Galloping sea lions could inspire land-sea robots | Science

Some robots swim and dive in the water; others rush across the country. Now, researchers want to build a machine that can do both. Their inspiration? The California sea lion.

Although they have a reputation for being lazy, sea lions are quick and graceful underwater. They can also sabotage it on land, galloping up to 6.7 meters per second on beaches and even climb and own rocks. (Humans are about a third of that speed.)

To help engineers design a potential land-sea robot, a graduate student recorded three trained California sea lions (Zalophus californianus) as they galloped on a short track outside (see video above), then analyzed their gait. She compared this gait to that of elephant seals – which are more than twice the size of sea lions, but also spend time on land. Data has shown that the sea lion’s ability to pull its posterior fins under its body to “walk” like a land animal provides a key benefit in both speed and agility.

The true posterior seal fins are on the side of the body. Therefore, elephant seals can only sway like a small worm, lifting their body high in the air, dragging their posterior fins under this mass, and ultimately pulling themselves forward with their front limbs. Sea lions don’t have to lift their bodies that high, the graduate student reported this week at the Society for Integrative and Comparative Biology virtual annual meeting. They can also synchronize the thrust with their hind fins.

The researcher calculated the power output of the sea lion and found it to be more efficient than harbor and gray seals, making them much faster and a better choice for inspiring a robotic marine mammal. So much for being lazy.