Scientists study sonar's
impact on whale behavior
By Nadia Drake
Posted: 12/13/2010 01:30:41 AM PST
SANTA CRUZ -- Many marine mammals rely on
sound for communication and navigation.
Whale songs can span oceans, and some
mammals routinely plunge thousands of feet into
salty darkness in search of supper. But what
happens when the whales' auditory environment
is overwhelmed by loud undersea noise from
Naval sonar?
Circumstantially, nothing good: For decades,
mass strandings have been reported in the wake
of sonar-using naval training exercises. Mid-
frequency tactical military sonar is used to
detect underwater objects like submarines, and
sonar noise levels exceed 230 decibels -- the
equivalent of multiple jet engines.
Many of the better-known, potentially sonar-
induced strandings involve dozens of whales and
multiple species. In March 2000, 16 whales
beached themselves in the Bahamas following a
training exercise. In September 2002, 14 beaked
whales washed up in the Canary Islands. Then, in
2004, as many as 200 melon-headed whales got
stuck in a shallow Hawaiian bay. Similar
incidents have been reported in Greece, Japan,
Washington state and Spain.
But scientists still don't know how sonar leads to
mass casualties, and whether it causes direct
physical harm, interferes with navigation,
induces panic or causes disorientation.
Santa Cruz researcher Brandon Southall is trying
to find out. Southall is affiliated with UC Santa
Cruz and is the president of Southall
Environmental Associates Inc. Earlier this fall, he
and colleagues from institutions
including the Cascadia Research Collective,
Scripps Institution of Oceanography, and the
Woods Hole Oceanographic Institute completed
the first stage of a five-year study addressing
marine mammal response to sonar-like sound.
The study -- called SOCAL-10 -- is funded in
part by the U.S. Navy, which by all accounts is
interested in using the results to lessen the
effects of its sonar use on marine mammals.
"Any information that comes from these studies
will be taken and applied to mitigation
measures," said Frank Stone, marine resources
project manager for the Chief of Naval
Operations, Environmental Readiness Division.
Stone said the Navy's policies are informed by
the available science -- and that since there is a
paucity of hard data on the effects of sonar, the
Navy would use SOCAL-10 results to guide future
practice.
"We have probably the best biologists and
marine scientists in the world working out
there," Stone said.
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Scientists spent two months in the waters off
Southern California, tracking, tagging and
playing sounds to dolphins and whales in their
natural environment. They assessed the
behaviors provoked by sonar-like sound.
"This is a controlled, safe way of looking at
acoustic effects on mammals," Southall said.
In principle the study design is simple, but
combining controlled experiments in an
unpredictable natural environment complicates
its execution. First, scientists identify test
animals in the open ocean. Then, they tag those
animals with acoustic or satellite tags and
establish a behavioral baseline. The heart of the
experiment is the sound playback, where
animals are exposed to sonar-like sound. Lastly,
scientists retrieve the data-containing tags,
which report the animal's location, behavior,
acoustic environment and vocalizations.
Tagging the animals was accomplished by
personnel from the Cascadia Research
Collective, including scientist John Calambokidis,
who piloted the rigid-hull inflatable vessels used
to approach whales. Researchers used 10- to
15-foot poles to tag the whales. They'd time
their approach and position to coincide with the
whale's surfacing pattern, then attempt to affix
the tag. "We were very careful, both for our own
safety and the animal's," Calambokidis said. "We
spend a lot of time trying to perfect our
techniques. It varies by species."
The acoustic tags each hold about 1 gigabyte of
data and are suction-cupped onto the whales.
Tags fall off after about 12 hours, according to
Southall, then emit a signal allowing researchers
to retrieve them. "These things are out there
riding around on whales," Southall said.
"Sometimes overnight."
He estimated that analyzing the data gathered
would take about a year.
At the conclusion of the study, scientists
deployed 62 tags and completed 28 playback
experiments on five species. During three years
of similar studies in the Mediterranean and the
Bahamas, Southall said scientists achieved only a
fraction of that: nine playbacks on four species.
"This was an extremely successful first step,"
Southall said. Among other accomplishments,
scientists achieved the first controlled sound
exposure on large whales, the first satellite
tagging of sei and Baird's beaked whales and the
first controlled playback experiment on a
Cuvier's beaked whale -- a species that is
commonly found in the mass stranding events.
"Beaked whales are particularly represented,"
Southall said. "That tells you something different
is going on."
Among the hardest animals to study, beaked
whales "are the most extreme of marine
mammals, in terms of how much you see them,"
Southall said. These deep-diving, 15-foot-long
mammals regularly reach depths of more than
1,000 meters -- sometimes descending to 2,500
meters, or more than a mile down -- in their
search for deep-dwelling squid. Because they
spend relatively little time at the surface, they
are not only difficult to track, but somewhat
mysterious.
"We're still discovering new species," Southall
said. "How often can you say that about a
mammal that size?"
In the future, Southall hopes to tag more beaked
whales and expand the study population to
include seals and sea lions. He'd also like to use
real military sonar instead of sonar-like sounds.
"That's what we need to understand," he said.
"We're building up to it. We're much closer than
we were five years ago."
The California Coastal Commission and National
Resources Defense Council are on board with
SOCAL-10's protocols and aims.
"It's good research, and enough protection
measures are built in so it won't harm animals,"
said Mark Delaplaine, manager of the Coastal
Commission's Energy Ocean Resources and
Federal Consistency Unit. Delaplaine reviewed
the SOCAL-10 project and determined that it
was consistent with policies promoted by
California's Coastal Act. "We're excited about the
research," Delaplaine said.
So is the National Resources Defense Council,
which in 2008 brought a case against the U.S.
Navy and its use of sonar. The California Coastal
Commission joined the NRDC as a co-litigant.
They won at every level except the U.S. Supreme
Court, which ruled 5-4 in favor of the Navy.
"The most important thing for sonar is for the
Navy to avoid or limit activities in important
habitats," said Michael Jasny, senior policy
analyst for the NRDC. "Up until now, the Pacific
fleet has completely resisted this, inexcusably."
Jasny hopes the data generated by SOCAL-10
will be used constructively by the Navy. "This
study has the potential to contribute significantly
to marine mammal conservation," he said.
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