Komodo Dragon (Varanus komodoensis)

File:Komodo dragon with tongue.jpg

(http://en.wikipedia.org/wiki/File:Komodo_dragon_with_tongue.jpg)

  •  Name: Komodo dragon
  • Latin: Varanus komodoensis
  • Classification: Reptile
  • Origin: Asia
  • Lifespan: Up to 50 years

Taxonomy

  • Kingdom: Animalia (animals)
  • Phylum: Chordata (vertebrates)
  • Class: Reptilia (reptiles)
  • Order: Squamata (scaled reptiles)
  • Family: Varanidae (carnivorous lizards)
  • Genus: Varanus (monitor lizards)
  • Species: Varanus komodoensis (Komodo dragon)

Appearance

  • Length: Male – 8-10ft (2.4-3m) Female – Up to 8ft (2.4m)
  • Weight: Male – 300-500lbs (136-226kg) Female – Up to 200lbs (90kg)

The Komodo dragon is the heaviest lizard in the world. They are dull black, grey or green in colour. Their heads look similar to snakes, with a rounded snout and a forked tongue. They have a heavy tail which can be the same length as its body. They also have bowed legs with long, curved claws on all four feet.

Young Komodos differ in appearance as they are dark in colouration but have patches of yellow, white, green and black on their scaled skin.

Relatives

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  • Bengal monitor (Varanus bengalensis) -LEAST CONCERN-
  • Lace monitor (Varanus varius) -LEAST CONCERN-
  • Yellow-headed water monitor (Varanus cumingi) -LEAST CONCERN-
  • Yellow monitor (Varanus flavescens) -LEAST CONCERN-

Habitat & Distribution

Populations of the Komodo dragon can be found on a few volcanic islands of the Lesser Sunda group such as Komodo, Rintja, Pandar and Flores. It mainly occurs in the harsh climates of tropical savannah forests where there is very little rainfall and temperatures can reach 82’F (27’C). Komodo dragons can range from the beaches to ridge tops of its islands homes in search of food.

Map showing the distribution of the Komodo dragon taxa

(http://www.bbc.co.uk/nature/life/Komodo_dragon)

Diet

Komodo dragons are carnivorous and eat mainly carrion. Their diet can include invertebrates, other reptiles, birds and their eggs, goats, deer, water buffalo, feral pigs and other reptiles. They can also display cannibalistic behaviour and eat young Komodo dragons. The young Komodos will eat insects, eggs and small lizards and mammals.

These dragons have sharp teeth that resemble that of a shark. Any animal that escapes the jaws of a dragon will only die later on from blood infection as its saliva is full of bacteria. It has also been recently discovered that these lizards have a venom gland in their jaw, however, it has not yet been confirmed if their bites are venomous.

Large prey will be torn into chunks by the dragon when eating it. Smaller prey (such as goats) can be eaten whole due to their loosely articulated jaws, flexible skulls and expandable stomachs. It will take a komodo dragon 10-20 minutes to swallow a small mammal during which can breathe through a small tube under the tongue leading to the lungs. A dragon can eat as much as 80% of its body weight in one sitting. Typically the vegetable content of the stomach and intestines are left untouched.

After eating, the Komodo dragon will sit in a sunny spot to speed up digestion. If left undigested for long, food in the stomach can rot and poison the animal. Their slow metabolism means they can survive on as little as 12 meals a year. After digestion has been completed, the dragon will regurgitate a pellet made up of horns, hair and teeth.

Occasionally, the Komodo dragon will consume human corpses dug from shallow graves. This has caused the villagers of Komodo to mode their graveyards from sandy to clay ground and pile rocks on top of the individual graves to deter the lizards.

Behaviour

Komodo dragons can be active during day or night and are solitary, gathering together only to breed or at large meals. They can sprint at speeds of 20kph for short distances, are good swimmers (can dive 4.5m deep) and can use their large claws to climb trees.

These dragons use their powerful forelegs and claws to dig holes for shelter, around 1-3m wide. By resting in these holes, they can maintain body heat during the night and reduce sunbathing time in the morning. The komodo dragons tend to take shelter during the hottest part of the day. Their hiding places located within the reach of a sea breeze, little vegetation and tend to have the inhabitants dung scattered about. These hiding places are also excellent places to wait for deer and strike from.

Reproduction

For the Komodo dragons, mating occurs between May and September. During this time, the males will fight over females and territory by scrapping with each other on their hind legs, the loser will eventually be pinned to the ground. Before a fight, the males have been known to vomit or defecate. The victor will then flick his tongue over the female to gain information about her receptivity.

During early courtship, the females will resist with their teeth and claws so to avoid injury, the male must fully restrain the female during coitus. Other behaviours displayed during courtship include licking and hard scratches along the back. These dragons can also be monogamous and form ‘pair bonds’, a behaviour rare in reptiles.

Clutches of eggs are laid in September and are laid in either a burrow dug into the side of a hill or in an abandoned nesting mount of orange-footed scrubfowl. The average clutch size is 20 eggs and incubation can last between 7 and 8 months.

The young hatch from their shells using an egg tooth which falls off shortly after. They are born defenceless and vulnerable to predation by animals including adults of their own kind. The young spend most of their first few years in the trees and will often roll in the faeces of other animals to deter predators. Komodo dragons take 3-5 years to mature and can have a total lifespan of up to 50 years.

Female komodo dragons are also able to reproduce sexually or asexually depending on their environmental conditions. Parthogenesis, the ability for an unfertilized egg to develop to maturity, occurs in 70% of all vertebrate species.

Adaptations

  • It has been recently discovered that the Komodo dragon has a venom gland located in its jaw. This venom rapidly decreases blood pressure, expedites blood loss and sends the victim into shock, slowing it down enough to be killed by the dragon.
  • The saliva of the komodo dragon is full of bacteria that can kill small animals and make their larger prey feel very sick. There are 50 kinds of bacteria in the dragons saliva.
  • The main food source of the komodo dragon is deer. To ensure the food source does not run dry, the komodo dragon has adapted to survive on only 1/10 of the food intake of carnivorous mammals.
  • The komodo dragon has the ability to regrow any lost teeth several times over, not unlike that of a shark.

Threats

There are around 5,000 individual komodo dragons in the world, only 350 or which are breeding females. Their population is thought to be only a fraction of what it was 50 years ago. Their main reasons for decline are habitat loss, loss of prey species and hunting.

They are susceptible to storms, fires and disease and are sought after by trophy hunters. The skins and feet are used to make novelty items. In the past, they have been trapped for sale to zoos and private collectors. Since the 1970’s, no komodo dragons have been seen on the island of Padar.

Conservation

  • IUCN Status: Vulnerable

The Komodo dragon has been protected by law since the 1930’s and has become an increasingly popular animal. This flagship species brings in over 18,000 tourists a year to the area, helping to raise funding for all the animals on the islands.

They are protected by CITIES (Appendix I) which prohibits all international trade in the animal. They are also part of an EEP breeding programme working to create an insurance population amongst zoos around the world.

Fun Facts

  • Male: Bull
  • Female: Cow, lizardess
  • Young: Hatchling, pup
  • Group: Lounge, clan
  • The komodo dragon is the largest and most powerful lizard in the world.
  • It is immune to its own venom.
  • The komodo dragon can throw up the contents of its stomach to make itself lighter when it feels the need to flee.
  • It is also called the ‘land crocodile’ by locals.

References

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