For the first time, scientists notice humpback whales moving along the tracks of a ship Science

Two years ago, a team of marine biologists were fast asleep on a research vessel off the coast of Brazil when the captain woke them with a tense announcement: There was a “huge animal” following the ship. The bleary-eyed scientists made their way to the stern, where they found three humpback whales riding the ship’s wake, a behavior never before documented in such large whales. For more than an hour, the researchers watched the whales swim less than 10 meters behind their vessel.

“I’ve been working with marine mammals for more than 10 years, but I’ve never seen a whale follow a boat so long and so close,” said Israel Maciel, a marine mammal researcher at Rio de Janeiro State University and co-author of a recent preprint describing the encounter.

Scientists have long known that smaller marine mammals such as dolphins will travel on waves that are emitted laterally by vessels, known as diverging waves. The low-pressure troughs created by these waves allow mobile animals to swim with very little effort. Humpbacked coastal brazils, however, drifted in waves radiating from the stern, known as transverse waves. These waves also create troughs of low pressure that can pull an animal—much like a bicyclist might pull behind a vehicle or another bicyclist.

The late-night encounter, which was captured on video, came as Brazilian scientists were studying how marine mammals respond to noise generated by sonic booms that energy companies use to map seafloor geology. The trio of humpbacks—mother, calf, and second adult—were barely visible in the ship’s bright lights. Still, the researchers believe the episode marks the first time scientists have been able to record a large whale “riding” behind a ship, they reported in a preprint posted on ResearchGate. And this is a rare case of observing the behavior of whales at night.

The whales, which can grow up to 17 meters in length, likely used the ship’s wake to conserve energy as they began their annual 4,500-kilometer migration from Brazil to their winter waters off Antarctica, the researchers said. (Their ship was traveling in the same direction.) Whale calves, in particular, may benefit from riding a wave, notes biomechanist Frank Fish of West Chester University, who was not involved in the study. Calves have to come to the surface more often to breathe than adults and thus experience more resistance. By hitchhiking along the transverse wave, a tired mother and calf may need to move a muscle, Fish says. “From the point of view of energy, this is completely logical. Animals will do whatever they have to to conserve energy.”

Humpback whales are a well-studied species, so it’s surprising that this behavior hasn’t been documented before, says John Long, a researcher at Vassar College who studies the biomechanics of swimming and serves as a program director at the National Science Foundation. He thinks several factors probably lined up perfectly to lead to the wake ride. For example, the ship was moving relatively slowly, at 9 kilometers to 11 kilometers per hour, which is the upper limit of a humpback’s potential speed. And the winds were relatively light, which probably allowed an attractive wake to form.

Brazilian researchers hope to find out if wake riding is widespread among humpbacks. The answer could help reveal how animals perceive and interact with ships, which can pose a significant collision threat. Riding directly behind a ship can help whales avoid collisions with other ships, but it can also cause the animals to venture into high-traffic sea lanes more often.

But spotting more hitchhiking whales — especially at night — can be difficult, notes whale researcher Steven Katona, managing director of the nonprofit Conservation International. “No one really looks for whales at night, it’s a pretty thankless task,” he says. “If Titanic I couldn’t see an iceberg, who will see a whale?’

Still, the sighting is a reminder of how much we have yet to learn about the ocean’s leviathans, Long says. “There’s the potential for them to try to exploit all sorts of things in their environment to help with these long-term migrations,” he says. “Which is absolutely amazing.”

Leave a Comment

Your email address will not be published.