As the largest mammal, blue whales have lived uncontested in the world’s oceans for millions of years. Now with a new kind of threat on the scene, that dominance may be coming back to haunt them.
The threat isn’t an animal — it’s massive thousand-foot long container ships that steam into and out of port at high speeds, frequently running over blue whales in the process.
“Blue whales pale in size to these ships so [a collision] wouldn’t even be noticeable,” says John Calambokidis of the Cascadia Research Collective in Olympia, Wash. “There are a number of cases where a whale has become impaled on the bow of a ship, and the ship comes into harbor without being aware it’s there.”
Calambokidis is coauthor of a new study, published recently in “Endangered Species Research,” that analyzes how blue whales behave as large ships approach. To gather this information, he and his coauthors place archival tags on blue whales that feed in the waters off the coast of Los Angeles-Long Beach Harbor, the busiest port on the West Coast. The tags, combined with GPS data, allowed the researchers to get a precise sense of the evasive actions that blue whales take as these behemoth ships bear down on them.
The short answer is they don’t do much. At best, the whales undertake a slow-moving, shallow dive that often begins too late to clear the approaching ship. Calambokidis and his coauthors observed that the descent rate on these dives is much slower than the whales’ descent rate when they dive for food. This leads them to hypothesize that the whales are startled by the ships and don’t really know how to react.
“Blue whales are not very adapted to making a response,” Calambokidis says. “As we thought about it, that makes sense because these animals have not evolved to deal with this kind of threat.”
In other words, the fact that blue whales have had it so good for so long has turned into a handicap now that they’re living in a human world.
What can be done to prevent these “ship strikes”? One potential solution would be to appoint spotters on ships, though that wouldn’t be very effective at night, when blue whales spend a lot of time near the surface and many collisions occur. Another would be to have ships broadcast an alarm signal. But, a 2004 study by researchers at the Woods Hole Oceanographic Institution found that such signals actually caused North Atlantic right whales to surface, increasing the chances a collision would take place.
Given all this, Calambokidis says the best — and maybe only — remedy is to keep whales and ships apart, steering the big boats around feeding grounds as much as possible.
Kevin Hartnett is a writer in South Carolina. He can be reached at firstname.lastname@example.org.