In 2014, Jeremy Goldbogen, a marine biologist at Stanford University, stuck video cameras on the backs of blue whales, hoping to learn more about their eating habits. When he pulled out the footage, he realized he had been bombed. Dozens of Remora australis treated his research topics like dance floors, gliding and twisting on them – even when whales swam at high speed.
They “circled the entire surface” of the whales, he said. “We didn’t expect that at all.”
Remors – also known as sukari or whaling fish – are strange, even for fish. They attach a ride with cetaceans, sharks and other larger creatures from the depths, attaching to them with the help of a “suction disk”
Despite their attractiveness, we know very little about them. Many scientists have “looked at past remorse to any charismatic megafauna to which they were attached,” said Brooke Flammang, an assistant professor of biology at the New Jersey Institute of Technology. For a study published Wednesday in the Journal of Experimental Biology, Dr. Flammang, Dr. Goldbogen and others are investigating how remorse maneuvers while their whale hosts are on the move, shattering our previous view of them as passive hangers.
Dr. Flammang, who has been working with remors for years, was filled with questions from Dr. Goldbogen’s footage when she first saw him in 2015: Why did remors seem to prefer certain places on the whale? And how did they manage to glide on the surface of their cetacean transports without being blown away?
To solve these mysteries, Dr. Flamman and her colleagues built a three-dimensional digital model of a blue whale. Reproducing a bus-sized creature to the millimeter was “a big problem, literally,” she said.
In videos, the remarks usually accumulate around the hole and dorsal fin of the whale. Analysis of how the liquid flows around the whale shows that these are low-drag areas protected from the sound of water – “something like a whirlwind behind a rock in a river,” said Dr. Flammang. In other words, a safe place to hang your suction disc.
They then looked at how the remors could surf between these sheltered places. This comes down to a piece of water next to the whale that flows relatively slowly, even if the whale walks fast. Consider walking in a city block in a windstorm, Dr. Flammang said, “The closer you get to the buildings, the less you feel the gusts.”
According to the simulations of the model, the boundary layer between the hole of the whale and the dorsal fin is thick enough for the remorse to fit mostly inside it. “It swims in liquid at a much lower speed than it would if it were only a few inches higher,” she said.
Another analysis, this time of fluid flow around the remorse, suggests that as the fish’s suction disk slides over the whale’s skin, a low-pressure zone forms between them – potentially helping to keep the fish close. (In some video clips, fish that dare to move too far away from the surface are thrown “upside down” by the whale, Dr. Flamman said, although they usually recover and return.)
The study successfully combines methods to turn a random set of observations into a stable understanding, said Marian Porter, a biologist at the Atlantic University of Florida who was not involved. “This is a great example of how science should work – an issue that moves from one place to another,” she said.
Dr. Flammang then hopes to investigate whether larger types of remorse use similar tactics in smaller hosts.
She is also developing an artificial suction disk inspired by the remorse, which she hopes researchers like Dr. Goldbogen will eventually be able to use to better fit the cameras to the whales. These latest findings could help them figure out where to put them on the whale for “long-term attachment,” she said. Who knows who may appear in future shots.