragons venomous?



Two Komodo dragons feed on a deer in Komodo National Park on Rinca Island/
Copyright (c) 2007 Chris Kugelman

The world’s largest lizard, the Komodo dragon, inspires fascination and fear. The thing is just totally cool. It’s a massive lizard, found on some Indonesian islands, that grows nearly ten feet long, and it can kill prey even larger than itself, like water buffalo, goats, and pigs – sometimes with a single bite. Scientists have speculated about this predatory behavior for some time now. How could a single bite take down a large mammal? Sometimes those prey would wander off, seeming to escape, only to croak not long after – and then the dragon got its meal. Biologists had previously argued that the dragon’s saliva had some sort of bacteria that infected the prey after a bite, causing it to die.

But in a recent study just published in the Proceedings of the National Academy of Sciences (PNAS), Bryan Fry, a biologist at the University of Melbourne in Australia who calls himself the Venom Doc, and colleagues disagree with that, arguing that the dragon uses venom rather than bacteria that kill the prey. It’s a new hypothesis, and until now, the only known venomous reptiles were snakes and another small family of lizards that includes only the Gila monster and the beaded lizard.

The PNAS study argued that the lizard’s lightweight skull and its dimensions are not really suited to delivering super strong bites, like crocodilians do, but rather well adapted to bite and pull at flesh, leaving large wounds that get bathed in venom. After several Komodo dragons mysteriously died at the Singapore zoo, the zoo allowed Fry to dissect their jaws to study the neck glands and search for venom, something not possible in wild animals because of the lizard’s endangered status. Fry and colleagus found two types of venom, one with anti-coagulation properties that exaggerates the effects of the deep wounds by preventing blood clotting, and another that induces low blood pressure and shock, hence immobilizing the prey. "This 'combined arsenel' is an effective way to dispatch a prey item," says Fry.

Up until recently, scientists thought venom in snakes and lizards evolved independently, but this study and another published by Fry and colleagues in 2006 in the journal, Nature argues instead that venom is a “basal characteristic,” or a trait shared by both snakes (Serpentes), and several lizard families, including the one with Komodo dragons, monitor lizards, and the gigantic extinct Varanus megalania.

"There are three living members of this spectacular, unusual clade that all have the same sort of large, blade-like serrated teeth: Komodo dragon, Crocodile monitor, and the lace monitor of Australia that is simply a smaller megalania but still big at up to 2.3 meters," says Fry. "They, and Megalania, are the most formidable lizards to have every lived."

Watch as Komodo Dragons take down prey nearly five times their size.

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