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WATER PLANET
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SUMMER 2012
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early 60 years ago Jacques Cousteau intro-
duced the public to the submerged visual
splendor of the sea in his book and film The
Silent World. Unfortunately, the title intro-
duced the misconception that all the ocean’s stunning
and majestic beauty occurs in a world of somber silence.
As it turns out, the ocean is anything but silent, a fact that
has been appreciated since the earliest days of seafaring.
Sailors’ fears of sirens and sea dragons were rooted in the
many strange and haunting sounds of marine fauna that
could be heard through the hulls of their boats.
The Marine SyMphony
The sea is the origin of all animal life on the planet.
Because light does not penetrate below a few hundred
feet, and at any given time half the sea is obscured under
the veil of night, it is also a perfect environment for the
evolution of acoustical adaptations. In these dark set-
tings marine animals have evolved a complex array of
adaptations for hearing as well as sounding — most of
which continue to evade our understanding.
Many of us are familiar with the evocative songs of
the humpback whale, but it remains a mystery why all
males in the same breeding group sing the same song
throughout the season. This doesn’t quite square with
our common conception that male animals sing to
advertise breeding fitness, a strategy that might be less
ambiguously expressed if they all sang different songs.
And why do they all change their songs every year?
We have known for some time that dolphins and por-
poises use biosonar to sense their surroundings. Their
high-frequency chirps and buzzes help them locate
food, navigate during cooperative, high-speed hunting
tactics and frolic in their surroundings. But we have
only recently learned their biosonar can also let them
“see” deeply into body tissues and identify extremely fine
details in their environment.
There is informed speculation that baleen whales’
low-frequency vocalizations are also a form of biosonar.
They may be using long-wavelength sounds to navi-
gate across large expanses of water — projecting these
sounds a thousand miles over the horizon to bounce
back to them off seamounts, trenches and continental
shelves as long-distance echolocation.
In chorusing, whales, fish and marine invertebrates all
sing in temporally coordinated vocalizations like crickets or
frogs. Croakers (sciaenids) synchronize in acoustical “sta-
dium waves” across 45 miles of coastal habitat, and minke
B y M i c h a E l S t o c k E R
The Enormous Din of the Sea