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(insects chirring)

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(wind whooshing)

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As calm as the natural world appears to be,

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it's home to some of the craziest

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and most interesting sounds, from the choruses of cicadas

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and frogs during courtship to the loudest call on land,

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underwater songs, flying calls,

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and the noisiest, most evolved adaptations on Earth.

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Discover with us how and why

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different species use the power of sound.

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(dramatic music)

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Animal alerts.

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The North American prairie.

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Large animals like the bison can see predators approaching

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in the tall glasses of the great plains.

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But for the little ones like this prairie dog,

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tall grass is not the best option.

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Mowing the lawn is an everyday task

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that helps these mid-sized rodents

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maintain a watchful eye on the colony.

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But a short lawn alone is not enough for safety.

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And these little fellas have another strategy.

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(prairies dogs chirping)

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Often called the architect of the prairies,

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prairie dogs form colonies of millions of individuals

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who excavate the plains with their burrows.

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These burrows become home to most species in the prairies.

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Communication is key to efficient colonial living.

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This is why prairie dogs have developed

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a wide repertoire of vocalizations,

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from territorial calls that let know

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other individuals they are at the wrong place

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to barely audible chirps between mothers and babies.

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(uneasy music)

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One call snaps everyone to attention.

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It warns: predator in the neighborhood.

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(yipping)

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The entire colony runs to the burrows for protection.

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The sharp, repetitive bark echoes across the area

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to assure that all the clan members will not miss the alert.

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The coast is clear.

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And they jump and yip to celebrate, a very important call

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to bring back peace and joy into the colony.

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(yipping)

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Not everything is a jungle out there.

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Howler monkeys take things slow.

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And spend great part of their day eating.

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(calm music)

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And after eating, they need to rest.

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This is basically what howlers do.

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This quickly becomes too boring for the babies,

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and they soon leave to play.

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The youngest are still fearful to leave the adult's side.

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It looks too much fun to miss it.

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It seems that just the kids have fun in the jungle.

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Some moms watch vigilantly, while most adults rest.

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It's hard to imagine that these adult monkeys

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could actually be loud.

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(growling)

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One would never know that these loud growls

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aren't from an angry jaguar but the sleepy howler monkeys.

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(growling)

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Male howlers have evolved

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a greatly enlarged, cup-shaped hyoid bone.

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The enlarged hyoid bone contains an air sac

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that functions like a resonance chamber,

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increasing the volume of their calls.

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(growling)

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The howling is thought to relate to territory protection

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as well as to guard mates possibly.

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The roar of the lion can be as loud as 114 decibels,

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similar to a rock concert, while the trumpet of an elephant

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can be as noisy as a clap of thunder, about 130.

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A male howler's call can reach up to 140 decibels,

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as strident as a jet taking off.

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(jet whooshing)

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Their distinctive call can be heard up to three miles away,

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making howler monkeys the loudest

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land animals on the planet.

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Mammals aren't the only ones

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that use sound to protect themselves.

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There are creatures that make themselves

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almost invisible to predators and to prey.

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(curious music)

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Yet camouflage can be risky as well.

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You might get stepped on.

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This unique warning sound might just avoid a fatal ending

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for both the snake and the human.

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(rattling)

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Rattlesnakes are a group of venomous snakes

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of the genera Crotalus and Sistrurus.

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The scientific name Crotalus

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is derived from the Greek meaning castanet,

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while Sistrurus means "tail rattler".

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It shares its root with the ancient Egyptian

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musical instrument the sistrum, a type of rattle,

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making its scientific name all about sound.

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Because of its rattle feature, evolutionary biologists

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classify rattlesnakes as the newest and most evolved snakes.

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A snake of this kind can waggle its tail in such a way

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that it produces a rattle 50 times in a single second.

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Even more impressive, it can sustain that rattle

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for more than three hours.

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(intriguing music)

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The rattle is made of keratin,

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the same material in fingernails.

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It is formed by hollow, interlocked segments

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that fit loosely inside one another.

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At birth, rattlesnakes only have

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a single segment of keratin, called the pre-button,

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unable to produce any sound.

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It's only after their first shed of skin,

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with the new button fully formed,

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that the rattle produces sound.

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When the snake vibrates the muscles in its tail,

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the segments collide with each other.

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It sounds like a baby rattle at the early stages,

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but the sound grows in volume as they shed skin

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while getting larger and add new segments.

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Then, they can produce the terrifying sound

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that gives rattlesnakes their name.

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Yet the rattle is what deters predators

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or serves as a warning to passersby

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and the reason why they rarely bite humans.

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In fact, biting is their last defense.

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Most rattlesnake bites are caused by humans

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stepping on them, and 20% of all venomous snake bites

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are dry, which means they don't inject venom.

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In fact, only one out of 500

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venomous snake bites result in death.

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Nevertheless, if you wander into their habitat,

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keep an eye on where you step,

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and be aware of their rattling noise.

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The high-pitched rattle, their striking pose,

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and a terrifying hiss is their attempt

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to keep danger away from them.

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(rattling)

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the next time you explore nature,

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try to pay close attention to its sounds.

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You might be listening to much more

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than just a chirp or a howl.

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It might be an alert, or a courtship call,

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or just a song to have some fun.

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It could even save you from a venomous encounter.

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This is the power of sound.

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(bright orchestral music)