New research finds that blue whales aren’t compelled to move out of the way of passing ships.
by Hannah Moore
May 11, 2015—Business and leisure sailors will want to carefully watch for blue whales while out on the water. New data reveals that the animals are not adapted to safely dodge an oncoming ship, according to Discovery News.
Published in Endangered Species Research, this study from Stanford University is the first time that whales’ reactions to passing ships have been tracked, reported the Contra Costa Times.
Blue whales don’t have an evolutionary history of ships killing them, so they haven’t developed the behavioral reflexes that would prompt them to avoid ships.
To conduct the study, researchers put GPS on several blue whales off the Long Beach, CA. They tracked nine whales for 24 hours and saw the whales closely encounter 20 ships separately. The distances between the whales and ships were from 60 meters to more than 3 kilometers.
Researchers saw that the whales tended to “play dead” when they saw the ships, when they should have plunged in a fast dive to get out of the way quickly. The whales even pivoted at a slighter angle and moved at a slower speed than usual during these close encounters with the ships.
Instead of kicking its tail up and moving vertically downward while diving, the blue whale sinks horizontally. This creates a slow dive and makes the whale vulnerable to a collision with a passing ship.
To safely avoid a ship, a whale must dive at least 30 meters. The observed whales sank at about half a meter per second.
Blues aren’t the only whales with lack of ability to avoid ship dangers, either. A lifeless humpback whale was found on a Pacifica beach last week, with injuries suggesting that it was killed by a moving ship.
Researchers hope to make a plan to help both shipping businesses and leisure sailors better avoid striking slow-moving whales.
Ship speed limits and re-routes to avoid known whale breeding areas have been implemented in some areas, but the efforts are not widely enforced. Jeremy Goldbogen, the study’s senior author, argues that enforced ship speed limits would help decrease the threat of ships to marine mammals.
Blue whales are the largest animals to ever roam the Earth. Adult-sized blues are up to 100 feet long and can weigh up to 200 tons. They typically dive for krill and consume thousands of pounds of it per day.
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