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00:00Humans navigate the world with five senses, but we often forget there are many
00:05aspects of this world we can't see, hear, smell, touch or taste. Many animals can
00:11sense far beyond our abilities, thanks to eons of evolutionary trial and error.
00:16Imagine if we could use the Earth's magnetism to get around, or if we could
00:20communicate by sensing seismic vibrations. What if we were able to hunt
00:25by detecting our prey's electricity? These incredible and highly attuned creatures
00:30have been given access to sensory inputs that humans can only dream of.
00:55When we picture elephants, one of the first features that comes to mind are
01:00its ears, whether the massive ears of the African elephant or the relatively
01:04smaller ones of their Asian counterparts. And in terms of senses, ears makes us
01:08think of hearing. But with the elephant, hearing with their ears is not the entire
01:13story. It is thought they can also listen with their feet. Engineers have even
01:17wondered whether these creatures could hold the answers to better hearing aid
01:21designs. Elephants, they're very charismatic creatures. They're the largest land mammal.
01:26They really have a vast number of different adaptations that really aren't that prevalent
01:33in the rest of the animal kingdom. Their ability to use subsonic sound to communicate
01:38and kind of act as the animal world seismometers.
01:42Conventional hearing involves the three sections of the ear working together to deliver sound to the brain.
01:48Because sound is a vibration, it moves the air around it. So when a bell is rung,
01:53the air around it moves to create sound waves, which hits the outer ear, then the middle ear,
01:58then the inner ear before traveling to the brain. Elephants use conventional hearing all the time,
02:03yet they also seem to pick up sounds that are not in the air. For example,
02:07they can sense rumblings well before a storm. There's a lot of evidence to say that elephants pick
02:13up seismic events, whether it be a tsunami or an earthquake, long before other animals pick it up,
02:19that they start moving away or changing their behavior in response to something before humans
02:25perceive it. So this tells us that elephants have some special sensory perception to the vibrations
02:32occurring in the ground. Hearing a massive seismic event is one thing, but in the 1990s, scientists
02:38realized elephant seismic detection might be much more subtle and sophisticated. Observing the animals
02:44congregated around a drinking hole, biologists noticed a set of strange behaviors. The elephants
02:50would lean forward, pick up one leg and freeze for no apparent reason. Biologists believed they caught
02:56them in the act of picking up a vibration from the ground. The human hearing range is from 20 hertz
03:02to
03:0320,000 hertz. So a hertz is a cycle per second. So 20 hertz would sound like a very deep
03:10bass drum,
03:11like as deep as you can imagine. Whereas 20,000 hertz would be extremely high pitch. Elephants are at the
03:18opposite end of the range. Elephants are only able to hear frequencies as high as 16,000 hertz and as
03:25low as
03:255 hertz, sounds that would be much too low for us to pick up. Elephants have much more sensitive
03:31cochlear ear components that allow them to be able to be more sensitive to these sounds and having
03:37that wide space in between their ears allows them to really fine tune the direction at which the sound
03:43is coming from. Elephants can also vocalize in lower frequencies and while the elephant's high frequency
03:49shrieks can be heard by anyone close by, their low level vocalizations can actually travel
03:55much farther. Elephants have eight times longer vocal cords than humans have. It allows them to
04:00vibrate at lower frequencies and with lower frequencies they're able to transmit to the
04:06ground like relay waves. Sound travels much better through high dense media than low dense media.
04:11So through the air when an elephant makes a rumbling sound that travels maybe 9 kilometers at most,
04:1810 kilometers. But when traveling through the ground it's much more efficient. So it can travel 16 to 30
04:24kilometers through the ground. In historic times when rail was common and you wanted to know if the
04:29train was coming because it was late, you'd lay down on the track and put your ear to the rail.
04:35Because of the higher density of the rail, the sound travels much more efficiently and you can
04:39clearly hear the train's movement long before you can ever hear it through the air. So much of the
04:45elephant has to do with size, the size of its body, the huge amount of land it traverses. It was
04:51not
04:51beyond human comprehension that elephants could produce massive vibrations with their weight
04:56alone and certainly that is part of their communication. During mating season a female
05:01elephant will stomp on the ground to let the male elephants know she's there and vibrations from her
05:06stomps can be picked up from a male 10 kilometers away. It's a really neat adaptation that's that's
05:12making use of that biology, that massive size. Amazingly, the elephant's foot might also be
05:19hearing one by way of bone conduction. While this sense might seem otherworldly, it helps to remember
05:25that one of the world's most famous composers used a similar tactic. Beethoven created some of his finest
05:31works after he had lost his hearing. By putting a rod in his mouth which tuned his piano, he used
05:37bone
05:37conduction to hear his music. When the elephant's, you know, pushing down on the ground it's actually
05:43feeling the mechanical energy directly rather than it going through the stages that it would in the
05:48ear. So it's more like somebody tapping on you and feeling the taps rather than actually hearing it.
05:55But how exactly does this conduction work? Like all mammals, elephants have receptors called
06:00piscinian corpuscles or PCs in their skin. These are hardwired to the part of the brain that processes touch
06:06and vibration. Elephants have a large amount of these PCs around the edges of their huge feet
06:12and toes. Researchers noticed that when picking up a far-off signal, elephants would press their feet
06:18into the ground, enabling them to enlarge the foot's surface by 20%. Scientists think they are able to
06:24interpret the sound either from the foot or from even the toenail. And it's through these piscinian
06:30corpuscles. And it basically takes that vibration into the brain. In other words, although the ear
06:36drum is completely bypassed, the vibration still makes it to the brain's hearing center. One could
06:42argue that this is feeling versus hearing, but those two concepts overlap due to their common basis
06:48in vibration. For elephants, this has vast implications. It really looks like elephants have
06:54the ability to communicate over longer distance and warn other groups of elephants that something's
07:00happening or provide some type of communication between groups. Especially in Africa, trucks,
07:06poachers, that sort of thing. If you hear the sounds of jeeps coming and you need to get out of
07:13the
07:13way or you need to tell your herd to get out of the way, it actually has such an advantage
07:16to avoid
07:17predators. The elephant's extrasensory ability to communicate through seismology has not only
07:22contributed to its success as a species, but has also inspired human technologies such as hearing aids
07:28that work via bone conduction rather than amplification. Soldiers now use bone conduction
07:33to hear in specially designed headsets integrated into their helmets. Even divers have felt the trickle
07:39down effect of elephant seismology research. New devices can be attached to diving goggles and pressed
07:45against the diver's head to relay messages from a diving partner via bone conduction. As elephants use
07:51their feet to hear and possibly talk in the skies above, another amazing creature uses a completely different
07:58sixth sense to hunt down its dinner in the dark. There's not much truth in the old saying blind as
08:04a bat. Not only can these animals see very well with their eyes when there's light, but they also have
08:09a way of seeing in the dark. Could bats give us the answers to more sensitive vehicles and flying machines
08:16of our own? What the bat's doing with echolocation has been something that mankind has been trying
08:21to do for decades. It is now just approaching to be able to do with autonomous driving vehicles. Basically,
08:27those vehicles have to build an image of the space around them and understand their space. Witnessing a
08:35colony of bats leave their cave is like seeing traffic at rush hour. Except since most bats are nocturnal,
08:41this usually happens in the dark of night. Hundreds or more of bats all usher out of the same space
08:47at
08:47the same time. They move in a much more erratic darting fashion than birds, yet they never crush into each
08:54other. There's no way that we would be able to create something that operates at the speed and accuracy
09:00and detail of what a bat can do with echolocation. Imagine trying to run a ship through a complicated
09:07landscape, like a reef system, and you're using sonar, and you're going incredibly quickly and
09:13maneuvering around. Like, it just wouldn't be possible with what we're able to do. We just know that bats
09:17do it better. Even more remarkable is how bats use echolocation to find and eat their prey. When it comes
09:23to hunting at night, bats are virtuosos. Given how small and quick the bugs they hunt are, they have
09:29developed an exquisite way to outsmart their prey and not become prey to other animals. In the meantime,
09:35their solution is to use clicks and echoes, nature's version of sonar. They're doing this high-speed
09:40chase in midair in the dark in a completely different way than we can imagine. For scientists
09:46and engineers, this creature has been a never-ending source of inspiration. For example, as unmanned vehicles
09:53become smaller, such as delivery drones, designers once again look to bats for clues. What biology has
10:01developed and perfected over millions of years, the ability to do echolocation continuously,
10:07regularly, and be something that the bat doesn't even have to think about is absolutely amazing.
10:12Bats are a mammal and make up a staggering one-fifth of the world's mammal population.
10:17More than 1,300 bat species are distributed across six continents.
10:21They have a patagium, which is between their body, their hands, and their fingers, which is just a
10:28membrane of skin that they use for flight. They're actually the only mammal that has evolved to fly.
10:33Researchers believe bats descended from a tree-dwelling creature that had no wings
10:37and jumped from tree to tree. Then, a mutation caused one of these creatures to have slightly more
10:43skin under its arm, which made gliding between trees easier. Natural selection allowed this skin to be
10:48transformed into wings. This, and the bat's ability to echolocate, make it a formidable animal.
10:55But how does echolocation work? The process begins with the bat making a sound by contracting its
11:00larynx or voice box, although a few species make it by actually clicking their tongues.
11:05Think about it. It's not just trying to make noise just for the sake of making noise. It's making
11:09noise to get the information on its environment. And what happens is the sound travels a specific
11:15distance, bounces off an object, comes back, and they're able to sort of piece that picture together
11:20as they go along. A simple way to visualize this is to think of yelling in a canyon and having
11:25your
11:25voice echo back to you after bouncing off a canyon wall. But unlike the canyon analogy, the bat is flying
11:31while it calls out. There are sometimes like hundreds of bats in a colony, so that echolocation,
11:36you've got to be able to figure out what's around you and be able to detect what's around you, whether
11:40that's friendly or not friendly or potential food. So there's a lot of information going back. Even
11:47when you're out at night and you listen and there are bats in the air, you listen to the sounds.
11:52It's
11:52never just one click. It's a series of clicks and it's just that animal taking in all that information.
11:58Although we can hear some of these clicks, most of them are actually ultrasonic.
12:02Echo location calls usually range in frequency from 20 to 200 kilohertz. Within this range,
12:08they combine low and high frequency sounds. The high frequency sound has a limited distance that
12:14it travels, but it gives very good resolution. So if you're trying to catch a moth in midair,
12:19that high frequency sound is really going to allow you to focus in on the direction, the size,
12:24and the speed of that moth. The lower frequencies can't pack as much information,
12:29but they can travel further out. The low frequency sound gives you a broader image
12:34of the space around you. So that's building the map of the trees and the landscape. Added to the
12:40complexity of this mapping is the fact that the main targets of the bat's echo location,
12:45its dinner, are also moving. So it must also use what we call the Doppler effect to compute incoming
12:51information. So the Doppler effect says that if something's moving away from you or towards you,
12:58the frequency of the reflected wave will change in pitch. This is most apparent in a train whistle.
13:05So if the train is traveling towards you, you'll hear a very high pitch. You'll hear
13:10and as the train passes, it will switch to low pitch. It'll go as the train goes by. And that's
13:17the
13:18Doppler effect, the apparent change in the frequency of the sound due to the motion of the object. And bats
13:25are going to do the same thing. So when they hear the pitch of the returning echoes change,
13:30they know not only their speed, but if the object is moving relative to them.
13:36So they're able to kind of stealth attack a lot of these creatures because these bats can
13:42essentially see or feel in the dark where they are. They're not being detected by their prey,
13:46they're just detecting their prey. It's a one-way relationship. And this ability helps,
13:50the birds, making them the ultimate nocturnal predator when it comes to catching bugs.
13:55They can catch more than a thousand insects an hour. Think about the processing time that it's doing
14:01by sending out that eco-location and eating that many insects. Engineers still dream of being able to pull
14:08off such intricate mapping mechanics with the efficiency of a bat. In terms of decibels,
14:12the sounds range from 50 to 120 decibels, which is louder than a smoke detector detonating 10
14:19centimeters from your ear. It's even too loud for the bats themselves. And they've developed another
14:24adaptation to deal with this. Incredibly, their middle ear muscle contracts six milliseconds before
14:30the click is emitted and relaxes two to eight milliseconds after, at which point the ear is ready
14:36to receive the echo of an insect as close as one meter away. It evolves so as to not deafen
14:42themselves,
14:43but still allowing them to hear back the echoes. And their outer ear contains folds that they can tell
14:47which level of vertical position that item may be or how large it may be as well. Like their brains,
14:53bat ears are also exceptionally well tuned into their own frequencies. Each ear has thousands of hair
15:00cells that help them with this. They can read a frequency change as subtle as one ten thousandth of a
15:05kilohertz. When you do seismic surveys, say in the ocean, you put sound into the bottom of the ocean,
15:10you wait for that sound to come back up. The interpretation of that information that comes back
15:14is done through an algorithm. You have a number of very high-powered computers that will process that
15:20algorithm as they move, and they'll be able to take a picture fairly, fairly quickly. When you think
15:26about eco-location in the bat, it's the same thing. They're actually processing that algorithm, and they're able
15:32to interpret that at a very, very fast pace. And they have to make it very fast because that animal's
15:37going to move. The fact that their eco-location sense is so refined is what makes humans think
15:43they might not need sight. Contrary to the saying, blind as a bat, they do have excellent vision that
15:48they can use. They just hide at night to be able to see those things that may be hidden. It's
15:53interesting
15:53that in the course of human history, we couldn't conceive of an animal that could see great in the day,
15:58you know, using light with their eyes in the same way that we do, and then also see in the
16:02dark using
16:02this completely new sense. Another faulty assumption humans make about bats is that their wings are like
16:08bird wings. The whole structure of a bat is really fascinating. So rather than, you know, a bird for
16:15instance, which has this kind of outstretched arm and hand and feathers are attached to it, a bat actually
16:21is like a really short arm and an enormous hand. So really their wings are just these enormous hands
16:26that they just kind of like are constantly clapping and flying around. And they use more of their body
16:32in kind of the creation of draft too, because their wings are often connected all the way to their to
16:37their legs. So it's really like a full body mechanism. The patagium membrane these wings are made of
16:43also makes them extra flexible, enhancing the bat's ability to glide and quickly change shape when it
16:48needs to weave and dive. While a bat's flight might not look as graceful as a bird's, it is perfect
16:54for
16:54catching 1000 mosquitoes an hour. If you ever watch a bat hunting, it's moving all over the place,
17:00especially if it's feeding, it's finding out that pattern and trying to figure out where that animal
17:04is. Not only has bat echolocation inspired engineers to better develop sonar and unmanned vehicles,
17:10but recently the phenomenon has been employed by neuroscience to fascinating results. In 2019,
17:16research was conducted on visually impaired people who had learned to use echoes to map their
17:21surroundings. It was discovered that the same area of the brain responsible for interpreting light was
17:27being adopted for mapping spatial locations through sound. Echolocation for the bat is not the only time
17:33evolution has bestowed a species with a special sense to hunt in the dark. A stranger example of this can
17:39be
17:40found down under. Australia is famous for its animals, from kangaroos to koala bears, to probably
17:47the most bizarre creature, the platypus, which can only be found in the freshwater areas of Tasmania
17:53and Australia's coasts. It possesses one of the most extraordinary extrasensory abilities in the animal
17:59kingdom. My first thought of a platypus is that it really doesn't fit with a lot of the other
18:09species on the face of the planet. It's sort of like a mammal and sort of like a reptile or
18:16bird and sort of like
18:18nothing at all. Platypus is nature's oddball. There's no doubt about that. It's got the mouth of a duck, the
18:26tail of a beaver, it's got claws, it's got webbed feet. It just looks like somebody sewed a number of
18:33animals
18:34together to make one animal. In fact, the first European naturalist to come across it in the late
18:391700s thought it was sewn together and they searched for stitches on the animal, which they assumed some
18:45taxidermist had Frankensteined together. This funny little creature has been generating confusion ever
18:52since. Given that it lays eggs and has the ability to produce venom, many originally thought it to be a
18:58reptile. It is a mammal. Mammals are defined as species that have hair and mammary glands specifically
19:06and these animals have that. They are one of only two mammals on earth to lay eggs. But of all
19:11the
19:12platypus's bizarre evolutionary distinctions, and there are many, the most remarkable is the creature's
19:18special ability to find prey. It is something that has gripped scientists, especially those working
19:23in biomimicry. For example, in fields like prosthetics, could replicating the platypus's sixth sense help
19:30design the perfect prosthetic limb? To better understand how this puzzling creature developed
19:35its remarkable senses, we have to look to its habitat. It somehow manages to catch its prey in murky waters.
19:42As soon as the platypus goes underwater, folds in its skin, cover its eyes and ears, and its nostrils
19:47close up completely. Essentially can't see, can't use any of those senses. So how does a platypus
19:53actually detect its prey? They can only remain underwater for two minutes, and they are bottom
19:58feeders. When they detect shellfish, worms, larvae, and insects, they open their mouths and catch the
20:04prey in their cheeks, then ingest them once they return to the surface. In order to score their dinner
20:09in the limited time they can hold their breath, they tend to forage in shallow bodies of water between
20:14three and sixteen feet deep. So if you think about where a platypus lives around rivers and streams,
20:21these streams are murky, and they're also a mammal that breathes air, so hunting has to be efficient.
20:28With neither vision, nor smell, nor sound at its disposal, one might think this animal keeps
20:33hunting to a minimum, quite the opposite. They're effective hunters and can eat almost 50% of their
20:39body mass when hunting, which can last about 10 to 12 hours. In order to pull this off,
20:44nature has engineered something of a superpower in the platypus, a vast and intricate system of
20:50receptors on their bill. The two receptors that they have on their bill are mechanoreceptors and
20:55electroreceptors. They have about 60,000 mechanoreceptors and also 40,000 electroreceptors.
21:01Both receptors work together to find their prey. The receptors are found in mucousy stripes on the upper
21:07and lower surfaces of the bill. They weren't fully discovered until the latter part of the 20th century,
21:12when scientists took a closer look at what they thought were relatively insignificant tiny pores.
21:17The first and more numerous mechanoreceptors each contain a simple pushrod device that triggers a
21:23nerve when pressed. Mechanoreceptors detect pressure and motions in the water. This could be generated by
21:28the prey themselves. While the mechanoreceptors feel pressure changes in the water, the electroreceptors
21:34pick up minute electrical impulses generated by the muscle activity and heartbeat of the prey.
21:40It's actually detecting electrical fields. So organisms that have a nervous system, it's an
21:45electrochemical system that produces very small amounts of electricity. And if you have a sensitive
21:51enough instrument, you can detect those electrical impulses. One analogy for this dual system is using
21:57thunder and lightning to anticipate a storm. The disturbance ripples of the water are like
22:03thunder, while the electrical pulses from the prey's muscles are like lightning. Together, these two
22:08types of signals travel to the platypus's brain, where a sonar-like image is created of the riverbed
22:14and any creatures within. So as it's moving through the water, if a small animal or crustacean moves,
22:20it can detect those electrical impulses and hone in on them. And then if it gets close enough,
22:25using the tactile sensors, grab and capture that food source. The large surface area of the bill
22:31makes it the perfect navigational tool, as the platypus waves it from side to side, orienting the
22:36receptor stripes towards its target. There's competition or threats that could be found in the
22:41area using these receptors. As they swim around, they're able to feel the pulses that can come back
22:46to them and see if they're moving in the right direction. As quirky as the appearance of the platypus,
22:52the sixth sense contained in its bill is what this animal owes its current success to.
22:57If you're underwater, you're not as exposed, you're in murky water,
23:00and you have that ability to detect prey in that murky water, you're at a pretty big advantage right now.
23:05We don't, as humans, have any direct sensors of electricity. It's just not part of our sensory
23:11system to detect electrical fields particularly strongly. Platypuses, on the other hand, are sensitive
23:17enough to pick up the tiny electrical impulses in their prey. So it's an extremely sensitive
23:24instrument that really is very far outside of the human understanding of electricity.
23:29Studying platypus's superpower could give us clues to advanced sixth sense technology,
23:35such as collision avoidance in vehicles or virtual worlds in video games.
23:40Our bodies don't know how to interpret direct electrical signals and there's no natural pathway for that.
23:48So it's very hard to build a brain machine interface. So there's a lot of research going
23:55into how to make those connections work because if I want a biomechanical limb to replace a severed hand,
24:03I need to be able to interpret the signals coming from the brain and cause the digits to move.
24:09The platypus inspires designers for having figured this out. One of the Earth's greatest survivors,
24:15some fossils suggest that this unorthodox little creature has been around for 110 million years.
24:21It is thought to be the last remaining member of the Ornithorhynchidae family,
24:25the earliest offshoot of the mammalian lineage. Yet we didn't begin to understand the secrets of its
24:30success until the 1990s. This is why it's really important as a human species to maintain diversity in
24:38systems is to protect animals around the world because you never know what a researcher or what
24:44a scientist or what somebody will discover, you know, about a particular animal that might have
24:49a human application. These animals have honed in on these skills to survive and so if we're able to
24:56harness those sort of honed in tools to use for ourselves, now we're talking.
25:02While we might never have thought to do something so bizarre with our noses as the platypus does,
25:07many of us have imagined being able to see in the infrared spectrum. The advances we've made in
25:12infrared camera technology in the past few decades have been impressive, but what if we had this built
25:17right into our biology? Again, this might sound like science fiction for us, but for the pit viper,
25:24after millions of years of evolution, it takes infrared vision for granted. It really kind of puts
25:29the pit viper on a on the same level as a character like the predator. It's a perfect
25:35machine in terms of how it is able to detect its prey. It's sleek, it's quiet. The pit viper,
25:42including rattlesnakes and lance heads, are a group of 151 snakes whose habitat ranges from deserts
25:49to rainforests. They are apex predators who prefer warm-blooded prey and who prefer to hunt at night.
25:55You're looking at a warm body on a relatively cool background. The contrast is huge. You're really
26:03going to be able to see it and figure out where it is, especially at night. The optical spectrum,
26:09the spectrum we use to see, you can almost see nothing. But in the infrared range, you have a vast
26:15amount of information. So if you have an exotherm, an animal that is producing heat as part of its
26:21biology, all of a sudden that heat becomes apparent because it's emitting infrared energy. Infrared light
26:28is an electromagnetic radiation with wavelengths longer than those of visible light. Therefore,
26:33it is generally not visible to the human eye. What gives this snake its infrared vision is the
26:39incredible organ it is named after, the pit organ. The snake has two of these, which are essentially
26:45cavities on either side of its head, about one millimeter wide. So this pit organ sits below
26:51their eyes, just above the nostrils, and essentially it has a membrane that has more than 1600 receptor
26:57cells. These cells are attached to the endings of nerves. These nerve cells are what send the snake's
27:03brain signals about its prey's temperature. Thermal cameras have microbillometers that are able to
27:10assign a color for each pixel that they recognize based on its temperature. And it's similar to the way
27:15that the pit organs of the pit vipers are connected to their somatosensory organ system,
27:21which relates to touch, pain, and temperature. So once heat is detected, it activates and then
27:28sends signals to the brain where they can then interpret that heat signal. So the more sensory cells
27:34you have along that membrane, the more accurate the picture is, even the distance of their prey. They can
27:39sense animals, probably about a meter away. I mean, that's like, that's such a helpful thing for a
27:45viper who's, who's hunting at night. One only has to look at the potential predators the pit viper faces
27:51to see how heat sensing has helped it survive and thrive. But how detailed a picture can the pit viper
27:57conjure? It's quite blurry. So what's important is they look at the edges of that object that they're looking
28:03at of where the heat is being emitted from. And that's how they can actually target where to aim for.
28:09When it goes to look for the mouse, with the, the pinhole, it basically gives it a more pointed
28:15direction. No heat, no heat, no heat, heat. I want to go this way. So it kind of acts as,
28:21as a focusing
28:22mechanism. The fact that the heat image lacks dimensional and spatial detail would make this
28:27trait less of an advantage if the pit viper were not already such a finely tuned predator without it.
28:33It already has good sight and hearing and when it strikes, it does so with extreme velocity.
28:39Africa's puff adder can strike in a quarter of a second. It's, it's super fast. It's lightning fast
28:44almost. They have to do it that fast because they're ambush predators. Those oftentimes just sit and
28:49waiting, wait till an animal passes by or prey passes by and they'll come out and they'll strike,
28:54putting their fangs, long fangs into them. They can actually open their mouths 180 degrees and just sort
29:00of open it to the point where it almost looks like it's dislocated and just bring in that prey.
29:06Being that they're venomous, they have solenoglyphous fangs. These types of fangs are the ones that can
29:13retract and fold over the roof of their mouth. And because it can fold over, this group of snakes can
29:19have the longest fangs in the world. And because of this, they have an excellent delivery of venom.
29:24Crowning all its other adaptations, the pit organ is like the trump card in this animal's exquisite
29:30predatory equipment. And while other animals possess infrared vision to some degree, the pit viper is
29:36the ultimate when it comes to this sixth sense. Recently, research in the Messel fossil pit in
29:41Germany turned up a fascinating discovery on the pit organ's evolution. It was found in snakes that
29:46preyed only on cold-blooded animals like crocodiles and lizards rather than warm-blooded rodents which were
29:52less abundant. The pit organs in these ancient snakes were less pronounced.
29:56A long time ago, they targeted cold-blooded animals. But as they began to eat more warm-blooded
30:01animals, that's when this feature became more useful because they were able to detect it better in
30:06their environment. It suggests that the organ evolved as a response to the increased availability of warm-blooded
30:13prey. The animal kingdom has taken advantage of so many different physical phenomena. And this is just
30:20yet another one looking in the infrared range because it gives such an advantage to those snakes.
30:26You can't ask for a better predator than that. I mean, it's successful for a reason.
30:31Infrared cameras give us a reference for what the pit viper might be up to. But another animal stalking the
30:36northern hemisphere uses an extra sense that we humans can hardly wrap our heads around. The red fox. A
30:43solitary expert hunter. And it has to be. The northern hemisphere where the fox resides is home
30:48to abundant prey. But these animals are quite fast and agile themselves. The fox makes use of hyper
30:55acute senses to track and kill prey. From extremely sensitive ears to eyes that see at night, the fox is
31:01well equipped. But it also has one unique skill that we can't even perceive. It can sense the earth's
31:08magnetic field. When you look at how it hunts using sound and magnetic field as a combination to
31:16triangulate an actual location of a small rodent. But it's an ultra efficient predator. The fact they
31:23create a map other than their own visual system, almost like an additional feature, like wearing like
31:28a set of another magnetic goggles, but it's just ingrained in them, is what makes them such excellent
31:34hunters. But how does this extraordinary sense work? How can a creature use a force such as a magnetic
31:40field? Biology blows my mind, but being able to to use a sense that's so far out of our perception
31:48is just amazing to me. I can hear echolocation. So I have a perception of what a bat's doing using
31:55echolocation because I kind of have a sense of that. But with respect to the fox, I have no perception
32:01of
32:02what the earth's magnetic field looks like. And the fox very well may have. While we have long
32:07understood the fox's evolutionary advantages in hearing as well as vision to help it hunt,
32:12it was only in 2010 that scientists realized there may be something else at play. Observing red foxes
32:19as they hunted rodents under the snow or hidden in long grass, scientists noticed that their success rate
32:25improved drastically when the fox was facing a northeast direction. Attacking from this angle,
32:31foxes were successful 75 percent of the time versus a hit rate of only about 20 percent from other
32:37directions. This was the case regardless of time of day, season, cloud cover or wind direction.
32:43I mean that is just unreal to understand how these animals learn that behavior just by saying,
32:50okay here's magnetic north, you know, how do you understand that? That's it's an algorithm that works
32:55almost subconsciously that allows this animal to just boom, just pop on that prey.
33:01The fox may be using a geomagnetic sense. As the fox creeps towards the rodent sound in the distance,
33:08it waits for that sweet spot where the angle of the sound hitting its ears lines up with the slope
33:13of
33:13the earth's magnetic field. At that point, the fox knows it is a fixed distance away from its prey,
33:19and it knows exactly how far it needs to pounce. It's really quite amazing to see how high they can
33:24pounce. Sensing the earth's magnetic field is called magnetoreception. Although we know that other
33:30animals use this for navigation, such as migratory birds, the red fox is the first animal known to use
33:36magnetoreception to hunt. A lot of people don't even think of the earth's magnetic fields. The fact that
33:42these animals are able to use that to their advantage must have evolved from millions of years. The secret is
33:48thought to be in cryptochromes, proteins in the fox's retina. Cryptochromes are very old in
33:54evolutionary terms. They exist in all kingdoms of life, including humans. Sensitive to blue light,
34:00these proteins sit on the retina and help mediate circadian rhythms. Cryptochromes are essentially
34:06photoreceptors that, for humans, it tells us when to wake up and when to go to sleep. But for foxes,
34:13it actually has a different meaning. Recent science suggests that cryptochromes also have a
34:18sensitivity to the earth's magnetic field. It's possible that, thanks to cryptochromes,
34:23foxes may actually see the magnetic gnaw as a shadowy ring, much like how we think birds see the
34:29shadowy ring as they navigate. For foxes, this additional sense would act like a rangefinder,
34:34making their blind jumps more accurate. The magnetic field is telling me, as a fox,
34:40what's my angle to the object? How am I oriented with respect to it? How am I going to come
34:47down
34:47exactly where I need to come down? So the senses as a whole are building a brain map of where
34:55that
34:55creature is and how I'm going to get to that creature to make sure I'm landing directly on it.
35:00You can see how useful it would be because they need to do this really minute mapping out of how
35:07far away creatures are. And because they are pounce hunters, they have to be incredibly accurate. And
35:13if they're off by a millimeter, well, then they were completely unsuccessful and they have to try again.
35:17What's even more astounding about the fox's ability to sense the earth's magnetism is that
35:22it's based on something that is always in flux. The earth's magnetic field changes continuously. It flips
35:28every so often, and the angle is constantly shifting. So it's amazing that these creatures,
35:33birds, red foxes, have created abilities around this continuously shifting baseline because they have
35:40to shift how they use that sense continuously as well. This isn't something that's foreign to
35:46engineers and scientists. We do use it. Prior to the advent of GPS satellites, we use autopilot that
35:54follow the earth's magnetic field. Most cars that you buy nowadays have a built-in compass that will
35:59tell you where north, south, east, west is. We can probably tell you where on the earth you are and
36:04your angular relationship to the surface, but we're not going to be able to have that triangulation
36:11capability that the fox has. Of course, our increased reliance on GPS technology suggests we would not
36:16trade in our cell phones for magnetic intuition. But it's fascinating to think we may have an additional
36:22super sense that we're not even aware of. As for the red fox, magnetoreception could be what gives
36:27it its evolutionary edge. Far from being at risk as a species, it is one of the most widely distributed
36:33carnivores on earth. And more than likely, its super sense is part of that success. While the red fox
36:39uses the magnetic field to find food, it is thought that another incredible creature uses magnetoreception
36:45to find home. In 2019, scientists at the California Institute of Technology made a startling discovery.
36:53They found that humans may be able to sense the earth's magnetic field via tiny crystals of iron
36:58in their brains. This opens up vast possibilities, the most impressive of which may be far from any
37:05high-tech labs swimming in the oceans. The sea turtle is one of those iconic species that everybody
37:11loves. It's when you see them in person, you are mesmerized. And I've human-dived with them many times.
37:17You just get this sense of wonder and awe when you see them. Sea turtles are an ancient species.
37:24They've been around for about 110 million years since the time of the dinosaurs, which is even more
37:30incredible, given that fewer than 0.1% of every sea turtle hatchling survives. You have 200 to 400
37:37hatchlings, and only one or two will survive to adulthood. You just look at how treacherous that
37:43life cycle is from hatchling to adulthood. From the moment its egg is laid, this life form
37:49must fend for itself. The mother's sea turtle will actually dig out a hole, lay her eggs, and then
37:55go back out to sea, never to see the hatchlings again. There are many reasons for the high death
38:00rate of her progeny. They're small, and they're vulnerable. They have no real way to fight off
38:05any type of predator. Immediately upon hatching, the turtles follow the moonlight into the safer
38:10waters out at sea. But because their shells are soft at first, they remain vulnerable to sea
38:15predators as well. However, if it can make it to harder-shelled adulthood, the sea turtle can live
38:21longer than we can. Turtles can live 70 to 100 years depending on the chances that they have in life.
38:27Today, largely due to human impact, six of the seven sea turtle species are endangered or face
38:34extinction. But in evolutionary time, this is a highly successful survivor. And the key to its success?
38:40A navigational wizardry that is based on sensing the Earth's magnetism.
38:45Sea turtles, they're able to migrate back to within feet of where they were born, which is
38:51absolutely astonishing to me. If I had that sense as a human, I would never get lost.
38:56Sea turtles seem to know exactly where they're going from the moment they're born. At birth,
39:01they head into the ocean where they can grow up in relative safety. Then, when they reach sexual
39:06maturity at about 10 to 15 years old, the females return to the beaches they were born on to lay
39:11eggs,
39:12then immediately go back to the sea, only to return to the same beach for egg laying every year thereafter.
39:18They go out as tiny little sea turtles. They leave this beach not much bigger than a hockey puck. They
39:24don't come back until they're mature adults to lay eggs for the first time. So they've gone,
39:28you know, if we're talking something about a leatherback, something that's, you know, a couple
39:32inches in diameter, to something that's almost car size. They haven't been back to that beach or even to
39:39that area possibly for decades. So this is a really amazing feat. It's not, it's not just that getting
39:46back is amazing. It's amazing that for such a long period, they can maintain a memory of this point on
39:54the earth. Considering the vast distances of ocean the turtle travels and depths at which it swims,
40:00it is inconceivable that it could solely be relying on such cues as landmarks or current changes or even
40:06stars. In February 2020, we saw a sea turtle go from Australia to Angola and back. You know,
40:1222,000 kilometer trip. And it's just amazing how far these animals can travel. So how do they pull off
40:18such staggering feats of navigation? They seem to be a swimming, breathing compass, constantly reacting
40:24and referring to the earth's magnetism. Sea turtles are believed to rely on these magnetic signatures
40:29that is ingrained in them when they're born. It's believed that they have the magnetoreception
40:35that allows them to use the earth's magnetic fields to know the direction where they're heading to.
40:40The concept of magnetoreception, or being able to sense the earth's magnetic field,
40:46is twofold. First, there is the source. The earth is a giant magnet. The iron core of the earth rotates,
40:54giving rise to our magnetic field. That magnetism is pervasive. It doesn't matter whether I'm standing
41:00on the surface of the planet or 50 feet underwater. Every location on earth has its own magnetic signature
41:07that is as accurate as a GPS coordinate. As well as the source of electromagnetism, there is the means
41:13of detecting that source. In other animals known to be magnetoreceptive, such as the red fox and some
41:19migratory birds, the means of detection seems to be by way of cryptochrome proteins on their retinas.
41:25But these require a lot of light, which is not always available to the deep swimming sea turtle.
41:31Rather, it is thought that the turtle senses the earth's magnetism via crystals of magnetite in its
41:36receptor cells. Magnetite is a mineral form of iron and is the most magnetic of earth's naturally occurring
41:43minerals. Magnetite crystals can be found at the cellular level of different animals, but because
41:50magnetic fields can be detected just like by passing through us, it's hard to pinpoint exactly where in
41:55that body those crystals can be found. Given that the research on humans at Caltech suggested magnetite
42:01response in the brain, it's possible that this is where the receptors are in the sea turtle, only they're
42:07much more effectively used in them than in us. Essentially, the turtles have GPS-type precision.
42:14As they orient towards the magnetic field, the magnetic crystals could either repel or attract one
42:19another, creating tiny forces that could be picked up by proteins, which in turn send signals to the brain
42:26about where to go. They line up when they're kind of like in a positive area, and then they don't
42:31line up
42:32when they're in a negative area, showing that it's not the right area to be in. That is absolutely amazing.
42:38Part of what's so mind-blowing to us as humans is that although we know the magnetic field to exist,
42:43we never actually sense it. Although it sounds fantastical, scientists have already observed
42:48navigation by way of magnetite response in bacteria, salmon, and trout. But sea turtles are the
42:54superhero of this power, especially as they seem to be born with some magnetic maps already programmed.
42:59There's probably some type of genetic memory there, as well as physical memory, and it's somehow
43:05combined. And as humans, we don't have a genetic memory that we're conscious of. It's all learned.
43:12But a lot of animals do have these genetic drives to do certain things and behave in certain ways,
43:19and the magnetic sense of the sea turtle is one of those that drives their lifespan in terms of their
43:26migrations. Part of the sea turtle's leading edge, of course, is its wise old age as a species.
43:31One of the amazing things about biology is it's been able to use so many of the different physical
43:39properties of our universe to its advantage, and one of them is using the Earth's magnetic field.
43:45Meanwhile, until we can find ways to tap into our cellular magnetite, we'll be stuck with our conventional,
43:51less perfect navigational tools. Historically, navigation via compass isn't particularly accurate.
43:58Compasses are somewhat determined by the local magnetic field, so generally points north,
44:04but if you want to go five degrees south of east, it's really hard to continuously judge that direction.
44:11I can't set a heading from England and hit a specific beach in Jamaica. I mean, this is some really
44:18serious underlying basic physics that goes into being able to tell you where on the surface of the
44:25Earth you are within a few meters. But somehow, this turtle's evolved with the same capability. It's astounding.
44:32And it is yet one more of the animal kingdom's extrasensory phenomena that pushes our human imagination.
44:38Whether the magnetoreception of the sea turtle or the red fox, or the flabbergasting bill sense of the
44:44platypus, nature has engineered additional senses sensitivities in many animals that are just outside of
44:50our comprehension. But despite being out of our grasp, as these traits provide inspiration for our own
44:56machines, devices, and technologies, they also continuously advance and improve our lives as human beings.
45:10So
45:31if you see a group of people who are interested in the world, who are interested in the world,
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