However, recent research suggests the large size of Komodo dragons may be better understood as representative of a relict population of very large varanid lizards that once lived across Indonesia and Australia, most of which, along with other megafauna, died out after the Pleistocene. Fossils very similar to V. komodoensis have been found in Australia dating to greater than 3.8 million years ago, and its body size remained stable on Flores, one of the handful of Indonesian islands where it is currently found, over the last 900,000 years, "a time marked by major faunal turnovers, extinction of the island's megafauna, and the arrival of early hominids by 880 ka."
Komodo dragons are carnivores. Although they eat mostly carrion, they will also ambush live prey with a stealthy approach. When suitable prey arrives near a dragon's ambush site, it will suddenly charge at the animal and go for the underside or the throat. It is able to locate its prey using its keen sense of smell, which can locate a dead or dying animal from a range of up to 9.5 km (5.9 mi). Komodo dragons have been observed knocking down large pigs and deer with their strong tails.
Komodo dragons eat by tearing large chunks of flesh and swallowing them whole while holding the carcass down with their forelegs. For smaller prey up to the size of a goat, their loosely articulated jaws, flexible skulls, and expandable stomachs allow them to swallow prey whole. The vegetable contents of the stomach and intestines are typically avoided]. Copious amounts of red saliva the Komodo dragons produce help to lubricate the food, but swallowing is still a long process (15–20 minutes to swallow a goat). A Komodo dragon may attempt to speed up the process by ramming the carcass against a tree to force it down its throat, sometimes ramming so forcefully, the tree is knocked down. To prevent itself from suffocating while swallowing, it breathes using a small tube under the tongue that connects to the lungs. After eating up to 80% of its body weight in one meal it drags itself to a sunny location to speed digestion, as the food could rot and poison the dragon if left undigested for too long. Because of their slow metabolism, large dragons can survive on as little as 12 meals a year. After digestion, the Komodo dragon regurgitates a mass of horns, hair, and teeth known as the gastric pellet, which is covered in malodorous mucus. After regurgitating the gastric pellet, it rubs its face in the dirt or on bushes to get rid of the mucus, suggesting, like humans, it does not relish the scent of its own excretions.