Study: Whales Lack Instincts to Dodge Ships

As the largest animals in the ocean, blue whales have not evolved defensive behaviors, which might explain why they are so prone to ship collisions, a Stanford biologist Jeremy Goldbogen suggests in his new research.

The first direct observations of blue whales attempting to avoid cargo ships suggest that this lack of an evasive response might make the whales particularly susceptible to deadly collisions.

“It’s not part of their evolutionary history to have cargo ships killing them, so they haven’t developed behavioral responses to this threat,” said Jeremy Goldbogen, an assistant professor of biology at Stanford’s Hopkins Marine Station, and the senior author on the study.

“They simply have no compelling response to avoiding these dangerous ships.”

Collisions with ships are a major threat to whales and pose a significant threat to the recovery of some endangered populations. Efforts to reduce collisions have mostly involved placing speed limits on ships passing through busy whale habitats or rerouting shipping channels around these areas altogether.

To evaluate the effectiveness of the measures, the researches conducted an experiment to find out how whales behave once they sense an oncoming ship.

In this first run of the experiment performed in a major shipping lane offshore Long Beach, California, the researchers observed 20 ship passages with nine individual whales, at distances ranging from 60 meters to more than 3 kilometers. In each of these instances, the whales exhibited behavior similar to the “startle response” that scientists observe during the tagging process, in which the whales essentially “play dead.”

“Blue whales have a subtle and not very convincing ability to get out of the way of oncoming ships,” said Goldbogen.

“Instead of diving, where the animal kicks tail up and goes down vertically, they just sink horizontally. This results in a slow dive and leaves them susceptible to ship strikes.”

A whale must dive 30 meters below the surface to escape the suction created by a ship’s propeller. In the study, the whales sank at about a half a meter per second and showed no evidence for swimming laterally to avoid the ship. In most cases, this was barely fast enough to get out of the ship’s way.

This is just the first step in figuring out the behavior of whales in the context of heavy shipping traffic, Goldbogen said.

The research team is already planning a second round of tests in which the GPS units will remain attached to the whales for several weeks, and will extend to species such as humpback whales.

With more data about both whale behavior and the frequency of near misses, Goldbogen hopes to be able to make a compelling recommendation to pleasure boaters and the shipping industry for how to minimize the risk of collisions.