Blown-up whale

Science World, March 31, 2008 by Cody Crane

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Last July, a ferry near Juneau, Alaska, reported a whale of a sight--a male humpback whale with a tongue swollen to the size of a car. When scientists arrived on the scene, the whale was alive but struggling to keep its blowhole above water so it could breathe. "We had never seen anything like this before," says Aleria Jensen, the National Oceanic and Atmospheric Administration's (NOAA) marine mammal stranding coordinator in Alaska. "There wasn't much we could do for the animal." The next day, the whale's dead body was discovered beached on a nearby island.

Judging by the whale's bloated tongue, Jensen and her team suspected an infection had caused the humpback's unusual death. To find out, a veterinarian performed a necropsy. During the exam, the vet probed the contents of the animal's digestive tract to learn about its diet, collected DNA (chemical that carries hereditary information) from its skin, checked its blubber (layer of fat) for toxins, and took other tissue samples.

Results: No evidence of disease. But the scientists did find a large bruise behind the whale's jaw--a sign it had likely been struck by a blunt object, most likely a ship. One hypothesis is that such an impact could have punctured the whale's trachea (airway to the lungs), forcing air into the whale's tongue, causing it to inflate.

Of the few reports Jensen's office receives each year of ships striking whales, most turn out not to be fatal for the animals. But as a growing Alaskan humpback population attracts more whale-watching boats, the increased traffic could pose a threat to this already endangered species. To protect the animals, NOAA encourages vessels to slow their speeds in whale-frequented areas. Laws also require ships to keep their distance from whales, but accidents still happen.

Jensen plans to re-examine the whale's body once its soft tissues have decomposed. There may be hidden signs of trauma--like broken bones--that will help Jensen determine once and for all whether a ship collision is to blame for the whale's death. It could take at least a year for the 40- to 50-ton carcass to break down.