Category Archives: SciTec

Walking

Why move at all?

Animals have a problem.  They need to eat.  To do that, at some point in their lives, they’ve got to move about and find food.  Plants never have to worry about this, they can make all the chemicals they need to live and grow by the process of photosynthesis.  By capturing the energy of sunlight, they are able to turn the simple chemicals around them: Carbon Dioxide, Oxygen and mineral compounds, into the complex organic chemicals: Carbohydrates, Proteins and Fats that they need.  If animals could photosynthesise it would be a very different world indeed, however, they can’t because they’re too dense and opaque.  The only way animals can get those essential energy-giving and bodybuilding chemicals is to eat either plants, or other animals.

There are of course some animals that move very little throughout their lives: corals, sponges, barnacles and sea anemones, to name but a few.  But even the world’s most sedentary animals often have a surprising double life, with a larval stage that travels far and wide before it attempts to settle in a suitable location.

The need to travel about in order to: find food, escape predation by bigger animals, find shelter and find a mate, is central to the lives of all animals.  So where do you start if you’re going to look at animal locomotion?  Well, how about walking?  We do it all the time and we do it for most of our lives.  It can’t be that complex?  Can it?

What’s so special about walking?

There are many land animals that don’t bother with walking (or legs) at all.  Nematode worms manage to burrow through the soil in much the same way as an eel swims through water.  Molluscs (slugs and snails) are swimmers too, travelling with the aid of ordered ripples of muscle contraction and a specially created sheet of watery slime.  The Annelids (earthworms) have a clever way of pulling themselves along by alternately anchoring and stretching their body segments.  You will find countless thousands of these animals living in the soil of every continent on Earth except Antarctica.  They are essential to the proper functioning of every ecosystem on the planet.  However, it’s the animals with legs that have really colonised the surface of the Earth and dominate to this day.

Why don’t animals have wheels?

Although legs and feet aren’t as efficient as wheels and an engine, they can cope with hills, rough tracks, ditches, stairs and all manner of obstacles that wheeled vehicles would find impassable.  But even animals that live in flat places don’t have wheels.  This is because there is no such thing in nature as an axle with a bearing which can rotate freely around it, an essential component of wheeled vehicles.  An animal’s limb can only go so far in any direction before it has to be “reset” by returning it to its starting position.  It’s attached to the rest of the animal by tendons, muscles, blood vessels and nerves that would all tear and snap if the limb rotated freely.  Humans and the other apes come close with their special “ball and socket” shoulder joint that allows us to reach all round with our arms and swing under branches (we still can’t spin them round in a true circle however).

A look at legs.

The first many-legged beasties to walk on earth were exactly that; many legged.  They were the arthropods: millipedes, centipedes, scorpions, spiders, woodlice, springtails, and insects (in roughly that order).  Their strong, chitin based exoskeletons protected them from damage by both the sun’s rays, and the harsh terrestrial environment.  But as well as protection, their body armour, made of segments that could move freely, gave them another great advantage: jointed legs.  These were animals really built for colonising the surface of the planet, and they did just that from around 420 million years ago.  Today, they are still the most successful group of animals on Earth.  80% of all the animals known to science are arthropods and you find them everywhere, including Antarctica.  The arthropods don’t win all the design awards however, as their exoskeletons cause them a few tricky problems.  Firstly, they can’t grow without shedding their skins, a dangerous thing to do as it leaves them temporarily soft-bodied, unable to move and at risk from predation, water loss and physical damage, whilst they wait for the new bigger skin underneath to dry.  Secondly, the skeletons, though strong for their weight, need to become so bulky and heavy to support the weight of a large animal that they become impractical.  This is one of the factors that creates an upper limit on the size of terrestrial arthropods (the other is breathing).

The next big step in leg design happened around 340 million years ago when some particularly muscle-bound fish started to take advantage of tasty terrestrial titbits of food.  Their strong “walking fins” formed the blueprint for the pentadactyl limb design that all tetrapod vertebrates (animals with four legs and backbones) share.  Their descendants were the amphibians, reptiles and eventually the mammals.  Unlike the arthropods, the internal skeletons of vertebrates are made of living tissue and grow as the animal does.  Although bony skeletons are much heavier than the skeletons of arthropods, vertebrate skeletons are incredibly strong and some terrestrial vertebrates, notably the Dinosaurs grew incredibly large.

Despite the differences between the skeletons of arthropods and vertebrates, when it comes to walking, both skeletons do the same job in much the same way.  They are strong, rigid, and act as levers to which the animal’s muscles are attached.  When the muscles contract, they exert a force against the skeleton, which is transferred to the ground in order to propel the animal along.

How many legs are best?

This is something robot engineers and biologists alike are keen to sort out, as it has wide implications.  Does an animal (or robot) use less energy swinging a large number of small legs than it would were it to swing fewer, larger legs?  Recent research by biomechanics specialists at the University of California has produced some surprising results.  They claim that it actually makes little difference to the overall efficiency of the animal.  According to them, animals bounce as they move using two alternating sets of legs as springs.  This means that one human leg ends up being equivalent to two dog legs, three cockroach legs or four spider legs, five crab legs, etc. in terms of energy output per kilogram of body mass.

The claims are startling, as traditionally the splayed leg arrangement that you see in many animals, both arthropods (scorpions and spiders) and tetrapod vertebrates (newts and toads), was always considered to be inefficient.  This was because this particular limb arrangement causes the animal to rock at each step so that any energy spent moving forward is also “wasted” moving from side to side.  Animals like dinosaurs and mammals, which have shoulders, positioned close together, narrow pelvises and limbs which extend down, almost vertically, from the body were thought to be more efficient because all their energy was directed into forward movement.  Also, the position of their legs allowed them to take longer strides than would otherwise be possible.  This research actually suggests that the rocking action, far from being a hindrance, is a good thing as it causes the animal to behave like a pendulum, aiding movement and making it more, not less efficient.

The scientists’ work continues, and soon we should have a better idea as to the real reason for the long straight strides that mammals take as they walk.  Until then, I’m inclined to stick to the old theory that it’s a more efficient way of getting from A to B than waddling!

There are, of course, many reasons why having lots of legs can be useful.  An animal needs a lot less brainpower to control and balance on four, six or eight legs, as it’s an arrangement that provides the animal with a wide base of support and a low centre of gravity.  It’s no accident that all the successful robots and automatic walking machines humans have created have six or eight legs, to allow them to move about with the minimum of computer power.

Two Legs is company, more’s a crowd!

Because humans are bipedal (we walk our hind two limbs), we tend to think of that as the normal way to be.  In actual fact, it’s unique.  No other animal can do it for any length of time.

Walking and balancing on two legs is a lot harder than it looks, it requires a huge amount of brainpower.  Even when you’re standing still, your brain has to constantly monitor the signals coming in from: your eyes, the pressure sensors on the soles of your feet, the tension sensors in your muscles and the balance sensors in your inner ear.  Based on all that information, your brain then sends out a constant stream of instructions to your muscles to tense or relax as necessary, to ensure that your centre of gravity stays “central” and doesn’t pull you over.  If you want to see how this combination of senses and fast reactions works, try this test:  Stand up, hold your arms straight out in front of you, keep your arms out, stand on tiptoe, hold it for twenty seconds.  That shouldn’t have given you any trouble, but now I want you to do it again – and when you’re on tiptoe, close your eyes!  It’s much harder to balance without your eyes providing that extra information.  Animals with four or more legs don’t have to try so hard as they are much more stable.

Being bipedal creates some other interesting problems for humans.  Because we need a big brain we naturally have babies with big brains.  However, babies with big brains have to have big heads.  Big headed babies need mothers with a wide pelvis and large birth canal through which they can fit, and be born.  All fine so far, except that in order to walk efficiently, us mammals need to have a narrow pelvis.  Humans have evolved a remarkable solution to the problem, they give birth prematurely!  At the point when they’re born, human babies are completely unable to do that most basic of human activities, walking.  After nine months in their mother’s womb, long enough for their bodies to fully form, babies’ brains are far from fully grown.  In fact, human babies; brains grow at the pre-birth (foetal) rate for a whole year after birth.  No other animal does this.

Champion Animals

What is it about animal record-breakers that makes them so cool?  I’m always getting asked about the most dangerous snake or the fastest flying bird and to be honest, some of the most exciting adventures I’ve had over the last ten years, travelling the world filming wild animals, have been when I’ve been on the tail (I mean trail) of a record breaking beast.

People who achieve something outstanding always attract our attention.  But even exceptional human athletes don’t come close to the feats that some animals are capable of.  On September 14th 2002, Tim Montgommery, sprinted 100 metres in 9.78 seconds (averaging 22.87mph) to take the world record.  A sprinting cheetah, running over rough terrain, can cover the same distance in 4.09 seconds (60mph).  If that doesn’t make you gasp, how about this, a cheetah can accelerate from standing still to flat-out faster than a Ferrari (cheetah, 0 – 60mph in under 3 seconds :  Enzo Ferrari, 0 – 62 mph in 3.65 seconds).

Why can’t the fastest human run as fast as a cheetah, carry trees like an elephant or dive as deep as a whale?  The simple answer is that we’re just not built for it, and I think that’s why these super-specialist animals fascinate us.  Primates like you, me, and our close relatives: the monkeys and apes, are remarkably similar in design.  We all have forward facing, distance judging, eyes, a five fingered hand, suitable for a variety of tasks and large brains that allow us to adapt our behaviour and cope with new situations quickly.  Although we are adapted physically for survival, but we’re more adapted mentally.  Humans are, of course, champions themselves: we can solve problems better and faster than any other animal thanks to our huge brains.  This has made us the most powerful creature on Earth, and the only animal that can sit down and read SciTec (instead of eating it or using it to wipe our bottoms’).

Studying record-braking animals is more than just the biologists’ version of train-spotting.  By looking in detail at the survival strategies of such animals, scientists have been able to advance our understanding in many areas of biology.  An awful lot of what we think we know about the process of evolution, about anatomy (the way animals are built) and physiology (how they work) has been learnt from this kind of work.  This is, however, just the tip of the iceberg, we’re beginning to realise that there’s a great deal more to be learnt.  A whole new area of study, biomimetics, has been attracting a lot of interest over recent years.  Why?  It’s a branch of biology devoted to understanding and, if possible, copying the best-kept secrets of the animal kingdom.

So, what are the champions to keep your eye on?  How do you spot an animal that could teach us a useful trick?  Here’s my hot selection of the ones to watch…

Champion Sniffer

The world’s best nose isn’t actually a “nose” at all, it’s an antennae.  Specifically, it is the antennae of the male lesser emperor moth.  These guys can track down the attractant perfume of a suitable female at a distance of 6.7 miles.  Amazingly, the female carries less than 0.10mg of the scent and only releases a few molecules at a time to tempt the males.  Thanks to their champion antennae, which are covered by 40,000 scent detector cells, the males manage to home in on potential mates with ease.  In one experiment, a caged female attracted 127 males from up to 2 miles away in just 3 hours.  The mechanism that guides the males is beautifully simple.  When the nerve cells of an antennae fire they stimulate the moth’s flight muscles directly, making it automatically turn in the direction of the scent.  When male is tracking down a female he follows a distinctive zig-zag path as a result.  A number of research groups around the world are trying to tap in to the secret of moth antennae as they can detect chemicals at as low a concentration as 1 molecule in an air sample.  This is far better than any palm-sized machine humans can currently make.  Other researchers are trying to understand the pheremones (scents) that the moths and other insects use.  If they master how these chemicals work they could attract or repel all kinds of insects with ease.

Toughest Skull

A bang on the head can cause your brain to knock against the inside of your skull, bruising it and causing temporary or permanent damage.   Amazingly, some animals regularly practise the kind of head-banging that would knock a human unconscious or even kill them.  Male mouflon, an impressive species of sheep found in Sardinia and Corsica show-off to the local females by head butting each other repeatedly, leaping in the air for aerial crunches and diving off rocks at each other.  Deer, particularly, in the UK, red deer stags are also champion head bangers, however their strong antlers lock together long before they get to bang skulls.

Studies of the exact composition and structure of skulls of head bangers like these have revealed super, strong honeycombed, bone structures.  Far from being “bone heads”, it has been discovered that the strength has more to do with structure of the bone rather than it’s thickness.  Researching how the bones are constructed is hopefully going to lead to new designs for safety helmets, load-bearing structures, novel light-weight materials and even artificial bone.

One animal definitely worth a closer look is the gannet.  For my money it deserves the prize for champion head-banger.  Bird bones have to be incredibly light, or the bird wouldn’t be able to fly.  The gannet has a skull that is no heavier than birds of comparable size and yet it does something rather special.  It dives, head-first, into the sea, at speeds of around 60 mph.  At that speed, the water surface presents a lot of resistance.  Their brains, however, escape scrambling, thanks to an incredibly aerodynamic head that scythes through the water combined by a skull full of air pockets that cushions their brain and dissipates the impact shock-waves.

Strongest Mussel

Shouldn’t that be muscle?  Well no, because mussels, a humble shellfish, have a muscle that is unique and it makes them a world champion.  Before you do anything else, put down the magazine and tense your arm muscles, really squeeze them.  Pulling against each other, they get tired quickly and soon start to ache.  When they a kept tensed, muscles fatigue quickly.  Your heart may beat all your life without stopping or missing a beat, but it tenses and relaxes at least once a second.  Only one muscle, in one animal, the mussel stays tensed without tiring.  It’s called the Byssus retractor muscle and it’s the muscle that the mussel uses to grip onto its Byssus, the threads that it glues onto the rocks or other substrate when it settles as a baby.  From the point it settles to the point it dies.

If that wasn’t enough, researchers are also pretty fascinated in what’s going on at the other end of the Byssus threads.  The mussel makes these threads, and then glues them to rock, concrete, steel, plastic, etc. with a biological glue that sets, hard, under water, and stays stuck for years.  The commercial applications for an underwater, instantly setting cement like that would be massive, if only we could crack the formula.

Strongest Animal

Forget about elephants and blue whales, think a little smaller.  The world’s strongest animal (when you take it’s weight into account) is the rhinoceros beetle.  Okay, so they can’t pull trees out of the ground, but, in tests, they’ve carried 30 times their own body weight for periods in excess of half an hour, without it affecting their normal walking speed of 1cm per second (0.02mph).  In one experiment the beetles demonstrated that they could still walk along (albeit slightly slower) whilst carrying 100 times they own body weight.  Most amazingly, whilst they were doing this, their oxygen intake didn’t increase as dramatically as it should.  It appears at first glance that the beetle is somehow breaking some fundamental laws of physics.  This is unlikely, but there’s definitely something very unusual going on.  Because the nervous systems of insects and their six legged body designs are already used as models to guide the construction of robots, understanding how such a small animal manages to carry so much is of immense interest.  Just imagine if we could construct small, six legged robots capable of carrying 100 times their own weight.  Some Bionics experts aren’t bothering to copy the insect design, instead, they’re using little insect sized backpacks of electronics that can tamper with the nerves of the animal.  That’s right ladies and gentlemen, it is my pleasure to introduce the radio-controlled cockroach (really, it’s been done).

Champion Chompers

No matter how scary the teeth of a tiger or a tyrannosaur appear at first glance, they really are nothing compared to the teeth of the brazilian leaf-cutting ant.  For their size and weight, these are some of the toughest teeth in the world, thanks to the way zinc is built into the structure of the cutting edge.  Impressed?  Well how about parrotfish.  They have teeth that are incredibly resistant to crushing and shattering.   It’s a good job too, they eat coral (including the rock part).   The strength of their teeth is due to the way they incorporate tiny mineral fibres millionths of a millimetre in diameter.

Another amazing rock cruncher that is well worth a mention is the piddock.  It drills holes in tough mud and rocks even though it, like all snails, doesn’t have any teeth at all.  Their secret is a shell that incorporates a tough ceramic.  It literally wears away the mud, rock or whatever it wants to drill in to.

In our constant quest for new, ever stronger materials for use in constructing everything from artificial body parts to miniature machine parts, the ability to copy structures like these and synthesise them in the laboratory is a goal many are pursuing.

Fastest Swimmer

Recently, human swimmers have started taking lessons from the animal champions and streamlining their bodies with the aid of special swimsuits that encase them completely and reduce turbulence.  Thanks to these technical inventions, we have seen a whole load of world records broken over the last couple of years.  The world’s fastest swimmer over 100 metres is Peter van den Hoogenband.  He can swim at 4.68 mph.  Impressive, but not as impressive as the gentoo penguin, the fastest swimming bird at 22.37 mph (only a bit slower than Mr Montgommery’s 100m land sprint record).  Thanks to their streamlined bodies and powerful wings they are super fast escapers.   A leatherback turtle can power away from trouble at a pretty impressive 22mph as well – making it the world’s fastest reptile (unless you count Iguanas when they throw themselves out of trees).

Whales and dolphins have a streamlined shape, incredibly soft, almost spongy outer layers of skin and often have ribs and indentations that, help them reduce turbulence. Their skin and body shape, is currently being used as the inspiration for a new generation of streamlined boat hull designs.  Some of  those super swimming costumes I mentioned earlier also have a ribbed design which mimics the body shape of some of the faster whales (Killer and Sei whales can sprint at around 35mph).

The champions of underwater speed are however, the fish.  Blue Finned-Tuna have been clocked at 45 mph, Swordfish at 57mph and the champion, is the amazing sailfish at 68mph.   Incredible.  I don’t give the top speed prize to the sailfish because that is a sprinting speed.  I think Tuna deserve to win because they swim at top speed, in shoals, for long distances.  They get extra power from their muscles by heating them up, a beautifully efficient fish.  The race is currently on to design a submarine with the energy efficiency and manoeuvrability of a tuna.  They are, however, a tough act to follow.

 Fastest Flier

I know almost every book in the world says that the peregrine falcon is the fasted flying bird but I disagree.  The speeds you see quoted for peregrine falcons are based on recordings and estimates of the bird’s average speed in a “stoop” this is when it’s closing in on prey, or in other words, falling from the sky.  Okay, what they do is clever and worth taking about so here goes.  Peregrines are like air-to-air missiles.  They have incredibly good eyesight and cruise around at high altitude looking for seagulls, ducks and their favourite food, pigeons to fly underneath them.  When they spot one (pretty impressive eyesight) they fold up their wings and plummet towards it at speeds of around 80-90 mph.  They don’t just fall, they fold their wings in such a way that they can steer and stay aerodynamic – like a magic arrow.  A fraction of a second before they hit their prey, they swing out their feet so that after they have stunned (or quite often killed) their target with the force of their impact, they can grab and hold it.  If this doesn’t sound impressive enough, bear in mind that a pigeon in flight is not a stationary target, they can fly at 60 or more miles per hour themselves.  The fastest bird in the world is actually the Spine Tailed Swift, recorded at 106 mph (really) whilst flying.

Copying bird wing design is perhaps the oldest example of biomimentics and goes back to Leanardo Da Vinci (or Daedilus if you believe your Greek myths).  Some bird inspired innovations can be seen on every single passenger plane in service.  For example, if you ever sit near the wing on a plane journey, look out of the window as the plane comes into land.  You’ll see flaps coming up to create great holes in the wing.  These are mimicking the action of the alula, a flap birds have on their wings that forces them to stall when required.  This is how birds and planes both manage to control the exact point they drop out of the sky and land.

Our attempts to learn from birds continue to this day, with varying degrees of success, and the very latest planes and guided missiles incorporate all kinds of bird tricks.   Unfortunately, some of the recent bird-inspired designs have resulted in aircraft that are so difficult to fly, humans can’t do it unnaided.  Such planes are so unstable that they have to be “flown by wire”: the pilot tells the plane what she wants it to do, the onboard computer works out how to do it and then the plane does it.  That’s the idea anyway, there have been some very expensive failures and a number of, initially attractive, design concepts have been abandoned after years of effort and billions of pounds/dollars wasted.

It just goes to show, we can’t always beat the animal champions with our brain-power alone.  Sometimes we just have to admit that they’re the best and let them get on with it.