Here’s a strange one: For the rest of the day on September 11, 2001 after the attacks on the Twin Towers and the Pentagon, whales in the North Atlantic must have been heaving a huge sigh of relief. They could hear properly again.
Rosalind Rolland, a researcher at the New England Aquarium, was at sea that day, collecting fecal samples from whales. When she analyzed the samples later, she saw a “highly significant” decrease in stress hormones. There was only one possible explanation: the dramatic reduction in ship traffic that had been ordered.
“It was like being on the primal ocean,” she said. “The noise levels from shipping fell by half, as transport was shut down in response the terror attacks.”
Scientists have long known that shipping noise causes chronic stress to whales. As well as propeller noise, there’s military sonar and explosions that are set off by companies prospecting for oil and gas. Sonar in particular is implicated in the sudden deaths of dolphins and other marine mammals.
Rolland’s report says that:
Reduced ship traffic in the Bay of Fundy, Canada, following the events of 11 September 2001, resulted in a 6 dB decrease in underwater noise with a significant reduction below 150 Hz. This noise reduction was associated with decreased baseline levels of stress-related fecal hormone metabolites (glucocorticoids) in North Atlantic right whales (Eubalaena glacialis). This is the first evidence that exposure to low-frequency ship noise may be associated with chronic stress in whales, and has implications for all baleen whales in heavy ship traffic areas, and for recovery of this endangered right whale population.
Northern right whales are among the most endangered whales. They suffered most from commercial whaling. There are currently only 475 known to be alive and the population is growing at just 1% a year. Southern right whales are rebounding at the rate of 7-8% a year. Rolland calls the northern right whale “the urban whale,” because they live in the busy eastern seaboard of North America. She says noise is very likely to be a factor in the population’s slow recovery, and may also be affecting other whales.