Scientists investigate the puzzling death of an endangered sea creature
The Canadian Coast Guard (CCG) receives a phone call. The caller says a dead whale is drifting off the coast of Yarmouth, Nova Scotia. The CCG immediately sails to the reported site. Members of the agency use ropes to tie the whale carcass to their boat and tow it onto a remote beach in Kelley's Cove, a seaside village in Yarmouth.
At first glance, it is hard to identify the dead 40-ton animal: a North Atlantic right whale. When alive, the marine mammal has a glossy black body. But the carcass lying on the beach looks like a giant white blob.
Agents from the Canadian Department of Fisheries and Oceans rush to the scene. As they study the whale carcass, they wonder how the animal died. They are particularly concerned because the North Atlantic right whale is an endangered species. Approximately 400 members of this species exist in the world today, and they are at risk of dying out. So whenever a right whale dies in Canadian or U.S. waters, that country's wildlife officials immediately call upon experts to perform a necropsy. This medical exam offers clues to how the animal died, and the information could help officials find ways to better protect the endangered whales.
September 4, 2006
Michael Moore, a veterinarian and biologist at the Woods Hole Oceanographic Institution (WHOI) in Massachusetts, arrives with his team of researchers. He eyeballs the whale remains and immediately picks up clues that the whale has been dead for a while.
When a living thing dies, it decomposes. Bacteria inside the organism eat away at the body, causing the carcass to decay over time. "During decomposition, the whale's external Features gradually fall off," says Moore. Nearly all of this whale's glossy black epidermis, or outer skin, has peeled off. Also, "a freshly-dead right whale is about 10 foot in diameter," says Moore. This dead whale looks greatly deflated.
A decaying whale is like a flattening tube of toothpaste, explains Moore, Just underneath the whale's skin is a thick layer of blubber. This spongy and oily material is very resistant to decomposition. But inside the whale is another story. During decomposition, the whale's muscles and viscera, or soft internal organs including the lungs and intestines, all slowly liquefy into a substance that is similar in consistency to toothpaste. But this soup of decayed flesh is a lot smellier than toothpaste, says Moore. This gunk gradually leaks out of the dead whale's mouth. By gauging the size of the deflated whale's body, Moore gets a sense of how much of the whale has decomposed inside.
A whale necropsy is messy; whale blood and oil could splatter onto the examiner. So Moore's team puts on protective gear such as foul-weather pants. The researchers start the examination by studying the whale's external features and taking its measurements. They learn that the whale is a female and that it is 1,465 centimeters (48 feet, 1 inch) long. They also look at the whale's body for signs of trauma or diseases. Besides dent marks from the ropes used to tow the animal onshore and a couple of shark bites, Moore finds no clues that point to the whale's death. The only way to dig deeper into this case is to look inside the whale.
Using sharp knives, Moore and his team cut into the whale blubber. Bingo! Blubber is normally light pink in color. But a large section of blubber on one side of this whale is red. "That's a sign of bruising," says Moore.
A bruise usually forms when a blunt object hits a body. Moore explains: When a baseball hits you, you don't get c-ut because the blunt ball doesn't pierce your skin. But the impact of the hit causes the various blood vessels that feed into the tissues beneath your skin to burst. As red blood cells spread into the tissues, a bruise forms. Similarly, a collision with a blunt object is likely To have caused the whale blubber to bruise.
September 5, 2006
A new clay begins and Moore and his team are eager to learn what hit the whale and how it died. So they proceed to peel the blubber off the whale to see what additional clues hide beneath.
Moore finds that 75 percent of the whale's muscles remain, but that all of its viscera had already liquefied and leaked out of its body. "The animal had decomposed so much that its rib cage had somewhat collapsed," says Moore. Through previous studies, Moore knows that this state of decomposition is usually seen in whales that have been dead for approximately two weeks.
The team continues dissecting the whale and soon disc-overs a large number of broken bones. The researchers remove the whale's bones and set them on the beach. Then, piece by piece, the scientists use the bones to reconstruct the whale's skeleton. The completed structure gives Moore and his team a better idea of which parts of the whale skeleton are intact and which parts are broken. The finding: Many vertebrae, or individual bones that make up the spine, were fractured near the whale's chest and lumbfir (lower back) regions.
Although the whale's tissues are still being analyzed, Moore feels confident that he has gathered enough clues to draw a conclusion: A large, blunt object hit the whale hard on one side-the side that was bruised. That impact broke the animais backbones. As a result, the nerves that send signals from the whale's brain down its spine were severed. Without brain signals to direct its tail and other hotly pails to move, the whale was probably paralyzed ami couldn't swim. "It was also in a lot of pain and bled a lot," says Moore. "The whale probably died within a few hours of being hit."
Over the years, Moore has learned that most North Atlantic right whales die from getting hit by cargo ships or from becoming iaiigled in fishing nets. The whale in this case most likely died from a ship strike.
To protect these endangered whales, the U.S. and Canadian governments have long-standing laws that prohibit ships from coming within 500 yards of right whales. Still, many right whales die from shipping and fishing activities every year. Moore and other scientists hope that their findings about each right whale's cause of death will help the KS, and Canadian governments find better ways to help save the species from extinction.
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