Komodo dragon

Class: Reptilia
Order: Squamata
Family: Varanidae
Genus and Species: Varanus komodoensis
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  • Lizard resting on the grass with its legs outstretched
  • Komodo Dragon
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Komodo dragon

Komodo dragons, or Komodo monitors, are the largest, heaviest lizards in the world — and one of the few with a venomous bite. These stealthy, powerful hunters rely on their sense of smell to detect food, using their long, forked tongues to sample the air. They can spend hours waiting for a sizable meal to wander within range before launching a deadly attack with their large, curved and serrated teeth.

Physical Description

Komodo dragons are large lizards with long tails, strong and agile necks, and sturdy limbs. Their tongues are yellow and forked. Adults are an almost-uniform stone color with distinct, large scales, while juveniles may display a more vibrant color and pattern.

The muscles of the Komodo's jaws and throat allow it to swallow huge chunks of meat with astonishing rapidity. Several movable joints, such as the intramandibular hinge opens the lower jaw unusually wide. The stomach expands easily, enabling an adult to consume up to 80 percent of its own body weight in a single meal, which most likely explains some exaggerated claims for immense weights in captured individuals. When threatened, Komodos can throw up the contents of their stomachs to lessen their weight in order to flee.

Although males tend to grow larger and bulkier than females, no obvious morphological differences mark the sexes. One subtle clue does exist: a slight difference in the arrangement of scales just in front of the cloaca. Sexing Komodos remains a challenge for human researchers; the dragons themselves appear to have little trouble figuring out who is who.

Size

The Komodo dragon is the largest living lizard in the world. These wild dragons typically weigh about 154 pounds (70 kilograms), but the largest verified specimen reached a length of 10.3 feet (3.13 meters) and weighed 366 pounds (166 kilograms). Males tend to grow larger and bulkier than females.

Native Habitat

Komodo dragons are limited to a few Indonesian islands of the Lesser Sunda group, including Rintja, Padar and Flores, and of course the island of Komodo, the largest at 22 miles (35 kilometers) long. They have not been seen on the island of Padar since the 1970s.

They live in tropical savanna forests but range widely over the islands, from beach to ridge top.

Food/Eating Habits

Komodo dragons eat almost any kind of meat, scavenging for carcasses or stalking animals that range in size from small rodents to large water buffalo. Young feed primarily on small lizards and insects, as well as snakes and birds. If they live to be 5 years old, they move onto larger prey, such as rodents, monkeys, goats, wild boars and deer (the most popular meal). These reptiles are tertiary predators at the top of their food chain and are also cannibalistic.

Although the Komodo dragon can briefly reach speeds of 10 to 13 mph (16 to 20 kph), its hunting strategy is based on stealth and power. It can spend hours in one spot along a game trail — waiting for a deer or other sizable and nutritious prey to cross its path — before launching an attack.

Most of the monitor's attempts at bringing down prey are unsuccessful. However, if it is able to bite its prey, bacteria and venom in its saliva will kill the prey within a few days. After the animal dies, which can take up to four days, the Komodo uses its powerful sense of smell to locate the body. A kill is often shared between many Komodo dragons.

Monitors can see objects as far away as 985 feet (300 meters), so vision does play a role in hunting, especially as their eyes are better at picking up movement than at discerning stationary objects. Their retinas possess only cones, so they may be able to distinguish color but have poor vision in dim light. They have a much smaller hearing range than humans and, as a result, cannot hear sounds like low-pitched voices or high-pitched screams.

The Komodo dragon's sense of smell is its primary food detector. It uses its long, yellow, forked tongue to sample the air. It then moves the forked tip of its tongue to the roof of its mouth, where it makes contact with the Jacobson's organs. These chemical analyzers "smell" prey, such as a deer, by recognizing airborne molecules. If the concentration of molecules present on the left tip of the tongue is greater than that sample from the right, the Komodo dragon knows that the deer is approaching from the left.

This system, along with an undulatory walk, in which the head swings from side to side, helps the dragon sense the existence and direction of food. At times, these reptiles can smell carrion, or rotting flesh, up to 2.5 miles (4 kilometers) away.

This lizard's large, curved and serrated teeth are its deadliest weapon, tearing flesh with efficiency. The tooth serrations hold bits of meat from its most recent meal, and this protein-rich residue supports large numbers of bacteria. Some 50 different bacterial strains, at least seven of which are highly septic, have been found in the saliva. Researchers have also documented a venom gland in the dragon's lower jaw. In addition to the harmful bacteria, the venom prevents the blood from clotting, which causes massive blood loss and induces shock.

The Komodo's bite may be deadly, but not to another Komodo dragon. Those wounded while sparring with each other appear to be unaffected by the bacteria and venom. Scientists are searching for antibodies in Komodo dragon blood that may be responsible. 

The lizard's throat and neck muscles allow it to rapidly swallow huge chunks of meat. Several movable joints, such as the intramandibular hinge, open its lower jaw unusually wide. The dragon's stomach also easily expands, enabling an adult to consume up to 80 percent of its own body weight in a single meal. When threatened, Komodo dragons can throw up the contents of their stomachs to lessen their weight in order to flee.

Komodo dragons are efficient eaters, leaving behind only about 12 percent of their prey. They eat bones, hooves and sections of hide, as well as intestines (after swinging them to dislodge their contents).

At the Smithsonian's National Zoo, the Komodo dragon eats rodents, chicks and rabbits. Occasionally, he consumes fish and carcass meals of beef.

Social Structure

Because large Komodos cannibalize young ones, the young often roll in fecal material, thereby assuming a scent that the large dragons are programmed to avoid. Young dragons also undergo rituals of appeasement, with the smaller lizards pacing around a feeding circle in a stately ritualized walk. Their tail is stuck straight out and they throw their body from side to side with exaggerated convulsions.

Reproduction and Development

Determining the sex of a Komodo dragon is challenging for researchers, as no obvious morphological differences distinguish males from females. One subtle clue is a slight difference in the arrangement of scales just in front of the cloaca. Courtship opportunities arise when groups assemble around carrion to feed, and mating occurs between May and August.

Dominant males compete for females in ritual combat. Using their tails for support, they wrestle in upright postures, grabbing each other with their forelegs as they attempt to throw the opponent to the ground. Blood is often drawn, and the loser either runs away or remains prone and motionless.

Females lay about 30 eggs in depressions dug on hill slopes or within the pilfered nests of megapodes — large, chicken-like birds that make nests of heaped earth mixed with twigs that may be as long as 3 feet (1 meter) in height and 10 feet (3 meters) across.

Delays in egg laying may occur, which could help the clutch avoid the brutally hot months of the dry season. Additionally, unfertilized eggs may have a second chance with subsequent mating. While the eggs incubate in the nest for about nine months, the female may lay on the nest to protect the eggs. No evidence of parental care for newly hatched Komodos exists.

The hatchlings weigh less than 3.5 ounces (100 grams) and average 16 inches (40 centimeters) in length. Their early years are precarious, and they often fall victim to predators, including other Komodo dragons. At 5 years old, they weigh about 55 pounds (25 kilograms) and average 6.5 feet (2 meters) long. At this time, they begin to hunt larger prey. They continue to grow slowly throughout their lives.

Sleep Habits

They escape the heat of the day and seek refuge at night in burrows that are just barely large enough for them.

Lifespan

Komodo dragons live about 30 years in the wild, but scientists are still studying this.

 While they have been hunted (legally and illegally), their population decline is due to their limited range. No Komodo dragons have been seen on the island of Padar since the 1970s, the result of widespread poaching of deer, the reptile's primary source of prey.

Komodo National Park, established in 1980, and strict anti-poaching laws have helped protect the dragons, although illegal activity still takes place. Villagers sometimes poison carrion bait to reduce the population, much like ranchers of the American West poison sheep carcasses to rid the area of coyotes and mountain lions. The Dutch colonial government instituted protection plans as early as 1915.

Each year, more than 18,000 people travel to Indonesia to visit sites that still have these animals. The tourism provides an economic incentive for local people to support the Komodo dragon's protection.

The Smithsonian's National Zoo was the first zoo outside of Indonesia to successfully hatch Komodo dragons. 

Reptile Discovery Center is home to one male Komodo dragon named Murphy.