The research was conducted by marine biologists at Oregon State University trying to better understand the migratory patterns and feeding behaviors of the giant blue whale -- the largest mammal on earth. Between 1993 and 2008, scientists tagged 171 blue whales off the coast of California.
By tracking their movements, biologists have been able to map their activity and the waters they frequent most. The results of the 15-year study -- published this week in PLOS ONE -- show their preferred feeding range conflicts with established shipping routes.
"The main areas that attract blue whales are highly productive, strong upwelling zones that produce large amounts of krill -- which is pretty much all that they eat," explained Ladd Irvine, a researcher at OSU's Marine Mammal Institute and lead author of the new study. "The whales have to maximize their food intake during the summer before they migrate south for the winter, typically starting in mid-October to mid-November."
Some 2,500 of the world's 10,000 blue whales spend their time off the North America's western coast. Each year, they travel as far north as Alaska and as far south as the equator. They spend most of the summer and fall off the coast of California, where their favorite spots are Santa Barbara and San Francisco -- regions criss-crossed by giant cargo ships.
"During one year, while we were filming the documentary, five blue whales were hit off of southern California during a seven-week period," said Bruce Mate, director of OSU's Marine Mammal Institute. "Blue whales may not be as acoustically aware as species that rely on echolocation to find prey and there is some evidence that the location of the engines in the rear of the ship creates something of an acoustic shadow in front of them, making it hard for whales to hear the ship coming."
The NOAA has moved shipping lanes before, and the agency says it will consider this new evidence when the lanes are next up for review.