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Published February 25, 2010

After dropping dead pigs into the sea and watching via Webcams, researchers were "very surprised" to see marine scavengers risk low-oxygen waters for a meal.

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© 2010 National Geographic; Video Courtesy VENUS/University of Victoria

Unedited Transcript

Sometimes a scientific study reveals things that were never expected to be part of the discovery.

While conducting forensic studies on human decomposition, scientists in Canada found deep sea dwelling animals taking a chance and going after a pig carcass where oxygen is at extremely low levels.

Pigs are used in decomposition studies because they are anatomically similar to humans.

The 4th pig deployment in the study was the most dramatic, recorded in the Strait of Georgia, British Columbia.

Several six-gill sharks annihilated the carcass, eliminating it within a day at more than 900 feet below sea level.

It’s at depths like this that oxygen drops to very low levels, leading to the term “dead zones”. In recent years, dead zones are occurring more frequently in many areas of the oceans and also in river deltas and other coastal areas in particular.

The lead researcher, Verena Tunnicliffe of the University of Victoria, said the scientists were very surprised to see how far animals pushed their limits to go after an enticing meal.

In this video recorded in British Columbia’s Saanich Inlet, the first animal on the scene was a squat lobster. Over several days, scientists observed more squat lobsters coming for a meal, as well as crabs and shrimp. This pig carcass was devoured by the 23rd day.

According to Dr. Tunnicliffe, the pigs used in this study, coordinated with Canada’s VENUS project, were originally raised for market. They were euthanized humanely under strict government regulations.

The findings were presented at a meeting of the American Geophysical Union in Portland, Oregon this week.

The scavenger animals usually hang out at shallower depths, where oxygen levels are higher. But the pig carcasses attracted a daring crowd.

If the crabs, squat lobsters and other animals stay too long in oxygen-depleted waters, they will suffocate.

One pig in the experiment sat untouched for nearly 2 months, apparently because the oxygen level was too low to support the hungry scavengers.

The findings will help scientists in their study of other locations, such as the Mississippi Delta, where fertilizer in upstream agricultural runoff lowers oxygen levels.

The so-called dead zones also diminish the success of fishermen’s attempts at catching shrimp, crab and other commercial species.


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