Varanus komodoensis

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.

• Biogeographic Regions
• oriental oriental
  • native native

• Other Geographic Terms
• island endemic island endemic

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.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest

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.

• Other Physical Features
• heterothermic heterothermic

• Sexual Dimorphism
• male larger

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.

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.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• sexual sexual
• oviparous oviparous

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.

• 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.

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.

• Key Behaviors
• arboreal arboreal
• terricolous
• diurnal diurnal
• sedentary sedentary
• dominance hierarchies dominance hierarchies

Home Range

The home range of Komodo dragons approximately 1.9 km^2 in size.

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.

• Communication Channels
• visual visual
• tactile tactile
• chemical chemical

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • scavenger scavenger

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

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.

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 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.

• 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.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

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

References

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.

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 Reptiles and Amphibians , Vol. 9, 1 Edition. Lakeville, CT: Grey Castle Press.

1998. Monitors and Gila Monster: Komodo Dragon. Pp. 448 in 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.