JOEL SARTORE/NATIONAL GEOGRAPHIC PHOTO ARK

Moles have one of the most unusual walks on Earth

Moles don’t walk like any other animal. A new study finds the velvet-coated critters have a gait akin to a speed-walking human, assuming that person was also using a cane.

To make the discovery, researchers rigged x-ray machines with high-speed video cameras and peered at eastern moles (Scalopus aquaticus, pictured) as they walked through a plastic tunnel in the lab. Any other four-legged animal with a back bone, a cat or dog for instance, will position its limbs underneath its body as it walks. But the videos revealed that moles always keep their arms sprawled out in front of them when they walk, and the rest of their body always lags behind.

To take a step, the moles plant the sixth digits of each hand—known as their “false thumb”—on the ground and use them drag their bodies forward, similar to the way humans pull themselves along with a walker or a cane, the scientists report today in Biology Letters. Moving this way means a mole’s hands make only brief contact with the ground, just like a speed walker whose foot touches the ground for just a moment before lifting up again.

This peculiar mode of locomotion allows moles to keep their arms stretched in front of their bodies as they scurry through their underground corridors. Sprawling out during walking may protect their painstakingly built tunnels as it prevents moles from having to crouch through the narrow passages with bent limbs, which could bump into the walls and break down the soil. The researchers say understanding the mechanics of how underground animals like moles move could inspire the design of rescue and recovery robots.