5 Amazing Feats of Animal Engineering

Humans are not the only engineers in the

animal

kingdom. Chances are you've heard of beavers, whose famous dams can be hundreds of meters long. But while beavers steal the show, there are plenty of other

animal

s quietly building impressive things! A while ago, we talked about some of the more interesting things created by bugs. And here are five more

amazing

feats

of

engineering

performed by all kinds of animals, from optical illusions to entire cities underground. Social weaver birds do not build small nests between a couple of branches like the average bird does. At about 14 centimeters long, these birds are quite small.

But they build their nests in the largest trees in the world: up to six meters high and three meters wide, capable of housing up to a hundred families at a time. And just as human engineers would do, they start with the foundation. The nests can weigh a few tons, so they need to be supported by very thick branches. After that, they collect progressively smaller branches and twigs to fill the rest of the structure before finally moving on to fine grasses for the outermost layers of the nest. Every family builds their own apartment and they constantly improve and change and expand it, because, you know, sometimes the things on the walls start to look stale.

Although your walls probably don't have pointy straws to keep snakes out. If so, you may want to move. The nests not only protect the sociable weavers from predators; They also protect birds from the intense temperatures of the Kalahari Desert in southern Africa. Summer days can reach 43 degrees Celsius, but the nests block much of that heat, keeping the birds inside cooler and allowing them to conserve water that most birds would have used to cool themselves. Winter nights, on the other hand, can drop to -10 degrees. And on those cold nights, the nests can be 30 degrees warmer than the air outside, again allowing the birds to conserve energy they would otherwise have had to use to stay warm.

With such ingenious houses, it's no surprise that weaver birds live in their nests all year round. They even pass nests down from generation to generation, with some nests lasting a century or more. Others are not so lucky. In the rainy season, the already heavy nests can become so flooded that they topple the tree on which they were built. But when that happens, weaver birds simply go back to

engineering

. To us, the projects of large male cocoons may not look as impressive as the nests of weaver birds, but that is only because we are looking from the wrong angle.

Birds don't just build something beautiful. They use a trick of psychology and optics to make him and themselves look even better. All types of bower species build elaborately colorful stages or caves, called “bowers,” collecting things from the world around them. If a female is impressed by a male's bower, the male dances to try to woo her further. However, compared to other bowerbirds, the great bowerbird's bower can seem a little... dour. Sure, there are plenty of rocks surrounded by loops of sticks where the male dances, but it's not usually the colorful arrangement found with other bower birds.

Scientists discovered the secrets of these arbors a few years ago, when they realized that birds tended to place larger stones towards the back and smaller ones towards the front. When man stands near the largest stones, he creates what photographers and architects know as forced perspective. They use it all the time to trick your brain into thinking something is a different distance from you than it really is, like when your friend comes back from a trip to Pisa with a photo that makes it look like he's holding up the Leaning Tower. . even if they are a few hundred meters away.

In the case of bower birds, having small stones near the front means that to the female, everything in the bower appears closer than it really is, and therefore the male, towering over everything, It's much bigger than it really is. So, by cleverly designing his bower, the big male bowerbird can nab all the ladies. Or, at least, the women who like what he has built. To find our next engineers, we have to go where few birds venture: the bottom of the sea. That's where you'll find the 12-centimeter male puffer fish and its underwater sand circles. It took scientists sixteen years to figure out where those two-meter circles came from after first noticing them off the coast of Japan in 1995.

And when they finally saw the fish in action in 2011, it appeared to be a previously unknown species. The details are still a little fuzzy, but we know that men make circles to impress women. They make long, wavy furrows by flapping their fins along the surface of the sand. And since that's still not enough to impress a potential partner, they decorate their circles with shells to liven things up. Then, as icing on the cake, they go out and find nice, fine sand to spread around the circle, especially in the center. Females choose the circle they like best and lay their eggs there, but no one is sure what exactly makes them choose one circle over another.

The clever engineering here is in fluid dynamics, which the puffer fish use to avoid having to collect all that nice central sand themselves. The wavy grooves around the outside of the circle slow the water as it moves toward the center, where it tends to drop fine sand in those cool wavy patterns. Even after all the effort that goes into building the circles, they still don't last long. Ocean currents tend to destroy them after a couple of weeks, meaning the male pufferfish has to build a new one every year. But the bright side is that it means that every year they can show off their skills in fluid dynamics.

Humans have only been using electricity to our advantage for a couple of centuries. But at least one species of hornet has used electricity to keep its babies comfortable for much longer. Eastern hornets lay their eggs in a nest, and the larvae that hatch from those eggs spin silk cocoons around them so they can continue developing. Baby hornets end up deformed if their cocoons get too hot or cold during development, so adults have several creative ways to keep their nests and those critical cocoons at the right temperature. When the temperature warms, they fan the cocoons with their wings or spray them with water droplets.

And when it gets too cold, they blow warm air stored in air sacs on their bodies to keep the cocoons warm. But adults are not always needed to keep the cocoons safe, because the nests are built to isolate them from the outside world and are also very humid inside. Water can absorb a lot of energy without changing its temperature much, so all that water in the nest keeps the interior temperature nice and level. So, even without adults around, it can take a few days for the inside of a nest to reach the same temperature as the outside air.

But hornets have one last trick to their exoskeleton: the silk around their cocoons is thermoelectric. Changing the temperature of a thermoelectric material causes electric current to flow through it. When a nest begins to get too hot, a small current begins to flow from one end of the cocoon to the other, building up electrical charge at one end. Since energy from the outside air is used to drive the current, it is used up before it can warm the cocoon, and the hornet inside stays cool. Then, when the temperature drops too low, the process reverses and the charges return to where they originally came from.

Since heat was needed to move them, they release heat as they retreat and the current warms the cocoon back to a more comfortable temperature. In the early 20th century, scientists found a prairie dog village in Texas. It was a set of interconnected underground tunnels, much like other prairie dog communities in the western United States at the time. But this one was huge: the largest ever seen. It covered about 64,000 square kilometers and was home to an estimated 400 million prairie dogs. It's a bunch of little rodents running underground. Today's prairie dogs have been pushed out of most of their historic habitat, but they still employ the same engineering intelligence they used to create that giant colony in Texas.

The simplest prairie dog houses are tubes that run from a ground-level entrance to a room a meter or two underground. But their burrows are usually much more complicated. For one thing, they tend to have multiple inputs. Between the entrances, there is a large U-shaped hallway, with the bottom of the U a few meters underground. And outside that main hallway are a bunch of individual chambers for families to raise their puppies. The most obvious reason for building multiple entrances is that if a predator comes in through the front door, everyone can run out the back. But there's another reason, too: The fact that the tunnels are so long and deep also means it's difficult for surface oxygen to reach the end and replace what's consumed when prairie dogs breathe.

To solve that problem, prairie dogs build an entrance downwind and another downwind. Wind passing through the downwind entrance pushes air through the tunnels and out the downwind exit, bringing fresh oxygen to the entire tunnel system even in a light breeze. Huge prairie dog towns can have miles of tunnels with tons of different entrances and ventilation tubes everywhere to keep the air flowing all the time. It's just one more way that other animals have been using technology to design our world for much longer than humans, from birds to fish to hornets. Thanks for watching this episode of SciShow!

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