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комо́дский вара́н

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Komodo dragon Temporal range: Pliocene–Holocene,[1] 3.8–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Male at the Cincinnati Zoo
Conservation status
Endangered (IUCN 3.1)[2]
CITES Appendix I (CITES)[3]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Family:	Varanidae
Genus:	Varanus
Subgenus:	Varanus
Species:	V. komodoensis
Binomial name
Varanus komodoensis Ouwens, 1912[4]
Komodo dragon distribution

The Komodo dragon (Varanus komodoensis), also known as the Komodo monitor, is a member of the monitor lizard family Varanidae that is endemic to the Indonesian islands of Komodo, Rinca, Flores, and Gili Motang. It is the largest extant species of lizard, growing to a maximum length of 3 m (9.8 ft), and weighing up to 70 kg (150 lb).

As a result of their size, Komodo dragons are apex predators, and 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 that secrete several toxic proteins. The biological significance of these proteins is disputed, but the glands have been shown to secrete an anticoagulant. Komodo dragons’ group behavior in hunting is exceptional in the reptile world. The diet of Komodo dragons mainly consists of Javan rusa (Rusa timorensis), though they also eat considerable amounts of carrion. Komodo dragons also occasionally attack humans.

Mating begins between May and August, and the eggs are laid in September; as many as 20 eggs are deposited at a time in an abandoned megapode nest 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 dwell in trees to avoid predators, such as 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 is likely to contract further from the effects of climate change; due to this, they are listed as Endangered by the IUCN Red List. They are protected under Indonesian law, and Komodo National Park was founded in 1980 to aid protection efforts.

Taxonomic history

Komodo dragons were first documented by Europeans in 1910, when rumors of a «land crocodile» reached Lieutenant van Steyn van Hensbroek of the Dutch colonial administration.^[5] Widespread notoriety came after 1912, when Peter Ouwens, the director of the Zoological Museum of Bogor, Java, published a paper on the topic after receiving a photo and a skin from the lieutenant, as well as two other specimens from a collector.^[4]

The first two live Komodo dragons to arrive in Europe were exhibited in the Reptile House at London Zoo when it opened in 1927.^[6] Joan Beauchamp Procter made some of the earliest observations of these animals in captivity and she demonstrated their behaviour at a Scientific Meeting of the Zoological Society of London in 1928.^[7]

The Komodo dragon was the driving factor for an expedition to Komodo Island by W. Douglas Burden in 1926. After returning with 12 preserved specimens and two live ones, this expedition provided the inspiration for the 1933 movie King Kong.^[8] It was also Burden who coined the common name «Komodo dragon».^[9] Three of his specimens were stuffed and are still on display in the American Museum of Natural History.^[10]

The Dutch island administration, realizing the limited number of individuals in the wild, soon outlawed sport hunting and heavily limited the number of individuals taken for scientific study. Collecting expeditions ground to a halt with the occurrence of World War II, not resuming until the 1950s and 1960s, when studies examined the Komodo dragon’s feeding behavior, reproduction, and body temperature. At around this time, an expedition was planned in which a long-term study of the Komodo dragon would be undertaken. This task was given to the Auffenberg family, who stayed on Komodo Island for 11 months in 1969. During their stay, Walter Auffenberg and his assistant Putra Sastrawan captured and tagged more than 50 Komodo dragons.^[11]

Research from the Auffenberg expedition proved enormously influential in raising Komodo dragons in captivity.^[12] Research after that of the Auffenberg family has shed more light on the nature of the Komodo dragon, with biologists such as Claudio Ciofi continuing to study the creatures.^[13]

Etymology

The Komodo dragon is also sometimes known as the Komodo monitor or the Komodo Island monitor in scientific literature,^[14] although this name is uncommon. To the natives of Komodo Island, it is referred to as ora, buaya darat (‘land crocodile’), or biawak raksasa (‘giant monitor’).^[15][5]

Evolutionary history

The evolutionary development of the Komodo dragon started with the genus Varanus, which originated in Asia about 40 million years ago and migrated to Australia, where it evolved into giant forms (the largest of all being the recently extinct Varanus priscus, or «Megalania»), helped by the absence of competing placental carnivorans. Around 15 million years ago, a collision between the continental landmasses of Australia and Southeast Asia allowed these larger varanids to move back into what is now the Indonesian archipelago, extending their range as far east as the island of Timor.

The Komodo dragon is believed to have differentiated from its Australian ancestors about 4 million years ago. However, fossil evidence from Queensland suggests the Komodo dragon actually evolved in Australia, before spreading to Indonesia.^[1][16]

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 afterwards.^[1][5] Fossils of extinct Pliocene species of similar size to the modern Komodo dragon, such as Varanus sivalensis, have been found in Eurasia as well, indicating that they fared well even in environments containing competition, such as mammalian carnivores, until the climate change and extinction events that marked the beginning of the Pleistocene.^[1]

Genetic analysis of mitochondrial DNA shows the Komodo dragon to be the closest relative (sister taxon) of the lace monitor (V. varius), with their common ancestor diverging from a lineage that gave rise to the crocodile monitor (Varanus salvadorii) of New Guinea.^[17][18][19] A 2021 study showed that during the Miocene, Komodo dragons had hybridized with the ancestors of the Australian sand monitor (V. gouldii), thus providing further evidence that the Komodo dragon had once inhabited Australia.^[20][21][22] Genetic analysis indicates that the population from northern Flores is genetically distinct from other populations of the species.^[2]

Description

In the wild, adult Komodo dragons usually weigh around 70 kg (150 lb), although captive specimens often weigh more.^[23] According to Guinness 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).^[24] The largest verified specimen in captive was 3.13 m (10.3 ft) long and weighed 166 kg (366 lb), including its undigested food.^[5] The largest wild specimen had a length 3.04 m (10.0 ft), a snout-vent length (SVL) 1.54 m (5 ft 1 in) and a mass of 81.5 kg (180 lb) excluding stomach contents.^[25][26] The heaviest reached a mass in 87.4 kg (193 lb).^[25] The study noted that weights greater than 100 kg (220 lb) were possible but only after the animal had consumed a large meal.^[25][26]

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.^[27] It also has a long, yellow, deeply forked tongue.^[5] Komodo dragon skin is reinforced by armoured scales, which contain tiny bones called osteoderms that function as a sort of natural chain-mail.^[28][29] The only areas lacking osteoderms on the head of the adult Komodo dragon are around the eyes, nostrils, mouth margins, and pineal eye, a light-sensing organ on the top of the head. Where lizards typically have one or two varying patterns or shapes of osteoderms, komodos have four: rosette, platy, dendritic, and vermiform.^[30] This rugged hide makes Komodo dragon skin a poor source of leather. Additionally, these osteoderms become more extensive and variable in shape as the Komodo dragon ages, ossifying more extensively as the lizard grows. These osteoderms are absent in hatchlings and juveniles, indicating that the natural armor develops as a product of age and competition between adults for protection in intraspecific combat over food and mates.^[31]

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.^[5][32] They were 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 Procter trained a captive specimen to come out to feed at the sound of her voice, even when she could not be seen.^[33]

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. It can distinguish colours, but has poor visual discrimination of stationary objects.^[34]

As with many other reptiles, the Komodo dragon primarily relies on its tongue to detect, taste, and smell stimuli, with the vomeronasal sense using the Jacobson’s organ, rather than using the nostrils.^[35] With the help of a favorable wind and its habit of swinging its head from side to side as it walks, a Komodo dragon may be able to detect carrion from 4–9.5 km (2.5–5.9 mi) away.^[34] It only has a few taste buds in the back of its throat.^[35] Its scales, some of which are reinforced with bone, have sensory plaques connected to nerves to facilitate its sense of touch. The scales around the ears, lips, chin, and soles of the feet may have three or more sensory plaques.^[27]

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.^[23] To catch out-of-reach prey, the Komodo dragon may stand on its hind legs and use its tail as a support.^[33] As it matures, its claws are used primarily as weapons, as its great size makes climbing impractical.^[27]

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.^[36] 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.^[37] The Komodo dragon hunts in the afternoon, but stays in the shade during the hottest part of the day.^[9] 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.^[38]

Diet

Komodo dragons are apex predators.^[39] They are carnivores; although they have been considered as eating mostly carrion,^[40] they will frequently ambush live prey with a stealthy approach. When suitable prey arrives near a dragon’s ambush site, it will suddenly charge at the animal at high speeds and go for the underside or the throat.^[27]

Komodo dragons do not deliberately allow the prey to escape with fatal injuries but try to kill prey outright using a combination of lacerating damage and blood loss. They have been recorded as killing wild pigs within seconds,^[41] and observations of Komodo dragons tracking prey for long distances are likely misinterpreted cases of prey escaping an attack before succumbing to infection.

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 undigested vegetable contents of a prey animal’s stomach and intestines are typically avoided.^[38] 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 that the tree is knocked down.^[38] A small tube under the tongue that connects to the lungs allows it to breathe while swallowing.^[27]

After eating up to 80% of its body weight in one meal,^[39] it drags itself to a sunny location to speed digestion, as the food could rot and poison the dragon if left undigested in its stomach for too long. Because of their slow metabolism, large dragons can survive on as few as 12 meals a year.^[27] 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.^[27]

The eating habits of Komodo dragons follow a hierarchy, with the larger animals generally eating before the smaller ones. The largest male typically 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.^[42][43]

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, pigs,^[44] deer, horses, and water buffalo.^[45] Young Komodos will eat insects, eggs, geckos, and small mammals, while adults prefer to hunt large mammals.^[40] Occasionally, they attack and bite humans. Sometimes they consume human corpses, digging up bodies from shallow graves.^[33] 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.^[38] 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.^[46]

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.^[41]

Saliva

Although previous studies proposed that Komodo dragon saliva contains a variety of highly septic bacteria that would help to bring down prey,^[42][47] research in 2013 suggested that the bacteria in the mouths of Komodo dragons are ordinary and similar to those found in other carnivores. Komodo dragons have good mouth hygiene. To quote Bryan Fry: «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.» Nor do Komodo dragons wait for prey to die and track it at a distance, as vipers do; observations of them hunting deer, boar and in some cases buffalo reveal that they kill prey in less than half an hour.^[48]

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 after escaping an attack. 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 US zoos.^[48]

Antibacterial immune factor

Researchers have isolated a powerful antibacterial peptide from the blood plasma of Komodo dragons, VK25. Based on their analysis of this peptide, they have synthesized a short peptide dubbed DRGN-1 and tested it against multidrug-resistant (MDR) pathogens. Preliminary results of these tests show that DRGN-1 is effective in killing drug-resistant bacterial strains and even some fungi. It has the added observed benefit of significantly promoting wound healing in both uninfected and mixed biofilm infected wounds.^[49]

Venom

In late 2005, researchers at the University of Melbourne speculated the perentie (Varanus giganteus), 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 (V. varius), a Komodo dragon, and a spotted tree monitor (V. scalaris) 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.^[50]

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 dragon 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.^[51][52] As a result of the discovery, the previous theory that bacteria were responsible for the deaths of Komodo victims was disputed.^[53]

Other scientists 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.»^[54] Evolutionary biologist Schwenk says that even if the lizards have venom-like proteins in their mouths 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.^[55][56]

Reproduction

Mating occurs between May and August, with the eggs laid in September.^[5][57] 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.^[33] The winner of the fight will then flick his long tongue at the female to gain information about her receptivity.^[39] 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.^[58] Copulation occurs when the male inserts one of his hemipenes into the female’s cloaca.^[34] Komodo dragons may be monogamous and form «pair bonds», a rare behavior for lizards.^[33]

Female Komodos lay their eggs from August to September and may use several types of locality; in one study, 60% laid their eggs in the nests of orange-footed scrubfowl (a moundbuilder or megapode), 20% on ground level and 20% in hilly areas.^[59] The females make many camouflage nests/holes to prevent other dragons from eating the eggs.^[60] Clutches contain an average of 20 eggs, which have an incubation period of 7–8 months.^[33] Hatching is an exhausting effort for the neonates, which break out of their eggshells with an egg tooth that falls off before long. After cutting themselves out, the hatchlings may lie in their eggshells for hours before starting to dig out of the nest. They are born quite defenseless and are vulnerable to predation.^[42] Sixteen youngsters from a single nest were on average 46.5 cm long and weighed 105.1 grams.^[59]

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.^[33] The habit of cannibalism may be advantageous in sustaining the large size of adults, as medium-sized prey on the islands is rare.^[61] 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.^[33] Komodo dragons take approximately 8 to 9 years to mature, and may live for up to 30 years.^[57]

Parthenogenesis

A Komodo dragon at London Zoo named Sungai laid a clutch of eggs in late 2005 after being separated from male company for more than two years. Scientists initially assumed she had been able to store sperm from her earlier encounter with a male, an adaptation known as superfecundation.^[62] On 20 December 2006, it was reported that Flora, a captive Komodo dragon living in the Chester Zoo in England, was the second known Komodo dragon to have laid unfertilised eggs: she laid 11 eggs, and seven of them hatched, all of them male.^[63] Scientists at Liverpool University in England performed genetic tests on three eggs that collapsed after being moved to an incubator, and verified Flora had never been in physical contact with a male dragon. After Flora’s eggs’ condition had been discovered, testing showed Sungai’s eggs were also produced without outside fertilization.^[64] On 31 January 2008, the Sedgwick County Zoo in Wichita, Kansas, became the first zoo in the Americas to document parthenogenesis in Komodo dragons. The zoo has two adult female Komodo dragons, one of which laid about 17 eggs on 19–20 May 2007. Only two eggs were incubated and hatched due to space issues; the first hatched on 31 January 2008, while the second hatched on 1 February. Both hatchlings were males.^[65][66]

Komodo dragons have the ZW chromosomal sex-determination system, as opposed to the mammalian XY system. Male progeny prove Flora’s unfertilized eggs were haploid (n) and doubled their chromosomes later to become diploid (2n) (by being fertilized by a polar body, or by chromosome duplication without cell division), rather than by her laying diploid eggs by one of the meiosis reduction-divisions in her ovaries failing. When a female Komodo dragon (with ZW sex chromosomes) reproduces in this manner, she provides her progeny with only one chromosome from each of her pairs of chromosomes, including only one of her two sex chromosomes. This single set of chromosomes is duplicated in the egg, which develops parthenogenetically. Eggs receiving a Z chromosome become ZZ (male); those receiving a W chromosome become WW and fail to develop,^[67][68] meaning that only males are produced by parthenogenesis in this species.

It has been hypothesised that this reproductive adaptation allows a single female to enter an isolated ecological niche (such as an island) and by parthenogenesis produce male offspring, thereby establishing a sexually reproducing population (via reproduction with her offspring that can result in both male and female young).^[67] Despite the advantages of such an adaptation, zoos are cautioned that parthenogenesis may be detrimental to genetic diversity.^[69]

Encounters with humans

Attacks on humans are rare, but Komodo dragons have been responsible for several human fatalities, in both the wild and in captivity. According to data from Komodo National Park spanning a 38-year period between 1974 and 2012, there were 24 reported attacks on humans, five of them fatal. Most of the victims were local villagers living around the national park.^[70]

Conservation

The Komodo dragon is classified by the IUCN as Endangered and is listed on the IUCN Red List.^[2] The species’ sensitivity to natural and man-made threats has long been recognized by conservationists, zoological societies, and the Indonesian government. Komodo National Park was founded in 1980 to protect Komodo dragon populations on islands including Komodo, Rinca, and Padar.^[71] Later, the Wae Wuul and Wolo Tado Reserves were opened on Flores to aid Komodo dragon conservation.^[13]

Komodo dragons generally avoid encounters with humans. Juveniles are very shy and will flee quickly into a hideout if a human comes closer than about 100 metres (330 ft). Older animals will also retreat from humans from a shorter distance away. If cornered, they may react aggressively by gaping their mouth, hissing, and swinging their tail. If they are disturbed further, they may attack and bite. Although there are anecdotes of unprovoked Komodo dragons attacking or preying on humans, most of these reports are either not reputable or have subsequently been interpreted as defensive bites. Only very few cases are truly the result of unprovoked attacks by atypical individuals who lost their fear of humans.^[42]

Volcanic activity, earthquakes, loss of habitat, fire,^[27][13] tourism, loss of prey due to poaching, and illegal poaching of the dragons themselves have all contributed to the vulnerable status of the Komodo dragon. A major future threat to the species is climate change via both aridification and sea level rise, which can affect the low-lying habitats and valleys that the Komodo dragon depends on, as Komodo dragons do not range into the higher-altitude regions of the islands they inhabit. Based on projections, climate change will lead to a decline in suitable habitat of 8.4%, 30.2%, or 71% by 2050 depending on the climate change scenario. Without effective conservation actions, populations on Flores are extirpated in all scenarios, while in the more extreme scenarios, only the populations on Komodo and Rinca persist in highly reduced numbers. Rapid climate change mitigation is crucial for conserving the species in the wild.^[2][72] Other scientists have disputed the conclusions about the effects of climate change on Komodo dragon populations.^[73]

Under Appendix I of CITES (the Convention on International Trade in Endangered Species), commercial international trade of Komodo dragon skins or specimens is prohibited.^[74][75] Despite this, there are occasional reports of illegal attempts to trade in live Komodo dragons. The most recent attempt was in March 2019, when Indonesian police in the East Java city of Surabaya reported that a criminal network had been caught trying to smuggle 41 young Komodo dragons out of Indonesia. The plan was said to include shipping the animals to several other countries in Southeast Asia through Singapore. It was hoped that the animals could be sold for up to 500 million rupiah (around US$35,000) each.^[76] It was believed that the Komodo dragons had been smuggled out of East Nusa Tenggara province through the port at Ende in central Flores.^[77]

In 2013, the total population of Komodo dragons in the wild was assessed as 3,222 individuals, declining to 3,092 in 2014 and 3,014 in 2015. Populations remained relatively stable on the bigger islands (Komodo and Rinca), but decreased on smaller islands, such as Nusa Kode and Gili Motang, likely due to diminishing prey availability.^[78] On Padar, a former population of Komodo dragons has recently become extinct, of which the last individuals were seen in 1975.^[79] It is widely assumed that the Komodo dragon died out on Padar following a major decline of populations of large ungulate prey, for which poaching was most likely responsible.^[80]

In captivity

Komodo dragons have long been sought-after zoo attractions, where their size and reputation make them popular exhibits. They are, however, rare in zoos because they are susceptible to infection and parasitic disease if captured from the wild, and do not readily reproduce in captivity.^[15] The first Komodo dragons were displayed at London Zoo in 1927. A Komodo dragon was exhibited in 1934 in the United States at the National Zoo in Washington, D.C., but it lived for only two years. More attempts to exhibit Komodo dragons were made, but the lifespan of the animals proved very short, averaging five years in the National Zoological Park. Studies were done by Walter Auffenberg, which were documented in his book The Behavioral Ecology of the Komodo Monitor, eventually allowed for more successful management and breeding of the dragons in captivity.^[12] As of May 2009, there were 35 North American, 13 European, one Singaporean, two African, and two Australian institutions which housed captive Komodo dragons.^[81]

A variety of behaviors have been observed from captive specimens. Most individuals become relatively tame within a short time,^[82][83] and are capable of recognising individual humans and discriminating between familiar and unfamiliar keepers.^[84] Komodo dragons have also been observed to engage in play with a variety of objects, including shovels, cans, plastic rings, and shoes. This behavior does not seem to be «food-motivated predatory behavior».^[39][5][85]

Even seemingly docile dragons may become unpredictably aggressive, especially when the animal’s territory is invaded by someone unfamiliar. In June 2001, a Komodo dragon seriously injured Phil Bronstein, the then-husband of actress Sharon Stone, when he entered its enclosure at the Los Angeles Zoo after being invited in by its keeper. Bronstein was bitten on his bare foot, as the keeper had told him to take off his white shoes and socks, which the keeper stated could potentially excite the Komodo dragon as they were the same colour as the white rats the zoo fed the dragon.^[86][87] Although he survived, Bronstein needed to have several tendons in his foot reattached surgically.^[88]

See also

• List of largest extant lizards
• Asian water monitor
• Komodo Indonesian Fauna Museum and Reptile Park
• Papua monitor (Varanus salvadorii), a monitor lizard often asserted to be the longest extant lizard
• Toxicofera, a hypothetical clade encompassing all venomous reptiles, including the Komodo dragon
• Varanus priscus (formerly known as Megalania prisca), a huge extinct varanid lizard of Pleistocene Australia

References

Further reading

• Attenborough, David (1957). Zoo Quest for a Dragon. London: Lutterworth Press.
• Auffenberg, Walter (1981). The Behavioral Ecology of the Komodo Monitor. Gainesville: University Presses of Florida. ISBN 978-0-8130-0621-5.
• Burden, W. Douglas (1927). Dragon Lizards of Komodo: An Expedition to the Lost World of the Dutch East Indies. New York, London: G.P. Putnum’s Sons.
• Eberhard, Jo; King, Dennis; Green, Brian; Knight, Frank; Keith Newgrain (1999). Monitors: The Biology of Varanid Lizards. Malabar, Fla: Krieger Publishing Company. ISBN 978-1-57524-112-8.
• Lutz, Richard L; Lutz, Judy Marie (1997). Komodo: The Living Dragon. Salem, Or: DiMI Press. ISBN 978-0-931625-27-5.

External links

Komodo dragon Temporal range: Pliocene–Holocene,[1] 3.8–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Male at the Cincinnati Zoo
Conservation status
Endangered (IUCN 3.1)[2]
CITES Appendix I (CITES)[3]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Family:	Varanidae
Genus:	Varanus
Subgenus:	Varanus
Species:	V. komodoensis
Binomial name
Varanus komodoensis Ouwens, 1912[4]
Komodo dragon distribution

The Komodo dragon (Varanus komodoensis), also known as the Komodo monitor, is a member of the monitor lizard family Varanidae that is endemic to the Indonesian islands of Komodo, Rinca, Flores, and Gili Motang. It is the largest extant species of lizard, growing to a maximum length of 3 m (9.8 ft), and weighing up to 70 kg (150 lb).

As a result of their size, Komodo dragons are apex predators, and 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 that secrete several toxic proteins. The biological significance of these proteins is disputed, but the glands have been shown to secrete an anticoagulant. Komodo dragons’ group behavior in hunting is exceptional in the reptile world. The diet of Komodo dragons mainly consists of Javan rusa (Rusa timorensis), though they also eat considerable amounts of carrion. Komodo dragons also occasionally attack humans.

Mating begins between May and August, and the eggs are laid in September; as many as 20 eggs are deposited at a time in an abandoned megapode nest 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 dwell in trees to avoid predators, such as 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 is likely to contract further from the effects of climate change; due to this, they are listed as Endangered by the IUCN Red List. They are protected under Indonesian law, and Komodo National Park was founded in 1980 to aid protection efforts.

Taxonomic history

Komodo dragons were first documented by Europeans in 1910, when rumors of a «land crocodile» reached Lieutenant van Steyn van Hensbroek of the Dutch colonial administration.^[5] Widespread notoriety came after 1912, when Peter Ouwens, the director of the Zoological Museum of Bogor, Java, published a paper on the topic after receiving a photo and a skin from the lieutenant, as well as two other specimens from a collector.^[4]

The first two live Komodo dragons to arrive in Europe were exhibited in the Reptile House at London Zoo when it opened in 1927.^[6] Joan Beauchamp Procter made some of the earliest observations of these animals in captivity and she demonstrated their behaviour at a Scientific Meeting of the Zoological Society of London in 1928.^[7]

The Komodo dragon was the driving factor for an expedition to Komodo Island by W. Douglas Burden in 1926. After returning with 12 preserved specimens and two live ones, this expedition provided the inspiration for the 1933 movie King Kong.^[8] It was also Burden who coined the common name «Komodo dragon».^[9] Three of his specimens were stuffed and are still on display in the American Museum of Natural History.^[10]

The Dutch island administration, realizing the limited number of individuals in the wild, soon outlawed sport hunting and heavily limited the number of individuals taken for scientific study. Collecting expeditions ground to a halt with the occurrence of World War II, not resuming until the 1950s and 1960s, when studies examined the Komodo dragon’s feeding behavior, reproduction, and body temperature. At around this time, an expedition was planned in which a long-term study of the Komodo dragon would be undertaken. This task was given to the Auffenberg family, who stayed on Komodo Island for 11 months in 1969. During their stay, Walter Auffenberg and his assistant Putra Sastrawan captured and tagged more than 50 Komodo dragons.^[11]

Research from the Auffenberg expedition proved enormously influential in raising Komodo dragons in captivity.^[12] Research after that of the Auffenberg family has shed more light on the nature of the Komodo dragon, with biologists such as Claudio Ciofi continuing to study the creatures.^[13]

Etymology

The Komodo dragon is also sometimes known as the Komodo monitor or the Komodo Island monitor in scientific literature,^[14] although this name is uncommon. To the natives of Komodo Island, it is referred to as ora, buaya darat (‘land crocodile’), or biawak raksasa (‘giant monitor’).^[15][5]

Evolutionary history

The evolutionary development of the Komodo dragon started with the genus Varanus, which originated in Asia about 40 million years ago and migrated to Australia, where it evolved into giant forms (the largest of all being the recently extinct Varanus priscus, or «Megalania»), helped by the absence of competing placental carnivorans. Around 15 million years ago, a collision between the continental landmasses of Australia and Southeast Asia allowed these larger varanids to move back into what is now the Indonesian archipelago, extending their range as far east as the island of Timor.

The Komodo dragon is believed to have differentiated from its Australian ancestors about 4 million years ago. However, fossil evidence from Queensland suggests the Komodo dragon actually evolved in Australia, before spreading to Indonesia.^[1][16]

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 afterwards.^[1][5] Fossils of extinct Pliocene species of similar size to the modern Komodo dragon, such as Varanus sivalensis, have been found in Eurasia as well, indicating that they fared well even in environments containing competition, such as mammalian carnivores, until the climate change and extinction events that marked the beginning of the Pleistocene.^[1]

Genetic analysis of mitochondrial DNA shows the Komodo dragon to be the closest relative (sister taxon) of the lace monitor (V. varius), with their common ancestor diverging from a lineage that gave rise to the crocodile monitor (Varanus salvadorii) of New Guinea.^[17][18][19] A 2021 study showed that during the Miocene, Komodo dragons had hybridized with the ancestors of the Australian sand monitor (V. gouldii), thus providing further evidence that the Komodo dragon had once inhabited Australia.^[20][21][22] Genetic analysis indicates that the population from northern Flores is genetically distinct from other populations of the species.^[2]

Description

In the wild, adult Komodo dragons usually weigh around 70 kg (150 lb), although captive specimens often weigh more.^[23] According to Guinness 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).^[24] The largest verified specimen in captive was 3.13 m (10.3 ft) long and weighed 166 kg (366 lb), including its undigested food.^[5] The largest wild specimen had a length 3.04 m (10.0 ft), a snout-vent length (SVL) 1.54 m (5 ft 1 in) and a mass of 81.5 kg (180 lb) excluding stomach contents.^[25][26] The heaviest reached a mass in 87.4 kg (193 lb).^[25] The study noted that weights greater than 100 kg (220 lb) were possible but only after the animal had consumed a large meal.^[25][26]

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.^[27] It also has a long, yellow, deeply forked tongue.^[5] Komodo dragon skin is reinforced by armoured scales, which contain tiny bones called osteoderms that function as a sort of natural chain-mail.^[28][29] The only areas lacking osteoderms on the head of the adult Komodo dragon are around the eyes, nostrils, mouth margins, and pineal eye, a light-sensing organ on the top of the head. Where lizards typically have one or two varying patterns or shapes of osteoderms, komodos have four: rosette, platy, dendritic, and vermiform.^[30] This rugged hide makes Komodo dragon skin a poor source of leather. Additionally, these osteoderms become more extensive and variable in shape as the Komodo dragon ages, ossifying more extensively as the lizard grows. These osteoderms are absent in hatchlings and juveniles, indicating that the natural armor develops as a product of age and competition between adults for protection in intraspecific combat over food and mates.^[31]

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.^[5][32] They were 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 Procter trained a captive specimen to come out to feed at the sound of her voice, even when she could not be seen.^[33]

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. It can distinguish colours, but has poor visual discrimination of stationary objects.^[34]

As with many other reptiles, the Komodo dragon primarily relies on its tongue to detect, taste, and smell stimuli, with the vomeronasal sense using the Jacobson’s organ, rather than using the nostrils.^[35] With the help of a favorable wind and its habit of swinging its head from side to side as it walks, a Komodo dragon may be able to detect carrion from 4–9.5 km (2.5–5.9 mi) away.^[34] It only has a few taste buds in the back of its throat.^[35] Its scales, some of which are reinforced with bone, have sensory plaques connected to nerves to facilitate its sense of touch. The scales around the ears, lips, chin, and soles of the feet may have three or more sensory plaques.^[27]

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.^[23] To catch out-of-reach prey, the Komodo dragon may stand on its hind legs and use its tail as a support.^[33] As it matures, its claws are used primarily as weapons, as its great size makes climbing impractical.^[27]

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.^[36] 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.^[37] The Komodo dragon hunts in the afternoon, but stays in the shade during the hottest part of the day.^[9] 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.^[38]

Diet

Komodo dragons are apex predators.^[39] They are carnivores; although they have been considered as eating mostly carrion,^[40] they will frequently ambush live prey with a stealthy approach. When suitable prey arrives near a dragon’s ambush site, it will suddenly charge at the animal at high speeds and go for the underside or the throat.^[27]

Komodo dragons do not deliberately allow the prey to escape with fatal injuries but try to kill prey outright using a combination of lacerating damage and blood loss. They have been recorded as killing wild pigs within seconds,^[41] and observations of Komodo dragons tracking prey for long distances are likely misinterpreted cases of prey escaping an attack before succumbing to infection.

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 undigested vegetable contents of a prey animal’s stomach and intestines are typically avoided.^[38] 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 that the tree is knocked down.^[38] A small tube under the tongue that connects to the lungs allows it to breathe while swallowing.^[27]

After eating up to 80% of its body weight in one meal,^[39] it drags itself to a sunny location to speed digestion, as the food could rot and poison the dragon if left undigested in its stomach for too long. Because of their slow metabolism, large dragons can survive on as few as 12 meals a year.^[27] 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.^[27]

The eating habits of Komodo dragons follow a hierarchy, with the larger animals generally eating before the smaller ones. The largest male typically 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.^[42][43]

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, pigs,^[44] deer, horses, and water buffalo.^[45] Young Komodos will eat insects, eggs, geckos, and small mammals, while adults prefer to hunt large mammals.^[40] Occasionally, they attack and bite humans. Sometimes they consume human corpses, digging up bodies from shallow graves.^[33] 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.^[38] 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.^[46]

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.^[41]

Saliva

Although previous studies proposed that Komodo dragon saliva contains a variety of highly septic bacteria that would help to bring down prey,^[42][47] research in 2013 suggested that the bacteria in the mouths of Komodo dragons are ordinary and similar to those found in other carnivores. Komodo dragons have good mouth hygiene. To quote Bryan Fry: «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.» Nor do Komodo dragons wait for prey to die and track it at a distance, as vipers do; observations of them hunting deer, boar and in some cases buffalo reveal that they kill prey in less than half an hour.^[48]

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 after escaping an attack. 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 US zoos.^[48]

Antibacterial immune factor

Researchers have isolated a powerful antibacterial peptide from the blood plasma of Komodo dragons, VK25. Based on their analysis of this peptide, they have synthesized a short peptide dubbed DRGN-1 and tested it against multidrug-resistant (MDR) pathogens. Preliminary results of these tests show that DRGN-1 is effective in killing drug-resistant bacterial strains and even some fungi. It has the added observed benefit of significantly promoting wound healing in both uninfected and mixed biofilm infected wounds.^[49]

Venom

In late 2005, researchers at the University of Melbourne speculated the perentie (Varanus giganteus), 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 (V. varius), a Komodo dragon, and a spotted tree monitor (V. scalaris) 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.^[50]

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 dragon 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.^[51][52] As a result of the discovery, the previous theory that bacteria were responsible for the deaths of Komodo victims was disputed.^[53]

Other scientists 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.»^[54] Evolutionary biologist Schwenk says that even if the lizards have venom-like proteins in their mouths 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.^[55][56]

Reproduction

Mating occurs between May and August, with the eggs laid in September.^[5][57] 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.^[33] The winner of the fight will then flick his long tongue at the female to gain information about her receptivity.^[39] 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.^[58] Copulation occurs when the male inserts one of his hemipenes into the female’s cloaca.^[34] Komodo dragons may be monogamous and form «pair bonds», a rare behavior for lizards.^[33]

Female Komodos lay their eggs from August to September and may use several types of locality; in one study, 60% laid their eggs in the nests of orange-footed scrubfowl (a moundbuilder or megapode), 20% on ground level and 20% in hilly areas.^[59] The females make many camouflage nests/holes to prevent other dragons from eating the eggs.^[60] Clutches contain an average of 20 eggs, which have an incubation period of 7–8 months.^[33] Hatching is an exhausting effort for the neonates, which break out of their eggshells with an egg tooth that falls off before long. After cutting themselves out, the hatchlings may lie in their eggshells for hours before starting to dig out of the nest. They are born quite defenseless and are vulnerable to predation.^[42] Sixteen youngsters from a single nest were on average 46.5 cm long and weighed 105.1 grams.^[59]

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.^[33] The habit of cannibalism may be advantageous in sustaining the large size of adults, as medium-sized prey on the islands is rare.^[61] 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.^[33] Komodo dragons take approximately 8 to 9 years to mature, and may live for up to 30 years.^[57]

Parthenogenesis

A Komodo dragon at London Zoo named Sungai laid a clutch of eggs in late 2005 after being separated from male company for more than two years. Scientists initially assumed she had been able to store sperm from her earlier encounter with a male, an adaptation known as superfecundation.^[62] On 20 December 2006, it was reported that Flora, a captive Komodo dragon living in the Chester Zoo in England, was the second known Komodo dragon to have laid unfertilised eggs: she laid 11 eggs, and seven of them hatched, all of them male.^[63] Scientists at Liverpool University in England performed genetic tests on three eggs that collapsed after being moved to an incubator, and verified Flora had never been in physical contact with a male dragon. After Flora’s eggs’ condition had been discovered, testing showed Sungai’s eggs were also produced without outside fertilization.^[64] On 31 January 2008, the Sedgwick County Zoo in Wichita, Kansas, became the first zoo in the Americas to document parthenogenesis in Komodo dragons. The zoo has two adult female Komodo dragons, one of which laid about 17 eggs on 19–20 May 2007. Only two eggs were incubated and hatched due to space issues; the first hatched on 31 January 2008, while the second hatched on 1 February. Both hatchlings were males.^[65][66]

Komodo dragons have the ZW chromosomal sex-determination system, as opposed to the mammalian XY system. Male progeny prove Flora’s unfertilized eggs were haploid (n) and doubled their chromosomes later to become diploid (2n) (by being fertilized by a polar body, or by chromosome duplication without cell division), rather than by her laying diploid eggs by one of the meiosis reduction-divisions in her ovaries failing. When a female Komodo dragon (with ZW sex chromosomes) reproduces in this manner, she provides her progeny with only one chromosome from each of her pairs of chromosomes, including only one of her two sex chromosomes. This single set of chromosomes is duplicated in the egg, which develops parthenogenetically. Eggs receiving a Z chromosome become ZZ (male); those receiving a W chromosome become WW and fail to develop,^[67][68] meaning that only males are produced by parthenogenesis in this species.

It has been hypothesised that this reproductive adaptation allows a single female to enter an isolated ecological niche (such as an island) and by parthenogenesis produce male offspring, thereby establishing a sexually reproducing population (via reproduction with her offspring that can result in both male and female young).^[67] Despite the advantages of such an adaptation, zoos are cautioned that parthenogenesis may be detrimental to genetic diversity.^[69]

Encounters with humans

Attacks on humans are rare, but Komodo dragons have been responsible for several human fatalities, in both the wild and in captivity. According to data from Komodo National Park spanning a 38-year period between 1974 and 2012, there were 24 reported attacks on humans, five of them fatal. Most of the victims were local villagers living around the national park.^[70]

Conservation

The Komodo dragon is classified by the IUCN as Endangered and is listed on the IUCN Red List.^[2] The species’ sensitivity to natural and man-made threats has long been recognized by conservationists, zoological societies, and the Indonesian government. Komodo National Park was founded in 1980 to protect Komodo dragon populations on islands including Komodo, Rinca, and Padar.^[71] Later, the Wae Wuul and Wolo Tado Reserves were opened on Flores to aid Komodo dragon conservation.^[13]

Komodo dragons generally avoid encounters with humans. Juveniles are very shy and will flee quickly into a hideout if a human comes closer than about 100 metres (330 ft). Older animals will also retreat from humans from a shorter distance away. If cornered, they may react aggressively by gaping their mouth, hissing, and swinging their tail. If they are disturbed further, they may attack and bite. Although there are anecdotes of unprovoked Komodo dragons attacking or preying on humans, most of these reports are either not reputable or have subsequently been interpreted as defensive bites. Only very few cases are truly the result of unprovoked attacks by atypical individuals who lost their fear of humans.^[42]

Volcanic activity, earthquakes, loss of habitat, fire,^[27][13] tourism, loss of prey due to poaching, and illegal poaching of the dragons themselves have all contributed to the vulnerable status of the Komodo dragon. A major future threat to the species is climate change via both aridification and sea level rise, which can affect the low-lying habitats and valleys that the Komodo dragon depends on, as Komodo dragons do not range into the higher-altitude regions of the islands they inhabit. Based on projections, climate change will lead to a decline in suitable habitat of 8.4%, 30.2%, or 71% by 2050 depending on the climate change scenario. Without effective conservation actions, populations on Flores are extirpated in all scenarios, while in the more extreme scenarios, only the populations on Komodo and Rinca persist in highly reduced numbers. Rapid climate change mitigation is crucial for conserving the species in the wild.^[2][72] Other scientists have disputed the conclusions about the effects of climate change on Komodo dragon populations.^[73]

Under Appendix I of CITES (the Convention on International Trade in Endangered Species), commercial international trade of Komodo dragon skins or specimens is prohibited.^[74][75] Despite this, there are occasional reports of illegal attempts to trade in live Komodo dragons. The most recent attempt was in March 2019, when Indonesian police in the East Java city of Surabaya reported that a criminal network had been caught trying to smuggle 41 young Komodo dragons out of Indonesia. The plan was said to include shipping the animals to several other countries in Southeast Asia through Singapore. It was hoped that the animals could be sold for up to 500 million rupiah (around US$35,000) each.^[76] It was believed that the Komodo dragons had been smuggled out of East Nusa Tenggara province through the port at Ende in central Flores.^[77]

In 2013, the total population of Komodo dragons in the wild was assessed as 3,222 individuals, declining to 3,092 in 2014 and 3,014 in 2015. Populations remained relatively stable on the bigger islands (Komodo and Rinca), but decreased on smaller islands, such as Nusa Kode and Gili Motang, likely due to diminishing prey availability.^[78] On Padar, a former population of Komodo dragons has recently become extinct, of which the last individuals were seen in 1975.^[79] It is widely assumed that the Komodo dragon died out on Padar following a major decline of populations of large ungulate prey, for which poaching was most likely responsible.^[80]

In captivity

Komodo dragons have long been sought-after zoo attractions, where their size and reputation make them popular exhibits. They are, however, rare in zoos because they are susceptible to infection and parasitic disease if captured from the wild, and do not readily reproduce in captivity.^[15] The first Komodo dragons were displayed at London Zoo in 1927. A Komodo dragon was exhibited in 1934 in the United States at the National Zoo in Washington, D.C., but it lived for only two years. More attempts to exhibit Komodo dragons were made, but the lifespan of the animals proved very short, averaging five years in the National Zoological Park. Studies were done by Walter Auffenberg, which were documented in his book The Behavioral Ecology of the Komodo Monitor, eventually allowed for more successful management and breeding of the dragons in captivity.^[12] As of May 2009, there were 35 North American, 13 European, one Singaporean, two African, and two Australian institutions which housed captive Komodo dragons.^[81]

A variety of behaviors have been observed from captive specimens. Most individuals become relatively tame within a short time,^[82][83] and are capable of recognising individual humans and discriminating between familiar and unfamiliar keepers.^[84] Komodo dragons have also been observed to engage in play with a variety of objects, including shovels, cans, plastic rings, and shoes. This behavior does not seem to be «food-motivated predatory behavior».^[39][5][85]

Even seemingly docile dragons may become unpredictably aggressive, especially when the animal’s territory is invaded by someone unfamiliar. In June 2001, a Komodo dragon seriously injured Phil Bronstein, the then-husband of actress Sharon Stone, when he entered its enclosure at the Los Angeles Zoo after being invited in by its keeper. Bronstein was bitten on his bare foot, as the keeper had told him to take off his white shoes and socks, which the keeper stated could potentially excite the Komodo dragon as they were the same colour as the white rats the zoo fed the dragon.^[86][87] Although he survived, Bronstein needed to have several tendons in his foot reattached surgically.^[88]

See also

• List of largest extant lizards
• Asian water monitor
• Komodo Indonesian Fauna Museum and Reptile Park
• Papua monitor (Varanus salvadorii), a monitor lizard often asserted to be the longest extant lizard
• Toxicofera, a hypothetical clade encompassing all venomous reptiles, including the Komodo dragon
• Varanus priscus (formerly known as Megalania prisca), a huge extinct varanid lizard of Pleistocene Australia

References

Further reading

• Attenborough, David (1957). Zoo Quest for a Dragon. London: Lutterworth Press.
• Auffenberg, Walter (1981). The Behavioral Ecology of the Komodo Monitor. Gainesville: University Presses of Florida. ISBN 978-0-8130-0621-5.
• Burden, W. Douglas (1927). Dragon Lizards of Komodo: An Expedition to the Lost World of the Dutch East Indies. New York, London: G.P. Putnum’s Sons.
• Eberhard, Jo; King, Dennis; Green, Brian; Knight, Frank; Keith Newgrain (1999). Monitors: The Biology of Varanid Lizards. Malabar, Fla: Krieger Publishing Company. ISBN 978-1-57524-112-8.
• Lutz, Richard L; Lutz, Judy Marie (1997). Komodo: The Living Dragon. Salem, Or: DiMI Press. ISBN 978-0-931625-27-5.

External links

Комодский варан^[1], или Гигантский индонезийский варан^[1], или Комодосский варан^[2] (лат. Varanus komodoensis) — вид пресмыкающихся (лат. Reptilia) из семейства варановых (лат. Varanidae).

Название и происхождение[править]

Комодский варан — это самая крупная ящерица в мире.
У него множество названий —

• варан острова Комодо,
• дракон острова Комодо, а местные жители называют его
• «ора» или «буайя дарат», что означает «наземный крокодил».

Происхождение[править]

Происхождение огромного ящера покрыто тайной.

Существует версия, что комодский варан — это прародитель современного крокодила. Палеонтологи выдвигают версию, что около 5—10 миллионов лет назад предки комодского ящера появились в Австралии.
И это предположение подтверждается одним весомым фактом: кости единственного известного представителя крупных пресмыкающихся были найдены в плейстоценовых и плиоценовых отложениях Австралии.^[3]

Считается, что после того, как образовались и остыли вулканические острова, ящер поселился на них, в частности на острове Комодо. Однако, возникает вопрос: как ящер добрался до острова, расположенного в 500 милях от Австралии? Ответ пока не найден, но по сей день рыбаки побаиваются отправляться в плавание возле острова Комодо. Возможно, «дракону» помогло морское течение.

Ученые утверждают, что в те времена на острове жили гигантские черепахи, слоны, высота которых достигала полтора метра. Вполне возможно, в таком случае, что предки современных комодских ящеров охотились на карликовых слонов.

Так или иначе, но комодские вараны — это живые ископаемые.

Распространение[править]

Родиной комодских варанов является Австралия, хотя свое название вид получил от острова Комодо. После развития популяции, около девятисот тысяч лет назад, эти животные расселились на близлежащих островах.

В мире есть на сегодняшний момент только четыре места, где обитает Комодский варан в естественных условиях — это четыре Индонезийских острова, входящих в состав Малых Зондских Островов:

• остров Комодо, где осталось всего 1700 особей этого животного
• остров Джили Мотанг, где насчитывается в настоящее время не более 100 ящеров
• остров Флорес, на котором обнаружено самое крупное поголовье варанов (около 2000 штук)
• остров Ринча, с 1300 животных этого вида.

Внешний вид[править]

Комодские вараны по строению своего тела сходны с другими видами ящериц, но, конечно же, имеют свои особенности.

Комодский варан может достигать в длину 2.5-3 м, его вес колеблется в пределах от 50 до 70 кг.
Самки более мелкие и достигают в длину всего 1,5-2 м. Длина хвоста варана составляет примерно половину длины тела.

Окраска — темно-бурая, у молодых особей на спине имеются яркие желтоватые пятна.

Пасть снабжена зубами с режущими краями, которые подходят для разрывания мяса на куски.

Образ жизни[править]

Комодский варан является дневным животным, он не охотится ночью. По ночам они крепко спят в своих убежищах. Хотя, были отмечены лишь единичные случаи ночной активности этих животных.

Молодые вараны прекрасно лазят по деревьям и в целях собственной безопасности живут в дуплах.

Комодские драконы — отличные пловцы. Они могут спокойно переплывать небольшие речки, заливы или преодолевать расстояние до соседних близлежащих островов. Однако они не могут продержаться в воде более 15 минут. И если они не успеют добраться до суши, то тонут. Возможно, именно этот фактор повлиял на естественные границы обитания этих животных.

Вараны быстро бегают. На коротких дистанциях его скорость может достигать 20км/ч. В случаях необходимости, они могут вставать на задние лапы, используя свой мощный хвост в качестве опоры.

Предпочитая жить в одиночку, эти огромные ящеры редко сходятся в группы, непродолжительное объединение варанов может вызвать только брачный период и кормление, но и эти периоды будут сопровождаться постоянными стычками и драками, как между самцами, так и между самками.

Длинный язык, которым наделен комодский варан — это очень важный обонятельный орган. Высовывая язык, варан улавливает запахи. Осязаемость языка варана не уступает чувствительности обоняния у собак.
Голодный зверь способен выследить жертву по одному единственному следу, оставленному жертвой несколько часов назад.

Регулирование температуры тела[править]

Выбираясь из своих нор, когда встает солнце, вараны предпочитают принимать солнечные ванны, полностью распластавшись и вытянув лапы.
Таким образом, комодский варан повышает температуру своего тела. С понижением температуры вараны не проявляют активности и быстроты реакции, их состояние скорее сонное, нежели подвижное.
Получив заряд солнечной энергии, Комодский варан обходит свои владения, ревностно наблюдая — нет ли незваных гостей на его территории.
От размеров Комодского варана напрямую зависит температура его тела — чем взрослее и больше ящер, тем дольше он способен удерживать в себе тепло, сохраняя его даже в ночное время, и тем меньше времени он будет тратить в утренние часы на прогревание тела.

Он плохо переносит жару, его тело не имеет потовых желез. И если температура животного превысит 42,7°С, варан умрет от теплового удара.

Получив заряд солнечной энергии, Комодский варан обходит свои владения, ревностно наблюдая — нет ли незваных гостей на его территории.

Яд[править]

Многие слышали, что укус варана может стать смертельным. Оказывается в их слюне содержатся 57 различных штаммов бактерий, вызывающих воспаление раны и заражение крови. Считается, что эти бактерии появились в результате поедания падали.

Совсем недавно, в 2009 году, ученые Мельбурнского университета доказали, что у варанов есть ядовитые железы, которые располагаются на нижней челюсти.^[4]
Они выделяют яд, содержащий различные токсичные белки, вызывающие прекращение свертываемости крови, снижение кровяного давления, паралич мышц и потерю сознания.
Протоки этих желез располагаются у основания зубов, и яд смешивается со слюной, содержащей множество бактерий.

Питание[править]

Варан — высший в местах своего обитания хищник, он может легко съесть геккона, крысу, птичьи яйца, змею (даже огромного сетчатого питона), поймать зазевавшуюся птицу. Но в целом, чаще они охотятся именно на крупных млекопитающих животных.

Местные жители и ученые рассказывают, что варан таскает собак и овец, нападает на буйволов, лошадей, оленей и диких свиней. Известны случаи, когда комодский варан нападал на жертву весом до 1200 килограмм. Для того чтобы одолеть и съесть такое огромное животное, дракон перекусывал ему сухожилия, тем самым обездвиживая жертву, а потом кромсал жертву своими острыми как бритва зубами.

В сухой сезон варану приходится придерживаться «поста», а в сезон дождей он ни в чем себе не отказывает.

В голодный засушливый сезон ящеры питаются собственным жиром. Также у этих ящериц распространен внутривидовой каннибализм. Особенно сильно это проявляется в голодные годы.
Взрослые особи часто съедают более мелких сородичей.

Самки и молодняк в основном питаются тем, что останется от обеда или птицей и мелкими животными.

Нередко Комодского варана можно встретить на побережье, где он ищет останки животных, выброшенных на берег, к тому же эти уникальные драконы очень хорошо плавают и любят купаться, а так же не откажутся поохотиться в воде, если присмотрят себе подходящую добычу.

Охота[править]

Охотится варан во второй половине дня, предпочитая пережидать полуденную жару в тени.
Охота происходит приблизительно так:

Свою добычу они поджидают в засаде.
Варан близко подбирается к своей жертве и молниеносно атакует. Иногда они сбивают ее с ног при помощи удара огромного хвоста, ломая ей ноги. После чего валит животное на землю и старается побыстрее её оглушить.
В случае нападения на человека варан сначала откусывает ноги, затем разрывает тело на части.

После того, как жертва варана убита, он вспарывает брюхо и съедает внутренности животного. Мясо варан поедает крупными кусками, проглатывая его вместе с костями. Для быстрого прохождения пищи, варан постоянно забрасывает голову вверх. Небольшую добычу варан может заглотить целиком, а крупную разрывает на куски.

Во время поедания животного «дракон» стоит на четырех вытянутых лапах. В процессе приема пищи видно, как живот варана наполняется и оттягивается до самой земли. Наевшись, варан уходит в тень деревьев переваривать пищу в тишине и спокойствии.

Крупные экземпляры часто едят падаль, которую сами того не ведая, себе и обеспечивают. Все дело в том, что своими зубами они наносят животному рваную рану, в которую попадает яд и, порой, множество опасных бактерий. Если животное уходит от варана, происходит воспаление раны и заражение крови. Через некоторое время несчастная жертва погибает. Варан, благодаря своему раздвоенному языку, который является органом обоняния, находит труп жертвы.
На запах падали сбегаются и другие вараны. Порой начинается драка, целью которой является установление главенства среди самцов. Неосторожные молодые вараны и дикие собаки, пытающиеся откусить кусок от добычи, нередко бывают убиты взрослыми драконами.

Размножение[править]

Период размножения у варанов наступает зимой, во время сухого сезона. Количество самцов в 2 раза превышает количество самок. Поэтому в это время происходят ритуальные бои за самок. Взрослые самцы Комодского варана встают на задние лапы, обхватив друг друга передними, и стараются повалить соперника на землю. Когда одному из соперников удается повалить второго на землю, победитель сильно прижимает поверженного к земле и долго царапает его когтями. После окончания ритуала, проигравший самец удаляется, а победитель уединяется с самкой.

Свою страсть самец показывает самке только в момент спаривания, он трется об ее шею, подергивая головой, и царапает ее хвост и спину. Позиция сверху на сопернике или на самке для Комодского варана очень значимая, своим царапанием он доказывает собственное превосходство над сородичами. После спаривания самка сразу же уходит от самца, в поисках места для кладки яиц.
Чаще всего ими становятся гнезда сорных кур, большие компостные кучи или высокие кучи опавшей листвы.
Она выкапывает там глубокую норку и откладывает 20 яиц, весом приблизительно по 200 грамм каждое. Самка охраняет свое гнездо в течение 8-8,5 месяцев, пока на свет не вылупятся маленькие варанчики.
Сразу после появления у них срабатывает инстинкт самосохранения и пока их не съели, они взбираются на соседние деревья. Там они живут первые 2 года.

Молодые особи комодского варана окрашены в темно-серые цвета. По всему телу животного располагаются оранжево-красные полосы-кольца. С возрастом расцветка варана меняется, он приобретает ровный темный окрас.

Молодые вараны, возрастом до года, небольшие. Их длина достигает 1 м. К концу первого года жизни варан уже начинает охотиться. Малыши тренируются на курах, грызунах, лягушках, кузнечиках, крабах и самых безобидных — улитках. Повзрослевший «дракон» начинает охотиться на более крупную добычу: коз, лошадей, коров, иногда на людей.

В размножении Комодосских драконов, помимо привычного полового процесса, очень часто присутствует партеногенез. Самки этих животных способны откладывать неоплодотворенные яйца, из которых по истечении срока появляются только особи мужского пола. Способность и к половому, и к неполовому воспроизводству у комодских варанов обусловлена изолированностью среды обитания.^[5] Это позволяет им основывать новые колонии, если в результате шторма самки без самцов оказываются выброшенными на соседние острова.

В среднем продолжительность жизни комодского варана составляет 40 лет.

Враги и конкуренты[править]

У комодских варанов нет естественных врагов, за исключением человека и, возможно, иногда встречающихся у побережий гребнистых крокодилов. Они сами уничтожат любых соперников. Только молодые вараны могут стать жертвой различных хищников.

Охрана и статус[править]

Этих животных запрещено убивать. Они занесены в Красную книгу МСОП. Специально для них на острове Комодо был организован национальный парк.

В настоящее время на островах Комодо и Ринджа организован национальный парк. Любая охота на этих ящеров запрещена законом, а отлов может производиться только для зоопарков по специальному разрешению комитета по охране природы при правительстве Индонезии.

Факты[править]

• Вараны опасны для человека, в большей степени это касается его ядовитых укусов. Если вовремя не обратиться за медицинской помощью, то смертельного исхода не избежать. Особую опасность они представляют для детей. В голодные годы известны случаи выкапывания варанами трупов из могил.
• При содержании в неволе (эти случаи очень редки) гигантские рептилии быстро привыкают к человеку и становятся практически ручными. Один такой представитель вида жил в Лондонском зоопарке, он отзывался на кличку, брал пищу из рук человека и бегал по пятам за своими смотрителями.
• В 2003 г. в журнале Nature Australia было опубликовано краткое сообщение о молодой варанихе по кличке Кракен, которая живет в зоопарке Вашингтона и любит играть с игрушками. Наблюдение за Кракен проводил доктор Гордон Бурхарт и его коллеги из Университета Теннесси. Ученые изучали игровое поведение варана в течение двух лет и за это время записали 31 видеосюжет, в которых видно, как ящерица играет с разными предметами — резиновым кольцом, ведром, заполненным рулонами туалетной бумаги, носовым платком и теннисной туфлей. Биологи не просто давали варану разные предметы, они пропитывали их различными запахами, чтобы пронаблюдать за последующей реакцией. В качестве источника запаха использовали кровь кролика, кукурузное масло и даже духи. Кракен могла выбирать между игрушкой-«жертвой», пропитанной кровью кролика, и игрушкой-«не жертвой», пропитанной другими запахами. Если игрушка не пахла кровью, Кракен могла, подобно собаке, трепать носовой платок, играть с резиновым кольцом или туфлей. Но если тот же предмет был пропитан кровью, варан демонстрировал поведение хищника. Ящерица била хвостом, охраняла предмет, как будто это кусок корма, и у нее наблюдалось обильное выделение слюны.^[6]

См. также[править]

• Список сверххищников

Источники[править]

Литература[править]

• Даревский И. С., Орлов Н. Л. Редкие и исчезающие животные. Земноводные и пресмыкающиеся: Справ. пособие. — М.: Высш. шк., 1988. — С. 293—295.
• Жизнь животных в 7-ми т. /Гл. редактор В. Е. Соколов. Т.5. Земноводные и пресмыкающиеся. / А. Г. Банников, И. С. Даревский, М. Н. Денисова и др.; под ред. А. Г. Банникова — 2-е изд., перераб.— М.: Просвещение, 1985.— С.249—252.
• Биология. Современная иллюстрированная энциклопедия. Гл. ред. А. П. Горкин; М.: Росмэн, 2006.
• Малеев Е. А. и Даревский И. С., «Драконы» острова Комодо, «Природа», 1963, № 3
• Даревский И. С. и Кадарсон С., О биологии гигантского индонезийского варана, «Зоологический журнал», 1964, т.43, в.9.
• Большая советская энциклопедия. — М.: Советская энциклопедия. 1969—1978.

Ссылки[править]

• Комодские вараны на сайте National Geographic Россия
• Reptile Database