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Old 04-30-2008, 10:36 AM
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Speaking of calamari ...

Sperm Whales Drawn To Waters Off Mississippi River Delta

ScienceDaily (May 28, 2001) — COLLEGE STATION, Texas -- 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 northeastern Gulf of Mexico.

In a Texas-Sea-Grant-funded project, Texas A&M University at 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.

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's several thousand meters deep within 50 or 60 miles of the coast, he said, and sperm whales are typically found in these deeper waters along the continental shelf.

"The unique aspect of the Gulf is we have a continental shelf that 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 lot of oil and gas exploration. 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, he said.

"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.

This information will help researchers learn more about the feeding behavior of sperm whales, Davis said. 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," he said.

The project is 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 would 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.

Adapted from materials provided by National Sea Grant College Program.

Much more at: http://www.sciencedaily.com/releases/2001/05/010525072138.htm

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Old 04-30-2008, 10:39 AM
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Ecologists Home In On How Sperm Whales Find Their Prey

ScienceDaily (May 29, 2006) — Ecologists have at last got a view of sperm whales' behaviour during their long, deep dives, thanks to the use of recently developed electronic "dtags". According to new research published in the British Ecological Society's Journal of Animal Ecology, sperm whales – like bats – use echolocation consistently to track down their prey at depth.

Working in the Atlantic, the Gulf of Mexico and the Ligurian Sea, scientists from Woods Hole Oceanographic Institution and the University of St Andrews attached acoustic recording tags to the dorsal surface of sperm whales with suction cups. The whales were then tracked acoustically with a towed hydrophone array.

The researchers used the tags to record the sounds that sperm whales produce while foraging. As sperm whales descended from the surface, they emitted a regular series of "clicks". When the whales reach the bottom of their dive, these clicks are emitted more often, eventually merging together to form "buzzes" of sound. This pattern reflects the whales homing in on cephalopods such as squid, with the buzzes reflecting the animals' final approach when detailed information on the squid's position and movement are required, the researchers believe.

Dr Stephanie Watwood and colleagues found that sperm whales produced buzzes on every deep dive they made, in all three locations, suggesting that they are highly successful at locating prey in the dark ocean depths.

The sperm whale is the world's largest deep-diving toothed whale, feeding mainly on squid, but until now little has been known about the timing of prey detection and capture during dives.

"Due to the difficulty of observing sperm whales during their long, deep dives, little has been known about their subsurface behaviour, giving rise to an array of speculations on how sperm whales find prey, including luring, touch, passive listening, echolocation and vision. Recording vocalisations of diving sperm whales presents a non-invasive opportunity to document feeding activity." says Watwood.

Adapted from materials provided by Blackwell Publishing Ltd., via EurekAlert!, a service of AAAS.

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