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Stressed-out animals unlikely to survive
Steven Schultz Princeton NJ -- Oil spills, droughts, fires, pollution -- all manner of natural or man-made calamities can overwhelm populations of birds, mammals and reptiles. Biologists often want to know just how bad the damage is going to be before the consequences play out. Princeton biologist Martin Wikelski has shown that a single blood sample can give a fair clue to the answer. In a letter published earlier this year in Science and an article in the Proceedings of the National Academy of Sciences, Wikelski showed that blood levels of the stress hormone corticosterone accurately predicted a population's probability for survival. Working with colleagues from Tufts University and the University of New Mexico, Wikelski studied marine iguanas on the Galapagos Islands during a drought and an oil spill. During an El Nino-induced drought, the researchers found that animals with highly elevated stress hormone levels died within two to four weeks of testing, whereas animals with normal levels continued to live healthy lives. As part of that research, they happened to take blood samples of iguanas on Jan. 14, 2001, just three days before the oil tanker Jessica ran ashore and dumped 750,000 gallons of oil into the heart of one of the world's most precious nature preserves. When they returned 10 days after the spill, they found that stress hormone levels were highly elevated. The levels were similar to those found in the animals that were within weeks of death during the drought. "For a lot of populations that are in danger, you need a rapid assessment of their condition," said Wikelski. Although researchers had known that animal stress hormones rise under adverse conditions, it had not been proven that the increased levels relate to survival in the wild. Wikelski and undergraduate Vanessa Wong plan to return to the Galapagos later this year to determine if their dire prediction for the fate of the oil-tainted iguanas was correct. Related story |
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