Underwater split image of a great white shark with a red tag attached to its dorsal fin

Tracking devices placed on great white sharks revealed the powerful animal’s leisurely habits. Credit: Andrew Fox/Rodney Fox Shark Expeditions

Biophysics

Why great white sharks dawdle their days away

To scientists’ surprise, the toothy predators fail to reach their most efficient cruising speed when swimming at the water’s surface.

Great white sharks do much of their swimming at a sluggish pace, saving their strength for chasing down food.

Unlike most fish, great white sharks (Carcharodon carcharias) maintain a warm body temperature, which requires a large amount of energy. To study the creatures’ energy-conservation strategies, Yuuki Watanabe at the National Institute of Polar Research in Tokyo and his colleagues put tracking devices on eight sharks living off Australia’s Neptune Islands.

The researchers monitored the sharks’ swimming speed and diving patterns over the course of many hours and found that the fish travel at a leisurely 2.9–4.9 kilometres per hour, slower than a theoretical estimate of the shark’s most efficient pace. The creatures also dived frequently, but made their descent by unpowered gliding rather than active swimming.

The authors suspect that because great white sharks must move constantly, frequent diving allows the animals to both forage and conserve energy that would otherwise be expended on surface swimming. This leaves them with more energy for chasing seals and other fast-moving prey.