Tag Archives: Komodo dragon

What are komodo dragons, the largest lizards in the world?

An impressive and ruthless predator, Komodo dragons are the largest living lizards on Earth. Their success is based on a very deadly bite, but there’s more than meets the eye to this endagnered, cold-blooded carnivore.

Image via Pixabay.

Reptiles used to rule the Earth, in the form of dinosaurs; today, they’re no longer top dogs. Some of their larger ancestors, such as crocodiles or alligators, bear hints of that fearsome legacy. Of others, such as lizards, for example, we tend to think of more as critters or cutesy pets basking under a heat lamp.

But not all lizards are born equal, and they can be quite fearsome creatures. The Komodo dragon (Varanus komodoensis) is living proof. Not only is it the largest, heaviest lizard on the planet, but the dragon is armed with vicious, shark-like serrated teeth and a potent toxic bite that bleeds its prey dry.

A living dragon

Komodo dragons are one branch of the monitor lizard family that is endemic to a few islands in Indonesia — they get their name from one of these, the island of Komodo, one of their prime habitats. They are the largest living lizards, growing up to 3 meters (10 ft) in length and approximately 70 kilograms (150 lb) of weight. Whichever way you cut it, that’s a lot of lizard. Wild specimens weigh around 70kg (150 lb), but those in captivity can weigh a lot more. The largest specimen officially found in the wild to date was 3.13 m (10.3 ft) long and weighed 166 kg (366lb), although that weight included an undigested meal.

The dragon’s tail is around the same length as its body, and they’re covered in very tough scales. Each scale is reinforced with a tiny bone (these are called osteoderms — ‘bony skins’), meaning that Komodo dragons are, essentially, encased in armor. Although such osteoderms are not unique to the Komodo dragons, they have been studied and described extensively in this species.

Their study was made possible by the Fort Worth Zoo, which housed the longest-living specimens bred in captivity, which lived for 19-and-a-half years. After its death, the zoo donated the body to the University of Texas at Austin, where researchers at the Jackson School of Geosciences examined it with a very powerful CT (computer tomography) device. The animal’s extensive age made for a well-developed, intricate, and striking suit of osteoderm armor.

Osteoderms, colored orange, cover the dragon’s body, as seen by this CT scan of its skull. Image credits The University of Texas at Austin / Jessica A. Maissano et al., (2019), The Anatomical Record.

The study revealed that the osteoderms in Komodo dragons differ in shape and overall coverage from other lizards — they’re more robust and cover more of the animal’s surface. A similar procedure on a baby Komodo dragon found no osteoderms, meaning that this bone skin develops as the animal becomes older.

Diet and behavior

As is befitting of a dragon, these lizards are top predators. They completely dominate their ecosystems, hunting and eating anything and everything from invertebrates to birds or mammals. They will happily eat carrion or other dragons, as well.

Their bite is vicious. Komodo dragons have serrated teeth that are ideal for ripping through flesh and bone. Their lower jaws house glands that secrete an anticoagulant toxin. This makes a bite from such a creature a very dangerous thing. When hunting, Komodo dragons bite down hard and pull back using powerful neck muscles; this tears flesh to shreds. The toxins then kick in to prevent clotting which leads to massive blood loss, sending their unlucky prey into shock.

Komodo dragons are not very active creatures, on account of their slow metabolism (a trait typical of most reptiles), so, most often, these reptiles rely on their camouflage and patience to pounce on unsuspecting prey. Despite their usual lethargy, Komodo dragons are capable of incredibly-fast strikes when hunting. Since they’re not very fast runners, their hunting strategy involves getting one good bite into their target, which virtually always escapes. Then, the dragons will calmly follow their victim, waiting for them to bleed out, using their keen sense of smell to follow the trail of blood. Such a hunt can take them miles away from the place where they delivered the bite.

But when they do happen upon the dead or dying prey, Komodo dragons feast in style. They can eat up to 80% of their body weight in a single feeding. This gluttonous nature, together with their slow metabolism, means that Komodo dragons in the wild typically eat only around once per month.

They are not above eating carrion, which they can detect using their sense of smell as far as six miles away. They are known for digging up graves in search of food. Komodo dragons can attack humans but only do so rarely.

An endangered species

First recorded by Western scientists in 1910, the Komodo dragon has never been an abundant species. Today, they are threatened with extinction as per the IUCN Red List. The main driver of their extinction historically was hunting for sport and trophy, with habitat destruction and climate change being the most pressing issues facing the species in modern times.

Komodo dragons are currently protected under Indonesian law. Authorities have gone so far as to temporarily ban tourist travel to the island of Komodo, and set up the Komodo National Park there in 1980 to aid in conservation efforts.

Such developments are especially surprising since female dragons can reproduce asexually — if no male is present, they can fertilize themselves. However, only males will result from such pregnancies. Combined with the Komodo dragon’s distaste from traveling far from their birthplace, this can quickly lead to inbreeding and collapse of isolated populations. Habitat destruction in the form of forest burning for agriculture leaves the species especially prone to inbreeding.

Credit: Pixabay.

Genome study reveals why the Komodo dragon is such a formidable predator

Credit: Pixabay.

Credit: Pixabay.

The Komodo dragon (Varanus komodoensis) is an awesome reptile that has dominated several Indonesian islands — including its namesake Komodo island — for millions of years. Out of over 3,000 species of reptiles, the Komodo dragon is the largest as well as one of the quirkiest. For instance, the cold-blooded predator is known for being capable of raising its metabolism to mammal-like levels, enabling it to chase down prey with remarkable speed and endurance. So, what’s its secret? In a new study, researchers sequenced the reptile’s genome, revealing genes that may underpin its phenomenal prowess when hunting prey.

A dragon’s genes

Full-grown Komodo adults can reach 10 feet (3 meters) long and weigh more than 300 pounds (140 kilograms). The first thing you’ll notice about them is their frightening appearance, with their wide, flat heads; bowed legs; huge, muscular tails; curved and serrated teeth; and sharp claws. To top it off, Komodos have a clumsy, yet menacing walk during which they constantly flick their long, yellow tongues in and out.

Komodos will basically eat anything they can find, from long-dead carcasses to water buffalo, smaller Komodo dragons, and sometimes even humans. To hunt, Komodos rely on their camouflage and patience, waiting for the right time to strike an unsuspecting prey lying in the bushes or tall grasses.

When they pounce, Komodo dragons do so at breakneck speeds, despite their large size. Speed and large size are a bizarre, unheard off combination elsewhere in the animal kingdom; especially reptiles which typically lack high aerobic capacity and have slow metabolisms. In a new study published in the journal Nature Ecology & Evolution, researchers at the Gladstone Institute of Cardiovascular Disease at the University of California, San Francisco, sequenced the genome of the dragon and discovered genetic adaptations involving mitochondria. Since mitochondria are the powerhouses of cells and are critical to the proper function of cardiac muscles, this may explain the lizard’s enhanced aerobic capacity.

“This is an apex predator living on isolated islands, and it’s absolutely gigantic. It’s just an awesome animal,” Benoit Bruneau, the director of the Gladstone Institute of Cardiovascular Disease, told Reuters.

“Reptiles are kind of like a playground for evolution. There is so much diversity in size and form and behavior and their physiology,” Bruneau added.

Credit: Pixabay.

Credit: Pixabay.

The researchers also found genes that are involved in the control of the lizard’s sensory system, which allows the Komodo dragon to detect the hormones and pheromones emanated by prey from long distances away.

Even if a detected prey somehow escapes the dragon’s clutches, its chances of survival are pretty slim. The dragon’s saliva contains highly septic bacteria which kills victims within 24 hours. The dragon calmly follows their bitten prey for miles until it finds the corpse. One important factor that contributes to the dragon’s high kill rate is a compound found in its saliva that prevents the blood of bitten pretty from clotting. The new study found that the dragons have genes involved in coagulation that make them immune to their own venom. Komodos often battle each other in epic fights, but this feature prevents members of their own species from dying from their own venom.

Komodo dragons are venomous

The Komodo dragon is definitely one of the most impressive and dangerous creatures to roam the Earth. Reaching 3 metres and more than 70 kilos and delivering one of the most fatal bites in the reptilian world, it’s no wonder that it inspired so many legends and fears. However, it does not all end here: it seems that this modern dragon is also among the few species of lizards that are venomous.

Until recently scientists had all kinds of assumptions related to the way the dragon kills its prey as it releases it after the bite. Did they let the prey die because of the severe bleeding or did the bacteria in their saliva finish the job?

Komodo dragons feed on large mammals such as wild boars, deers or goats and they spend hours motionless waiting for the prey to show up. The attack is surprising as the huge lizard ambushes it with its jaws open, which must be an image worse than any nightmare.

The mystery of its killing methods remained until magnetic resonance imaging scans revealed the fact that the bite, which is clearly weaker than the one of a crocodile for example, hid a dirty secret: venom glands.

komodo

After this discovery, the glands of a terminally-ill dragon from a zoo were removed for further study. It seems that the poison is similar to the one found in Gila monsters or snakes. The effect is sudden and devastating: it causes a sudden drop in blood pressure which sends the prey into shock. Moreover, it stops the blood from clotting, thus making the animal bleed to death.

The discovery suggests that other lizards may as well hide a trick like this; util recently only the Gila monster and the Mexican beaded lizard, both living in southern US states and Mexico were known to possess venomous glands.

source: The Guardian