Special Report

The Komodo Dragon is an All-Purpose Killing Machine

A visit to one of Indonesia’s most popular tourist destinations could be your last

Previously off the beaten path, Komodo island is now one of Indonesia’s most popular travel destinations. (Reinhard Dirscherl / Visuals Unlimited. Inc.)
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In fact, scientists now say that the dragons evolved to full size on mainland Australia, where they had a lot of competition. In 2006, Scott Hocknull, a paleontologist at the Queensland Museum, discovered some puzzling fossils in a cave in northeastern Australia, and later confirmed that they were the remains of Komodo dragons that lived 3.8 million years ago. Rather than being the specialized product of island evolution, Hocknull argues, the dragon is really a “generalist carnivore” that feeds on multiple types of prey in a variety of environments. Relatives of the Komodo—monitor lizards that can grow five to six feet long—still live in Australia.

Auffenberg also popularized one of the biggest misconceptions about the Komodo—that its mouth is full of nasty bacteria that cause deadly lesions in bite wounds, enabling it to take down large prey, including water buffalo. He based the idea on bacteria he’d found in Komodo saliva and the infected wounds he’d observed in horses and water buffalo in western Flores.

“An enchanting fairy tale,” says Bryan Fry, a herpetologist at the University of Queensland. “It makes no evolutionary sense.” One problem is that water buffalo were introduced to the region by humans and have never been the dragon’s natural prey. Moreover, the dragons seldom succeed in killing such large animals. Fry says water buffaloes attacked by dragons develop infected wounds from wallowing in filthy water; if they die and become a dragon’s meal, that’s more of a lucky break (for the dragon, not the buffalo) than an evolutionary adaptation.

But there’s no denying the dragons are effective when they strike smaller prey, such as deer and pigs. Tim Jessop, a University of Melbourne ecologist, who has spent more time studying dragons in the field than anyone since Auffenberg, observed that 70 percent of the prey die within minutes, 20 percent die of blood loss within four hours and only 10 percent survive.

Why so lethal? Fry has discovered the secret is the mouth after all—dragons are venomous. When he scanned a dragon’s head with an MRI device, he found in its gums a series of glands that produce venom. It is secreted into the saliva and enters the wound created by the dragon’s sawlike teeth. This venom, Fry has shown, prevents blood clotting and causes muscles around blood vessels to relax, hastening blood loss and leading to a dangerous drop in blood pressure. “This is a sustained march toward unconsciousness,” says Fry.

At first glance, the discovery presents an evolutionary enigma. We usually think of venom, whether deployed by a rattlesnake or a scorpion, as a weapon that a small animal uses to kill larger prey, or to protect itself from becoming someone else’s meal. But the dragons aren’t exactly small. The answer, Fry realized after designing a computer model of the dragon’s jaw, was that the animal doesn’t have a strong bite. A saltwater crocodile, whose skull is about the same size, produces 6.5 times more bite force than a dragon. Komodos can barely hold onto prey, preferring to wound, release—and wait. “They grab whatever they can and slice it,” Fry says.

Previously, there were only two known venomous lizards: the Gila monster of the American Southwest and the Mexican beaded lizard. Their venoms lower blood pressure and impair coagulation, but also attack muscle tissue and disrupt the nervous system. Fry, having documented vestiges of venom glands in dozens of species, from Chinese crocodile lizards to seasnakes, concludes that the ability to produce venom emerged just once in the evolution of lizards and snakes 170 million years ago. If a species evolved another, perhaps more efficient means of subduing prey—like a rat snake’s constricting embrace—its venom glands atrophied over time, a phenomenon that biologists call a trait loss. The dragon evolved a slimmer skull—a precision cutting instrument—while retaining the venom. The result is a lethal dual-weapons system.


August is the height of the breeding season and, during our visit, most Komodo dragons were defending their nests or looking for mates far from established trails and water holes. Fred and his family were chipper as usual as we passed mounds of dirt and rock that were 10 to 20 feet in diameter and at least as tall as his 9-year-old son. The mounds are the nests of chicken-like birds called orange-footed megapodes, which don’t incubate their eggs with body heat but bury them atop plant matter that produces heat as it decays. The dragons remodel these nests for their own eggs, and guard them for six months, a rather long incubation.

Reptiles aren’t known for brains, but Komodo dragons create dummy chambers with dead ends, thwarting wild pigs and perhaps other, now-extinct scavengers—“the ghost of predation past,” says Jessop. When the dragons finally hatch, they take to the trees to avoid being eaten by larger dragons. At one point we spotted a tiny dragon that had risked a visit to the ground and was hunting for insects in the leaf litter.

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