Komodo dragon

Appearance

In the wild, an adult Komodo dragon usually weighs around 70 kg although captive specimens often weigh more. According to the Guinness Book of World Records, an average adult male will weigh 79 to 91 kg and measure 2.59 m, while an average female will weigh 68 to 73 kg and measure 2.29 m.

The Komodo dragon has a tail as long as its body, as well as about 60 frequently replaced, serrated teeth that can measure up to 2.5 cm in length. Its saliva is frequently blood-tinged, because its teeth are almost completely covered by gingival tissue that is naturally lacerated during feeding. This creates an ideal culture for the bacteria that live in its mouth. It also has a long, yellow, deeply forked tongue. Komodo dragon skin is reinforced by armoured scales, which contain tiny bones called osteoderms that function as a sort of natural chain-mail. This rugged hide makes Komodo dragon skin poorly suited for making into leather.

Naming

The Komodo dragon is also known as the Komodo monitor or the Komodo Island monitor in scientific literature, although this is not very common. To the natives of Komodo Island, it is referred to as "ora", "buaya darat", or "biawak raksasa".

Status

The Komodo dragon is a vulnerable species and is on the IUCN Red List. There are approximately 4,000 to 5,000 living Komodo dragons in the wild. Their populations are restricted to the islands of Gili Motang, Gili Dasami, Rinca, Komodo, and Flores. However, there are concerns that there may presently be only 350 breeding females. To address these concerns, the Komodo National Park was founded in 1980 to protect Komodo dragon populations on islands including Komodo, Rinca, and Padar. Later, the Wae Wuul and Wolo Tado Reserves were opened on Flores to aid with Komodo dragon conservation.

Habitat

The Komodo dragon prefers hot and dry places, and typically lives in dry, open grassland, savanna, and tropical forest at low elevations. As an ectotherm, it is most active in the day, although it exhibits some nocturnal activity. Komodo dragons are solitary, coming together only to breed and eat.

They are capable of running rapidly in brief sprints up to 20 km/h, diving up to 4.5 m, and climbing trees proficiently when young through use of their strong claws. To catch out-of-reach prey, the Komodo dragon may stand on its hind legs and use its tail as a support. As it matures, its claws are used primarily as weapons, as its great size makes climbing impractical.

For shelter, the Komodo dragon digs holes that can measure from 1–3 m wide with its powerful forelimbs and claws. Because of its large size and habit of sleeping in these burrows, it is able to conserve body heat throughout the night and minimize its basking period the morning after. The Komodo dragon hunts in the afternoon, but stays in the shade during the hottest part of the day. These special resting places, usually located on ridges with cool sea breezes, are marked with droppings and are cleared of vegetation. They serve as strategic locations from which to ambush deer.

Reproduction

Mating occurs between May and August, with the eggs laid in September. During this period, males fight over females and territory by grappling with one another upon their hind legs, with the loser eventually being pinned to the ground. These males may vomit or defecate when preparing for the fight. The winner of the fight will then flick his long tongue at the female to gain information about her receptivity. Females are antagonistic and resist with their claws and teeth during the early phases of courtship. Therefore, the male must fully restrain the female during coitus to avoid being hurt. Other courtship displays include males rubbing their chins on the female, hard scratches to the back, and licking. Copulation occurs when the male inserts one of his hemipenes into the female's cloaca. Komodo dragons may be monogamous and form "pair bonds", a rare behavior for lizards.

The female lays her eggs in burrows cut into the side of a hill or in the abandoned nesting mounds of the Orange-footed Scrubfowl, with a preference for the abandoned mounds. Clutches contain an average of 20 eggs, which have an incubation period of 7–8 months. Hatching is an exhausting effort for the neonates, which break out of their eggshells with an egg tooth that falls off soon after. After cutting out, the hatchlings may lie in their eggshells for hours before starting to dig out of the nest. They are born quite defenseless and are vulnerable to predation.

Young Komodo dragons spend much of their first few years in trees, where they are relatively safe from predators, including cannibalistic adults, as juvenile dragons make up 10% of their diets. According to David Attenborough, the habit of cannibalism may be advantageous in sustaining the large size of adults, as medium-sized prey on the islands is rare. When the young approach a kill, they roll around in fecal matter and rest in the intestines of eviscerated animals to deter these hungry adults. Komodo dragons take approximately three to five years to mature, and may live for up to 50 years.

Food

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. 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. 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.

The largest animals eat first, while the smaller ones follow a hierarchy. The largest male asserts his dominance and the smaller males show their submission by use of body language and rumbling hisses. Dragons of equal size may resort to "wrestling". Losers usually retreat, though they have been known to be killed and eaten by victors.

The Komodo dragon's diet is wide-ranging, and includes invertebrates, other reptiles, birds, bird eggs, small mammals, monkeys, wild boar, goats, deer, horses, and water buffalo. Young Komodos will eat insects, eggs, geckos, and small mammals. Occasionally, they consume humans and human corpses, digging up bodies from shallow graves. This habit of raiding graves caused the villagers of Komodo to move their graves from sandy to clay ground and pile rocks on top of them to deter the lizards. The Komodo dragon may have evolved to feed on the extinct dwarf elephant "Stegodon" that once lived on Flores, according to evolutionary biologist Jared Diamond.

The Komodo dragon drinks by sucking water into its mouth via buccal pumping, lifting its head, and letting the water run down its throat.

Evolution

The evolutionary development of the Komodo dragon started with the "Varanus" genus, which originated in Asia about 40 million years ago and migrated to Australia. Around 15 million years ago, a collision between Australia and Southeast Asia allowed the varanids to move into what is now the Indonesian archipelago, extending their range as far east as the island of Timor. The Komodo dragon was believed to have differentiated from its Australian ancestors 4 million years ago. However, recent fossil evidence from Queensland suggests the Komodo dragon evolved in Australia before spreading to Indonesia. Dramatic lowering of sea level during the last glacial period uncovered extensive stretches of continental shelf that the Komodo dragon colonized, becoming isolated in their present island range as sea levels rose afterwards.