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the animal within s02e04
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00:08Survival of the fittest isn't merely a contest of strength.
00:12It often comes down to a chess-like game of stealth,
00:16where predators and prey try to outwit each other
00:19by hiding in plain sight, by moving unseen and unheard.
00:26Humans have used stealth for hunting and war for millennia.
00:30But it's still nothing compared to the natural world.
00:34Millions of years of evolution have engineered the bodies of some animals
00:38to make them the stealthiest creatures on the planet.
00:41Nature has built these incredible creatures from the cells up to avoid detection.
00:46But other creatures have evolved to find them.
00:49In the evolutionary arms race between the masters of deception
00:53and the masters of detection,
00:55the lives of both predators and prey hang in the balance.
01:00How has nature equipped these creatures for a deadly game of hide-and-seek?
01:05And what might we learn from their clever adaptations?
01:29Consider the chameleon.
01:32These slow-moving, tree-dwelling insectivores are instantly recognisable
01:37for their helmet-shaped heads, prehensile tails, independently mobile eyes,
01:44and deadly projectile tongues.
01:49But they're most famous for one evolutionary superpower,
01:53their ability to change color.
01:55Chameleons are one of the first creatures that come to mind
01:58when people think of animals that depend on stealth for survival.
02:01In fact, we use the word chameleon to refer to people
02:04who can change their behavior or appearance to blend in.
02:08It's one of the most unique tricks in the animal kingdom.
02:11So how does this master of disguise pull off such a breathtaking transformation?
02:17And more importantly, why is it needed?
02:25Found mainly in tropical rainforests and scrub savannas,
02:29the chameleon habitat extends from the Canary Islands
02:32all the way across southern Europe and through sub-Saharan Africa.
02:38Nearly half of the 200 species are found in one place, Madagascar.
02:45Chameleons vary in size.
02:46Some can be as small as your thumbnail,
02:48and others can be as large as a house cat.
02:51Here, the lizard stealthily moves among the trees and leaves
02:55with the help of a powerful grip.
02:58Chameleons have very highly adapted feet.
03:02They're called zygodactylus feet.
03:04That means the orientation of the toes are forwards and backwards,
03:08so it looks more like a pincer grip.
03:11And where its toes reach their limit,
03:14the chameleon's grasp is aided by a long, sturdy tail.
03:18Chameleons are an arboreal animal,
03:20and being able to maintain their position in the trees is really important.
03:25And prehensile tails really act like a fifth limb, if you would.
03:29When we think about humans and climbing trees, we always give ourselves a safety tether.
03:35We have a harness and we clip on to some type of attachment point.
03:39Really, the prehensile tail of a chameleon is a simpler thing in that it gives you an additional safety mechanism
03:45as a chameleon
03:46to make sure that if something goes wrong, you're still going to remain attached to the branch.
03:52Blending in is crucial to the chameleon's survival.
03:56Lacking defensive capabilities like speed, armor, or venom,
04:00they must rely on stealth to keep them safe from predators.
04:05Chameleons are predators, but they're pretty low in the food chain.
04:08Shrikes, hornbills, eagles, and castrels all prey on chameleons,
04:12as do snakes like the boomslaying and vinesnake.
04:15These are all highly capable predators.
04:18Fast-moving, equipped with flight, lightning-fast strikes, or deadly poison.
04:24The chameleon would seem to be outmatched,
04:27except for one thing, its incredible defense of camouflage.
04:32Some chameleons look just like leaves.
04:35Their bodies can have a bit of a curve.
04:37Sometimes they have a ridge down their back to make it look like a variegated leaf.
04:41And some of them have the crest on their head that looks like the point of a leaf.
04:46The colors they can change into can look like variations of leaf color.
04:50They can make themselves look like shaded leaves, bright leaves,
04:54and sometimes they can even look like leaves that have some sunshine hitting it.
05:00Most chameleons' natural resting color is brown or green, depending on their habitat.
05:06Some chameleons also have horns and spikes on their back.
05:11In addition to providing some defense against predators, or even other chameleons,
05:16they break up their silhouette and help them resemble the irregular shapes of twigs and branches.
05:24Even when they're on the move, the chameleon won't break character.
05:29Chameleons have a very interesting walk.
05:32They walk slowly, and as they walk, they kind of sway back and forth.
05:36It's like a little bit of a strut.
05:37They're trying to trick predators and prey to thinking that they're a leaf blowing in the wind.
05:42Even with all this, chameleons still need a leg up to stay ahead of their enemies.
05:47And this is where the most famous adaptation comes in, their ability to change color.
05:53But it doesn't work quite the way many people think.
05:57Chameleons have this reputation where people think that they can change into any background they want.
06:01For example, if they walk over a chessboard, they think that they can look like the chessboard.
06:05But that's just not true.
06:06But some species of chameleon can change color based on the type of predator that they detect.
06:11It turns out chameleons need a slightly different stealth strategy, depending on who they're trying to hide from.
06:19Some animals use countershading for survival.
06:21For instance, a shark will be dark on the top and light on the bottom.
06:25That's advantageous because when you're looking from the ocean's surface and you're looking down, you see the ground, which tends
06:30to be darker.
06:31However, if you're down below and you look up, you see the sunlight, you see the surface, which tends to
06:35be lighter.
06:36Chameleons can actually go one step further.
06:38They can change color depending on where the predator is situated.
06:42So if there's a predator that's coming from the top, it'll darken.
06:45And if the predator's coming from the bottom, it'll change into a lighter color.
06:48It's incredible that nature has engineered these species to change their color based on the predator that's looking at them.
06:56Chameleons lighten and darken their skin by manipulating special pigment cells called chromatophores.
07:03Chromatophores are found only in cold-blooded animals like octopus, reptiles, and some fish.
07:13Chameleon skin has several layers of chromatophores.
07:16The bottom layer are melanophores, which contain the brown pigment melanin.
07:21This is really similar to the melanocytes that we have in our human skin, which affect the coloration of hair,
07:27skin, and eye color.
07:28These star-shaped cells can move to manipulate their concentrations of melanin to adjust the shade of a chameleon's skin.
07:38Pulling it inward to lighten the lizard's hue, or pushing it out to the cell's extremities for a darker effect.
07:45They can do this rapidly, which allows for a rapid defense mechanism when the species are threatened.
07:52The exact biochemical mechanism that allows these changes to take place isn't fully understood.
07:58But it's believed to result from an interaction between the chameleon's hormones and autonomic nervous system.
08:05Imagine if you can turn a suntan on or off in an instant.
08:09That's what the chameleon does.
08:11Evidently, the chameleon's stealthy approach has been a successful strategy.
08:16After all, they've been around since the time of the dinosaurs.
08:20Based on fossil evidence, the chameleonidae family likely evolved in Africa around 100 million years ago, during the late Cretaceous
08:30period.
08:32For a family of animals to exist that long means they have to be doing something right.
08:37And stealth might very well have been one of the keys to their survival.
08:44But chameleons aren't just prey.
08:47They're formidable hunters, too.
08:49While keeping one eye open for predators, the other eye searches for their next meal.
08:54When we think about chameleons' eyes, they can act independently or together.
08:59And basically that means they can be monocular or binocular.
09:04In monocular view, the eyes work independently of each other.
09:08And they're able to scan essentially 360 degrees around the chameleon, looking for predators and prey.
09:16But then when the chameleon wants to focus on its prey, it uses its binocular vision.
09:22Basically both eyes point at the prey.
09:25And by doing so, it can judge the distance to its prey.
09:28And that's the advantage of having binocular vision, is that you can judge distance.
09:32But how can a slow-moving chameleon catch a fast-moving bug without giving itself away and making it vulnerable
09:40to attack?
09:41The solution is the chameleon's incredible tongue.
09:45It allows the chameleon to launch an ambush while remaining hidden.
09:49As its weapon and its prime means of hunting, the chameleon has this exceptionally fast tongue.
09:57This tongue has a huge amount of muscles in it that allow it to propel it very quickly forward.
10:05And the sticky end of the tongue then sticks on its prey and pulls it back.
10:09It's really like a tethered harpoon that gets fired from the chameleon to capture its prey.
10:19The chameleon's tongue is a marvel of evolutionary bioengineering.
10:23It can be two and a half times as long as the animal's body and reach speeds of up to
10:298,500 feet per second.
10:31The chameleon tongue is fascinating.
10:35Inside the tongue is a long, skinny, tubular bone wrapped in layers of elastic tissue made of collagen.
10:43All of this is surrounded by a layer of muscle.
10:45The chameleon loads its tongue by squeezing the collagen fibers, compressing them like coiled rubber bands.
10:52When it launches the tongue, the collagen slides off the end of the bone and expands.
10:57This gives the tongue muscle a kind of springy turbo boost and allows it to achieve its incredible speed and
11:04power.
11:07After snagging its prey, the chameleon reels its tongue back into its mouth, where sharp teeth make quick work of
11:15its meal.
11:19For all its stealthy capabilities, there are times that the chameleon actually wants to be seen.
11:26Yet, why would a creature so intent on remaining hidden suddenly feel the need to reveal itself?
11:33Certain chameleons are capable of jaw-dropping changes in colors and patterns.
11:39Some, like the panther chameleon of Madagascar, are well known for their vibrant array of amazing colors.
11:47Chameleons can change color to display their emotions and communicate with other chameleons.
11:53Male chameleons are highly territorial, and they'll engage in battles, displaying their colors to establish dominance.
12:00They'll face off with these dazzling colors, almost like warring billboards in Times Square.
12:06When the loser is determined, their color will fade and dull, and they'll slink off in defeat.
12:12Additionally, chameleons can change color for thermoregulation.
12:16As cold-blooded animals, their body temperature is mainly determined by the sun, and by changing to darker colors, they
12:23can absorb more sunlight and heat up their bodies.
12:26On the other hand, if it's getting too hot, they can use their color-changing abilities to reflect more sunlight
12:31and stay cool.
12:33So, how does a chameleon change its color?
12:36It does so by manipulating a group of chromatophore cells called iridophores.
12:42Iridiophores are full of tiny, plate-like nanocrystals.
12:46And these have the ability to reflect light in different wavelengths, depending on how bunched up or spread apart they
12:52are.
12:53When a chameleon relaxes its skin, these nanocrystals are bunched together, and this tends to reflect shorter wavelengths of light,
13:01like blues.
13:02But first, this blue light has to travel through a layer of yellow-tinted cells on its way out.
13:08Like mixing paint on a palette, the blue light pierces the yellow cells and creates the chameleon's signature green hue.
13:17But when danger strikes, or the chameleon gets excited, something even more incredible happens.
13:23The nanocrystals move further apart, and this is what reflects longer wavelengths of light, like red, yellow, and orange.
13:30This is what gives the chameleon its miraculous ability to change colors, from greens and browns and blues, to bright
13:38yellow and pink and orange.
13:41The chameleon has long inspired scientists, trying to develop innovative and adaptive camouflage systems.
13:49Engineers and scientists look to nature to produce technologies.
13:54This is called biomimicry.
13:56We're mimicking what's done in biology.
13:58If you want to try and camouflage things, producing something that mimics a chameleon is really ideal.
14:06The color-shifting properties of the chameleon's skin has inspired scientists to invent fabric that changes color when pulled or
14:14stretched.
14:15These experiments are in the early stage, but you can imagine applications where fabrics change color for camouflage, fashion, or
14:23just to reflect the wearer's mood.
14:25The chameleon isn't the only stealth expert living among the trees.
14:33The ninja of the bird world, long-eared owls, are stealthy killers who strike silently and unseen.
14:40Hunting at night, the mice and voles they prey upon never see them coming.
14:45The long-eared owl is a stealth predator, and if you ever watch an owl hunt, you would have to
14:51watch them because you can't hear them.
14:57Owls are unique among birds of prey because they're capable of near-silent flight.
15:03They're considered the quietest birds in the world.
15:06Nature has basically engineered them to be the stealth fighters of the animal kingdom.
15:11Standing around 38 centimeters tall, with a wingspan of approximately one meter,
15:17the long-eared owl is itself vulnerable to attack from larger aerial predators, such as hawks and eagles.
15:27So how does this bird of prey evade detection while still ensuring a successful hunt of its own?
15:37The long-eared owl is particularly fascinating because not only does it have silent flight,
15:41but it has these anti-stealth capabilities to find hidden prey, and it can camouflage itself from predators.
15:47Long-eared owls are found across North America and Eurasia.
15:52They roost in dense forests with heavy canopies.
15:55They're also found at the edges of open fields and grasslands where they hunt.
15:58Sitting on a tree branch, its whitish-gray and tawny-brown speckled plumage
16:03allows the long-eared owl to nearly vanish against a background of bark and branches.
16:09They can make themselves look so skinny.
16:11They can make themselves look just like a branch.
16:14They have the coloration of wood, and if they close their eyes,
16:17you could not tell the difference if it was a branch or an owl.
16:21The long-eared owl is built for stealth.
16:24Even the tuft-like projections that give the owl its name are part of their disguise.
16:29Long-eared owls' ear tufts are actually not their ears.
16:33They're just feathers.
16:34Their ears are on the side of their head like all other birds.
16:37The feathers resemble twigs and help the owls blend in with the surrounding foliage,
16:43especially when they're standing in the tall, thin position.
16:47The camouflage hides them not only from predators, but conceals them from their prey.
16:56Although the long-eared owl is a master of stationary camouflage,
17:00it's in the air that its stealth capabilities come fully online.
17:05Long-eared owls will fly over grasslands in search of mice, shrews, voles, and other small mammals.
17:12They'll also eat small birds, bats, lizards, and snakes.
17:18Like a radar-avoiding aircraft, the owl flies low, sometimes barely more than two feet above the ground.
17:25Relying on its keen vision and superlative hearing, it zeroes in on its prey with razor-like precision.
17:33Watching an owl hunt is breathtaking.
17:36They'll glide silently across a field and then pivot, swerve, dive suddenly to catch some prey.
17:43And the long-eared owl can even do this in the dark.
17:47The long-eared owl's preferred time to hunt is at night, when it's practically invisible to prey that relies on
17:53sight.
17:54But mice and voles have keen hearing.
17:58Fortunately, long-eared owls are the undisputed masters of acoustical stealth.
18:04The sound of the long-eared owl in flight is about 18 decibels quieter than other birds.
18:15Aerodynamically, if you want to move really slow through the air, you need very large wings.
18:20The amount of lift produced by wings is a function of how fast the air flows over the wings.
18:27And the slower and slower you want to go, the larger your wing surface has to be because you're going
18:33to get less and less lift as the speed goes down.
18:36But the true secret of the owl's stealthy flight is hidden in the composition and structure of its flight feathers.
18:44When feathers rub against each other, especially if they're stiff, they vibrate and create noise.
18:51The velvety structure of the long-eared owl's feathers makes these feathers much quieter when they do move with respect
18:59to each other.
19:02Bird wings and airplane wings are designed to make air move faster over the top of the wing.
19:07When air moves faster, the pressure of the air decreases.
19:12This creates lift, which is what allows birds and airplanes to fly.
19:17But when the upper and lower streams of air meet behind the wing, they create turbulence.
19:23And this produces sound, the characteristic whoosh of a bird in flight.
19:35The long-eared owl has serrated or comb-like feathers at the leading edge of its wings.
19:41These comb-like or serrated structures break the flow of air up into smaller streams.
19:47Because the feathers at the trailing edge are very velvety and downy, basically those fine little bits of feather absorb
19:56sound rather than allowing aerodynamic sound to develop.
20:01A pinnacle of aeronautical stealth.
20:04It's no wonder human engineers have long looked to owls as a model for aviation design.
20:10A lot of what we're trying to do in designing airfoils and wings is make them more efficient.
20:15And the owl's ability to be silent is really a testament to how efficiently their wings operate.
20:24The long-eared owl's exquisitely bioengineered stealth capabilities also have applications outside of flight.
20:32Engineers look to birds like the long-eared owl to help innovate in airfoil design.
20:39Aerofoils refer to things that have the shape of wings.
20:43And wind turbines are a great example of that.
20:47One of the drawbacks of wind turbine blades is that they make a large whooshing sound as they go by.
20:56That's a loss of energy.
20:58Not only is it a loss of energy, but it's quite annoying to residents in the area and potentially a
21:04distraction for animals that may drive local wildlife away.
21:08Putting serrated leading edges on wind turbine blades like owls have on the leading edge of their wings, we can
21:15make them not only more efficient, but quieter.
21:18The long-eared owl's incredible ability to fly silently means it can employ another one of its superpowers, super-hearing.
21:27Quiet flight means there's no acoustical noise to hamper the long-eared owl's hearing.
21:31The long-eared owl's hearing isn't only precise.
21:34It's ten times more sensitive than human hearing in the middle and upper frequencies, exactly the range that its prey's
21:42movement and vocalizations fall into.
21:46Owls are nocturnal animals, so they can't rely solely on their sight to find their prey.
21:51It's just too dark, so owls rely on their hearing.
21:55The feathers on the long-eared owl's face act very much like a parabolic dish.
22:02Basically, the feathers funnel sound to the ears.
22:05In addition, the ears are offset vertically on the owl's head.
22:10This basically gives the owl better spatial resolution vertically to determine where its prey is.
22:17So when the owl changes the position of its face, it can detect increases or decreases in the sound level.
22:29So if the owl locates a prey, it can actually, by moving its head slightly in all directions,
22:39basically determine the location of that prey, so that when it does choose to take its flight to attack the
22:46prey,
22:46it's well locked in it, and it knows where it needs to go.
22:51Once this bird is locked in on the source of its meal, it swoops in for the surprise attack,
22:57a silent hunt unlike any other.
23:07The long-eared owl's mastery lies in this hushed approach,
23:11disappearing into the dark canopy of the trees
23:15until it's time to strike.
23:18But far from the dense forests and open fields where these clever birds hunt,
23:25another stealth expert contends with an entirely different environment.
23:31One barren and uniform where any wrong move could be spotted with ease.
23:38This sneaky mammal uses the winter wasteland to its advantage, masterfully matching itself to the snow.
23:46But what is one to do when the winter snow melts and spring arrives on the tundra?
23:54Arctic foxes sit in a tricky spot as stealth experts.
23:57Because they don't hibernate, they need to hunt year-round,
24:01and so they rely on their camouflage to catch their prey.
24:04But they're also prey for larger animals,
24:06like bears, wolves, golden eagles,
24:09even their larger cousins, the red fox.
24:12Because of this, they need to use their camouflage both for offense and defense.
24:17The Arctic fox solves these challenges by changing its coat of fur.
24:22So if one coat doesn't work, why not use two?
24:25The Arctic fox can change the color and thickness of its fur in different seasons,
24:30just like how we might switch a heavy parka in the winter to a light jacket in the spring and
24:35summer.
24:36This amazing ability is called seasonal coat color malting,
24:41and it's the key to what makes the Arctic fox an elite stealth predator and survivor
24:46in a harsh and unforgiving biome.
24:51Smaller than their southern red cousins,
24:53Arctic foxes range in size from 46 to 68 centimeters,
24:58and weigh from 3 to 8 kilograms.
25:01The Arctic fox is found in tundra and coastal regions across its circumpolar range,
25:06including the northernmost parts of North America,
25:09Europe, Asia, Greenland, and Iceland.
25:13There are few places to hide in the Arctic tundra, even in the summer.
25:18Here, survival depends on a single desperate strategy, becoming invisible.
25:25In the spring and summer months, the face, legs, and upper parts of the Arctic fox
25:30are covered a gray-brown, and its abdomen is a yellowish-white.
25:34This allows it to easily blend in into the rocks, dirt, and sand of the tundra environments.
25:40But as the seasons begin to change, the landscape is transformed.
25:45The muted grays and browns slowly surrender to the bright white snow of winter.
25:51Luckily, the Arctic fox is already one step ahead.
25:55From September to October, the Arctic fox begins its autumn molt.
26:00White fur grows in, and the darker fur coat falls out.
26:03This new coat allows the Arctic fox to practically vanish into the snowy white landscape.
26:12There's a lot of analogies between the Arctic fox and combat gear,
26:16in that if you look at soldiers that are deployed to the Arctic,
26:20they'll wear very, very white snowsuits to help them blend in with their environment.
26:25And soldiers deployed to a desert to wear very brown, very beige outfits.
26:32Like camouflage donned by the military, the Arctic fox uses its coat to seamlessly blend into the background.
26:40But this layer of fur does far more than cloak this creature from prying eyes.
26:46It also offers protection from the harsh Arctic winter environment,
26:50where temperatures can reach an almost unbearably cold, minus 50 degrees Celsius.
26:57In the dead of winter, Arctic foxes must endure incredible temperature differences
27:03of almost 100 degrees Celsius between their internal core temperature and the temperature outside.
27:10Fortunately, Arctic foxes wear the warmest coats in the animal kingdom.
27:15Their winter fur is longer and twice as dense as their summer coat.
27:19The coat is formed of two separate layers of fur.
27:23The long outer layer is called the guard hairs.
27:26It overlaps a thicker layer called the undercoat.
27:29This works exactly like a winter parka,
27:32which combines an outer protective layer with an insulating inner layer.
27:38They even wear little boots, which is just adorable.
27:42Their footpads are covered in fur, which is unique among wolves, dogs, and other foxes.
27:47Even the coat's white color helps keep the fox warm.
27:51Because it lacks pigment, white hair contains extra space in the cells to trap air.
27:57This makes it more efficient at retaining heat than darker hair.
28:00But how does the Arctic fox know when to change its dark summer coat for a light winter one?
28:06And how does it do it?
28:08It's not the cold or the snow that causes the Arctic fox to change the color of its fur.
28:12It's actually the amount of light or the lack of light.
28:16Shorter daylight hours stimulates the secretion of hormones,
28:19which promote the growth of white hair and the loss of the summer coat.
28:24Here's how it works.
28:26Daylight affects the production of the hormone melatonin,
28:29which occurs in the pineal gland located deep in the fox's brain.
28:33The more hours of darkness, the more melatonin is produced.
28:38As the days shorten with the oncoming of winter,
28:41increased melatonin reduces the production of another hormone called prolactin.
28:48Prolactin is produced by the pituitary gland
28:51and is connected to hair growth and loss.
28:56Basically, an Arctic fox has a built-in light sensor.
28:59Instead of turning the lights on when it gets dark,
29:01it tells the fox's hormonal system to produce white fur.
29:04And when light returns in the spring,
29:06it tells the fox's fur to turn darker for the summer.
29:08Now draped in its perfectly timed disguise,
29:11the Arctic fox is ready to continue its ongoing hunt.
29:16Stealth is the key to the Arctic fox's hunting strategy.
29:20Foxes are omnivorous and very opportunistic feeders.
29:24They'll basically eat anything they can get their little paws on,
29:27from berries, eggs, insects, to birds, mice, voles.
29:33They'll even eat carrion left by bears or other hunters if they have a chance.
29:37Yet even for this cunning predator, the hunt is far from guaranteed.
29:42Some prey, like certain species of lemming and many northern stoat,
29:47have also evolved the ability to change color with a shifting season.
29:53Their small size lets them disappear beneath the snow,
29:58tunneling deep to evade capture.
30:01So, to outsmart these crafty critters,
30:05the Arctic fox has developed its own arsenal of anti-stealth adaptations.
30:10The Arctic fox in the winter environment
30:13is an environment that's all snow.
30:16So, the Arctic fox really can't hunt by sight.
30:19It really has to rely on its other senses.
30:22So, the Arctic foxes can smell their prey
30:24and get in relatively close by sensing their prey by smell.
30:28But then once they're there, they can't see it.
30:31So, they need another mechanism
30:33to determine exactly where their prey is.
30:36The Arctic fox has highly directional and sensitive hearing.
30:41Just like a parabolic microphone uses a dish to focus sound waves
30:45and amplify faint noises,
30:47the Arctic fox's small, rounded ears minimize wind interference,
30:52making it easier to focus on the sound that matters.
30:56By rotating the ears and moving with respect to their prey,
31:02the Arctic fox can very accurately determine where their prey is,
31:06even up to a half to three quarters of a meter below the snow.
31:10Once they zero in on their prey, they pounce.
31:14The Arctic fox has a unique strategy for hunting.
31:16It's called mousing.
31:18Essentially, they'll jump several feet in the air
31:21and dive face-first into the snow.
31:23The fox's rounded snout lets it penetrate the snow
31:26without resistance and without injury to itself.
31:30Yet, even as it stalks its prey,
31:32the Arctic fox must remain vigilant.
31:35In this environment,
31:37every hunter can just as easily become the hunted.
31:41Natural predators are a threat year-round.
31:43Basically, everything bigger than this fox is trying to eat it.
31:47Golden eagles, wolves, grizzly bears, polar bears, and wolverines
31:52are all constant threats on the winter landscape.
31:56Golden eagles are a particular risk.
31:58They can spot an animal the size of a fox
32:00from up to five kilometers away.
32:03If they see a fox, they'll hover above.
32:06They'll wait until the fox is distracted or looking down
32:09and then dive at it,
32:10reaching speeds of up to 193 kilometers per hour.
32:14These eagles have enough strength in their claws
32:17to puncture a car tire.
32:18An Arctic fox doesn't stand a chance.
32:25Thanks to the stealthy benefits
32:27of their seasonally appropriate attire,
32:30adult Arctic foxes are well-equipped
32:32to deal with dangerous predators and elusive prey.
32:35But what about pups who are just starting out?
32:39Pups are born in late May and early June.
32:41They're born blind, deaf, and toothless,
32:44so they're basically as helpless as can be.
32:47They don't start to fend for themselves
32:48until about three months old.
32:50A golden eagle can easily carry away a pup.
32:54Fortunately, the Arctic fox's den
32:56is constructed with stealth in mind.
32:58Female foxes will stay in this den with the pups
33:01until they're old enough to venture out.
33:03During this time,
33:04they'll at least be safe from all aerial attacks.
33:06The dens often form a complex maze of tunnels,
33:10sometimes spreading as large as a football field.
33:13The dens have multiple entrances.
33:15Up to 150 have been recorded,
33:18which gives them plenty of opportunity
33:19to slip in and out unnoticed
33:21by both predators and prey.
33:24Foxes will return to the same den year after year.
33:27It's believed that some dens have been in use for centuries.
33:31Talk about a heritage home.
33:33The Arctic fox's stealthy approach to offense and defense
33:37has made it a northern success story.
33:40But this animal now faces an unprecedented test.
33:44The Arctic foxes, when they're in their winter coat
33:47with their white, white fur,
33:50normally would blend into a white landscape,
33:53assuming there's snow on the ground.
33:55And we all know with climate change,
33:56we're starting to see species like the Arctic fox
33:59not able to camouflage as well
34:01because there's less snow.
34:03So they're finding a hard time being able to catch prey.
34:05Prey can see them coming a mile away
34:07if the ground is brown and they're bright white.
34:11While a changing climate poses a real threat
34:14to this small mammal,
34:15evolution has also equipped it
34:17with the valuable trait of adaptability.
34:21As it contends with these environmental changes,
34:24scientists hope it will unlock surprising new strategies,
34:28ensuring it can continue moving undetected
34:31against both food and foam.
34:40The Arctic foxes' challenge of transforming
34:43against shifting terrain
34:44is one that echoes across the animal kingdom.
34:47And while some creatures prefer to blend into distant vistas,
34:51others might be hidden right below your feet.
34:55When it comes to mimicking the twigs and leaves
34:58of the forest floor,
35:00none is more talented than the stick insect.
35:02In fact, stick insects may be the true champion of krypsis,
35:07the ability to blend into the background.
35:10Stick insects are incredible.
35:13They are found on every single continent
35:15except Antarctica.
35:16There's over 3,000 known species of these animals,
35:19and they cover a huge variety of shapes and sizes.
35:23Some have evolved to look like moss or lichen,
35:26and some have even evolved to look like
35:28different types of leaves in their environments.
35:30Your classic stick insect looks like a twig or a branch.
35:35It is perfectly adapted to blend into its surroundings.
35:38It's either brown or maybe green in color.
35:41It has an elongated body
35:43with six skinny, skinny legs hanging off of it.
35:46Their size ranges from only a few centimeters in length
35:50to truly nightmarish proportions.
35:54Stick insects might look really freaky, a bit alien-like,
35:58but they're actually very peaceful.
35:59They're herbivores.
36:00They eat leaves.
36:02These solitary creatures form the phasmid order of insects.
36:06The word phasmid comes from the Greek word phasma,
36:10which means phantom.
36:11And like ghosts,
36:13stick insects have the ability to seemingly disappear.
36:16Stick insects are really amazing.
36:18They just blend in with their environment so perfectly.
36:21They're kind of the ultimate camouflage.
36:24Over my life,
36:25I've been lucky enough to see many of them,
36:27but it's only in situations
36:28where they're no longer in their prime habitat.
36:31They've fallen out of the tree,
36:32onto a walkway,
36:34or onto a deck where they're quite obvious.
36:37But I don't think I've ever actually found one
36:39when it's been in a tree.
36:41They just blend in so perfectly.
36:43Stick insects depend on their brilliant disguises
36:46because they're a popular item on the dinner menu
36:49for so many other animals.
36:51They have to watch out for small mammals,
36:54reptiles, birds, you name it.
36:56Lots of things like to eat stick insects.
37:00Perfectly evolved to fill their niche as nocturnal herbivores,
37:04stick insects have been stealthily fooling predators
37:06for over 100 million years.
37:09The first fossilized record of a stick insect
37:11is from the Cretaceous period,
37:13about 126 million years ago.
37:15It's believed that stick insects evolved their stealthy form
37:19around the time that the first flying birds evolved.
37:22It's thought that these early birds hunted insects
37:26just like they do today.
37:27Stick insects literally look like walking sticks and leaps.
37:32These distinct stealthy features
37:34would have allowed phasmids to survive until the present day.
37:38Stealth is more than just a means of defense for stick insects.
37:43It's an entire way of life.
37:46Even their eggs are camouflaged.
37:48Their eggs tend to look like teensy tiny little seeds.
37:51A female will lay between 2 and 15 eggs every single night.
37:56Some stick insect mums will hide their eggs underneath little leaves.
38:00Other ones will just scatter them along the ground.
38:03This is actually an excellent strategy
38:05for ensuring some of the babies survive.
38:08Even if a bird or other insect finds some of the eggs,
38:11they won't get the entire clutch.
38:14The eggs are coated with a hard substance called calcium oxalate crystals.
38:19This is the same substance that makes up kidney stones.
38:23This coating allows the eggs to survive in stomach acid,
38:27so they may hitch a ride in the digestive tract of a bird.
38:31Eggs can travel hundreds of kilometers this way.
38:34Once they hatch, stick insect juveniles, called nymphs,
38:39are stealthy from the get-go.
38:41Most juvenile stick insects are born as tiny versions of their adult selves.
38:46They're born camouflaged.
38:48Stick insects don't just depend on shape for their disguises.
38:51They have the incredible ability to match their color to their surroundings
38:55by literally chewing the scenery.
38:58Stick insects eat the leaves off of trees, shrubs, and plants.
39:01In so doing, they eat a pigment called carotenoids.
39:04When they eat that carotenoid, it turns them the same color as the leaf.
39:08If the leaf is green, they will turn a green color.
39:11It's very similar to if humans eat carrots.
39:14If they eat too many carrots, their skin will turn an orange tinge.
39:18So how do these conscious eaters make use of the carotenoids they consume?
39:23In the summer, stick insects accumulate a carotenoid called beta-carotene,
39:27which gives them their green color.
39:29In the fall, some stick insects will convert the beta-carotene
39:32into a reddish pigment, which allows them to blend in with the autumn foliage.
39:37The problem, however, is that leaves and sticks don't walk around,
39:41and stick insects can give themselves away if they move.
39:45To counter this, evolution has bestowed an unusual superpower.
39:49Stick insects can freeze and remain motionless for long periods of time.
39:54This is called catalepsy, and it can confuse predators
39:57who often use motion to zero in on their prey.
40:01Stick insects can even take their immobility one step further.
40:05When they detect a predator, some stick insects will fall off a branch and play dead.
40:10This behavior is called thanatosis.
40:13This is an effective defense strategy because lots of animals don't like to eat dead prey.
40:17But staying still on a leaf or the ground for too long can pose a risk,
40:22particularly if the world around you is moving.
40:26When you see a stick insect and you see it actually move,
40:29they don't really walk in the traditional sense.
40:32They kind of rock, and it very much looks like a twig blowing in the wind
40:37in that they're moving back and forth.
40:39When we think about the gait of most animals, especially multi-legged animals,
40:46almost invariably there's a pattern to the movement of the legs.
40:51Stick insects don't follow that pattern in that they can move each of their legs independently.
40:57It's almost like each leg of the stick insect is moving and thinking for itself.
41:03Scientists have turned to stick insect locomotion as a model for six-legged robots called hexapods.
41:10When we think about robotic-limbed vehicles, it's very difficult for them to actually move.
41:17And the act of moving more than one leg at a time is complex technologically to synchronize it.
41:26So when we design robots, we use the stick insect's mode of locomotion
41:31in that we tend to want to move one leg at a time
41:34because that way we ensure stability for the robot as a whole.
41:54The Australian walking stick has an incredible defense.
41:57It can curl its tail up to look like a scorpion's tail if it's threatened by a potential predator.
42:03Several species of stick insects actually have some wings.
42:06They're weak flyers, but these wings are often brightly colored
42:10and they can be used in predator defense.
42:12If the stick insect is detected by a predator,
42:15it can flash the bright colors and startle the predator,
42:18allowing the stick insect a little bit of time to escape.
42:21This is called a startle display.
42:23And if a predator is still determined to take a bite,
42:26some stick insects can even deploy a chemical defense.
42:30Several species of stick insects can actually excrete chemicals when threatened by a predator.
42:36For example, the devil rider stick insect has glands at the front of its thorax
42:40from which it can shoot chemicals that are noxious to predators.
42:45It's almost like having a built-in bottle of pepper spray for defense.
42:50Having chased off its attacker,
42:52the stick insect can go back to doing what it loves most,
42:56munching on leaves and stealthily blending into the lush foliage it calls home.
43:05Just as the stick insect disappears among twigs and leaves,
43:09below the surface of the ocean lives a creature that takes its stealthy lifestyle
43:14to a whole other level.
43:17This may look like a piece of seaweed, but it's not.
43:21It's an animal called the leafy sea dragon,
43:23and it's one of the stealthiest and strangest-looking fish on Earth.
43:28Leafy sea dragons look crazy.
43:31They are actually a fish.
43:33They're in the group of bony fish, osteocthese,
43:36as opposed to chondrichthese,
43:37which would be our cartilaginous fish,
43:39our sharks, rays, and ratfish.
43:43But they are a fish.
43:45They're a bony fish just like a trout is,
43:47but they are so highly adapted to camouflage
43:50that they look the way they do.
43:52Leafy sea dragons are masters of marine mimicry.
43:55They essentially evolved to look like floating pieces of seagrass.
43:58A relative of seahorses and pipefish,
44:02the leafy sea dragon is found in only one place in the world,
44:06the temperate waters off the coast of southern Australia.
44:10Leafy sea dragons live on rocky reefs,
44:13seaweed beds, or seagrass meadows.
44:15They're found at depths between 3 meters and 50 meters.
44:19They're solitary creatures.
44:20They live alone.
44:21They don't travel very far from where they were born,
44:23maybe a few hundred meters.
44:25Like seahorses, the male sea dragons carry the eggs.
44:27They incubate the eggs on a specialized sponge-like section
44:30of the skin under the tail called the brood patch.
44:35Once the eggs hatch,
44:37these young sea dragons will be forced to contend
44:40with dangerous seas where predators lurk
44:43around every rock and coral.
44:46Although leafy sea dragons have spear-like spines
44:50and are covered in bony armor-like plates,
44:52they lack other means of self-defense,
44:55such as sharp teeth or speed.
44:58Instead, they rely almost entirely on stealth to keep them safe.
45:03Nearly every aspect of this animal,
45:05from the way it looks, from the way it moves,
45:06from the way it eats,
45:07has evolved to hide itself from predators and prey.
45:11In fact, their disguise is so effective
45:13that leafy sea dragons seem to have outsmarted
45:16every potential predator.
45:18The leafy sea dragon shares its habitat
45:20with some formidable predators.
45:22Sharks, harlequin fish, groupers.
45:25But as far as marine biologists are aware,
45:28none of these feed on the leafy sea dragon.
45:31Obviously, looking like kelp pays off.
45:34Even though we don't know of any modern predators
45:37for the leafy sea dragon,
45:39there must have been very strong predation pressure
45:42on them in the past
45:43to drive such drastic physical features today.
45:47So what makes the leafy sea dragon
45:50such a uniquely successful stealth expert?
45:53Sea dragons belong to a group called Tilios.
45:56They represent about 96% of fish on the Earth,
45:58anywhere from minnows to marlins.
46:01But they have evolved a radically different body shape
46:03from their regular fish design.
46:05They have a long, thin body with a kinked spine
46:07that looks like a stalk of seaweed.
46:09Instead of a jaw, they actually have a long snout,
46:11which adds to the illusion that they're a plant
46:13and not an animal.
46:14Instead of scales,
46:16sea dragons are covered with rigid plates
46:17that are made of bone,
46:18which limit their flexibility and movement,
46:20which gives them the appearance of a plant
46:22rather than a fish.
46:24Their most distinguishing feature
46:26are the leaf-like appendages
46:27that resemble kelp fronds.
46:30These aren't fins,
46:31but modified spiny projections made of bone.
46:34The lobes at the end are filled with collagen
46:37and connective fibers
46:38that make them look as flexible as real seaweed.
46:42Even their color is a perfect match for their surroundings.
46:46And like chameleons and stick insects,
46:48leafy sea dragons can manipulate pigment
46:50in their chromatophore cells
46:52to blend in better with the background.
46:57Mimicking its backdrop comes easy.
47:00But how does this fish move from place to place
47:03across the open ocean floor
47:04without drawing attention?
47:07Sea dragons use their pectoral fins
47:09and their dorsal fin for propulsion.
47:11They basically undulate these transparent fins
47:14to allow them to move.
47:16To maintain their position in the water column,
47:19they use an air bladder.
47:21The sea dragon's pectoral fins undulate
47:23at 25 to 30 times a second,
47:25giving them the ability
47:26to propel themselves through the water.
47:31Small fins mean the leafy sea dragon
47:34moves very slowly,
47:35but they also allow for very precise movement.
47:39Sea dragons are really interesting.
47:41Where fish are kind of like zeppelins
47:43that use their tail for propulsion
47:45and their pectoral fins for steering,
47:48sea dragons are more analogous to helicopters
47:50in that they use their pectoral fins
47:53to kind of hover in the water column.
47:56This undulating style of movement,
47:59common to both the leafy sea dragon
48:01and the weedy sea dragon,
48:02is so efficient it has inspired novel designs
48:05for aquatic robots.
48:08Scientists are starting to construct
48:10biomimetic robots,
48:11robots that mimic creatures
48:13like the leafy sea dragon.
48:16Traditional propeller-based marine robots
48:18can get tangled in seaweed,
48:20and they can damage sea life.
48:22At slow speeds,
48:23they're not very maneuverable or efficient.
48:27Biomimetic robots that can mimic
48:29the undulating movement style
48:31of the leafy sea dragon
48:32can use less energy
48:33and be more precise
48:35at those slower speeds.
48:36This makes them useful
48:38for underwater research,
48:39mining, rescue,
48:41and exploration.
48:43But don't let their covert appearance fool you.
48:47Stealthily concealed among swaying kelp beds,
48:50this delicate-looking species
48:52are actually deadly ambush hunters.
48:56Sea dragons feed on larval fishes
48:58and amphipods,
49:00like small shrimp-like crustaceans
49:03called sea lice.
49:04They'll hunt by lying in wait
49:06and waiting for prey to float on by.
49:09Like chameleons,
49:10they have independently mobile eyes,
49:12so they can keep a watch for prey
49:14in all directions.
49:18All sea dragon species
49:19hunt the same way,
49:21maneuvering themselves close,
49:23then striking with their tube-like mouths.
49:30Because the sea dragon
49:31is so adapted to camouflage,
49:33they don't have the moving jaw
49:35like a lot of other fish do.
49:37They have this long snout
49:38that looks like a straw,
49:40and they use it to suck in their prey.
49:43Sea dragons are a marvel
49:45of evolutionary engineering,
49:46and the genetic blueprint
49:48they are built from
49:49may explain
49:50their uniquely stealthy adaptations.
49:52The leafy sea dragon
49:54has been described
49:54as evolution gone crazy.
49:57They have a very unusual
49:58and interesting genome.
50:00They lack several key development genes
50:02that are responsible
50:03for growing things like teeth
50:04and face structure.
50:05That is why the sea dragon
50:07has a fused jaw and no ribs.
50:08But they also have an abundance
50:10of what are called transposons,
50:12or jumping genes.
50:13These genes move around
50:14in the genome.
50:15They cause genetic diseases
50:16and mutations,
50:17but they are also responsible
50:19for rapid genetic change.
50:28The leafy sea dragon's
50:29unique genome
50:30might explain
50:32why they developed
50:32such radically unusual
50:34characteristics
50:34in a relatively short time.
50:37They seem to have
50:38branched off
50:39from more conventional
50:40looking fish
50:41in the last 50 million years or so.
50:43This is a pretty short
50:45amount of time,
50:46at least in evolutionary terms,
50:48for such a strange
50:49and unique looking creature.
50:52Sea dragons
50:53are so well equipped
50:54to hide
50:55that an entirely new species
50:57was only recently discovered.
50:58A new species of sea dragon
51:00called the ruby sea dragon
51:01was only spotted in the wild
51:02for the first time in 2015.
51:04That brings the total number
51:05of known sea dragon species
51:07to three.
51:08But they're so good at hiding
51:10that it's possible
51:11that there are species
51:11that we don't even know of yet.
51:13Could there be more
51:14of these tantalizing creatures
51:16hidden among our waters?
51:18One of the most stealthily
51:20camouflaged animals on Earth,
51:21the leafy sea dragon,
51:23is living proof
51:24of nature's inexhaustible creativity
51:26when it comes to survival
51:29and adaptation.
51:30The next one is a nation.
51:32The next one is a nation.
51:37The next one is a nation.
52:01The third one is aなた.
52:09A young man who's a human
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