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Surveying
Sealife
Traditionally,
when biologists want to know more about animals they go out
and look for them. But many animals, such as deep diving whales,
are often hard to observe in their natural habitats. That's
why since 1991, the National Marine Mammal Laboratory-part
of the National Oceanic and Atmospheric Administration (NOAA)-has
been making use of Cold War technology to record whale song.
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| Listening
to whale song in the Pacific gave biologists their first
good population census of this region's Bryde's whales. |
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The
U.S. Navy began installing a network of underwater microphones-or
hydrophones-in the world's oceans in the 1950s. Part of the
Navy's Integrated Undersea Surveillance System (IUSS), the
Sound Surveillance System (SOSUS) consists of groups of hydrophones
anchored to the seafloor and linked to shore via underwater
communication cables. Once used to listen for enemy submarines,
SOSUS is today helping scientists survey whale populations
all over the world.
The
unobtrusive technology records whale vocalizations and allows
biologists at the Pacific Marine Environment Lab (PMEL) in
Newport, Oregon to eavesdrop on whales far out in the open
ocean, where little is known about their behavior. By analyzing
the recordings, scientists hope to learn more about what species
are out there, where, and when.
Listening
in has already yielded some surprising results about blue,
fin, humpback, sperm, minke and Bryde's whales. Recently,
the PMEL researchers deployed a hydrophone array in the Gulf
of Alaska to study whale population patterns over the course
of a year.
"Nobody
does visual surveys in the Gulf of Alaska in the winter,"
says Dr. Dave Mellinger, a bioacoustician from Oregon State
University who works on the project. "It's just too rough."
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| Scientists
deploy a hydrophone- an underwater microphone- off a research
vessel. |
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When
the researchers retrieved the sound recordings a year later,
they found that about half the sperm whales who summer there
stay year-round. That surprised biologists, who had assumed
they all migrated south come winter.
Another
surprising result came from a warmer, if more remote, part
of the ocean. Hydrophones placed in the equatorial Pacific
gave marine biologists the first good census of this region's
Bryde's whales, which turn out to be relatively common.
According
to Mellinger, the PMEL researchers also hope to document manmade
sound underwater and how it may be affecting whales and dolphins.
Click
here
for more information on the PMEL Whale Acoustics Project.
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Images::U.S.
Minerals Management Service
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