Why Komodo Dragons Are Like The Entire Cat Family

As a fully grown adult, a Komodo dragon is a formidable 10-foot (3-metre), 200-pound (90-kilogram) predator, whose steak-knife teeth and sizeable claws can bring down large prey, and whose bulk and chain-mail skin make it impervious to everything except humans. But when it first hatches, a Komodo is just a hand-sized lizard that weighs a tenth of a kilogram, hides in trees, and relies on mottled scales for camouflage. It takes around a decade reach its final form.

What happens during those years?

To find out, Deni Purwandana and Achmad Ariefiandy from the Komodo Survival Program, a Indonesian non-profit, have been monitoring the lizards in the wild since 2002. They’ve watched at least 25 individually identified dragons taking down their prey. They’ve analysed vomited remains. They’ve wrangled the lizards with noose-poles, photographed them with camera traps, and mapped their movements with radio trackers. Their efforts have painted a comprehensive portrait of a Komodo dragon’s life.

Video: Living Among Ancient Dragons. See how these predators bring down prey.

The team found, unsurprisingly, that the dragons take on larger prey as they get bigger. But this transition isn’t smooth. At first, they stick to small, lightweight prey like rodents. But when they hit the 20 kilogram mark, they switch to taking down prey much larger than themselves, including 50-kilogram rusa deer and water buffalo. The change is sudden and total. One year, they’re going after scurrying, lightweight meals. The next, they’re feeding entirely on hoofed quarry.

This abrupt switch is mirrored in other aspects of their lives. As youngsters, they forage actively for small prey, moving a lot but sticking to a small range. Once they hit the 20-kilogram threshold, their average daily movement rates go down, but they start wandering over larger areas. They become ambush predators, which mostly sit in wait for passing prey, but stride over large distances to find new lurking spots.

You can find similar transitions in other groups of predators. The cats, for example, range from the diminutive rusty-spotted cat to the mighty Siberian tiger, 300 times heavier. It’s been said that “all cats over 25 kilograms kill large prey, and all cats under 15 kilograms kill small prey.” Again, there’s a 20 kilogram threshold where species go from killing things smaller than themselves to tackling bigger prey.

But here, we’re talking about species of different sizes, not individuals of different ages.

Among mammal carnivores, youngsters and adults tend to feast on prey of similar sizes, because parents provide the juveniles with food. But reptiles typically aren’t that social, and their hatchlings must fend for themselves. That’s why their tastes in prey change so radically as they get bigger. You see this in everything from snakes to scorpions, but it’s especially obvious in Komodo dragons because they span such a wide range of sizes.

The youngsters behave like small rodent-hunters, like ocelots or wildcats, while the grown-ups are the equivalents of leopards or lions. As Purwandana and Ariefiandy write, Komodo dragons “function as an entire vertebrate predator guild.” In other words, these lizards play the role of the entire cat family.