Komodo, Bearded, and Frilled Dragons: Impressive Lizards
Dragons in Our World
Dragons do exist! A number of lizards are known as dragons, including the Komodo dragon, the bearded dragon, and the frilled dragon. It's not hard to think of the mythical beasts when we see some of these animals' activities. They are interesting reptiles with some surprising characteristics.
Komodo dragons are the heaviest lizards in existence. They may be as long as ten feet and weigh over 300 pounds. Their saliva is loaded with bacteria and may be venomous as well. Bearded dragons expand the spiny pouch on their throat when they feel threatened. The pouch turns black and gives the lizards their name. When a frilled dragon feels threatened, it opens its mouth in a gape and displays a frill of skin around its head and neck.
Smaug is the name of the fearsome dragon in J.R.R. Tolkien's book "The Hobbit". The name seems appropriate for the popular Komodo dragon who lived at the Houston Zoo. Unfortunately, he died in 2015 after major health problems.
Komodo dragons belong to the family Varanidae, which is often known as the monitor lizard family. The animals live in Indonesia. One of their habitats is the island of Komodo, which gives them their name. Komodos are the largest lizard alive today. Despite their huge size, they weren't discovered by western scientists until 1910. Their scientific name is Varanus komodoensis.
The lizards are strong animals with very muscular bodies, a long tail, and short, stocky, and bowed legs. The largest Komodo ever measured was 10.1 feet long and 365.9 pounds in weight. Most animals weigh up to 150 pounds, however.
Komodo dragons are carnivorous. They hunt for live prey and also eat carrion. They can reportedly detect chemicals coming from carrion located as far away as six miles. They do this by using their forked tongue and the Jacobson's organ. This organ is made of two pits and is located in the roof of the mouth.
A Komodo frequently flicks its tongue out of its mouth as it explores its environment. The tongue picks up molecules from the air and places them in the Jacobson's organ. This organ contains cells that bind to the molecules and then send a message to the lizard's brain, enabling it to detect the chemicals.
Hunters and Scavengers
Komodos prey mainly on mammals, especially deer, wild pigs, and water buffalo. When they aren't actively hunting, the lizards look quite awkward as they move over the ground in a lumbering fashion. However, anyone near a Komodo dragon should be aware that the animals can accelerate suddenly and rapidly and that they do attack humans in self defence. Komodos can run up to thirteen miles an hour. They usually approach their prey with stealth, though, or hide and wait patiently for the prey to approach them.
A Komodo uses its powerful body to hit the legs of a large prey such as a deer and force the animal to the ground. The reptile then lunges at the deer with its teeth and claws, tearing the body and causing the deer to bleed to death. Komodos sometimes fell smaller prey by lunging at the animals' necks.
Komodos frequently eat carrion instead of hunting. They are generally solitary animals. Unusually for lizards, the reptiles sometimes scavenge for food in a group. They have a hierarchy and take turns eating carrion. The largest males feed first. The smaller males and the females take their turn at the carcass once the big males have finished. The young komodos have to wait until everyone else has fed before they can eat.
Unlike the older lizards, the youngest Komodos spend most of their time in trees. They leave the trees to live on the ground when they are large enough to avoid becoming prey for the adults.
Like other reptiles, Komodo dragons are ectothermic. They regulate their temperature by their behavior instead of by processes inside their body. They absorb heat from a sunny spot in their environment in order to raise their body temperature and retreat to the shade in order to lower it. The dragons are often said to be "cold blooded", but this term isn't accurate. On a hot day they are warm blooded, just like us.
Male Komodo dragons often fight for the right to mate with a female. The two copulatory organs of the male are known as hemipenes. They are actually branches of the same structure. Each branch is known as a hemipenis. Only one hemipenis is inserted into a female's cloaca during mating.
After mating, the female dragon either digs a depression in which to lay her eggs or lays them deep inside a nest built by a ground-dwelling bird called a megapode. The visible part of the bird's nest is a mound on top of the ground. About 30 eggs are present in each clutch laid by the dragon.
The female may leave the eggs to develop on their own during the seven to nine month incubation period. Some females have been observed lying on top of the nest, however, presumably to protect the eggs. To date, though, no adults have been seen caring for the youngsters once they hatch. The youngsters must protect themselves as soon as they emerge from the egg. The lizard has an estimated lifespan of thirty years or more (if it survives its infancy).
Scientists have discovered that a few captive Komodos have reproduced by parthenogenesis, a process in which a female produces offspring without obtaining sperm from a male. Genetic tests have confirmed that all the genes in the offspring of these Komodos came from their mother.
Are Komodo Dragons Venomous?
There is no doubt that the bite of a Komodo dragon is very dangerous to its prey and to humans. There is some controversy about why it's dangerous, though (apart from the physical wound and blood loss that it creates).
The dragon will follow an animal that it's bitten but not killed for a long time. When the animal dies from the bite, as it often does, the dragon eats it. For a long time it was thought that the prey died due to infection by bacteria in the Komodo's saliva. Researchers have discovered more than 50 different kinds of bacteria in the saliva. At least seven of these are very dangerous (but not to Komodos). While these bacteria may play a role in the prey's demise, there may be a more important factor at work.
Some scientists have concluded that the Komodo dragon is venomous and that their lower jaw contains two venom glands. They say that the glands produce toxic proteins that reduce the ability of the prey's blood to clot, lower blood pressure, and cause the prey to go into shock. Other scientists have disputed these claims, however.
Both bearded dragons and frilled dragons belong to the family Agamidae. This is sometimes known as the dragon family. A number of lizards in the family have "dragon" in their common name.
The most common species of bearded dragon kept as a pet is Pogona vitticeps, also known as the inland or central bearded dragon. Some other species in the genus Pogona are also known as bearded dragons and kept as pets.
The inland bearded dragon lives in dry areas of Australia. It has a wide body and is one to two feet long, including its tail. The lizard is light tan to brown in color. Its head is triangular in shape and bears a pouch on the underside. The scales on the pouch look like spikes, especially along the sides of the pouch. The lizard also has a row of spikes along each side of its body and on the back of its head. Its legs are strong and are capable of lifting its body up so that it doesn't absorb heat from hot ground.
Bearded dragons live in a wide variety of habitats, including desert, scrubland, woodland, and grassland. They're classified as semi-arboreal and divide their time between trees and the ground. The animal is an omnivore and eats insects, spiders, small lizards, small rodents, and plant parts.
Bearded dragons are generally reproductively mature when they are one to two years old. Females are able to store sperm after mating so that fertilization can occur later. A female may lay several clutches of eggs from a single mating.
The female lizard digs a burrow in the ground in which to lay each clutch, which often consists of around twenty-four eggs. The number varies considerably, however. Neither the female nor the male take care of the eggs. As in many lizards, the incubation time depends on the temperature. The eggs usually hatch after sixty to eighty days.
The young dragons live in trees until they mature. They are more vividly colored than the adults and often have yellow, orange, or red-brown markings, like the youngster in the video above. Bearded dragons live for about ten to twelve years in captivity.
Bearded dragons are territorial animals and perform several interesting displays to assert their dominance or to express their submissiveness when they meet other dragons. Even when they are the only lizard pet in a home, they still perform these behaviors.
The Hand Wave
One display is a graceful, slow motion hand wave. The "fingers" are extended as the arm moves in a circular motion. The hand wave is used as a sign of submission, but it may have additional meanings, such as species recognition.
The Head Bob
Another interesting behavior is the head bob, which may be rapid or slow. Head bobbing is generally a sign of dominance and is often performed when two lizards approach each other. Males head bob more than females.
The Beard Display
Bearded dragons are named for their most famous behavior—displaying their beard. The "beard" is an expandable throat pouch that not only enlarges but also turns black. Both males and females have a beard. The inflated beard is a sign of aggression and is also used as a mating display. A lizard may open its mouth in a gape as well as inflate its beard, which makes it look even more threatening.
Bearded Dragons as Pets
Bearded dragons are often bred as pets due to their generally calm and friendly personality. They seem to enjoy being stroked, as long as they're handled from an early age and are used to humans. Pet owners say that the dragon is quite intelligent compared to other lizards. It shows curiosity and often likes to explore.
The dragons are generally kept in glass tanks or terrariums. It's important that this is set up properly for a pet's needs. The lizard is clever enough that it shouldn't be left in its terrarium all day, however. It needs to perform activities outside of its enclosure and to interact with humans in order to maintain its confidence and friendliness. It shouldn't be allowed to explore a room unattended due to the presence of potential dangers.
Anyone who keeps a lizard as a pet should have access to a knowledgeable veterinarian who has experience in treating reptiles.
The Frilled Dragon or Lizard
The frilled dragon (Chlamydosaurus kingii) lives mainly in Australia and New Guinea. It's also called the frilled lizard or the frill-necked lizard. It may be as long as three feet and as heavy as two pounds. It's generally brown or grey in color and has a mottled appearance that camouflages its body when it's clinging to tree bark.
The frilled dragon spends most of its life in trees but descends to the ground at times. It eats insects and spiders. Very occasionally, it eats smaller lizards and small mammals.
The Threat Display
The lizard's main claim to fame is its threat behavior. During the threat display, the animal stands on two legs, opens its mouth, which has a yellow or pink lining, and then unfurls its pleated hood. The hood surrounds the lizard's head, neck, and upper chest and makes the animal look much bigger than it really is. It often has brightly colored scales, which adds to the drama of the situation. The lizard may jump on its hind legs and hiss at the same time as displaying its hood. Male lizards erect their hoods during mating displays as well as during territorial disputes.
If the lizard's threat display doesn't work, it usually runs away on its two back legs, still erect and still with its frill unfurled. It only relaxes when it finds a tree to climb. The frill collapses and hangs around the animal's neck and shoulders. If the animal feels that it's in danger while it's on a tree trunk it freezes, relying on its camouflage to protect it.
Frilled dragons lay their eggs in an underground nest. The clutch consists of anywhere between eight to twenty eggs. Adults provide no parental care for the eggs. Interestingly, the gender of the hatchlings depends on the temperature at which the eggs are incubated. When the environment is very hot, all the youngsters are females. When the environment is slightly cooler, the number of females and males is approximately equal. Incubation lasts from eight to twelve weeks.
The babies are independent as soon as they hatch and will erect their hoods if necessary. The lizards seem to live for around twelve to fifteen years in captivity, although there have been reports that they can live as long as twenty years.
Frilled Dragons as Pets
Frilled dragons are bred for pets in some areas. They seem to lack the amiable disposition of bearded dragons. I've read far more reports of people developing a close relationship with a "beardie" than with a frilled dragon. A pet frilled dragon may accept being handled and can be "reasonably friendly", as one report says. Some animals don't enjoy being taken out of their enclosure, though. If one is kept as a pet, it should never be deliberately stressed in an attempt to force it to display its hood.
Like the bearded dragon, the frilled dragon performs head bobs and hand waves, as shown in the video of pet animals below. The animals are shown feeding on live crickets in the video.
Population Status of the Three Reptiles
According to the IUCN (International Union for Conservation of Nature), the Komodo dragon population is classified as "Vulnerable". This status is based on 1996 data. As the IUCN Red List entry says, the classification badly “needs updating.” The Red List classifies animals according to their nearness to extinction and also gives other information about the animals. Some people familiar with the Komodo dragon say that it's facing population stresses.
The status of Pogona vitticeps (wild and captive) was assessed by the IUCN in 2017. The species has been placed in the “Least Concern” category. The Chlamydosaurus kingii population was assessed in 2014. Like the bearded dragon, this species has been placed in the “Least Concern” category of the Red List.
Other Kinds of Dragons
There are other dragons in nature, including the flying dragon, which is another lizard, the leafy sea dragon, which is a relative of the sea horse, and the blue dragon, which is a type of sea slug. The dragons of myths have captured people's imagination and encouraged them to see these creatures in the natural world. Studying dragons is a fun pursuit.
- Information about the Komodo dragon from the Smithsonian National Zoo and Biological Conservation Institute
- The Komodo dragon's remarkable physiology from PBS (the Public Broadcasting Service)
- Information about the central bearded dragon from the Australian Museum.
- Facts about caring for bearded dragons from Vetstreet
- Frilled lizard facts from the Toronto Zoo
- Chlamydosaurus kingii Red List entry from the International Union for Conservation of Nature
Questions & Answers
© 2013 Linda Crampton