Komodo dragons (Varanus komodoensis) can't chomp as hard as crocodiles and aren't as massive as grizzly bears, so how do they kill huge deer and even humans?

It's all in the bite and a dose of venom—not bacteria, as some previous research had suggested. The dragons, native to a handful of central Indonesian islands, use serrated teeth to "grip and rip" prey, creating a deep wound. Then they add their own special blend of venom, according to study results that were just published online in Proceedings of the National Academy of Sciences.

"The dragon is truly poisonous," Stephen Wroe, a biological research fellow at University of New South Wales in Australia and study author, said in a statement.

Biologists have long assumed that the big lizards, which measure about 6.5 to 9.8 feet (2 to 3 meters) and weigh about 150 to 220 pounds (68 to 100 kilograms), kill prey by infecting it with pathogenic bacteria. But the new study shows that dragons carried different pathogens in the their mouths. Most of the bugs weren't terribly unusual.

Instead, the researchers found that the lizards actually have the most complex venom-delivery system known in reptiles, which had been overlooked because the animal's teeth are so different than those of most venomous creatures.

The dragons produce toxic proteins—not unlike those of gila monsters and some snakes—that cause a drop in blood pressure and decreased clotting. Specialized ducts move the venom from five separate small compartments to openings between serrated teeth. After venom enters a substantial wound, victims can go into shock and bleed to death.

The discovery of the Komodo's venom system leads the researchers to believe that its extinct relative, the Megalania (Varanus prisca), which, at as much as 4,400 pounds (2,000 kilograms), could have been the biggest venomous animal ever to stalk the earth.

Image of a Komodo dragon and prey on Komodo Island courtesy of Chris Kegelman