Describer (Date): P.A. Ouwens (1912) On a large Varanus species
from the island of Komodo. Bull. Jard. Bot. Buitenzorg. 2(6):1-3. Earliest
official mention by H. Zollinger (1850). Verslag van eene reis naar Bima en
Sumbawa en naar eenige plaatsen op Celebes, Saleyer en Flores gedurende de
maanden Mei tot December, 1847. Vehl. Batav. Gennotschap. 23:10-22.
Kingdom: Animalia Phylum: Chordata Class: Reptilia Subclass:
Diapsida (Crocodiles, tuataras, lizards, snakes) Order: Squamata (lizards, snakes and amphisbaenians or "worm-lizards") Suborder: Sauria (Lacertilia) Infraorder: Autarchoglossa Family: Varanidae Genus:Varanus (50 recognized species) Species: V. komodoensis
Taxonomy
The genus name "Varanus" was introduced in 1820 by
German professor, Blasius Merrem. It is a latinization of the Arabic
"waran," the Egyptian name for the Nile monitor. (Egyptians believed that these lizards served as "monitors,"
alerting people to the presence of crocodiles.)
70 species and subspecies of Varanus have been described but
only 50 species are currently recognized. Size is the most variable
anatomical characteristic in the family (length varies from 0.32m to
3.5m). All species are similar in appearance.
The family Varanidae includes the largest living lizards.
First mention of Komodo dragon in scientific literature: Peter Owens in 1912 mentions "Varanus species of an unusual size" from Komodo Island.
Common Names
Komodo Dragon. (Komodo is the name of one of the islands on which they
are found).
"Ora" is a local name in the Mangarrai dialect.
The Hindi name "biscobra" implies that it is twice as deadly
as the cobra.
The Malaysian name "buaja darat" means land crocodile.
Members of the Varanidae family are commonly referred to
"varanids," "monitors," or (in Australia)
"goannas."
Phylogeny
The oldest varanoid fossils (95 million years ago, Cretaceous) are related to the early mososaurs and snakes; lived in Europe and Asia
Genus Varanus first appeared in the fossil record 45 million
years ago in central Asia but paleontologists suggest an ultimate African origin for the genus based on phylogenetic studies.
A possible direct ancestor of the Komodo Dragon is thegigantic Pleistocene fossil Megalania prisca from Pleistocene deposits in eastern Australia.
DISTRIBUTION & HABITAT
(Auffenberg, 1981)(CBSG, 1995)
Restricted to the islands of Komodo, Flores, Rinca and Gilli Motang in
the middle of the Lesser Sunda Islands, Republic of Indonesia. Less
than 1000 sq km of is officially protected and designated Komodo
National Park.
Different methodologies have produced different population figures.
Best current estimate from the IUCN/SSC/CBSG : 5000
Distribution
map from Ciofi, 1999
In Komodo National Park:
1600 on Komodo
1100 on Rinca
70 on Gilli Montang
Flores:
100 on W. Flores (Wae Waul Reserve)
2000 scattered in non-protected areas
One of world's major volcanic areas. Slight tremors felt every few
weeks; volcanic ash fall occurs periodically.
Largest komodo habitat is on the island of Komodo where they occupy the
entire island. On Flores they occupy 400 sq km and on Rinca 278 sq km
Regions inhabited are arid and mountainous. Komodos are usually found
in the rocky valleys between 500-700 m. They prefer the extensive flat
savannas. The driest savanna is studded with lontar palms. Moister
grasslands have tamarind and jujube trees.Adult Komodos frequently
occupy the transition zone between tropical monsoon forest (tamarind
and kapok trees, cycads and ferns) and the savanna.
Found from sea level to 800 m.
Average temperature 26.7 C at sea level (Range: 17C - 43C)
Largest living lizard. (Males: 3 m, 90 kg; Females 2 m, 70 kg)
Average field weight: about 47 kg. (Heaviest 54 kg)
Average field length: Up to 260 cm
Head raised to full extent is approximately 40 cm above the ground.
When lowered the animal is less than 20 cm high (Long neck can stretch
to give the dragon a better view of its surroundings in tall grass.
Toes have sharp, recurved claws.
Teeth are specialized for a carnivorous diet. They are serrated,
compressed laterally, and curved posteriorly with a sharp tip and
broad base, (Curved teeth are better than straight teeth for catching
and holding prey). Although many varanids have one or two replacement
teeth at each position, the komodo has four or five. Longest teeth are
approximately 2 cm.
Short intestine is typical of carnivores (Diets high in proteins and
lipids don't require a great deal of digestive processing)
Juvenile Komodos are slender and agile. Adults are massive with flatter
bodies and proportionately shorter tails
Skin is like "chain-mail" with numerous osteoderms. Shedding
occurs in patches and lasts about 6 months each year (In the Komodo
this begins in September)
Tongue is long and narrow with a deep fork at its tip. It does not move
freely in the mouth, but retracts into a sheath. It is partially
supported by a complex structure of bone and cartilage called the
hyoid apparatus. Varanids are unique in using their tongues only as a
sensory organ for locating prey and as a socialization tool. Other
lizards use the tongue to manipulate food.
Males are bulkier and larger than females.
Coloration
Most adults are uniformly gray or clay-colored. Until the age of four
they have much brighter, speckled skin. (Komodos of Flores retain
brighter coloration)
There is little sexual dimorphism. The flanks of adult females have
more red than males. Yellowish-green nose spots are more common in
males
The light yellow tongue is species specific. (V. salvator has a
blue tongue, V. dumerili and V. grayi have pink tongues)
Olfaction
Sense of smell extremely important in food detection. Komodos can
detect the scent of carrion from as far as 11 km. (Decomposition
releases volatile oils - wind and size of prey are important factors)
Each external nostril leads to a multi-chambered nasal capsule. (One of
the chambers functions to excrete excess sodium.) A pair of Jacobson's
organs open into the roof of the mouth. Scent particles are collected
by the forked tongue and delivered to these sense organs which
stimulate the brain to react.
Vision
Eyes are placed laterally and covered by two unequal lids.
Upper lid has little mobility.
Lower lid contains a cartilaginous plate which slides over surface of
the eye
Hearing
The ear important for maintaining balance as well as sound reception.
Behavior seems to be more scent than sound oriented
Respiration
Varanid lungs are larger than most reptiles.
Take in relatively larger amounts of oxygen and their physiology
produces a more efficient system of air circulation.
Breathing rate is regular and low but varanids can voluntarily hold
their breath for long periods.
Circulation
Varanids have a more complex heart structure and blood chemistry
than other lizards.
This allows them to achieve intense activity without becoming
exhausted.
Water/Salt Balance
Water makes up 70% of a lizard's body weight. (10% more than humans).
Varanid skin is covered with scales and contains no sweat glands.
Excess sodium is removed by a special salt-secreting glands in the
nasal capsules (many lizards have them)
Ridding body of excess heat impacts behavior patterns
Primarily diurnal. (Range is from 4:30-23:30). Usual waking time is
between 6:00 and 6:30 AM.
Two activity peaks: 9:30 and 15:30
Travel about 2 km/day (Adults may travel as much as 10 km/day).
Adults spend an average of 26 days searching for prey. 10-20 minutes
eating. (A 50 kg female was observed to swallow a 31 kg boar in 17
minutes). 3-6 days is spent in digestive pause.
Activity levels are lowest in early part of dry season. At the end of
the season and throughout the rainy season activity increases
(probably related to weaker prey)
Basking = 72% of morning activity. 33% of afternoon activity
Shade-seeking = 22% of morning activity; 58% of afternoon activity
Largest Komodos spend all waking hours on the ground. Younger animals
readily climb into trees to feed, rest, or escape predation
Sleep about 12 hours every day. Shelters are burrows, natural cavities
and overhanging vegetation
Range (Auffenberg, 1981)
Factors influencing range: topography, prey density, social status,
size and sex
Range consists of a foraging area and a scavenging area
Foraging area has a core area related to shelter/burrows and
thermoregulatory/basking sites
50% of activity occurs in core area
Foraging area is 5-28 times larger than core area. For hatchlings this
area may be a clump of trees; for an adult the average area is 4.2 sq
km
Scavenging area is determined by the location of dead animals
and can be extremely large (young oras do not scavenge)
Locomotion
Quadrupedal, plantigrade.
Body, head, and tail are undulated gently from side to side in walking
rhythm. Normal speed 4.8 km/hr (3 mi/hr)
When running body and tail are held fairly rigid. Tail is off the
ground. Hind feet move in wide lateral arc. 14-18.5 km/hr over short
distance (8.7-11 mi/hr)
Swimming:
Most monitors are good swimmers. Diving and swimming under water
is effective escape behavior.
Longest known swim: between the islands of Komodo and Nusa
Mbarapu, a distance of at least 450 m. (a bit over 1/4 mile)
Tree climbing:
At young ages dragons are fairly good but cautious climbers.
They lose their skill as they get older and heavier.
Only very young lizards jump from branch to branch.
Digging
Common activity. Komodos regularly excavate burrows, dig out megapode
eggs, search for rodents, lizards and snakes.
Digging is done with the front feet. One leg digs repeatedly for
several strokes, then the other. Hind legs are not used to throw out
dirt. Lizard backs up slowly, throwing the dirt with fore limbs.
Rubbing
Smaller Komodos rub their bodies on the ground near or in carrion. Most
rub themselves in hair or intestinal contents.
Rubbing behavior not practiced by adults.
Thermoregulation
All varanids are ectotherms. (Heat their bodies by basking and
absorbing energy from the sun or warm surfaces. Cool themselves by
seeking shade, or burrowing
"Gular fluttering" or "hyoid panting" is used only
in cases of extreme overheating. (Mouth is held open and gular region
of throat is inflated with air. Air is expelled in fluttering
fashion).
Dig dens to protect themselves from the heat of the sun. They may also
occupy thickets or burrows at night to regulate their temperature
Optimal body temperatures do not differ significantly from most other
reptiles but deep body temperatures tend to remain more uniform than
any other reptile.
Body temperatures of individuals drop to as low as 20 degrees
Centigrade at night and can reach above 40 degrees Centigrade during
the day.
Drinking is similar to snakes: immerse snout to the eyes, suck up water
then raise head and allow water to run down throat. Most manage
without free water from April through December.
Communication
General
Komodo dragons are solitary animals, meeting only to reproduce.
Territorial Behavior
Foraging and scavenging areas are very large and not easily defensible
so territoriality is minimal if it exists at all.
Dominance hierarchies are based on sex and size. This determines
position at feeding sites.
Displays / Visual signals:
No sexual displays but an aggregation of Komodos may be essential to
successful breeding. Aggregations are also believed to be important in
establishing and reinforcing hierarchies
Threat display includes loud hissing. Tail lashing and/or quivering,
gaping mouth, guilar inflation, arched back
Appeasement: licking, ritual walking. Mouth closed (no hissing)
Subdominant individual usually flees.
Strongly scented fecal pellets are deposited on trails and are
investigated by other animals with their tongues
Flight/escape includes lunging and biting, scratching, and defecation
Regurgitation may occur in younger animals.
Fighting between males often results in severe lacerations and even
death.
Vocalizations
Hissing is one of few sounds made.
It is usually associated with defensive behavior and is used during
feeding, during attacks and frequently by females during mating.
Olfactory signals
As with all snakes and lizards, many of their responses are completely
dependent on chemical cues.
Scent plays an important role in territorial marking while hunting
Ethogram (=behavior inventory): See Auffenberg (1981: 124-127), The
Komodo Monitor
Interspecies Interaction (Auffenberg, 1981)
In addition to Komodo dragons, at least 190 species of terrestrial
animals co-habit the Indonesian islands
Feral dogs, man and medium Komodos compete for the same major resouces
(deer & boar)
Varanus salvator coexists on only one island and avoid contact
with the larger Komodo
Smaller animals: Snakes, lizards, and rats utilize Komodo burrows for
shelter.
Opportunistic carnivores. Feed on a wide variety of prey
Hatchlings feed exclusively on insects (beetles and grasshoppers)
Small komodos tend to be arboreal and feed on smaller lizards, insects
birds and their eggs.
Medium Komodos feed largely on rodents (rats, shrews) birds (megapodes
and various small species) geckos, skinks and small snakes.
Large Komodos feed on carrion or hunt animals along game trails: wild
boar, sunda deer, water buffalo, large snakes, occasionally smaller
Komodos.
About 16 scavenging dragons occupy a sq km
Large Komodos kill about one large prey ungulate (deer or boar) per
month. This is supplemented with small prey (birds, rats)
Most lizards have broad flat tongues that are used primarily for food
handling but varanids have snake-like tongues which lack tastebuds and
can be retracted into a sheath. As the lizard searches for food or
explores, the tongue is moved up and down through an arc sampling
about 7 sq cm of air. Odor molecules are then carried back to the
vomeronasal organs
Jaws close rapidly (enabling capture of fast-moving prey.) Prey is held
(sometimes thrashed) until all movement ceases. Small prey is
swallowed whole, usually head first. Large prey is sliced in pieces
and devoured.
Tongue is partially attached to a skeletal structure called the hyoid
apparatus. All snakes and lizards have such a structure which helps in
swallowing large food items.
Swallowing is accomplished by pushing prey down the throat while the
flexible jaws move forward to engulf it. Large prey is torn apart. The
hyoid apparatus moves it back to the esophagus. Neck muscles bend from
side to side to move food through the esophagus.
Ingestion rate may be as much as 2.5 kg/min - higher than any other
predator except large snakes.
After a heavy feeding, Komodos drink from water holes produced by wild
boar
High digestive efficiency (70-90%) Time is dependent upon temperature
(about 26 hours at normal body temperature) Cool nights can delay to
almost 5 days. Stress can slow or even stop digestion (defecation of
partially digested prey may occur)
Similar to owls, all varanids regurgitate gastric pellets of
undigestible material.
Fecal pellets may include hair, feathers, partly digested bones,
hooves, teeth, and claws and are excreted covered with a semisolid,
white uric acid paste.
Many species of Varanus have been thought to have poisonous
bites but it is more likely that the bacterial culture in their saliva
produces a severe septic wound. (Four bacterium species have been
identified: Staphilococcus sp, Providencia sp, Proteus
morgani and Proteus mirabilis)
REPRODUCTION & DEVELOPMENT
(Auffenberg, 1981)(IUCN/SSC CBSG, 1994)(Judd & Bacon, 1977)
Courtship
Sexual maturity for both males and females occurs between 5 and 7 years
(Data from captive population indicates first reproduction for females
occurs 7-10 years)
Adult sex ratio: Auffenberg's 1981 study reports 3 males to 1 female.
Lilley reports 3.4 males to 1 female in his 1994 CAMP report.
Courtship and mating in Zoos and the field have been observed from Jan
19-October 1. Successful coition from June 28 to October.
Territories are not established. Courtship and mating takes place in
small aggregations of Komodos near carrion (other lizards usually mate
alone).
Monitors (like fishes and some birds) have a very brief courtship.
Mating occurs quickly. Attacks of males upon females are common at the
time of, and immediatley after, coitus. Most female acts are agonistic
(use teeth and tails) during early phases of courtship. Males must be
able to completely restrain females in order to remain uninjured.
Visual display is not significant. Other cues: rubbing chin on top of
body and neck of female. Hard scratches to back. Tongue-licks to area
around hind legs, shoulders, neck and head
Mounting occurs several times in each courtship sequence
Nesting
Nest is an excavation in soil or in nests of megapods (mound-builder birds)
1-30 eggs laid in a clutch (average is 18) Females may lay one or more
eggs several times during several, successive days. Most females lay
only one clutch per year. (July to early September)
Eggs of all varanids have a soft, leathery shell.
Incubation: 2.5 - 8 months (probably dependent on temperature and soil
moisture)
220 days when in captivity
Young appear in April or May and may remain together in small groups
for several months. Hatchlings weigh about 80 grams and average length
49 cm
Development
Young are arboreal during their first year
Adults largely terrestrial and rarely climb. May construct burrows
along vertical banks of stream beds or under boulders and fallen
trees. May also spend the night sleeping in high grass or dense brush.
Female breeding ability thought to decline around age of 20 and cease
around 30 yrs
Longevity: About 25 years in captivity. (Frankfurt Zoo & Berlin
Aquarium) Auffenberg estimates a lifespan of 50 years in wild.
PATHOLOGY & DISEASES
Reptiles are generally resistant to bacterial diseases
Ticks found on wild dragons. (Aponomma komodoense,Amblyomma robinsoni, A. helvolum)
Little evidence of parasitemia in the wild
Problems in captivity:
Amoebiasis and bacterial infections (of hepatic
ducts or cloaca)
Skin and foot infections
Humid conditions can
result in skin discoloration
Respiratory infections (collection of
mucus around the mouth or nostrils and closed eyes) can result from
too cool conditions without a proper basking site
Gaping and gular
pumping signify pneumonia
Causes of death: liver necrosis, acute hemorrhagic proctitis severe
colitis and enteritis
In 1934 the first Komodo Dragon was placed on exhibit at the Smithsonian's National Zoological Park.
SD Zoo received first dragons in 1968, two females and a male (no
offspring)
Few successful breedings worldwide: 3 Indonesian Zoos
(Ragunan, Surabaya and Gembira Loka), plus the National Zoological Park, Miami Metrozoo, Honolulu Zoo and the
Cincinnati Zoo.
POPULATON AND CONSERVATION STATUS
(CBSG, 1995) (Hudson, et al, 1994)
IUCN status: Vulnerable (A taxon is vulnerable when not
Critically Endangered or Endangered but facing a high rate of
extinction in the medium-term future)
CITES appendix I : komodo dragon is threatened with extinction
and affected by international trade.
Protected under Indonesian law (1931,1990) and 1991 Ministerial Decree
Different methodologies have produced different population figures.
Best current estimate from the IUCN/SSC/CBSG : 5000
In Komodo National Park:
1600 on Komodo
1100 on Rinca
70 on Gilli Montang
Flores:
100 on W. Flores (Wae Waul Reserve)
2000 scattered in non-protected areas
Conservation Efforts
Komodo National Park established in 1980: First management unit - 1984.
173,300 hectares on 3 major islands - Komodo, Rinca and Gilli
Motang
Funded from central government office in Jakarta
Management team is called " Perlindungan Hutan Dan
Pelestarian Alam" or PHPA and is based at Labuan Bajo
on the west coast of Fores. Staff of 90 (54 rangers)
Park Administration has initiated a conservation awareness program for
young people in the region - some training of tour guides -
participation in annual census.
Future plans: Extend KNP boundaries to two further islands; restrict
population growth of island villages (two on Rinca and one on Komodo)
Threats to Survival
Main threat is human interference - habitat destruction due to logging,
increased population
Wild dogs
Forest fires started by poachers to drive prey
Dynamite and cyanide poisoning used to collect fish for food has
disturbed population
Poaching of deer on Padar led to Komodo's disappearance from this
island
Because the wild population is geographically restricted it is
sensitive to fluctuations in environmental conditions, disease
epidemics, genetic drift, and inbreeding
Small closed populations are predicted to have low levels of genetic
variability and increased disease susceptibility.
Deposition of volcanic ash can destroy vegetation and alter habitat.
Flores populations have declined markedly in the past few years because
of logging concessions