[Animals] Why do some aquatic animals swim in circles when they go?

[#Steeven.™]

Not only sharks, green turtles, penguins and certain marine mammals do something quite unusual: swim in circles, according to a study that indicates that this behavior could be used to search for food, interact with other specimens or for navigation.

This is the main conclusion of a work published in the journal iScience, of the Cell group, in which the researchers indicate that they do not yet understand the reasons for this curious pattern.

"We found that a wide variety of marine megafauna exhibited similar circling behavior, in which the animals circled more than twice at a relatively constant speed," summarizes Tomoko Narazaki of the University of Tokyo in a note.

Narazaki's team, which used technology to reconstruct these movements in 3D, made their discovery while studying the reproductive behavior of green turtles.

"To be honest, I couldn't believe my eyes when I first studied the data because the turtles were going around in circles so constantly, like a machine!" Narazaki details.

When she returned to her lab, she reported this "interesting discovery" to her colleagues who use the same 3D data records to study a wide range of marine megafauna taxa, the researcher says.

What came next surprised the researchers even more: They noticed that various species of marine animals showed more or less the same movements in a circle.

"This finding is surprising, in part, because swimming in a straight line is the most efficient way to get around," says Narazaki, adding that there must be some good reason for the animals to go around in circles.

The scientific team points out that some circular movements were recorded in the feeding areas of the animals, which suggests that this behavior could have some benefit in finding food; for example, a total of 272 events like these were observed in four tiger sharks tagged off Hawaii.

However, it was observed that sea lions circulate mainly during the day, although they feed mainly at night. Other circling actions that were not related to foraging were also observed. For example, they saw a male tiger shark circling to approach a female for courtship.

The researchers add that evidence in sea turtles suggests that the circles may also play a role in navigation.

"What surprised me the most was that the home-seeking turtles move in circles in seemingly important places from a navigational point of view, such as just before the final approach to their target," Narazaki concludes.

The circles may help these animals detect the magnetic field to orient themselves.