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Komodo Dragon

Taxonomy

Order: Squamata
Family: Varanidae
Genus/species: Varanus komodoensis


In 1992, Komodo dragons hatched for the first time outside of Indonesia at the National Zoo. Four clutches have hatched and the resulting 55 offspring may be seen in more than 30 zoos around the world. The Zoo's Komodo dragon can be seen in the outdoor enclosure behind the Reptile Discovery Center.

Description:

The Komodo dragon is the largest living lizard. The largest verified specimen reached a length of 10.3 feet (3.13 m) and weighed 366 pounds (166 kg). This may have included a substantial amount of undigested food. More typical weights for the largest wild dragons are about 154 pounds (70 kg). Although the Komodo can run briefly at speeds up to 13 mph (20 kph), its hunting strategy is based on stealth and power. They can spend hours in one spot, waiting for a deer, boar, goat, or anything sizable and nutritious.

Monitors can see objects as far away as 985 feet (300 m), 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. The result is an animal that can not hear such sounds as a low-pitched voice or a high-pitched scream.

Vision and hearing are useful, but the Komodo's sense of smell is its primary food detector. The Komodo detects odors much like a snake does. It uses its long, yellow forked tongue to sample the air, after which the two tongue tips retreat to the roof of the mouth, where they make contact with the Jacobson's organs. The chemical analyzers "smell" a deer by recognizing airborne molecules. If the concentration present on the left tongue tip is higher than that sampled from the right, it tells the Komodo 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 odoriferous carrion from as far away as 2.5 miles (four km), when the wind is right.

When the Komodo is hunting and catches its prey, a deer for example, it attacks the feet first, knocking the deer off balance. When dealing with smaller prey, it may lunge straight for the neck. The dragon’s basic strategy is simple: try to smash the quarry to the ground and tear it to pieces. Strong muscles driving powerful claws accomplish some of this, but the Komodo's teeth are its most dangerous weapon. They are large, curved, and serrated, and tear flesh efficiently. If the deer fails to escape immediately, the Komodo will continue to rip it apart. Once convinced that its prey is incapacitated, the dragon may break off its offensive for a brief rest. The deer is now badly injured and in shock. The dragon then launches the final blow, a belly attack. The deer quickly bleeds to death, and the Komodo begins to feed.

In 2009, researchers concluded that Komodo dragons produce venom whose toxins cause the prey animal to go into shock and decrease its blood from clotting. Biologists had believed that bacteria in the dragon's mouth infected the bitten animal and caused its death. Scientists had found some 50 different bacterial strains, at least seven of which are highly septic, in the saliva. If a bitten deer somehow maneuvers away and escapes immediate death, chances are that its victory, and it, will be short-lived. The venom from the Komodo bite will probably kill it within one week; its attacker, or more likely other Komodos, will then consume it, usually as a group. The Komodo bite is not deadly to another Komodo, however. Dragons wounded in battle with their comrades appear to be unaffected by the otherwise deadly venom. Scientists are searching for antibodies in Komodo blood that may be responsible for saving them from the fate of the infected deer.

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, open 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. Komodos can throw up the contents of their stomachs when threatened to reduce their weight in order to flee.

Large mammalian carnivores, such as lions, tend to leave 25 to 30 percent of their kill unconsumed, declining the intestines, hide, skeleton, and hooves. Komodos eat much more efficiently, forsaking only about 12 percent of the prey. They eat bones, hooves, and swaths of hide. They also eat intestines, but only after swinging them vigorously to scatter their contents. This behavior removes feces from the meal. Because large Komodos cannibalize young ones, the young often roll in fecal material, thereby assuming a scent that the large dragons 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.

Distribution and Habitat:

Komodo dragons are limited to a few volcanic Indonesian islands of the Lesser Sunda group including Komodo, the largest at 22 miles (35 km) long, Rintja, Padar, and Flores.

Komodo dragons are found in tropical savanna forests, but range widely over the islands, from beach to ridge tops. They escape the heat of the day and seek refuge at night in burrows that are barely big enough for them.

Diet in the Wild:

Komodo dragons eat almost any kind of meat. They scavenge from carcasses or stalk animals ranging in size from small rodents to large water buffalo. The young mostly feed on small gecko lizards or insects. They are tertiary predators (predator at the top of the food chain) and are cannibalistic. They can detect carrion from a considerable distance, about 2.5 miles (4 km), and actively seek it out. Komodos hunt along game trails, where they wait for prey, deer or boar, to pass by. They then attack the prey; most are unsuccessful in bringing down an animal. However, if the dragon was able to bite the deer the toxic bacteria in their saliva will kill the prey within the next few days. At that time, they can use their powerful sense of smell to locate the dead animal. A kill is usually shared by many Komodo dragons and very little is wasted.

Zoo Diet:

They are fed rodents, chicks, and rabbits weekly.

Reproduction:

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 to researchers; the dragons themselves appear to have little trouble figuring out who is who. With a group assembled around the carrion, the opportunity for courtship arrives.

Most mating occurs between May and August. Dominant males can become embroiled in ritual combat in their quest for females. 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 usually drawn, and the loser either runs or remains prone and motionless.

The victorious wrestler initiates courtship by flicking his tongue on a female's snout and then over her body. The temple and the fold between the torso and the rear leg are common spots. Stimulation is both tactile and chemical, through skin gland secretions. Before copulation can occur, the male must evert a pair of hemipenes located within his cloaca, at the base of the tail. The male then crawls on the back of his partner and inserts one of the two hemipenes, depending on his position relative to the female's tail, into her cloaca.

The female Komodo lays about 30 eggs in September. The delay in laying may serve to help the clutch avoid the brutally hot months of the dry season. In addition, unfertilized eggs may have a second chance with a subsequent mating. The female lays in depressions dug on hill slopes or within the pilfered nests of Megapode birds. These chicken-size land dwellers make heaps of earth mixed with twigs that may reach three feet (1 m) in height and ten feet (3 m) across. While the eggs are incubating, about nine months, females may lie on the nests, protecting their future offspring. No evidence exists, however, for parental care of newly hatched Komodos.

The hatchlings weigh less than 3.5 ounces (100 g) and average only 16 inches (40 cm) in length. Their early years are precarious, and they often fall victim to predators, including their fellow Komodos. They feed on a diverse diet of insects, small lizards, snakes, and birds. Should they live five years, they can weigh 55 pounds (25 kg) and stretch 6.5 feet (2 m) long. By this time, they have moved on to bigger prey, such as rodents, monkeys, goats, wild boars, and the most popular Komodo food, deer. Slow growth continues throughout their lives, which may last more than 30 years.

Life Span:

Dragons may live about 30 years in the wild, but scientists are still studying this.

Status:

Komodo dragons are endangered due in part to their limited range. It would appear that they have been hunted (legally and illegally) over the years, but not to the extent of decimating the population. 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.

Dutch colonial government instituted protection plans as early as 1915.

Fun Fact:

The ora, or "land crocodile" as they are called by locals, are the largest living lizards. They can reach lengths of more than ten feet and weigh over 300 pounds. The average size for males is eight to nine feet and about 200 pounds.