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 In the 20th century, it was an important technological
breakthrough.
But it was old technology as far as whales go. These marine mammals
have been using echolocation — bouncing high-frequency sounds off
underwater objects — to find prey for tens of millions of years.
U.S. scientists on Wednesday announced the discovery of the most
ancient whale known to have used echolocation — a creature called
Cotylocara macei, a bit larger than a bottlenose dolphin, that lived
about 28 million years ago.
The discovery suggests that echolocation evolved in toothed whales — the group that includes modern day varieties like sperm whales,
killer whales, dolphins and porpoises — perhaps 32 million to 34
million years ago, the scientists said.
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.
Cotylocara, whose fossilized 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, Geisler
said.
The fossils were unearthed near Summerville, South Carolina, outside
Charleston, said College of Charleston geology professor James
Carew, another of the researchers.
"AN EXTINCT FAMILY"
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. They went
extinct 25 million or 26 million years ago and they don't have any
living relatives," Geisler said in a telephone interview.
Whales that use echolocation produce very high-frequency
vocalizations 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.
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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," Geisler said.
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. 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.
(Reporting by Will Dunham; editing by Gunna Dickson)
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