Underwater noise from ships regularly extends into frequencies used by orcas and other toothed whales to communicate, according to a study published February 2 in the journal PeerJ. Of particular concern is that the research took place in Washington state's Haro Strait, home to a population of endangered southern resident killer whales.
In the study, the scientists noted that most of the noise came from container ships, with significant auditory peaks in the range the animals communicate—between 16,000 and 20,000 Hz.
Like all whales, orcas use sonar to bounce sound off of prey to help them hunt, but more importantly, to communicate and negotiate their relatively complex social networks. Previous research has shown that ship noise interferes with the communication of various species such as humpback, blue and North Atlantic right whale species. One 2006 study suggests that such noise reduces the hunting efficiency of Cuvier's beaked whales by 50 percent.
There is some positive news, though: Noise can be reduced simply by slowing down. If ships go only one knot slower, which is just over one mile per hour, that translates to one less decibel of noise. And going six knots slower cuts the noise in half, study author Scott Veirs told the Guardian.
