Reinventing the Wheel: 5 Species That Roll

[Music] if you have somewhere to go there's a good chance that you're using wheels to get there cars trains bikes and skateboards i mean even planes have wheels wheels and rolling in general can be an extremely efficient way to get around but for as widespread as wheels are in civilization they're surprisingly rare in the natural world but that doesn't mean that there are no species that can get around by rolling today let's look at five of them let's start on the southwestern coast of africa in the namib a desert whose name literally means vast place in this 800 000 square kilometer sea of sand lives the golden wheel spider whose body is only around two centimeters in size a wheel spider is what's known as a huntsman a family of spiders known for hunting prey on the ground instead of using webs and rather than living up in a tree or a plant it burrows into the sand to form its nest now you'd think that would offer good protection from its main predator the spider hunting wasp but these wasps can excavate up to 10 liters of sand to dig out their prey once it's exposed the wheel spider has to act quickly to save itself unfortunately on the steep sand dunes of the namib it has gravity on its side the spider begins its escape by running downhill if the slope of the dune is greater than 15 degrees after it picks up a little speed it flips onto its side and tucks in its legs to form a rough wheel shaped structure that's able to roll and once these spiders get going they can really move one study observed them rolling at speeds up to one and a half meters per second and rolling isn't just a fast way to get away either it also turns their body into a blur and makes it harder for the wasp to land a sting finally after making an escape the golden wheel spider has little trouble finding a new place to burrow in the endless sand of the namib another species that can get moving quickly at least relative to its usual pace is a type of ant known as myrmecina grumannicola where messina is about the size of a sesame seed and it can be found in grasslands and forest floors throughout europe north africa and parts of asia and small colonies of just a few hundred members these ants scour their habitat for food which is where they run into their primary predators which include spiders and other species of ants but when they find themselves in trouble they're known for making a quick rolling getaway like the wheel spider their role is gravity powered meaning that conditions have to be right for it to happen when researchers recreated attacks in the lab they found that while some ants could begin rolling on inclines of only 10 degrees others required up to 25 degrees before they would tuck into a roll when it did happen though it could happen fast on average stressed ants took around half a second to go from walking to rolling in that half second they would tuck their heads under their bodies and then push up and forward with their hind legs a lot like you might do if you were trying to somersault which i'm not going to demonstrate and with the right incline they could get going at speeds of almost 40 centimeters a second which is nearly 80 times faster than their usual walking speed the catch is they don't go very far on a hard surface the biologists observed them only going up to 17 centimeters in total and on softer materials like soil they might only roll a few centimeters but still the maneuver is unique among ants and it allows this one to move much faster than its common predators and buy itself some time to find a safe place to hide now another creature that can't roll far but can get there quickly is the mother of pearl caterpillar as an adult the mother of pearl moth is pretty mobile you know because it can fly but like many larvae the caterpillar is slow moving it can be found munching on nettle plants all over europe but when it runs into trouble the caterpillar escalates through a series of responses to back away from the threat ordinarily it walks with the classic inchworm movement and when it encounters a mild threat it just reverses its direction lifting its hind segments first to go backwards if the threat is more urgent it can start doing what one study described as galloping backwards basically it just speeds up the process of walking by thrusting its whole middle section up at once but in response to the most extreme stresses the mother of pearl larvae can curl up and begin to roll the act of rolling begins the same way a gallop does with the caterpillar flinging much of its body into the air but then it curls its tail underneath itself rolling up until only its front legs are still attached to the ground finally those legs let go and it starts rolling backward it uses the momentum from throwing itself backward to get the roll started that means that unlike the spider and the ant in the last two examples the mother of pearl doesn't need an incline to get rolling but it also means that it doesn't go very far in fact most rolls end after only around 6 revolutions which for an animal of this size is only around a few centimeters but it crosses that distance in a hurry traveling nearly 40 times faster than it could normally walk now another insect larva that can roll without the help of gravity is that of the southeastern beach tiger beetle which is about a centimeter long and has evolved to roll with the wind these larvae are native to the east coast of the u.s where they live under the sand in the intertidal zone that's the part of the beach that's underwater at high tide but exposed to the air at low tide and like the wheel spider scientists suspect tiger beetle larvae are threatened by a species of wasp that can dig down into their sandy burrows and they're pretty vulnerable because while tiger beetles themselves are some of the fastest insects out there their larvae are definitely not they have a few tricks for escaping predators but in really dire circumstances they can initiate a special escape sequence to get away they start by arching their head backwards towards their rear to form a tiny lube by flexing this loop they can spring themselves into the air to take advantage of something that's almost always present in their seaside habitat the wind studies seem to show that if the wind catches them mid-air they can start to roll once they hit the ground but even once they're in motion the larvae aren't entirely passive they can hold their legs out to the side to improve their balance and nudge the ground with their tail to keep up their momentum still it's the wind that's the driving force and it comes with a neat side effect young tiger beetles can travel uphill that's almost unheard of in species that roll but it's especially important for these larvae since beaches often curve up and away from the intertidal zone and these larvae can really get going with moderate wind they commonly travel 10 to 25 meters but in windier conditions one study observed them going as far as 60 meters and some even reached a speed of several meters per second finally we have a rolling species that's a little bit different from the others it relies on rolling more than anything else we've seen today but it only does so after it's dead of course i'm talking about tumbleweeds which aren't actually a single species but a group of organisms that have all evolved a similar strategy one of the most successful examples is the russian thistle although it probably originated in russia it's been accidentally introduced in the americas africa asia and europe and in most of those places the thistle has thrived like after making its way to the u.s in contaminated grain shipments in the 1870s it has since spread to every state except alaska and florida basically anywhere there's a flat dry environment you can probably find a russian thistle and that has a lot to do with the fact that these plants can move the tumbleweeds begin as plants that grow in a roundish shape up to a meter high and two meters across as they die in the late summer and early fall the part above ground dries out and the base of the stem contains a special layer of cells called abscission cells which can break easily and cleanly detach the plant from its root system that severed bushy part can be covered in hundreds of thousands of seeds and now that it's not anchored to the ground when the wind catches it the dead plant begins its iconic roll all the while the seeds which are shaped like tiny hooks can catch on things and break off so by slowly spreading their seeds over long distances russian thistles usually end up spread out enough that they don't compete with one another for resources which makes them both extremely successful and also kind of a nuisance since they can quickly crowd out native plants so if you're ever out on the prairie and you see a bushy plant where it doesn't seem like it belongs you might have a unique role to thank for it the common thread among all these kinds of life is that while they can roll that's not their main way of getting around which seems a little bit strange i mean if wheels and rolling have proven so efficient for humans why hasn't evolution pushed at least some other species in that direction well the key is that wheels aren't always that efficient imagine say trying to push your shopping cart through the grass or riding your bike on a sand dune you're probably not having a very good time wheels work for us because we've built roads rails and sidewalks to make them efficient most other species aren't moving around on those types of surfaces and there are physiological problems to deal with too if you're an animal with a wheel that wheel and the axle it spins on would probably be made of some kind of living tissue but how could they be connected with blood vessels to provide the cells with energy and remove their waste those blood vessels would be twisted up in no time besides it seems like it would take a pretty large evolutionary leap to get from legs to wheels if it is possible for a bunch of small adaptations to eventually result in a wheel as a primary mode of transportation well it doesn't seem like evolution ever found its way there in a way all of this makes the rolling species that we do have seem even more impressive so rolling might not be a common way of getting around but now and then a surprise move can be a good survival strategy and what's more surprising than a spider doing cartwheels thanks for watching this episode of scishow and thank you to our patrons on patreon for making videos like this possible if you'd like to join the amazing community of supporters helping us make science education free on the internet you can find out more at patreon.com [Music] scishow

Channel: SciShow

Views: 165,232

Rating: 4.9289942 out of 5

Keywords: SciShow, science, Hank, Green, education, learn, wheel, rolling, roll, Golden Wheel Spider, huntsman, Myrmecina graminicola, ant, Myrmecina, mother-of-pearl caterpillar, mother-of-pearl, caterpillar, mother-of-pearl moth, Southeastern Beach Tiger Beetle larva, Tiger Beetle, Tiger Beetle larva, larva, Beach Tiger Beetle, Russian thistle, tumbleweed, abscission cell

Id: KIE7iET7yBo

Length: 9min 47sec (587 seconds)

Published: Sun Sep 13 2020