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Varanus komodoensisKomodo Dragon

By Leanne Lawwell

Geographic Range

Varanus komodoensis is found only in the lesser Sunda region of the Indonesian archipelago, including the islands of Komodo, Flores, Rinca, and Padar. ("Komodo Dragon", 2005; De Lisle, 1996)

Habitat

Adult Komodo dragons live mainly in tropical savannah forests. They prefer open lowland areas with tall grasses and bushes, but are also found in other habitats, such as beaches, ridge tops, and dry riverbeds. Young Komodo dragons are arboreal and live in forested regions until they are eight months old. ("Komodo Dragon", 2005; De Lisle, 1996; Wikramanayake, 1997)

  • Range elevation
    0 to 820 m
    0.00 to 2690.29 ft

Physical Description

Komodo dragons are the largest lizards, reaching 165 kg and greater than three meters in length. Juveniles are green with yellow and black bands. Adults dull and uniform in color, from brown to grayish red. Their robust bodies are uniformly covered in rough scales. They have strong limbs and a powerful, muscular tail. The heads of Komodo dragons have a rounded snout and ear openings. Their skulls are flexible and have sharp, serrated teeth. Although males tend to grow larger, there are no obvious morphological differences between the sexes. ("Komodo Dragon", 2005; Cogger and Zweifel, 1992; De Lisle, 1996)

  • Sexual Dimorphism
  • male larger
  • Range mass
    165 (high) kg
    363.44 (high) lb
  • Range length
    3.1 (high) m
    10.17 (high) ft

Development

Varanus komodoensis hatches from eggs. Young Komodo dragons live in trees to avoid falling prey to older members of the species. They are also much smaller and more sinuous than the adults, allowing them to live in trees. At 8 months, they grow too large to be arboreal, alter their diet, and become terrestrial. ("Komodo Dragon", 2005; Murphy, et al., 2002)

Reproduction

Males engage in a ritual combat to mate with females. They wrestle in an upright position to try to throw the loser to the ground, often drawing blood. When ready to mate, females give off a scent in their feces that males can detect. Male Komodo dragons then locate the female, rub their chin on her head, scratch her back, and lick her body. If the female exhibits interest, she licks him back. He then grasps her with his claws, lifts her tail with his, and mates with her. After mating, some males will stay with the female for a few days to prevent other males from mating with her. ("Komodo Dragon", 2005; "Lizards and Worm Lizards - Sauria and Amphisbaenia", 1991; Ciofi and Jessop, 2004; Murphy, et al., 2002)

The mating season of Varanus komodoensis occurs yearly in July and August. Females lay up to thirty eggs about a month later (September) to avoid the hot summer months and allow a chance for a second mating. The eggs are buried in the earth and take about 8 months to hatch. Hatchlings are about 37 centimeters long and have a high mortality rate, frequently falling prey to adults and other species. As a result, they move to nearby trees as soon as they are able. It is estimated that females reach sexual maturity after 9 years and males reach it after 10 years. ("Komodo Dragon", 2005; De Lisle, 1996; Wikramanayake, 1997)

  • Breeding interval
    Varanus komodoensis breeds once yearly, but females will often mate more than once to ensure that their eggs are fertilized.
  • Breeding season
    Breeding occurs from July to September.
  • Range number of offspring
    30 (high)
  • Average number of offspring
    22
    AnAge
  • Average gestation period
    8 months
  • Average gestation period
    49 days
    AnAge
  • Average age at sexual or reproductive maturity (female)
    9 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    1825 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    10 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    1825 days
    AnAge

Female Komodo dragons dig a nest chamber in the ground for their eggs and cover it with earth and leaves. They then lie on the nest while the eggs are incubating, but there is no evidence of any parental care once the eggs hatch. ("Komodo Dragon", 2005; "Lizards and Worm Lizards - Sauria and Amphisbaenia", 1991)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • female

Lifespan/Longevity

Although many Varanus komodoensis individuals fall prey to other animals as hatchlings, ones that live to adulthood usually have a lifespan of around 50 years. (Cogger and Zweifel, 1992)

Behavior

Komodo dragons spend the day roaming their home ranges, which can be as large as 1.9 square kilometers. They do not defend these home ranges, so ranges can overlap, but if food is found in a shared area, the dominant dragon gets to eat first. When food is found, the largest males are always first to eat, followed by smaller males and females, and then by juveniles who descend from the trees to eat once the adults have left. Varanus komodoensis often scavenges for food, but individuals can also run quickly and hunt stealthily and powerfully, smashing its prey to the ground and tearing it with its claws and teeth. Their saliva contains more than 50 different strains of bacteria that can result in the death of prey from infection even after only being bitten. Varanus komodoensis digs burrows that it retreats into at night and when the weather is very hot. ("Komodo Dragon", 2005; Cogger and Zweifel, 1992; De Lisle, 1996; "Komodo Dragon", 2005; "Lizards and Worm Lizards - Sauria and Amphisbaenia", 1991; Cogger and Zweifel, 1992; De Lisle, 1996)

Home Range

The home range of Komodo dragons approximately 1.9 km^2 in size. ("Komodo Dragon", 2005; "Lizards and Worm Lizards - Sauria and Amphisbaenia", 1991; Cogger and Zweifel, 1992; De Lisle, 1996)

Communication and Perception

Although Varanus komodoensis can see 300 meters away and can hear a restricted range of sound, its sense of smell is its primary method for detecting food and the tip of its tongue is its primary scent detector. Males communicate dominance in mating and feeding order by wrestling in upright positions. Females give off a scent in their feces to communicate that they are ready to mate and the male replies by rubbing his chin on her and licking her body. ("Komodo Dragon", 2005; "Lizards and Worm Lizards - Sauria and Amphisbaenia", 1991; Murphy, et al., 2002)

Food Habits

A normal adult Komodo dragon diet consists mainly of carrion, but it is not uncommon for them to attack and eat a variety of large prey, including goats, pigs, deer, wild boar, horses, water buffalo, and smaller Komodo dragons. Komodo dragons hunt larger prey by ambushing them and delivering a bite. They then follow the injured animal until they succumb to either blood loss or infection. The saliva of Komodo dragons is rich in bacteria that rapidly leads to infection in their prey. A recent discovery of venom in the bites of Varanus species implies that venoms may be used in subduing prey also, although specific research on Komodo dragon venom action has not been completed. Juveniles feed on grasshoppers, beetles, small geckos, eggs, birds, and eventually small mammals. Varanus komodoensis is able to swallow large pieces of food by expanding its throat and its flexible skull. They eat most of their prey, leaving very little to be wasted. ("Komodo Dragon", 2005; "Lizards and Worm Lizards - Sauria and Amphisbaenia", 1991; Cogger and Zweifel, 1992; Fry, et al., 2006)

  • Animal Foods
  • birds
  • mammals
  • reptiles
  • eggs
  • carrion
  • insects

Predation

Adult Komodo dragons are at the top of their food chain and do not have any predators. Juveniles often fall prey to adults, larger mammals, and birds. They avoid predation by being arboreal until they become larger. ("Komodo Dragon", 2005; De Lisle, 1996)

Ecosystem Roles

Varanus komodoensis is a top predator in its habitat and one of the largest animals present in the area. It is also a scavenger that eats recently dead animals and removes them from the landscape. ("Komodo Dragon", 2005; "Lizards and Worm Lizards - Sauria and Amphisbaenia", 1991)

Economic Importance for Humans: Positive

Komodo dragons are an important ecotourism draw. Scientists are also conducting studies on how they are able have strains of lethal bacteria living in their saliva without being affected by them.

  • Positive Impacts
  • ecotourism
  • research and education

Economic Importance for Humans: Negative

Varanus komodoensis individuals have been known to attack and kill humans in a few rare occurrences. They also have attacked and harmed livestock in the area. (Cogger and Zweifel, 1992; Wikramanayake, 1997)

  • Negative Impacts
  • injures humans

Conservation Status

Komodo dragons are currently classified as endangered throughout their range. This status is the result of a combination of prey depletion, poaching, and habitat encroachment by humans. (Cogger and Zweifel, 1992; Cohn, 1994; Murphy, et al., 2002)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Leanne Lawwell (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College.

Glossary

acoustic

uses sound to communicate

arboreal

Referring to an animal that lives in trees; tree-climbing.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

native range

the area in which the animal is naturally found, the region in which it is endemic.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scavenger

an animal that mainly eats dead animals

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

2005. Komodo Dragon. Pp. 94-97 in World of Animals: Amphibians and Reptiles, Vol. 3, 1 Edition. Danbury, CT: Grolier.

1991. Lizards and Worm Lizards - Sauria and Amphisbaenia. Pp. 1606-1608 in M Corliss Pearl, ed. Reptiles and Amphibians, Vol. 9, 1 Edition. Lakeville, CT: Grey Castle Press.

1998. Monitors and Gila Monster: Komodo Dragon. Pp. 448 in P Whitefield, ed. The Simon and Schuster Encyclopedia of Animals: A Visual Who's Who of the World's Creatures, 1 Edition. New York, NY: Simon and Schuster Editions.

Ciofi, C., T. Jessop. 2004. Tracing the Dragon. BBC Wildlife: 52-58.

Cogger, H., R. Zweifel. 1992. Reptiles and Amphibians. New York, NY: Smithmark.

Cohn, J. 1994. Indonesian treasure has a Jurassic appeal. BioScience, 44: 40-44.

De Lisle, H. 1996. The Natural History of Monitor Lizards. Malabar, Florida: Krieger Publishing Company.

Fry, B., N. Vidal, J. Norman. 2006. Early evolution of the venom system in lizards and snakes. Nature, 439: 584-588.

Mattison, C. 1989. Lizards of the World. London: Blandford.

Murphy, J., C. Ciofi, C. De La Panouse, T. Walsh. 2002. Komodo Dragons: Biology and Conservation. Washington: Smithsoniam Institution Press.

Wikramanayake, E. 1997. Everyone knows that the dragon is only a mythical beast. Smithsonian, 28: 74-79.

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