Tag Archive: parthenogenesis


Komodo Dragon

Komodo dragon, resting on a rock. Image taken at Woodland Park Zoo, Seattle.

Komodo dragons are crazy cool lizards, with no natural enemies. They’re only found on a few small islands in Indonesia and most of what we know about them we’ve only learned in the last 30 years. They are the largest living lizards in the world, averaging 150 lbs (68kg) and 8 ft. (2.4m) in length, though they’ve been known to grow as much as 300 lbs and 10 ft. in length. And actually, since they can eat 80% of their body weight in one sitting (!!), a male that just finished a large meal can be weighed at more than 550 pounds. This big lizard had big ancestors. Their largest ancestor was the Megalania prisca, which grew to over 23 ft and 1,400 pounds and was the largest venomous animal to have ever lived (as far as we know).

Sleeping Dragon

A resting Komodo dragon. Image taken at the Woodland Park Zoo, Seattle.

Predominantly ambush predators, these lizards can hunt animals 5 times larger than themselves and 15 times their weight, including deer and water buffalo.  Although they appear toothless, because their gums cover their teeth until they’re ready to bite, they have 60 inch-long teeth and deliver deeper and more damaging wounds than a crocodile. When they eat, their gums tear and bleed. The blood mixes with the saliva and makes a slime that allows them to swallow their food whole. Every part of the prey is eaten, even hooves, and it all gets dissolved in their strong stomach acids. The lizard may have to sleep for up to an entire week while its food digests after eating a big meal.

Sleepy Komodo Dragon

Resting Komodo dragon at the Woodland Park Zoo, Seattle.

Oh and they’re venomous. What’s that you say? No they’re not? You learned a long time ago that the Komodo dragon has bacteria in its mouth and it’s a bacterial infection that causes the slow, agonizing death of the prey? Yeah, so did I. It wasn’t until 2009 that scientists discovered that they are venomous. They have venom glands in their mouth and venom causes their prey to continuously bleed. They die from blood loss and infection.

Cutey Pie

Komodo dragon. Image taken at the Woodland Park Zoo, Seattle.

Nothing is safe from a Komodo dragon-not even Komodo dragons. They are cannibalistic, with healthy dragons eating the young, old or injured dragons. Young Komodo dragons make up about 10% of an adult dragon’s diet. For this reason, when young dragons hatch, they dash up into the trees to avoid being eaten. But many won’t make it. Birds, snakes and other Komodo dragons-sometimes even their mothers- will catch them before they can reach the safety of the tree. They have to be cautious and quick when they come down for water and sometimes they may roll around in feces to mask their odor from adults.

I see you

A Komodo dragon. Image taken at Los Angeles Zoo.

One reason why they eat their own young may be that they need to in order to reach their huge size. The young eat insects, and small lizards and mammals, but there are very few medium sized animals on the islands. Those that are there were introduced and so weren’t always around. Perhaps eating their own young gets them to the next size level where they can go after bigger animals.

adorable lizard

Komodo dragon resting on a big rock. Image taken at the Woodland Park Zoo, Seattle.

These predators have excellent senses. They have a forked 16-inch tongue that works like a snake’s tongue-flicking it out into the world, they can taste/smell with their tongue. They can find carrion more than 5 miles away. They are covered in hard scales, each one with a sensory plaque for increased sensitivity. On their face and feet, each scale has 3 or more sensory plaques, further heightening their sensitivity. They can see in color. We used to think they were deaf, but that was disproved by a zookeeper that trained one to come when it heard her voice. Now we know that they only hear sounds in the low range of pitches. They can even distinguish between different human voices.

I see you

A Komodo dragon checking us out. Image taken at the Los Angeles Zoo.

Male Komodo dragons are territorial. Females and young can inhabit their territory, but males are only allowed to pass through when the visitor is tracking prey. They will fight other males to breed, standing on their hind legs and balancing on their tales. After the loser falls, he will lie still while the winner scrapes his claws along the loser’s back and tail as a sign of dominance.

Females use their claws to dig egg chambers. Since Komodo dragons will raid each others’ nests, the mother dragon will dig mazes of false tunnels to confuse any would-be egg raiders.

dragon claws

Komodo dragon claws, front foot. Females use their claws to dig egg chambers. Males will scrape them across defeated Komodos. Image taken at Los Angels Zoo.

dragon claws

Front feet of the Komodo dragon.  Image taken at the Los Angeles Zoo.

back claws

Komodo dragon claws, hind leg. Image taken at the Los Angeles Zoo.

Females will also guard their nests for up to 3 months. She’ll leave once the rainy season hits, since the chances of her eggs being disturbed are substantially less.

In 2006, we discovered another surprising fact about Komodo dragon reproduction. The females can be parthenogenetic! In London’s Chester Zoo, a female produced 8 offspring without ever having met a male, giving us our first glimpse at this cool adaptation.

Komodo dragons can live 50 years in the wild and up to 9 months without water. They are strong swimmers, able to travel between islands and dive to depths of 15 feet.

Swim time

Time to cool off. A Komodo dragon about to take a swim. Image taken at the Los Angeles Zoo.

Komodo Swimming

Komodo dragon going for a swim. Image taken at the Los Angeles Zoo.

People in Komodo and Rinca take precautions to avoid attacks from Komodo dragons. They don’t wander into the forests or grasslands alone and they never antagonize or approach the dragons. They’ve also had a long-held belief that if they feed the old dragons that could no longer hunt, throwing them old deer heads and hides and fish heads and guts, it was sort of a peace offering and it kept them and their children safe from getting attacked. Younger dragons sometimes ate the food as well. There was only 1 human death recorded in 30 years (since records started) from 1965-1995.

However, in 1995 Komodo park authorities banned the feeding of Komodo dragons, which environmentalists thought would make them grow lazy and forget how to hunt themselves. They also outlawed the dogs, which are considered an invasive species, which have been used to keep the dragons out of the villages. Since these things have been put in place, several people have been killed by Komodo dragons since 2000 and some dragons have recently begun to enter school buildings and homes. That’s right. Imagine a giant 8-foot venomous lizard walking down your school hallway.

K. dragon

Komodo dragon. Image taken at the Los Angeles Zoo.

It may surprise you to know that King Kong was actually based on an expedition to collect Komodo dragons. The best trappers had extreme difficulty and the dragons were escaping. The movie producer Merian C. Cooper took the story and changed the giant lizard to an ape.

Komodo dragons appear in a few other movies as well. In The Freshman they used an Asian water monitor to be a “Komodo dragon.” In Komodo Dragon, the dragons are computer generated. It turns out that real Komodos don’t do well with handling.

You can also find cool Komodo dragon art, like this awesome statue that lives at the Woodland Park Zoo in Seattle, that kids are allowed to climb on.

Dragon statue

A Komodo dragon statue in Woodland Park Zoo, Seattle. There are brightly colored tiles along its back. Children are allowed to play on it.

Alright, one last cool tidbit on this really long post. At a Singapore Zoo, they’ve used acupuncture to treat a sick dragon. It’s thought to have been successful.

Have one last photo of these beautiful animals.

Komodo Dragon

Komodo dragon, clearly contemplating the meaning of life. Image taken at the Los Angeles Zoo.

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Giant Thorny Phasmid

This giant thorny phasmid enthralled us with her most amusing antics. Image taken at the Insect Discovery Lab in San Francisco.

 

Walking sticks are most known for their amazing camouflage. But their camouflage often involves a lot more than simply their good looks. While having the shape and coloration of a leaf, like the one pictured above, or a stick, like the one shown below, certainly helps, it’s really just the beginning.

 

Stick insect

Stick insects can look like leaves or sticks. In some species, the females look like leaves and the males like sticks. Image taken at the Insect Discovery Lab.

 

Even their eggs are camouflaged, looking like plant seeds. But in addition to this, they also have behavioral adaptations that help them blend in or in some cases, mimic other animals.

For example, obviously, if you are trying to mimic a stick, then remaining still most of the time is pretty important. But, these animals take it a step further and will even flex their legs in such a way that keeps them in exact motion with the plant, which may be gently swaying in a breeze. Brown nymphs, or young walking sticks that haven’t reached the adult stage yet will hang from a twig and if they are disturbed, they will drop like a dead leaf. They’ve even been shown to hold their legs at exactly the same angle from the tree that the twigs around them are. All of these are behaviors that help keep them invisible to potential predators. That’s probably why these guys are in the Order Phasmida, which is from the Greek phasm, meaning phantom or apparition. They vanish from sight. Here’s a young insect among leaves, so you can see how well their camouflage works.

 

stick insect

A young stick insect clings to some leaves, which provide camouflage as well as food. Here's a challenge-Can you find a cuter baby bug? Image taken at the San Francisco Zoo.

 

Still, some species can also mimic other animals. For example, Australian walking sticks are thought to curl their tails when discovered and threatened, perhaps to appear like a much more threatening scorpion.

 

Australian walking stick

This young Australian walking stick is curling its tail, perhaps to mimic a dead, curled leaf, or perhaps to mimic a scorpion. Image taken at the Insect Discovery Lab.

 

I have actually come across conflicting ideas about this strategy. On one side, some say they are not mimicking scorpions, but dead, curled up leaves. Since scorpions are on the ground and they generally live in trees it wouldn’t make sense to mimic them. But would the predator know that? Perhaps both ideas are in play. On a side note, these guys as adults also have wings that are brightly colored on the inside, which they can flash and startle predators with as well.

Another species of walking stick that mimics another invertebrate is the Spiny leaf insect, aka macleay’s spectre stick. In this case, when the insect lays its eggs, the eggs have little knobs on them which attract ants. The ants will carry them to underground nests, where they eat the knob, but leave the rest of the egg alone. Being in this underground nest grants them protection from predators. 1-3 years later, the eggs will hatch and the nymphs will emerge looking and behaving exactly like the red-headed black ants, until they molt.

The spectre stick is not the only walking stick with an interesting reproductive strategy. For example, there are a couple of other species where the females eject their eggs from their abdomens and scatter them about. Cyphocrania gigas can expel her eggs almost 20 feet away! By scattering their eggs, they reduce predation and competition between siblings.

Also, many walking sticks can reproduce asexually! That is, the females don’t have to mate with a male at all to produce offspring. It’s the true virgin birth. In some cases, it takes longer to reproduce asexually, but it’s still possible. For some walking sticks that do this, males are often hardly ever found.

Another interesting reproductive behavior-generally a male walking stick finds his mate by scent and then climbs onto her back to mate. The male will remain there for hours at a time, staying on the female so that no other male will have a chance to mate with her, thus insuring her offspring will be his. The much larger female seems to hardly notice, as she goes about her daily business as if nothing unusual is happening.

However they do it, if the eggs survive, they hatch and a new walking stick begins its life. The walking stick will go through several different molts (6-7 seems to be the general range) until they become adults. The Australian walking stick, might eat its exoskeleton after each molt and tend to get darker with age. The stage of life of an insect (actually arthropods, the larger group including insects) between molts is called an instar. Below are pictures of a couple of young walking sticks in different instars, so you can see some more juveniles.

 

walking stick

A young walking stick. Image taken at the Insect discovery Lab.

 

 

walking stick

Two more young walking sticks. Image taken at the Insect Discovery Lab.

 

These are the same species, just different sexes and instars.

Now here’s a different juvenile walking stick. Notice something missing?

 

Walking stick

A young walking stick missing its leg. Image taken at the Insect Discovery Lab.

 

Young walking sticks will give up a leg to a predator if it has to in order to get away. But this is not the tragedy it seems to be, because after several molts, they can actually regenerate their limbs! So none the worry for this little guy; he’ll be good as new before he’s an adult.

 

giant thorny phasmid

A giant thorny phasmid, crawling along my camera. Image taken at the Insect Discovery Lab.

 

Now this picture is of the giant thorny phasmid, aka the Maylayan Stick Insect. This is the same bug as in the first picture, but I included this picture to show the scale (and her useless wings). You can see that she is roughly the size of my hand, full grown. Now, that’s a big insect. But not the biggest. I wouldn’t be doing stick insects justice if I left out the fact that the largest insect discovered in the world so far is a phasmid. They can range in size from a small half of an inch to a record 1.86 feet or 22.32 inches. Not including it’s legs, it’s 14 inches long. And yet, I suppose if there has to be an almost 2-foot long insect, I’m glad it’s a walking stick. They are fascinating, pleasant-to-be-around insects. This girl shown above goes to schools and meets kids on a regular basis, to teach them about insects and the rain forest her relatives live in.

Well, just in case you haven’t had enough of stick insects yet, here is a cool picture of one nomming a leaf. Stick insects eat plants. Is that cannibalism?

 

walking stick

A walking stick nomming a leaf. Image taken at the San Francisco Zoo.

 

Now, you might think that a plant-eating animal that sits still and hides all day poses no threat to potential predators. But a few walking sticks do have some other defenses. For example, some have giant spines on their legs, like this one shown below. They will use these spines as a defense, but also in competition between males.

 

Phasmid's spiny legs

The spiny legs of a phasmid. Image taken at the Insect Discovery Lab.

 

Ouch! But that’s not the winner. No, I think the award goes to the musk mare, aka the two-striped walking stick. This insect can shoot out a chemical spray with pretty high accuracy. If they get their potential predator in the eye, they can cause temporary blindness and in extreme cases, they can cause corneal damage. And they can spray more than a foot away.

Anyway, this post is just a glance at a few of the ~3,000 known species of stick insect, and just a small fraction of the cool things they can do. If you’d like to learn more, a good place to start is with the Australian Museum’s site, which discusses several species I didn’t mention here. Also, many zoos and aquariums have stick insects, so checking out your local facilities might yield some cool experiences and observations as well.

And last, but not least, special thanks to phasmid wrangler Will Mckennet for raising these animals since they were eggs, and sharing them with us.