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Whales and dolphins live in a world of sound. Sunlight fades within a few hundred metres of the surface, but sound carries far through seawater, more than four times faster than through air. They sing, whistle and click to keep in touch, to hunt and to find their way.

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Sound moves through seawater at about 1,500 metres per second, and low-pitched calls lose little energy on the way. Christopher Clark of Cornell University, using US military underwater recordings, showed that whale calls can carry for thousands of kilometres. Toothed whales, such as dolphins and sperm whales, also use echolocation: they send out clicks and listen for the echoes to find prey in the dark. Each bottlenose dolphin develops its own signature whistle, which works much like a name; other dolphins copy it to call that individual. Humpback whale song became famous in 1970, when the biologist Roger Payne released the album Songs of the Humpback Whale, which helped start the Save the Whales movement. Today, noise from ships, sonar and seabed surveys worries scientists, because it can drown out the sounds these animals depend on.

Türkçe oku
Balinalar ve yunuslar seslerle dolu bir dünyada yaşar. Denizde güneş ışığı ancak birkaç yüz metre derine inebilir; ses ise suda çok uzaklara gider ve havadakinin dört katından da hızlı yayılır. Bu hayvanlar haberleşmek, avlanmak ve yollarını bulmak için şarkı söyler, ıslık çalar, tıkırtılar çıkarır.

Ses deniz suyunda saniyede yaklaşık 1.500 metre yol alır; kalın sesler yolda çok az enerji yitirir. Cornell Üniversitesi'nden Christopher Clark, ABD ordusunun su altı kayıtlarını inceleyerek balina seslerinin binlerce kilometre öteye ulaşabildiğini gösterdi. Yunuslar ve ispermeçet balinaları gibi dişli balinalar yankıyla yön de bulur; buna ekolokasyon denir. Tıkırtılar gönderip dönen yankıları dinleyerek karanlıkta avlarının yerini saptarlar. Her afalina yunusunun kendine özgü bir ıslığı vardır ve bu ıslık bir isim gibi işler; öteki yunuslar o yunusa seslenmek için onun ıslığını taklit eder. Kambur balinaların şarkısı 1970'te ünlendi: Biyolog Roger Payne'in yayımladığı Songs of the Humpback Whale albümü, “Balinaları Kurtarın” hareketinin doğmasına yardım etti. Bugün gemilerden, sonarlardan ve deniz tabanı taramalarından yayılan gürültü bilim insanlarını kaygılandırıyor, çünkü bu hayvanların dayandığı sesleri bastırabiliyor.

Sources and further reading

Background reading: Whale vocalization
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