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(upbeat music)
(bird calls)

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(tiger growls)

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(insects chirp)

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(wind whistles)

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Anyone fascinated by the natural world

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has probably wondered why some animals

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have such strange-looking sense organs.

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(insects chirp)

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(elephant rumbles)

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The elephant with its

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huge ears,
(elephant trumpets)

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the antennae of a butterfly,

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which up-close look like feathers,

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the snake with its
(snake hisses)

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split tongue.

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And what about less obvious enhancements,

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like the sensory cells on a crocodile's skin?

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Surely these evolutionary traits aren't just for decoration.

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(suspenseful music)

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In fact, the size, shape, and location

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of these animal sense organs is all for a purpose

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and just like us, animals rely on their senses

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to communicate with each other, find their way around,

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stay safe,
(wolf howls)

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and most importantly, to find food.

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When you see how superior some animal senses are

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compared to those of humans,

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you might wonder how we ever managed

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to stay on top of the food chain.

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"Animal Super Senses."

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You won't believe what's possible.

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(gentle music)

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(dramatic music)

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(birds calls)
Welcome to

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"Animal Super Senses,"

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the show that plugs you in

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to how animals experience the world,

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often with sharper and more-evolved senses

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than the one species who likes to think of itself

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as the top of the food chain.

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(dramatic music)

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That would be us, of course.

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(dramatic music continues)

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While all life began in the oceans,

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(water rushes)
(whale splashes)

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human beings now rely on technology

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to navigate the seven seas.

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Left to our own devices,

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(dramatic music)

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we're like the proverbial fish out of water,

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only the other way around.

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Once underwater, with light diminished,

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our vision becomes blurred.

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Our hearing becomes muffled and distorted,

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and our sense of smell is rendered completely useless.

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(upbeat music)

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Now compare that, for example, to that renowned predator,

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the great white shark.

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(suspenseful music)

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This elegant killing machine is perfectly attuned

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to every sight, sound, scent,

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chemical and electrical signal

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of its marine environment.

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(suspenseful music)

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We'll pay a slightly nervous visit to the great white

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a little later in the episode.

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(suspenseful music)

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But first, listening carefully?

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Because the sense of hearing enters a whole nother dimension

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when applied to

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creatures of the deep.
(whale sings)

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Hearing is critical for animals

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such as the sperm or humpback whale.

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(whale sings)

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(whale splashes)

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For one thing, light fractures and weakens underwater,

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so vision becomes a less important tool for survival.

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(whales sing)
(water ripples)

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Sound, however, travels further in the water

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than in the air.

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So for whales, it's critically important

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as a way of communicating,

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most famously as in the song of the humpback whale.

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(whales sing)
(water ripples)

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Humpback whales are members of the cetacean family

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which includes whales, dolphins, and porpoises,

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all of which have well-developed senses of hearing.

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(dolphin clicks)

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(upbeat music)

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(water rushes and ripples)

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In the case of this humpback whale,

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its outer ears have very small opening

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that closes once under water.

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Instead it picks up on waterborne vibrations

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through bones in its head,

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good vibrations that ultimately reach

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its middle and inner ears.

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(upbeat music)

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(electronic beeping)

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(sonar beeps)

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Fascinatingly, the ancestors of the whale

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actually walked on land.

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Pakicetidae or Pakistani whales

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lived on the shores of the Indian sub-continent

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and began to diversify,

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making for the water some 53 million years ago,

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give or take.

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More about them and their ancestors later in the show.

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(water ripples)
(whales sing)

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Meanwhile, to be a little bit more specific

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about what hearing is,

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(whales sing)

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it's the ability to sense sonic vibrations, sound,

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and what is known as vibrational stimuli.

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They pretty much amount to the same thing underwater.

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The scene now is the Coral Triangle.

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This is the area of tropical marine waters

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around Malaysia, the Philippines, Indonesia, and East Timor,

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a tropical paradise in many regards

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sometimes known as the Amazon of the seas,

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(gentle music)

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(waves whoosh)

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(water ripples)

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(gentle music)

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but one that the World Wildlife Foundation

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is keeping a close eye on

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to ensure human activity

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doesn't spoil this particular paradise too.

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(gentle music)

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Among the countless species

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that call the Coral Triangle home,

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you'll find plenty of cephalopods.

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Plenty of what?

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Cephalopods, like cuttlefish and this octopus,

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are invertebrate, spineless mollusks

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with generally large heads and symmetrical bodies.

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(gentle music)

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For over a century, there's been a debate

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as to whether these creatures are capable of hearing.

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(gentle music)

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But the consensus seems now to be that they can,

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either by something called the statocyst organ,

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a fluid-filled sac lined with sensory hairs

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that also helps them to maintain balance,

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or they can hear via lateral lines

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similar to that found in fish,

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visible lines on the fish's body

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comprised of sense organs

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which detect pressures and vibrations.

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(gentle music)

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(water ripples)

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Now, of course, there are more fish

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than you can shake a million fish sticks at

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in the Coral Triangle.

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And chances are, they'd hear you

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when you shook those sticks at them

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because as any goldfish owner can tell you,

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at any kind of threatening sound

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a fish will curl into a tight C shape

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and head in the opposite direction.

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(water ripples)

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So whether in a goldfish bowl or the Coral Triangle,

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we know that fish can hear,

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but believe it or not,

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scientists are somewhat divided as to how.

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(water ripples)

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Here are the two main theories.

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The bodies of fish have about the same density as water,

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which means that sound passes through their bodies.

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But fish have bones in their inner ear

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which are called otoliths.

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These bones are denser

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than both the water and the fish's body.

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This means these bones move at a slower pace

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than the rest of the fish's body

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and also the speed of the sound waves.

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(water ripples)

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The upshot of this is that the difference in speed

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between the otolith bones and the rest of the fish's body

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ruffles the hairy sensor cells located in its inner ear.

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This differential movement

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is interrupted by the brain as sound.

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(percussive music)

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Then there are the lateral lines we mentioned before.

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These are essentially a set of tubes

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located just under the fish's,

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or in this case, the shark's body.

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Water enters these tubes through the pores of the skin.

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The tubes are lined with hair cells

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which are connected in turn to sensory nerves.

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(percussive music ends)

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When anything gets close to a shark,

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the water running through the lateral lines

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moves to and fro.

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(eerie music)

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(dramatic chord)

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This stimulates the sensory cells,

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which alerts the animal to whatever prey or predators

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may be in the vicinity.

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(dramatic music)

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(water splashes)

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(dramatic music)

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(water ripples)

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When we talk about animal super senses,

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perhaps no animal fits the bill more than the shark.

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In the popular imagination,

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we imagine them like this blacktip shark

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moving stealthily through the water

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and then seizing their prey without mercy,

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relentless and unstoppable.

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(dramatic music)

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And that's about the size of it.

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(dramatic music)

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Their senses are also supremely well adjusted

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to make them effective underwater predators.

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For one thing, they have

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a particularly acute sense of smell.

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Unlike for example, human beings,

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sharks have separate and distinct openings

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for breathing and for smelling.

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The gills on the side of their heads

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are for breathing only

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and serve to capture oxygen in the water.

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(dramatic music)

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(water ripples)

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Meanwhile, two nostrils to the front of their heads

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pull water into a nasal chamber,

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specifically dedicated to detecting smells.

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Perhaps one reason a shark's nose works so well

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is because it doesn't have to do anything else.

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Breathing is accomplished with their gills.

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And a shark's sense of smell

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is not in any way connected to its mouth.

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(dramatic music)

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But a shark's sensory arsenal doesn't end there.

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Sharks come with a unique sense organ as standard equipment,

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something called the of ampullae of Lorenzini.

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They were first described back in the 17th century

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by one Stefano Lorenzini.

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They consist of small clusters

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of electrically sensitive receptor cells

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found just under the skin.

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These are connected to the water

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by pores on the shark's snout and head.

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(dramatic music)

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What the ampullae of Lorenzini do for the shark

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is to outfit it with electro-reception.

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In a nutshell, electro-reception means

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the shark can sense the bioelectric fields

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generated by other animals

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and use it to locate them.

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(dramatic music)

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And hey, you'd expect the ultimate predator

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to know where its next meal is coming from, right?

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(dramatic music)

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Blacktip sharks like these

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share the waters of the Coral Triangle

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with a cetacean known for its hearty appetite,

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the sperm whale.

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(whale breathes)

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(gentle music)

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And also with the sperm whale's distant cousin,

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the dolphin, a marine mammal

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who's no slouch in the appetite department either.

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They may be enthusiastic eaters,

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but they don't exactly enjoy their food

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in any way we might understand.

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(water ripples)

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You see, just about all vertebrates

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enjoy five primary tastes:

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sweet, salty, sour, bitter, and umami,

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except, that is, for cetaceans such as dolphins and whales.

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(gentle music)

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(water ripples)

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(whale splashes)

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New research has revealed,

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at some point in their evolutionary journey,

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they lost the ability to perceive anything but salt.

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(gentle music)

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Scientists believe this took place

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between 53 million years ago,

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at the point when whale ancestors, pakicetidae,

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took to the seas,

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and 36 million years ago,

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when they split into two groups,

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toothed and baleen whales.

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(whale breathes)

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Then again, if you swallow your food instead of chewing it,

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perhaps not having a sense of taste isn't such a great loss.

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(gentle music)

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00:14:54,748 --> 00:14:58,209
(water ripples)

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(whale splashes)

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(birds call)

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What about underwater vision?

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All you need to do is hold your head underwater

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for a few seconds,

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and you'll see that our eyes are not adapted

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for vision underwater.

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No, they've evolved for viewing in air.

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Everything is a blur underwater, right?

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That's because light rays bend

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00:15:28,802 --> 00:15:30,960
when they travel from one medium to another,

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from air to water.

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Water refracts light at roughly the same degree

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as the cornea of the human eye,

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which effectively eliminates our ability to focus.

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(water ripples)

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(gentle music)

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Fish eyes are more spherical in shape,

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allowing them to focus under the waves.

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In many cases, they're also sensitive

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to a larger range of the color spectrum,

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including ultraviolet light.

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As light passes through deeper and deeper waters,

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more color is absorbed and diluted.

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00:16:03,138 --> 00:16:05,721
(gentle music)

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The water filters out the color red at first,

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then yellow, then green, and then violet.

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The color blue is the last to go.

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And yet as recent studies show,

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ultraviolet light penetrates far deeper into the water

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than used to be thought.

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(water ripples)

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Could this be the reason why

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so many fish are so very colorful,

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that while their colors might, to the human eye,

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be muted by the ocean depths,

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to a fish with ultraviolet sight,

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these creatures still stand out as bright and beautiful.

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(upbeat music)

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The answer appears to be yes, in some cases.

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Many coral reef fish, for example, are brightly hued,

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coming in a dazzling array of colors.

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00:16:55,890 --> 00:16:58,473
(gentle music)

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00:17:00,172 --> 00:17:04,372
The harlequin tuskfish, mandarin fish,

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00:17:04,372 --> 00:17:09,372
coral trout, regal angelfish, and stoplight parrotfish

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all spring to mind.

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(gentle music)

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Scientists believe that

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some fish use their brightly colored skins

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00:17:18,262 --> 00:17:19,872
to attract a mate,

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00:17:19,872 --> 00:17:22,422
but as with so much in nature,

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it's more complicated than that,

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(gentle music)

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for color is also employed by some fish

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as a warning system, a warning to back off and stay away.

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00:17:42,202 --> 00:17:43,982
Lionfish, for example,

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00:17:43,982 --> 00:17:46,322
are thought to utilize their brightly colored bodies

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to communicate to other animals

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that it's best to stay away from them

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and more specially, their highly venomous spines.

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(water ripples)

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Then again, there are instances

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when fish like to blend in with their surroundings.

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Literally it's called cryptic coloring

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and it enables some species of fish

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to camouflage themselves.

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(suspenseful music)

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00:18:18,342 --> 00:18:19,962
(water ripples)

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A predator like the great white shark

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might seem like the last customer

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who would need to hide itself away.

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00:18:26,149 --> 00:18:28,792
(suspenseful music)

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00:18:28,792 --> 00:18:32,832
But the great white, along with many other open sea fish,

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00:18:32,832 --> 00:18:35,182
uses counter shading to camouflage itself

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on a regular basis.

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00:18:36,604 --> 00:18:39,604
(suspenseful music)

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(water ripples)

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But one of the strangest and most effective

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underwater senses is known as echolocation.

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(dramatic music)

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This is very much what it sounds like, in a way,

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being able to locate something because of its echo.

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(water ripples)

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It's also known as sonar,

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which humans have studied and replicated,

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for example, for use in submarines in naval warfare.

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This is a system for detecting objects underwater

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00:19:10,272 --> 00:19:11,899
by emitting a sound pulse,

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00:19:11,899 --> 00:19:15,592
(dolphin clicks and squeaks)

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00:19:15,592 --> 00:19:19,216
and then being able to detect and measure it upon its return

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00:19:19,216 --> 00:19:23,744
to find out where something is, its size, and so on.

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(upbeat music)

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Call it seeing with sound,

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because in effect that's what it is.

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(sonar beeps)

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Dolphins use echolocation all the time.

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(upbeat music)

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Like all toothed whales,

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dolphins have specialized fat located in their jaws

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which conveys sound waves from the ocean to their ears.

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00:19:45,666 --> 00:19:48,067
(dolphin clicks)

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00:19:48,067 --> 00:19:50,442
(upbeat music)

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They use echolocation to crater feed,

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meaning to find prey underneath the sand,

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because unlike other senses,

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echolocation can penetrate or see through solid matter.

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(dolphins squeak and click)

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It's a primary sense for dolphins

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and other species of toothed whales.

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That's right, a dolphin is also a type of whale,

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00:20:12,432 --> 00:20:15,152
a type of toothed whale to be precise.

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00:20:15,152 --> 00:20:18,161
(dolphin clicks)

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00:20:18,161 --> 00:20:20,412
Other varieties of toothed whales

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include sperm whales, killer whales, and beaked whales.

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All of these creatures use sonar or echolocation

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00:20:27,742 --> 00:20:29,562
to guide them through the oceans,

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00:20:29,562 --> 00:20:32,125
to communicate, and to detect prey.

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00:20:34,547 --> 00:20:37,852
(water rushes)

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As you'll recall, the distant,

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00:20:40,452 --> 00:20:42,122
50-million-years-plus distant,

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00:20:42,122 --> 00:20:45,902
ancestors of whales were actually land dwelling-mammals,

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00:20:45,902 --> 00:20:48,942
who probably saw things quite well in the open air.

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00:20:48,942 --> 00:20:52,930
Echolocation helped them adapt to life underwater.

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00:20:52,930 --> 00:20:56,288
(water rushes)

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00:20:56,288 --> 00:20:58,871
(gentle music)

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00:20:59,902 --> 00:21:01,992
Navigating the open ocean

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00:21:01,992 --> 00:21:04,512
with its shifty currents and expansive water,

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for most animals is no easy feat.

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00:21:08,552 --> 00:21:11,585
But sea turtles have to face up to the challenge.

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00:21:12,522 --> 00:21:14,582
There are seven species of sea turtles

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00:21:14,582 --> 00:21:16,975
found in the oceans all around the world.

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They spend their first few years

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00:21:19,722 --> 00:21:21,322
floating in the open sea

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00:21:21,322 --> 00:21:24,358
where they feast on jellyfish and other creatures.

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00:21:24,358 --> 00:21:26,941
(gentle music)

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00:21:31,242 --> 00:21:33,582
But at some point they need to find their way

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00:21:33,582 --> 00:21:35,700
to the beach to breed.

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00:21:35,700 --> 00:21:38,392
(water ripples)

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00:21:38,392 --> 00:21:41,232
And it's not just any beach.

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00:21:41,232 --> 00:21:45,055
They return to the one they were born on.

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00:21:45,055 --> 00:21:47,638
(waves whoosh)

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00:21:50,212 --> 00:21:53,702
How they actually do this is still being debated,

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00:21:53,702 --> 00:21:55,042
but it's thought they may use

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00:21:55,042 --> 00:21:56,892
the earth's magnetic field as a cue

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00:21:56,892 --> 00:22:01,019
and perhaps their sense of smell plays a role as well.

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00:22:01,019 --> 00:22:03,602
(water rushes)

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00:22:04,462 --> 00:22:07,202
On this stretch of South American shoreline,

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00:22:07,202 --> 00:22:10,625
an olive ridley turtle clambers slowly up the beach.

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00:22:12,002 --> 00:22:16,127
This female adult is about to lay a clutch of eggs.

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00:22:16,127 --> 00:22:18,680
(upbeat music)

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00:22:18,680 --> 00:22:21,097
(birds call)

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00:22:24,146 --> 00:22:25,232
(eggs plop)

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00:22:25,232 --> 00:22:30,052
Over 100 eggs can be deposited in a nest at any one time.

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00:22:30,052 --> 00:22:33,176
(flippers scrape sand)

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00:22:33,176 --> 00:22:34,885
(upbeat music)

447
00:22:34,885 --> 00:22:37,218
(eggs plop)

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00:22:39,242 --> 00:22:40,792
Once the eggs are buried,

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00:22:40,792 --> 00:22:42,785
the adult returns to the water.

450
00:22:46,005 --> 00:22:47,552
(birds call)

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00:22:47,552 --> 00:22:50,308
After incubating for over 45 days,

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00:22:50,308 --> 00:22:54,619
hatchlings emerge to begin a perilous journey.

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00:22:54,619 --> 00:22:57,612
(birds call)

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00:22:57,612 --> 00:22:59,675
They race to the water's edge,

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00:23:00,832 --> 00:23:04,388
but vultures with a taste for turtle are patrolling.

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00:23:04,388 --> 00:23:07,055
(turtle chirps)

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00:23:09,883 --> 00:23:12,466
(birds mutter)

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00:23:14,332 --> 00:23:17,876
And even when they reach the sea, it's still not safe.

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00:23:17,876 --> 00:23:20,132
(birds call)

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00:23:20,132 --> 00:23:22,052
Few hatchlings make it to the feeding grounds

461
00:23:22,052 --> 00:23:23,692
in the open ocean.

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00:23:23,692 --> 00:23:25,352
It could be why the olive ridleys

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00:23:25,352 --> 00:23:27,411
have a remarkable nesting strategy.

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00:23:27,411 --> 00:23:28,882
(water ripples)

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00:23:28,882 --> 00:23:31,322
In a spectacular mass nesting get together

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00:23:31,322 --> 00:23:33,062
known as an arribada,

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00:23:33,062 --> 00:23:37,207
thousands of females come ashore simultaneously to lay eggs.

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00:23:37,207 --> 00:23:39,790
(waves whoosh)

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00:23:40,862 --> 00:23:44,282
How the females know the time is right is unknown.

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00:23:44,282 --> 00:23:47,242
They may release a scent that cues the start,

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00:23:47,242 --> 00:23:49,392
but with no conclusive answer,

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00:23:49,392 --> 00:23:54,392
the arribada continues to be one of nature's great secrets.

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00:23:54,419 --> 00:23:57,169
(dramatic music)

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00:24:01,842 --> 00:24:03,722
On "Animal Super Senses,"

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00:24:03,722 --> 00:24:05,162
we've taken you from the surface

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00:24:05,162 --> 00:24:06,992
to the depths of the seven seas

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00:24:06,992 --> 00:24:09,212
to seek out the treasures below,

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00:24:09,212 --> 00:24:11,962
from the tiny colorful fish of the coral reef

479
00:24:11,962 --> 00:24:13,902
to the mighty sperm whale.

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00:24:13,902 --> 00:24:15,832
We've explored how these creatures

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00:24:15,832 --> 00:24:19,385
hear the vast beauty of the ocean world.

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00:24:20,342 --> 00:24:23,132
It could make you wonder why our ancestors

483
00:24:23,132 --> 00:24:26,642
ever came out of the water in the first place.

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00:24:26,642 --> 00:24:29,552
Just be sure we'll come to our senses again,

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00:24:29,552 --> 00:24:32,675
next time on "Animal Super Senses."

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00:24:32,675 --> 00:24:35,425
(dramatic music)

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00:24:47,527 --> 00:24:50,194
(water ripples)

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00:24:54,802 --> 00:24:57,719
(dolphin splashes)

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00:25:00,886 --> 00:25:03,469
(waves whoosh)

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00:25:07,943 --> 00:25:10,693
(dramatic music)