Placeholder Image

Subtitles section Play video

  • Communicating underwater is challenging.

  • Light and odors don't travel well, so it's hard for animals to see or smell.

  • But sound moves about four times faster in water than in air,

  • so in this dark environment,

  • marine mammals often rely on vocalization to communicate.

  • That's why a chorus of sounds fills the ocean.

  • Clicks,

  • pulses,

  • whistles,

  • groans,

  • boings,

  • cries,

  • and trills, to name a few.

  • But the most famous parts of this underwater symphony

  • are the evocative melodies, or songs, composed by the world's largest mammals,

  • whales.

  • Whale songs are one of the most sophisticated communication systems

  • in the animal kingdom.

  • Only a few species are known to sing.

  • Blue,

  • fin,

  • bowhead

  • minke whales,

  • and of course, humpback whales.

  • These are all baleen whales

  • which use hairy baleen plates instead of teeth to trap their prey.

  • Meanwhile, toothed whales do use echolocation,

  • and they and other species of baleen whales

  • make social sounds, such as cries and whistles, to communicate.

  • But those vocalizations lack the complexity of songs.

  • So how do they do it?

  • Land mammals like us generate sound by moving air over our vocal cords

  • when we exhale, causing them to vibrate.

  • Baleen whales have a U-shaped fold of tissue between their lungs

  • and their large inflatable organs called laryngeal sacs.

  • We don't know this for sure

  • because it's essentially impossible to observe the internal organs

  • of a living, singing whale,

  • but we think that when a whale sings,

  • muscular contractions in the throat and chest

  • move air from the lungs across the U-fold and into the laryngeal sacs,

  • causing the U-fold to vibrate.

  • The resulting sound resonates in the sacs like a choir singing in a cathedral

  • making songs loud enough to propagate up to thousands of kilometers away.

  • Whales don't have to exhale to sing.

  • Instead, the air is recycled back into the lungs,

  • creating sound once more.

  • One reason whale songs are so fascinating is their pattern.

  • Units, like moans, cries, and chirps are arranged in phrases.

  • Repeated phrases are assembled into themes.

  • Multiple themes repeated in a predictable pattern create a song.

  • This hierarchical structure is a kind of grammar.

  • Whale songs are extremely variable in duration,

  • and whales can repeat them over and over.

  • In one recorded session, a humpback whale sang for 22 hours.

  • And why do they do it?

  • We don't yet know the exact purpose, but we can speculate.

  • Given that the singers are males and they mostly sing during the mating season,

  • songs might be used to attract females.

  • Or perhaps they're territorial, used to deter other males.

  • Whales return to the same feeding and breeding grounds annually,

  • and each discrete population has a different song.

  • Songs evolve over time as units or phrases are added, changed, or dropped.

  • And when males from different populations are feeding within earshot,

  • phrases are often exchanged,

  • maybe because new songs make them more attractive to breeding females.

  • This is one of the fastest examples of cultural transmission,

  • where learned behaviors are passed between unrelated individuals

  • of the same species.

  • We can eavesdrop on these songs using underwater microphones

  • called hydrophones.

  • These help us track species when sightings or genetic samples are rare.

  • For example, scientists have been able to differentiate

  • the elusive blue whale's populations worldwide based on their songs.

  • But the oceans are getting noisier as a result of human activity.

  • Boating,

  • military sonar,

  • underwater construction,

  • and seismic surveys for oil are occurring more often

  • which may interfere with whale's communication.

  • Some whales will avoid key feeding or breeding grounds

  • if human noise is too loud.

  • And humpback whales have been observed to reduce their singing

  • in response to noise 200 kilometers away.

  • Limiting human activity along migratory routes

  • and in other critical habitats,

  • and reducing noise pollution throughout the ocean

  • would help ensure whales continued survival.

  • If the whales can keep singing and we can keep listening,

  • maybe one day we'll truly understand what they're saying.

Communicating underwater is challenging.

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

B2 US TED-Ed whale underwater breeding feeding fold

【TED-Ed】Why do whales sing? - Stephanie Sardelis

  • 811 109
    陳雨昕 posted on 2017/01/08
Video vocabulary