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Comodo Dragon

Published on January 2017 | Categories: Documents | Downloads: 21 | Comments: 0




The Komodo dragon also known as the Komodo monitor, is a large species of lizard found in
the Indonesian islands of Komodo, Rinca, Flores, Gili Motang, and Padar. A member of the
monitor lizard family Varanidae, it is the largest living species of lizard, growing to a
maximum length of 3 metres (10 ft) in rare cases and weighing up to approximately 70
Their unusually large size has been attributed to island gigantism, since no other carnivorous
animals fill the niche on the islands where they live. However, recent research suggests the
large size of Komodo dragons may be better understood as representative of a relict
population of very large varanid lizards that once lived across Indonesia and Australia, most
of which, along with other megafauna, died out after the Pleistocene. Fossils very similar to
V. komodoensis have been found in Australia dating to greater than 3.8 million years ago, and
its body size remained stable on Flores, one of the handful of Indonesian islands where it is
currently found, over the last 900,000 years, "a time marked by major faunal turnovers,
extinction of the island's megafauna, and the arrival of early hominids by 880 ka kiloannum
As a result of their size, these lizards dominate the ecosystems in which they live. Komodo
dragons hunt and ambush prey including invertebrates, birds, and mammals. It has been
claimed that they have a venomous bite; there are two glands in the lower jaw which secrete
several toxic proteins. The biological significance of these proteins is disputed, but the glands
have been shown to secrete an anticoagulant. Komodo dragon group behaviour in hunting is
exceptional in the reptile world. The diet of big Komodo dragons mainly consists of deer,
though they also eat considerable amounts of carrion. Komodo dragons also occasionally
attack humans in the area of West Manggarai Regency where they live in Indonesia.
Mating begins between May and August, and the eggs are laid in September. About 20 eggs
are deposited in abandoned megapode nests or in a self-dug nesting hole. The eggs are
incubated for seven to eight months, hatching in April, when insects are most plentiful. Young
Komodo dragons are vulnerable and therefore dwell in trees, safe from predators and
cannibalistic adults. They take 8 to 9 years to mature, and are estimated to live up to 30 years.
Komodo dragons were first recorded by Western scientists in 1910. Their large size and
fearsome reputation make them popular zoo exhibits. In the wild, their range has contracted
due to human activities, and they are listed as vulnerable by the comimittees. They are
protected under Indonesian law, and a national park, Komodo National Park, was founded to
aid protection efforts.

Evolutionary history :
The evolutionary development of the Komodo dragon started with the Varanus genus, which
originated in Asia about 40 million years ago and migrated to Australia. Around 15 million
years ago, a collision between Australia and Southeast Asia allowed the varanids to move into
what is now the Indonesian archipelago, extending their range as far east as the island of
Timor. The Komodo dragon was believed to have differentiated from its Australian ancestors
4 million years ago. However, recent fossil evidence from Queensland suggests the Komodo
dragon evolved in Australia before spreading to Indonesia.Dramatic lowering of sea level
during the last glacial period uncovered extensive stretches of continental shelf that the
Komodo dragon colonised, becoming isolated in their present island range as sea levels rose

Description :
In the wild, an adult Komodo dragon usually weighs around 70 kg (150 lb), although captive
specimens often weigh more. According to the Guinness Book of World Records, an average
adult male will weigh 79 to 91 kg (174 to 201 lb) and measure 2.59 m (8.5 ft), while an
average female will weigh 68 to 73 kg (150 to 161 lb) and measure 2.29 m (7.5 ft). The
largest verified wild specimen was 3.13 m (10.3 ft) long and weighed 166 kg (366 lb),
including undigested food. The Komodo dragon has a tail as long as its body, as well as about
60 frequently replaced, serrated teeth that can measure up to 2.5 cm (1 in) in length. Its saliva
is frequently blood-tinged, because its teeth are almost completely covered by gingival tissue
that is naturally lacerated during feeding. This creates an ideal culture for the bacteria that
live in its mouth. It also has a long, yellow, deeply forked tongue. Komodo dragon skin is
reinforced by armoured scales, which contain tiny bones called osteoderms that function as a
sort of natural chain-mail. This rugged hide makes Komodo dragon skin poorly suited for
making into leather.

Senses :
As with other varanids, Komodo dragons have only a single ear bone, the stapes, for
transferring vibrations from the tympanic membrane to the cochlea. This arrangement means
they are likely restricted to sounds in the 400 to 2,000 hertz range, compared to humans who
hear between 20 and 20,000 hertz. It was formerly thought to be deaf when a study reported
no agitation in wild Komodo dragons in response to whispers, raised voices, or shouts. This
was disputed when London Zoological Garden employee Joan Proctor trained a captive
specimen to come out to feed at the sound of her voice, even when she could not be seen.
The Komodo dragon can see objects as far away as 300 m (980 ft), but because its retinas
only contain cones, it is thought to have poor night vision. The Komodo dragon is able to see
in colour, but has poor visual discrimination of stationary objects.

Komodo dragon using their tongue to sample the air.

Behaviour and ecology :
The Komodo dragon prefers hot and dry places, and typically lives in dry, open grassland,
savanna, and tropical forest at low elevations. As an ectotherm, it is most active in the day,
although it exhibits some nocturnal activity. Komodo dragons are solitary, coming together
only to breed and eat. They are capable of running rapidly in brief sprints up to 20 km/h
(12 mph), diving up to 4.5 m (15 ft), and climbing trees proficiently when young through use
of their strong claws. To catch out-of-reach prey, the Komodo dragon may stand on its hind
legs and use its tail as a support. As it matures, its claws are used primarily as weapons, as its
great size makes climbing impractical.
For shelter, the Komodo dragon digs holes that can measure from 1 to 3 m (3.3 to 9.8 ft) wide
with its powerful forelimbs and claws. Because of its large size and habit of sleeping in these
burrows, it is able to conserve body heat throughout the night and minimise its basking period
the morning after. The Komodo dragon hunts in the afternoon, but stays in the shade during
the hottest part of the day. These special resting places, usually located on ridges with cool
sea breezes, are marked with droppings and are cleared of vegetation. They serve as strategic
locations from which to ambush deer.

Komodo dragons are carnivores. Although they eat mostly carrion, they also ambush live
prey with a stealthy approach. When suitable prey arrives near a dragon's ambush site, it will
suddenly charge at the animal and go for the underside or the throat. It is able to locate its
prey using its keen sense of smell, which can locate a dead or dying animal from a range of
up to 9.5 km (5.9 mi). Komodo dragons have been observed knocking down large pigs and
deer with their strong tails.
Komodo dragons eat by tearing large chunks of flesh and swallowing them whole while
holding the carcass down with their forelegs. For smaller prey up to the size of a goat, their
loosely articulated jaws, flexible skulls, and expandable stomachs allow them to swallow
prey whole. The vegetable contents of the stomach and intestines are typically avoided.
Copious amounts of red saliva the Komodo dragons produce help to lubricate the food, but
swallowing is still a long process (15–20 minutes to swallow a goat). A Komodo dragon may
attempt to speed up the process by ramming the carcass against a tree to force it down its
throat, sometimes ramming so forcefully, the tree is knocked down. To prevent itself from
suffocating while swallowing, it breathes using a small tube under the tongue that connects to
the lungs. After eating up to 80% of its body weight in one meal, it drags itself to a sunny
location to speed digestion, as the food could rot and poison the dragon if left undigested for
too long. Because of their slow metabolism, large dragons can survive on as little as 12 meals
a year. After digestion, the Komodo dragon regurgitates a mass of horns, hair, and teeth
known as the gastric pellet, which is covered in malodorous mucus. After regurgitating the

gastric pellet, it rubs its face in the dirt or on bushes to get rid of the mucus, suggesting it
does not relish the scent of its own excreations.
The largest animals eat first, while the smaller ones follow a hierarchy. The largest male
asserts his dominance and the smaller males show their submission by use of body language
and rumbling hisses. Dragons of equal size may resort to "wrestling". Losers usually retreat,
though they have been known to be killed and eaten by victors.
The Komodo dragon's diet is wide-ranging, and includes invertebrates, other reptiles
(including smaller Komodo dragons), birds, bird eggs, small mammals, monkeys, wild boar,
goats, deer, horses, and water buffalo. Young Komodos will eat insects, eggs, geckos, and
small mammals. Occasionally, they consume humans and human corpses, digging up bodies
from shallow graves. This habit of raiding graves caused the villagers of Komodo to move
their graves from sandy to clay ground and pile rocks on top of them to deter the lizards. The
Komodo dragon may have evolved to feed on the extinct dwarf elephant Stegodon that once
lived on Flores, according to evolutionary biologist Jared Diamond.
The Komodo dragon drinks by sucking water into its mouth via buccal pumping (a process
also used for respiration), lifting its head, and letting the water run down its throat.

Auffenberg described the Komodo dragon as having septic pathogens in its saliva (he
described the saliva as "reddish and copious"), specifically the bacteria E. coli,
Staphylococcus sp., Providencia sp., Proteus morgani, and P. mirabilis. He noted, while these
pathogens can be found in the mouths of wild Komodo dragons, they disappear from the
mouths of captive animals, due to cleaner diets and the use of antibiotics. This was verified
by taking mucous samples from the external gum surfaces of the upper jaws of two freshly
captured individuals. Saliva samples were analysed by researchers at the University of Texas,
who found 57 strains of bacteria growing in the mouths of three wild Komodo dragons,
including Pasteurella multocida. The rapid growth of these bacteria was noted by Fredeking:
"Normally it takes about three days for a sample of P. multocida to cover a Petri dish; ours
took eight hours. We were very taken aback by how virulent these strains were". This study
supported the observation that wounds inflicted by the Komodo dragon are often associated
with sepsis and subsequent infections in prey animals. How the Komodo dragon is unaffected
by these virulent bacteria remains a mystery.
Research in 2013 suggested that the bacteria in the mouths of Komodo dragons are ordinary
and similar to those found in other carnivores. They actually have surprisingly good mouth
hygiene. As Bryan Fry put it: "After they are done feeding, they will spend 10 to 15 minutes
lip-licking and rubbing their head in the leaves to clean their mouth... Unlike people have
been led to believe, they do not have chunks of rotting flesh from their meals on their teeth,
cultivating bacteria." The observation of prey dying of sepsis would then be explained by the
natural instinct of water buffalos, who are not native to the islands where the Komodo dragon

lives, to run into water when attacked. The warm, faeces-filled water would then cause the
infections. The study used samples from 16 captive dragons (10 adults and six neonates) from
three U.S. zoos.

In late 2005, researchers at the University of Melbourne speculated the perentie , other
species of monitors, and agamids may be somewhat venomous. The team believes the
immediate effects of bites from these lizards were caused by mild envenomation. Bites on
human digits by a lace monitor , a Komodo dragon, and a spotted tree monitor all produced
similar effects: rapid swelling, localised disruption of blood clotting, and shooting pain up to
the elbow, with some symptoms lasting for several hours.
In 2009, the same researchers published further evidence demonstrating Komodo dragons
possess a venomous bite. MRI scans of a preserved skull showed the presence of two glands
in the lower jaw. The researchers extracted one of these glands from the head of a terminally
ill specimen in the Singapore Zoological Gardens, and found it secreted several different
toxic proteins. The known functions of these proteins include inhibition of blood clotting,
lowering of blood pressure, muscle paralysis, and the induction of hypothermia, leading to
shock and loss of consciousness in envenomated prey. As a result of the discovery, the
previous theory that bacteria were responsible for the deaths of Komodo victims was
Kurt Schwenk, an evolutionary biologist at the University of Connecticut, finds the discovery
of these glands intriguing, but considers most of the evidence for venom in the study to be
"meaningless, irrelevant, incorrect or falsely misleading". Even if the lizards have venom-like
proteins in their mouths, Schwenk argues, they may be using them for a different function,
and he doubts venom is necessary to explain the effect of a Komodo dragon bite, arguing that
shock and blood loss are the primary factors.
Other scientists such as Washington State University's Biologist Kenneth V. Kardong and
Toxicologists Scott A. Weinstein and Tamara L. Smith, have stated that this allegation of
venom glands "has had the effect of underestimating the variety of complex roles played by
oral secretions in the biology of reptiles, produced a very narrow view of oral secretions and
resulted in misinterpretation of reptilian evolution". According to these scientists "reptilian
oral secretions contribute to many biological roles other than to quickly dispatch prey". These
researchers concluded that, "Calling all in this clade venomous implies an overall potential
danger that does not exist, misleads in the assessment of medical risks, and confuses the
biological assessment of squamate biochemical systems".
Reproduction :

Mating occurs between May and August, with the eggs laid in September. During this period,
males fight over females and territory by grappling with one another upon their hind legs,
with the loser eventually being pinned to the ground. These males may vomit or defecate
when preparing for the fight. The winner of the fight will then flick his long tongue at the

female to gain information about her receptivity. Females are antagonistic and resist with
their claws and teeth during the early phases of courtship. Therefore, the male must fully
restrain the female during coitus to avoid being hurt. Other courtship displays include males
rubbing their chins on the female, hard scratches to the back, and licking. Copulation occurs
when the male inserts one of his hemipenes into the female's cloaca. Komodo dragons may
be monogamous and form "pair bonds", a rare behavior for lizards.
Young Komodo dragons spend much of their first few years in trees, where they are relatively
safe from predators, including cannibalistic adults, as juvenile dragons make up 10% of their
diets. The habit of cannibalism may be advantageous in sustaining the large size of adults, as
medium-sized prey on the islands is rare. When the young approach a kill, they roll around in
faecal matter and rest in the intestines of eviscerated animals to deter these hungry adults.
Komodo dragons take approximately three to five years to mature, and may live for up to 50

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