‘Aural tattoos’: sperm whales use sounds to signal social identity, say scientists

Research says clicks emitted from whales' heads are symbolic marking like human social expression

Sperm whales are among the deepest divers on the planet. They are natural submarines, spending 70% of their time foraging for squid in the dark ocean for up to 80 minutes at a time. When they break through what Herman Melville called the ocean's skin", they socialise, twisting and turning their grey bodies around one another in a sensual, enigmatic choreography.

They measure up to 18 metres long and have the biggest brains on Earth. For at least 200 years, scientists have wondered what these mammals do with those brains. Now, evidence has emerged that may revolutionise the way we think about whales.