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Around the same time, another researcher, Susan Parks, was getting acoustic recordings on mothers and their calves for research on the social behavior of the whales. The data didn't come together until late 2009, when Rolland started researching stress and underwater noise to prepare for a workshop organized by the Office of Naval Research. She realized Parks had four days of sound recordings from the bay, two days before and two days after Sept. 11, and she had five years of data on stress hormone levels for the whales that included that time. A hunch, and then quick analysis by Rolland, showed a possible correlation between a drop in sound and the drop in whale stress hormone levels. The naval office eventually agreed to fund the work that led to Wednesday's paper, she said. The more rigorous analysis showed a significant decrease in background noise in the bay post-Sept. 11, including a drop in the low frequency sounds that ships emit and which the whales use to communicate. Scientists compared the stress hormone levels found in the whale feces during the five-year period and found them to be markedly lower only during the time when ship traffic was down immediately after Sept. 11. Rolland said caveats come with any accidental study. A planned study would have had more acoustic and hormone data. This study obviously can't be repeated. And it's also unclear how much chronic stress from noise the whales can take before the population is affected, largely because it's impossible to conduct controlled experiments on 50 ton animals. But even with the caveats, Rolland said, "It's pretty good evidence. We have no other explanation for these findings."
[Associated
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