While humans have been using sonar since the 1940s, marine mammals have been hunting prey with it for tens of millions of years.
Now a new fossil study suggests an ancient whale used sound beams to find food 28 million years ago.
The new whale species, called Cotylocara macei, was found to have air pockets in its skull that had similarities to those used by modern day porpoises and dolphins to send out focused sound beams.
The skull of the 28-million-year-old Cotylocara macei. Its anatomy and density variation indicate that this early toothed whale used echolocation to find its prey
The discovery places the evolution of the technique, called echolocation, to around 32 million years ago
That was relatively soon after whales, around 35 million years ago, split into two major cetacean groups – toothed whales that were active hunters and toothless baleen whales that were filter feeders, straining food like krill from the ocean.
Jonathan Geisler, an anatomy professor at New York Institute of Technology who led the research published in the journal Nature, called echolocation ‘an amazing trait.’
‘It’s a sonar-like system which allows them basically to navigate and find food, particularly in waters where there’s little light, either at great depth or in very turbulent waters with a lot of mud, like estuaries or around marshes,’ he added.
An artistic reconstruction of the 28 million-year-old Cotylocara macei as it patrolled the shallows near present-day Charleston
HOW DOES ECHOLOCATION WORK?
Whales that use echolocation produce very high-frequency vocalisations through a soft-tissue nasal passage located between the blowhole and skull.
Other mammals, including people, produce sounds using the voice box, or larynx, inside the neck.
When air is pushed through the whale’s nasal passage, it produces extremely high frequency clicks, squeaks and squeals that then echo off objects in the water, enabling the whale to get a high-resolution audio image of its surroundings.
Cotylocara, whose fossilised remains include a 22-inch skull, neck vertebrae and ribs, was about 10 to 11 feet long and probably swam in a shallow ocean environment, feeding on fish and squid.
The fossils were unearthed near Summerville, South Carolina, outside Charleston, said College of Charleston geology professor James Carew, another of the researchers.
While Cotylocara looked superficially like some smaller modern-day toothed whales, it was not closely related to them.
‘This is a member of an extinct family that split off very early from other echolocating whales, dolphins and porpoises,’ Professor Geisler added.
‘They went extinct 25 million or 26 million years ago and they don’t have any living relatives.’
Whales that use echolocation produce very high-frequency vocalisations through a soft-tissue nasal passage located between the blowhole and skull.
Other mammals, including people, produce sounds using the voice box, or larynx, inside the neck.
When air is pushed through the whale’s nasal passage, it produces extremely high frequency clicks, squeaks and squeals that then echo off objects in the water, enabling the whale to get a high-resolution audio image of its surroundings.
‘They can “see” the fish and then they know to swim in that direction to catch it,’ Professir Geisler said.
Nearly a decade ago, scientists unearthed a complete toothed whale skull, along with a few neck vertebrae and some ribs in a fossil-rich region near Charleston
The sound-producing mechanism is complex, with big muscles, air pockets and bodies of fat – all in a small facial area.
The sound is too high frequency for human ears to hear.
Modern-day whales that use echolocation possess a melon, or a fat-filled organ in the head, that focuses the sound wave. Professor Geisler said he suspects that Cotylocara already had this organ.
The whale’s genus name, Cotylocara, means ‘cavity head’ in recognition of a very deep pocket atop its skull thought to be associated with an air sinus used in echolocation.
Whales are not the only animals that use echolocation. Bats, which also first appeared more than 50 million years ago, use it while flying to pinpoint insects and other prey.
The first whales appeared more than 50 million years ago, arising from wolf-size land dwellers.
Whales gradually became better suited to sea life and grew larger – one called Basilosaurus that lived about 40 million years ago was at least 56 feet long. Echolocation was a later adaptation.
Toothed whales, dolphins, and porpoises produce their high-frequency vocalisations through a constricted area in the nasal passages below the blowhole
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