How many legs are best for megamonsters?

About a year ago I wrote two posts about what happens to legs when an animal is scaled up (here and here). In a nutshell, if you make an animal's body twice as big, the new body will weigh eight times as much as the old one and not twice as much. If you make the legs twice as big, they will not be strong enough to carry the new weight, so the only solution is to make the legs more than twice as thick. The result of all this is that legs have to make up a larger proportion of a very large animal than of a small one. There is a limit to how big you can make an animal: at some point the legs need more food than the body can deliver, or something equally silly.

Click to enlarge; copyright Gert van Dijk

Last week Jan asked a question on the bulletin board of the Furaha site asking which body plan would be best for really big animals. That question made me think: the more legs there are, the smaller each leg can be to carry the body. What does that do to the mass of all legs together? If the total mass of six slender legs would be less than that of two thick legs while doing the same job, than having six legs would be a better design for very large animals than having two. That would be a nice outlandish and unearthly solution! It is shown above in a rather silly image (the human figure came with the program and is there for scale only).

Whether it would work or not was not intuitive to me, so I did some homework and came up with the work of Robert McNeill Alexander (if you are interested in biomechanics you will encounter his work many times). In this case, part of the answer was described in this book Optima for Animals.

Click to enlarge; copyright Gert van Dijk

The reasoning starts with tubes. There are excellent reasons why vertebrate leg bones and insect legs are tubes, and why tubes are such important structural elements in technology. They are about as strong as solid rods of the same diameter, but weigh a lot less, and doing the same job with less bone is a good idea. The three tubes above all have the same outer diameter, but the hole down their lengths differs in diameter. In papers on the subject you will find an very important parameter 'k': it describes the width of the inner hole as a fraction of he outer diameter. In the left one k is 1, so the hole is tiny. In the middle bone k is 0.5, and in the right one k is 0.9, meaning there is just a thin shell of bone. A value of 0 means no hole at all, and a value of 1 would mean the bone is infinitesimally thin (in simple words: there is no bone!).
Are all these bones equally strong? No, they are not. If you just take bending forces, there is a nice formula which contains three items of interest: the 'bending moment' M (the force that the bone needs to withstand), our friend 'k', and the radius r of the outer side of the bone (there is only one thing else and that is a constant K for the material - ignore it-).

Here it is: r=[M/K(1-k^4)]^0.33

If you keep the force M constant you can calculate what the radius is for any given value of k. Let's do so.

Click to enlarge; copyright Gert van Dijk

The image above shows what happens for four values of k: 0, 0.3, 0.6 and 0.9. As you can see, the value of the radius increases as well: the thinner bones have to be wider to withstand the same pressure. Note that that is hardly the case when the holes are fairly small. In fact, the effect is only really noticeable when k increased form 0.6 to 0.9. Does it matter? yes: the cubes in front of the bones represent the mass of the bone itself, and that nicely shows why tubes are good. They are all equally strong, but the thin-walled ones weigh a lot less.
On Earth, things are more complicated for mammals because the holes in the bones contain marrow. Marrow, while less heavy than bone itself, still makes the bone as a whole heavier. A bone with a very thin shell will be wide and will contain lots of marrow, defeating the purpose to make bones light. For mammals with marrow in their bones there is an optimal value for k, at which the bone as a whole weighs the least; that value turns about to be about 0.63. If, however, you manage to put air in the hole instead of marrow like birds, than the story becomes different and you can increase k. Above around 0.9 the bones the become too susceptible to buckling, so there is another optimum value for air-filled bones: a value of 0.9 is excellent. Our hypothetical megamonster shall therefore have air-filled tubular bones with a value of k of 0.9!

We still are not there yet. The real question was what happens if we give the animal more legs. Let's assume that the forces are simply divided among the legs, so with four legs each leg has to carry exactly one fourth of the burden. Remember that there were three parameters of interest in the formula: The bending moment M, the outer bone radius r and k. Set k to 0.9, and then we can calculate r for four bending values. The values per leg are 1 (the animal has one leg), 0.5 (two legs), 0.25 (four legs) and 0.125 (eight legs).

Click to enlarge; copyright Gert van Dijk

This picture show the resulting bones, along with the number of bones. As you can see, the bone for an animal with eight legs is a lot less thick than for the one with just one leg. So far so good. The smaller bone must weigh a lot less than the bone for the one-legged animal, which is what we wanted. Then again, there are now eight such bones, so the question is what their combined weight is.
Each bone of the two-legged megamonster weighs 63% of the one-legged one, so the two bones together weigh 126% of the one bone. That is not what we wanted, as the two legs weigh more than the one leg. Does it get better if we add more legs? Well, for four legs each one weighs about 40% of the one bone, and together they weigh 159%. For eight legs, each one weighs 25% of the one bone, so the total weighs 200% of the one bone.

How disappointing... I had hoped it would be the other way around. Now it seems that fewer legs is the better way to save weight if you need a mega-monster. Obviously, giving it just one leg is not practical; there would be a big risk of falling, and the only way to move would be to jump in a series of bone-shattering hops. Two legs is quite feasible; just think of carnivorous dinosaurs. Four is also good. In a last-ditch attempt to save the concept of multi-legged megamonsters I could say that having six or eight legs provides safety as a possible advantage. A two-legged monster with a broken leg is doomed with certainty, and a four-legged one probably is. But a six-legged one could deal with one broken leg and hobble away.
You might expect animals with a multi-legged body plan to lose some limbs as they grow bigger and bigger as a measure to save weight. Such limbs might be given another purpose than locomotion, so they could develop into, well, just about anything. They could develop clavigerism or centaurisation, also interesting.

I'm still disappointed though...

Wildlife in the Star Wars universe

The Star Wars films are great adventure movies, but you wouldn't think that there was much biology going on, would you? The Star Wars universe is obviously swarming with intelligent creatures from many different worlds, and these worlds must equally obviously be filled with animals, but you do not get to see many of those. it's not what the films are about. In the second film there was the 'tauntaun' on the ice planet Hoth, and as a hairy mammal-like animal with the body plan of a bipedal carnivorous dinosaur that was an intriguing invention. Otherwise, not many in the early stages came across as great exobiological inventions. In fact, quite a few some could not be taken seriously at all: just think of the gigantic snake-like animal living in an asteroid (in a vacuum!), large enough to have the Millennium Falcon fly between its teeth. Or take the 'Sarlacc', a carnivorous monster buried in the sand on Tatooine: all you see of it is a gigantic mouth in a pit in the sand, reminiscent of an antlion but scaled up to a gigantic level. Its very existence implies that there are lots of rather stupid animals ready to stumble into it maws. No-one would take such a creature seriously from a biological point of view, and no-one should; it's not what the films are about. Still, there is a book about the animals in the Star wars universe, showing someone cared. It is called 'The Wildlife of Star Wars. A Field Guide', by Terryl Whitlatch and Bob Carrau. Terryl Whitlatch has been working as a 'creature designer' for several of the Star Wars films. Typing her name into Google results in so many hits that I do not need to provide many links. Still, here is one with a video interview, and here are two on character design (one and two). The 'Wildlife' book first came out in 2001. I had somehow missed it completely until recently, when a reprint was issued. I found another book of hers showcasing other work, not related to Star Wars: 'Animals Real and Imagined'. The Star Wars book seems to have many creatures in it that did not appear in the films as far as I know. I have to be careful here, as the three newest films (I, II and III) did not make much of an impact on me, aimed as they seemed to be at children. I suspect that most of the animals in the book were not in the films at all, which would imply that Ms Whitlatch had more or less free reign in designing them. The sillier animals such as Giant Space Slugs of over 900 meters long, and the above-mentioned sarlacc occur in the book, should you wish to know more about them. The animals that I assume to be Ms Whitlatch's inventions were much more to my liking. In a way they conform to the general exobiological theme of Star Wars. In it, intelligent beings are almost always humanoid, with two legs, two arms and a sort of alien-looking head that is rather larger than the standard Earth issue human head. The films started when digital creature design did not exist, and alien design followed time-honoured principles, involving actors in rubber suits. Hence the big heads. Ms Whitlatch's aliens more or less follow such principles. The book deals with life on several planets, but you will not be able to determine their planet of origin by looking at their body plan: an animal could come from one planet as well as from the next. Whereas nearly all intelligent beings are humanoid, animals also share many design principles with Earth animals. Quite a few are 'mammaloid', meaning they look a lot like mammals with odd heads. There are also plenty of aviforms and reptiloids, as well as combinations of designs. It is interesting to compare this design strategy with that of Mr Broadmore's Victorian Venusian life forms discussed recently: these were specifically designed to evoke a sense of displacement, i.e. of 'alienness'. Instead, Ms Whitlatch's life forms might be just around the corner. That makes them more believable, but inevitably less alien. Regardless of the degree of their 'alienosity', the animals are all superbly well drawn, with an intimate knowledge of animal anatomy and behaviour. The 'Animals Real and imagined' book contains drawings of existing animals in addition to fantasy ones, proving once more that Ms Whitlatch is a very skilled artist. I will go through a few of her drawings, scanned from the two books. As I did not wish to damage the books, I had to crop some drawings a bit, for which I apologise (you could all get the books yourselves...).

Click to enlarge; copyright Lucasfilm Ltd.

These are Motts from the planet Naboo, revealing how mammalian their body plan is. The way the legs fold, the number of joints, the general shape of the head, all these things say 'earth mammal'; 'ungulate' in fact. But look at the ease with which their poses are captured, and the green thingy walking away from the motts is much more 'alien'!

Click to enlarge; copyright Lucasfilm Ltd.

Also from Naboo, these gullipuds are, as the text says, amphibians. They resemble puffer fish or indeed, some Earth amphibian in being able to inflate their bodies. I like the sense of humour in this and other drawings.

Click to enlarge; copyright Lucasfilm Ltd.

The tree-dwelling Shaupaut. This is another mammaloid. Its elongated fingers are apparently used to 'fish' for avians flying by.

Click to enlarge; copyright Lucasfilm Ltd.

These animals are apparently extinct. They are labelled as stalking birds from Alderaan, and are obviously modelled on large African ground living birds, called 'ground hornbills'. These walk in rows over open fields, hoping to disturb smaller animals so they can be caught and eaten. These birds are doing the exact same thing.

Click to enlarge; copyright Lucasfilm Ltd.

These flying animals are urusais, and while they are members of the same species, there is an enormous difference in anatomy: the male is the one sitting upright balanced on its tail. It has four wings, while the female admiring him only has two. Now that is a rather fundamental difference. I doubt that any animals on Earth take 'sexual dimorphism' to such extremes. You would think that such large differences in shape would result in the two sexes being subjected to very different evolutionary pressures, with resulting different sets of genes for male and female bodies. Earth's insects may be thought to have two sets of bodies as well, but there the two act in different stages of life. It is an interesting concept to have something like that defining the two sexes. I have my doubts however that the differences can go so far as a having different numbers of wings. The text says that their span is about two meters, which means that they must be very heavy. Their bodies and thick tails look good, but do not appear to be designed to save weight. Light bones? A heavy atmosphere?

Click to enlarge; copyright Design Studio Press

This one is not from the Star Wars book, but from the other one. It represents one of the few designs that I do not really like. The reason is that it reminds me too much of the six-legged forms in Avatar that I discussed earlier. Like the Avatar animals, this one does have six limbs, but not as three pairs with their own characteristics, but as one pair of hind legs and two pairs of identical front legs. In fact, their muscle anatomy shows the same problem as Avatar's thanator: the front limbs are, like those of Earth mammals, connected to the axial skeleton almost entirely by muscles. Note that the two sets of muscles seem to run through one another...

Click to enlarge; copyright Lucasfilm Ltd.

I would rather end with something I like better: the Nuna from Naboo, which is a very interesting and humorous drawing. The one on the left is a male, inflating his wattles and hissing to underline his dominance. You can see how well Ms Whitlatch combines animal anatomy with the expression of emotions. The emotions are very readable to us, which is probably not at all would you would expect from alien life forms. Then again, emotions help tell a story, and that is done very well here.

Three years on

More than once in the three years I have been writing this blog I thought there were no more interesting speculative biology projects to be found on the internet, but each time I was wrong. Will the supply dry up? Perhaps not: there are more and more exquisitely detailed Z-Brush monsters, but mostly those are orcs, dragons and the like. In other words: they are not very interesting from a biological point of view. The reverse situation can also be found: well-thought out projects with artwork that does not do it justice. I guess I will simply have to wait and see how much content I can find to fill the 'allied matters' component of the blog. The number of page views slowly went up over time, which is rewarding.

So how about the 'Furahan biology' component? There is progress, if you account for the glacier-like advance of a very large project that you do not really have time for. Then again, in the last three years I got to grips with InDesign, Photoshop, Painter and XBrush (not that I am proficient in any). The most noteworthy skill I am trying to acquire is digital painting, which is the most needed one. I think I need to do some 10 additional illustrations of the "It's a fish" type, and then I will have some 15 two-page spreads to show to potential publishers. An example of those can be found in the New Hades book shop on the Furaha site: got to the brand new 'Living World Series' and you will find the 'Encyclopaedia of Furahan Wildlife' (also shown here). I aim to use that lay-out to present the book to publishers.

Rough tetropter animation; copyright Gert van Dijk

It is not difficult to think up many new animals or plants; many forms that I have now could do with some adaptive radiation. But my interest is mostly aroused by more complex puzzles. As an example I will explain the struggle to produce a good tetropter flight animation. The basic principles have been outlined before (start here to work back in time), but for good measure I have repeated an old animation above. As you can see the animal is shown from below, and the four wings move to and fro while rotating. They also move through one another, because the animation uses stiff planes for the wings: it is not good enough. I want a better one firstly, because I am curious: I wish to see what a spotted farfalloid looks like, when its beating wing reveal electric blue surfaces at one point in their cling and flap cycle, and bright orange ones the next! The second reason is that I would like to paint a variety of tetropters -talk about infinite variety-, and getting the perspective right of four warped surfaces in complex motion can be done by hand, but would be easier to manipulate by computer. I will break the problem into pieces:

Problem 1: defining movement
The wings can easily be modelled as surfaces in Matlab. These move through the wing cycle, meaning there are different requisitions for movement around the x- y and z-axes. To control them I wrote editing programs, now nearly done. The surfaces cannot remain simple planes throughout the movement cycle, but will have to be bent and warped. The animation above shows where I am now, meaning at the phase where all the 'warp factors' have to be tweaked to get it right. What you see here represents 'untweaked warping' though!

Problem 2: exporting the wings
The 3D program I am most familiar with is Vue Infinite. I had already written a program to convert Matlab patches to obj. files, which helps. But I then stumbled upon a new program, ad that was the imported wings for successive frames did not end up at the same spot in the scene. Apparently Vue calculates the mean of all x-, y- and z-coordinates to calculate the centre of an object, and if the object changes shape so does it centre. Well, I can counter that by shifting the object each frame to compensate. This needs work...

Click to enlarge; copyright Gert van Dijk

Problem 3: texturing the wings
Obviously, the wings will need interesting patterns on them as well as partial transparency. That, as well as bump maps, proved to be in the obj. definition and could be manipulated.
Here is a rough example of a warped wing with transparency and all in Vue.


So now you may understand why it has taken such a long time to put up a 'Flying with...' page, along the 'Walking with..' and 'Swimming with...' pages: the tetropter flight animation has to be ready first, and that is a big job.

"A Venusian Bestiary", in Which Greg Broadmore Illustrates Monsters Before They Are Gracefully Slaughtered

"By golly, that's a splendid specimen! Blast its head off so we can turn its legs into umbrella stands, what?!"

This is not a literal quote from Lord Coxswain, but it might perhaps be one, suggesting a somewhat utilitarian and egocentric attitude. Lord Coxswain is a character from the 'Dr Grordbort' universe, in which Victorian style people (well, men, really) travel to Venus and have a jolly good time, helped by rayguns designed by 'socially inept boffins'.

Here is a short video to set the atmosphere: "Venus is doomed part II" (also found on YouTube or on the Dr. Grordbort page. As you can see, Lord Coxswain's attitude is that the last surviving animals of a species had best be bagged quickly, lest some other fellow acquire it for a foreign museum, and that wouldn't do, would it? Hence, Coxswain and his fellows -good chums all- take a healthy pleasure in shooting anything alive, animals, natives, whatever.

The person behind this yarn-ripping steampunkish universe is Greg Broadmore: a painter, creature and prop designer working for Weta in New Zealand. If neither 'Weta' nor 'Greg Broadmore' rings a bell, let me remind you of the dinosaurs and other creatures in King Kong, District 9 and other Weta work. Absolutely brilliant illustrations. In fact, Mr. Broadmore's work has featured twice before on this blog: once as a riddle animal (also here) and once when the King Kong book was discussed. He now develops the 'Dr Grordbort' universe, which has already yielded two books, rayguns you can buy (really!) as well as some stuffed Venusian insect-analogues that you can hang on your wall (really! Here's one and another).

I think his creatures are fascinatingly creative; he does dinosaurs, insectoids and various other stuff, and all of it so lively and so extremely well painted. There is also quite a lot of his material to be found on the internet. The 'Dr Grordbort' pages show that particular universe, and besides that he has his own website with a few galleries of work. If that is not enough he was interviewed at some length (part one and part two) on a website on creature design that most of you will probably like a lot even without Mr Broadmore's work on it.

In fact, those links should be enough to make this post worthwhile, but let me add a fairly large series of paintings on Venusian wildlife (these are not all). In time-honoured fashion I shall present my ramblings on what I think of their anatomy. The images were all taken from the sites mentioned above and are presented at a nicely large size, so be certain to enjoy them as best you can.

Click to enlarge: copyright Stardog

The shallow-beaked grogan's four columnar legs suggesting a large size (Venus' gravity is about that of earth, so relationships between body mass and leg diameter should resemble those on Earth, assuming bones of equal strength. I like the neck design: like limbs, necks could consist of a few large segments instead of a larger series of small ones. The 'biramous' (split) design of the front legs is also interesting, and is a basic characteristic of Earth arthropod limbs. Having part of the limbs fused must call for some dextrous motor programming, as I wrote earlier.

Click to enlarge: copyright Stardog

I cannot immediately think of a purpose for the sail on the back of this thingy, and in such cases sex is always something to keep in mind; perhaps the sail is a prop to impress its mates. The arms functioning as jaws are rather nice. Again, such designs work well in Earth's arthropods, and there is no reason to assume they would not work on bigger animals. But are there no eyes? Or are the spots arranged in a row along the head all eyes?

Click to enlarge: copyright Stardog

A large knuckle-walker with switch-blades for toes; is it a predator or are those for defence? It does not look particularly fast, so to be a a predator its prey should be very slow. The other Venusian beasties look quite athletic, so I would guess it's a herbiore or omnivore. There are more 'headarms' here, and I think there are eyes. lots of them.

Click to enlarge: copyright Stardog

Now this one needs some explaining. Its body is slung low, and the legs zigzag a lot and are splayed, meaning that this stance calls for lots of energy. It could be a jumper, but it looks very large for an ambush predator. The whole front looks like a giant mouth, with the four black prongs resembling canines. This time I really see nothing looking like eyes. Not having eyes is probably a very unlikely event in animal evolution. Eyes seem to evolve so easily and must convey such advantages that it is hard to think of a reason to stop them evolving. All you need to start is some light sensitive tissue, some movement ability and the most basic of nervous systems, and you are off (unless there is total darkness).

Click to enlarge: copyright Stardog

Ooh, another jumper: Unwin's double-backed shrovel. The viewpoint does not suggest great size, and the Grodbort pages show it to reach knee height. It is wonderfully alien.

Click to enlarge: copyright Stardog

This one reminds me a bit of an okapi: that must be the sloping back and the colour pattern. I wonder why there is a segment of both the hind and front legs that cannot do much mechanical work as depicted, because these segment more or less double up against the next segment. Then again, perhaps that is the point: these segment don't do anything in their current stance and are not supposed to. Once unfolded, they might be used to advantage, and this is just their 'fold after use' aspect. Well, if it isn't true, please admit that it is a nice idea.
Again, no eyes, I think. Barlowe tried animals without eyes (Darwin IV in Expedition), and I thought that that was a mistake, particularly if you do have bioluminescence.

Click to enlarge: copyright Stardog

Ha, some action! Coxswain in motion against the dimple backed vroxel! As I said, the feet, once divulged of bones and cleaned of flesh, do make excellent umbrella stands gracing any home.

Click to enlarge: copyright Greg Broadmore

More action! But just wait a minute... That's not a Furahan rusp, is it? (rusps are on the land page or directly here). It might be; it could be! What! We cannot have people like Coxswain murdering Furahan animals left and right!? That's no way to behave! Is he mad? The murderous swine! Stay off my planet!

Swimming in Sand III: real and robotic sandswimmers

The previous two blog entries on sandswimming animals (here and here) made it clear that those who wish to populate their fictional worlds with animals swimming in sand will either have to restrain their fantasy or choose to forgo realism. Sand is not a forgiving medium; a 400 m sandworm, as in Dune, must shift millions of tons of sand to move, which is simply too unlikely to consider. While that reasoning argued against giant sandswimmers, the fact that any sandswimmer must lift all the sand above its body restricted the choices even more: sandswimmer cannot dive deeply. Facts can and often do spoil beautiful fantasies; sorry, but that can't be helped. This leaves sandswimmers as fairly small animals that swim just beneath the surface. Not surprisingly, this describes real sandswimmers quite succinctly. There appear to be several: there are various lizards and at least one mammal, the African golden mole rat.

http://www.nordicphotos.com/en/details/1350398

Here is an image of such a mole rat: Eremitalpa granti. There do not appear to be many studies focusing on how mole rates 'sandswim', but what there is reveals some interesting facts. Apparently someone has already measured how much energy it costs: sandswimming costs 80 times as much energy as running on the surface! That is a heavy price to pay, but sandswimming is still much less costly in energy terms than burrowing, i.e. scraping at the soil and carrying it away to create a tunnel that will last for a while. Of course, you can use a tunnel many times, meaning its cost decreases as you use it more often, in contrast to sandswimming: each trip is as expensive as the next. Unfortunately I could not find any video material of a mole rat sandswimming, so I cannot show you that (the main -but not only!- reason being that such a video might show some sand moving, but not the mole rat underneath...). But if you wish to know more about them, there is at least one nice entry on them in Darren Naish' justly famous Tetrapod Zoology blog.

I did find something else that is interesting for those who wish to design sandswimming animals: how do they breathe? There are two problems here; if breathing involves expanding the chest against the outside world, the sandswimmer is in trouble, as that would require some additional shifting of sand. So you had better design an air pump that only shifts volumes within the body, keeping the external volume unchanged. The second problem is whether the poor sandswimmer can extract enough oxygen from the air between the grains of sand; if it then breathes out, does the air circulate fast enough to get fresh air with the next breath? Perhaps it should suck in air at one end of its body and exhale it at the other (that is what Furahan hexapods do, but not to enable sandswimming). Problems, problems...

You had better make the animal small and give it a low metabolism, so it will not need that much oxygen. Well, someone studied how mole rats breathe (Seymour & Seeley. J Arid Environments 1996; 32: 453-461). The authors did some mathematical modeling and concluded that mammals weighing up to 200 grams could comfortably exist completely encased in loose sand. Mole rats are a lot smaller than that, at 15-40 grams, but that upper limit of about 200 grams does not exactly allow for an impressively large sandworm. Before anyone corrects me, I am aware that Dune's sandworms are supposed to produce oxygen, not use it. But if anyone wishes to create a sandswimmer with a more conventional type of metabolism, this is something to reckon with.

Sandfish disappearing under the surface
Baumgartner et al PLoS One 3(10): e3309. doi:10.1371/journal.pone.0003309

Click to enlarge; Baumgartner et al PLoS One 3(10): e3309. doi:10.1371/journal.pone.0003309

There is much more research going on concerning sandswimming lizards (perhaps they are easier to keep in a terrarium). One species is even called the 'sandfish' (Scincus scincus). Over the last few years people have studied their mechanics and came up with a few interesting results, the main one being how they actually swim. At first there was a notion that they used their small legs to loosen the sand to make it more fluid, allowing them to swim through it by undulating their bodies. These researchers used nuclear magnetic resonance to take a look through the sand. The image above shows such an NMR of a sandfish beneath the surface. As the legend says, the legs are sticking out; but is it at rest or actively moving?

Click to enlarge; Maladen et al. Science 2009; 325: 314-318

Afterwards other researchers went one further and used high-speed x-ray imaging. While diving the animal does use its legs, but while sandswimming it keeps its legs close to its body. Here are some images of how it does so. Above the surface its legs stick out in typical reptilian fashion (C) but they are held back when the animal is swimming (E). The body goes through very pronounced sideways movements in order to move forward a bit; it does not look like an effective means of propulsion at all.

You might think that that is the end of the story, but not so. People actually built a sandswimming robot that undulates just like the sandfish does. That is what the video above shows, along with some more footage of an actual sandfish. There is a nice page at PhysicsCentral with some more data on this particular study.

Compared to a 400 m Sandworm of Dune a 40 gram mole rat or a sandfish lizard are less imposing. Then again, they are real, and I personally find the scientific story of how sandswimming really works just as exciting -in a different way- as a good science fiction story. I can't wait to find out what's next.

Hot Summer on Furaha

While thinking of new posts, I finally took some scenes I had prepared much earlier and assembled them. I have tried my hand at making animations before (here and here), but will stop doing so for a while. The program I used to to define plants (XFrog), does not allow for a full wind animation, and without that you cannot really animate natural scenes well. Vue Infinite, the program I used to render scenes, can in fact take care of moving foliage quite well, but its plant editor is sadly not open enough to allow me to define interesting alien plants. That is the main reason that this scene depicts a hot day: there is no wind at all. For fairly obvious reasons there are no animals to speak of, or at least none galloping through the landscape. You will need your imagination for that, I am afraid.

When an animation is lacking in movement it cannot work very well. Then again, I did like the way the 'time lapse' scenes came out, particularly the one in which you see the planet spinning during the night. The direction of movement of the stars (straight up) tells you that we are near the equator.

[Later addition: I guess I did not pay enough attention to logic. In the last scene you see the sun setting at a fairly low angle. If we would really have been near the equator, as suggested by the movement of the stars at night, the sun should dive towards the horizon at a more or less right angle...]


Anyway, here it is. There is a large ballont passing by, and look out, or rather, keep an ear out for splatterbugs at sunset.

There is a larger version on YouTube.

The Creatures of Bobby Chiu

It is quite possible that just about everyone with an active interest in paintings of fantastic animals has already seen the work of Bobby Chiu. If not, well, then I am happy to introduce his work to you. It does not really fit that well with what I normally discuss on this blog: I like a hefty dose of science in my creatures, and Mr Chiu's work does not provide that. But I have made exceptions in the past before (for instance here and here). On looking back at the exceptions I realised that I am never much impressed by fire-breathing dragons and aggressive mean-looking monsters. There are plenty of those to be found on covers of books or on Deviant Art, so it is not a lack of availability. Instead, a sense of humour is more important to me, and Mr Chiu's painting have that in abundance. If you wish to have a closer look, here is his own site, and you will also find him on Deviant Art and on the CG society. Or just try 'Bobby Chiu' on Google.

Click to enlarge; copyright Bobby Chiu

Did I mention that he is an incredibly good painter? Just look at the composition of this one. You really have to know what you are doing in order to lay out your subject in this way.

Click to enlarge; copyright Bobby Chiu

A 'Kangamolerat bunny'. I guess the name says a all: bits of kangaroo, naked molerat and bunny. I do not think I have to point to this cutie's dark side. I love the way the light strikes the rock wall behind the bunny.

Click to enlarge; copyright Bobby Chiu

A Baterpillar Farret. What else?

Click to enlarge; copyright Bobby Chiu

And a 'Big Bad Bunny Eater'. Mind you, there is some serious biology here: the real bunnies are obviously attracted by the fake one, so this is a nice example of 'aggressive mimicry'. Mimicry describes the situation where one living species resembles another one for some purpose. It is not camouflage, in which an animal merely tries to blend in with its environment. In defensive mimicry animals may look like more dangerous ones, which stops them from being attacked. But in aggressive mimicry the predator does the trickery, usually by mimicking something the prey is interested in. In this case, you wonder what it is about the fake bunny that so mesmerises the real bunnies? Could it be sexual attraction? It wouldn't be the first time a pair of pretty eyes led a man/bunny to his doom.

Click to enlarge; copyright Gert van Dijk

All this reminded me that I had once also painted a fictional animal displaying aggressive mimicry. The painting was done when I was about 20, and now, some decades later, it is lost; all I have is a poor black and white image. That is just as well in a way, as I would not dare to compare my painting skills with those of Mr Chiu. But the subject matter does lend itself well to a comparison: somewhat dumb herbivores are lured to a sinister fate by a predator with a cunning plan.

Oddly, both Mr Chiu's predator and mine seem to take a perverse delight in what they are doing. Perhaps there is 'aggressive mimicry' going on at different levels here: the humour hides something sinister, creeping through...