Friday, 8 November 2019

Echolocation found to be cheap for deep-diving whales

NOVEMBER 1, 2019



A new international study led by Aarhus University in Denmark, in collaboration with the Universities of St Andrews and La Laguna, Tenerife, reveals how whales have evolved to live in the world's deepest oceans.

Many whales and dolphins, including the champion deep-diving beaked whales, use echolocation, the ability to locate objects by reflected sound, to find food in the dark of the deep ocean. Scientists have not been able to agree on how much energy this remarkable sensing ability takes, until now.

A new study published today (Thursday 31 October) in the journal Scientific Reports reveals that, at least for short-finned pilot whales, echolocation is cheap. This may help explain how echolocating whales evolved to live in deep waters throughout the world.

In a throwback to terrestrial ancestors, whales use air to make their intense echolocation click sounds and this raises a problem for deep divers. Air compresses with depth so that at 700m deep, where pilot whales hunt, a lung-full of air has shrunk to 1.5% of its volume. But the new study shows that pilot whales use tiny amounts of air to make each click so this volume goes a long way. Even so, whales need to capture the air used by each click and recycle it, like a SCUBA rebreather, to be able to echolocate throughout their dives.

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