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New Orleans Jazz, Riverboats, Jambalaya….&
Sperm Whales??
When people think of the Mississippi Delta, a few things are likely
to come to mind -- jambalaya, New Orleans jazz, riverboats, cotton,
swamps, and sperm whales. Sperm whales?
Researchers have found that endangered sperm whales frequent the deeper
waters off the Mississippi Delta. Scientists estimate that at least
530 sperm whales can be found in the northern Gulf of Mexico, especially
in the north-central region.
Since sperm whales almost always behave in the same manner - surfacing
for about 10 minutes, then fluking up before diving for about
40-minutes - this is a highly unusual sighting. For unknown reasons,
this whale in New Zealand kept lifting his head for a few seconds
before again swimming. He repeated this behavior for about 20
minutes, providing a rare opportunity to view his strange anatomy
-- a real bulky head yet a very narrow lower jaw. Sperm whales
have teeth only on their lower jaws, and unlike humans all of
their teeth are the same shape.
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In a Texas SeaGrant-funded project, Texas A&M University/Galveston marine
biologists Randall Davis and Bernd Würsig will use satellite tracking,
direct observation, genetic analyses and photographic identification
to learn more about these large marine mammals that live so close to
the coast.
Randall Davis said coldwater eddies and the outflow of nutrients from
the Mississippi River may enhance the production of food for these marine
mammals and draw the animals nearer to coastal waters. The Mississippi
Delta region of the Gulf also has water that is several thousand meters
deep within 50 or 60 miles of the coast. Sperm whales are typically
found in these deeper waters along the continental shelf.
Sperm whales can be identified by distinct marks on the trailing
edge of their tails, or flukes. Because sperm whale flukes are
so well marked, almost the entire population can be individually
identified. Researchers follow each whale, photographing the fluke
after the whale logs at the surface for about 10 minutes, then
"flukes up" at the start of about a 40-minute dive. As a key to
sperm whale research, these photo-IDs become tools for investigating
social organization, residency time, movements, abundance, and
more. This photo was taken off Kaikoura, a New Zealand coastal
town.
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"The unique aspect of the Gulf is our continental shelf which is only
about 25 miles wide off the Mississippi Delta, so we have this influx
of freshwater nutrients into a deepwater environment very close to the
coast," he said.
While this area of the Gulf of Mexico is popular with sperm whales,
it is also home to a major area of deepwater oil and gas exploration
and development. These activities, and the increasing boat traffic they
bring, may be a cause for concern as far as their effects on the region's
whales. "Basically, we probably have a breeding population of endangered
sperm whales right in the middle of one of the hottest areas for offshore
oil development in the continental U.S," Davis said.
As part of the study, researchers will tag whales with tracking devices
that will follow the movements of the whales and record information
on how often a whale dives -- which can be linked to feeding, the duration
of the dive and the depth of the dive. When the whale surfaces, the
device relays the information back to researchers via satellite.
Just as other "tooth whales," such as dolphins, killer whales
and porpoises, sperm whales have a single blow hole. Breathing
like humans, they use it to inhale and exhale. Unlike all other
tooth whales, the sperm whale's blow hole is not in the middle
but off to the left side. This sperm whale was curious enough
to approach the boat, a rare move for a mature sperm whale. Usually
just calves will come so close. This whale's blow hole almost
touched the rigid-hulled inflatable. Then he blew, completely
fogging the camera.
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This information will help researchers learn more about the feeding
behavior of sperm whales. Currently, they can only get this information
from observing sperm whales feeding and analyzing the stomach contents
of a whale - neither of which is easily done.
"Without being able to make direct observations on these deepwater whales,
it's surprising how little we know about their natural history," Davis
said. The project is primarily set up as a basic science study that
looks at the natural history of sperm whales in the northern Gulf of
Mexico. However, Davis said the study's findings will likely be of interest
to the Marine Mammal Commission, National Marine Fisheries Service as
well as the Minerals Management Service, which oversees development
of offshore oil and gas deposits.
The Endangered Species Act requires officials to monitor not only oil
pollution but also noise pollution, which comes from boat traffic and
seismic activity that is used to search for oil.
This whale is "breaching" in the Galapagos Islands off Ecuador's
coast. As a likely form of communication and perhaps other functions,
sperm whales usually breach during the few hours each day when
they socialize with other sperm whales in a group at the sea's
surface.
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Mark Evans
Texas Engineering Experiment Station (formerly of Texas Sea Grant) Texas
A&M University
Photos by Nathalie Jaquet and Mary Dillon
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