Scientists have tracked the movements of large ocean-dwelling animals in three dimensions, both in time and space. They found that some species of marine animals circled in place and suggested why they behave so unusually.

In their study, the researchers found that many of the marine megafauna exhibited circular motion, in which the animals circled sequentially at a relatively constant speed more than twice. The results of the work are published by iScience magazine.

Scientists at the University of Tokyo first discovered the mysterious circling behavior in homing green turtles during an experiment on their movement and homing. Researchers transported nesting turtles from one location to another to study their navigational abilities.

Later, scientists realized that different types of marine animals make more or less the same circular movements. The discovery is surprising in part because swimming in a straight line is the most efficient way to get around. This suggests that there must be some good reason why the animals are circling.

Some cases of whirling have been recorded in places of animal feeding. Scientists have suggested that circling is useful for finding food. However, it turned out that this is not suitable for all species: seals circle mainly during the day, although they feed at night. Other incidents of whirling were also not related to the search for food. For example, biologists observed a male tiger shark circling to approach the female for courtship. That being said, data on sea turtles suggest that circling helps them navigate.

Scientists say studies of such small-scale movements, including circular motion, in more marine species may reveal important behaviors that would otherwise not be accounted for. In future research, they would like to study the movements of animals depending on the internal state and environmental conditions in search of additional explanations.