Tag Archives: reptiles

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.

Back when reptiles took on dry land

It was more than 300 million years ago that reptiles made tracks on earth. The exact moment when this happened is unknown, however; oh, and by exact moment, I’m talking about pinning it down to a couple million years (you gotta love geologists for their sense of time).

So, a discovery of fossilized footprints was recently made in the Bay of Fundy, New Brunswick, Canada. The track is 318 million years old, and it’s the oldest fossil found so far, so it’s probably very close to the “moment” I was mentioning above.

The footprints were discovered by Dr Howard Falcon-Lang of Royal Holloway, University of London. The results of his study, undertaken with Professor Mike Benton of the University of Bristol and Canadian colleagues, are published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

It has long been suspected that it was reptiles and not their amphibian cousins that made this big leap, because amphibians need to return to the water in order to breed, while reptiles don’t. According to professor Benton:

“The footprints date from the Carboniferous Period when a single supercontinent (Pangaea) dominated the world. At first life was restricted to coastal swamps where lush rainforest existed, full of giant ferns and dragonflies. However, when reptiles came on the scene they pushed back the frontiers, conquering the dry continental interiors.”

Dr Falcon-Lang added: “The Bay of Fundy is such an amazing place to hunt for fossils. The sea-cliffs are rapidly eroding and each rock-fall reveals exciting new fossils. You just never know what will turn up next.”

So the Bay of Fundy, fossil hunting – on my to do list.