Immediately after the terrorist attacks of September 11, 2001, commercial ship traffic in the North Atlantic was temporarily reduced. In what way did the decreased ship traffic during this time offer scientists a chance to examine the effects of ships on right whales? What were the scientists' conclusions of the data collected during this time?

North Atlantic right whales are faced with chronic noise pollution from ship traffic. Normally, it would be impossible to ask commercial ships to stop their engines for days to monitor how noise affects whales. The reduced ship traffic that immediately followed the terrorist attacks on September 11, 2001, offered a quiet period. During this time, scientists were collecting whales' feces to test their level of cortisol, a hormone whose secretion increases with stress. The scientists found that the brief decline in shipping noise was accompanied by a significant drop in the whales' cortisol level. There was no drop in cortisol immediately after September 11 of other years. These data suggest that the normally high noise level related to shipping causes a chronic stress response in right whales.