A seahorse's tail is a bizarre one in the animal kingdom because it's square—or more precisely, it's made up of about three dozen "square plates," explains Gizmodo. Why? Researchers set out to discover just that with a method that sounds, well, pretty fun: They printed 3D replicas of the tail, along with round tails of a similar size, then took a mallet to them, Popular Science reports. In doing so, they realized the square version is harder to smash and "tends to snap naturally back into place once it's been twisted and deformed," a researcher says, per LiveScience. That means in the wild, a square tail is more resilient when it suffers, say, a predator bite. The trade-off is that the plates cut motion in half, but the tail can still bend about 90 degrees.
The flat surface of the tail also lets a seahorse get extra close to seaweed and coral, and is perfect for twisting and gripping, the study finds. What does that mean for us? Well, researchers say in a post at Eureka Alert that the tail could provide "inspiration for the next big technological breakthrough in robotics, defense systems, and biomedicine." They argue the superior square could be used to create stronger, more flexible robotic arms or even armor, particularly for a search-and-rescue "snake" robot that moves along the ground. Its body sections are susceptible to rips and tears, and "the seahorse tail gives us an idea of how we might add armor on to these," a researcher says. (Seahorses do this surprising thing when mad.)