Ability to dig very well
The Mogmas are a new race in Skyward Sword who live around Eldin Volcano. Their appearance a kind of cross between a prairie dog and an ape, and they are skilled diggers. Each Mogma has a unique hairstyle. When Mogmas speak with Link, they pop the top half of their bodies out of the ground and go back under immediately after they are done. They seem to have a jazzy, upbeat theme song.
The Mogmas appear to be a friendly race that helps Link, allowing Link to keep a Bomb Bag that he originally got for them, and warning Link about shady characters clad in red. At some point around the volcano area, two Mogmas are seen talking about a key for the nearby temple. They broke the key into several pieces and Link must use Phi's treasure detecting ability to locate them. It is unclear why these two Mogmas are hiding the key, but it is possible they are trying to protect the temple from intruders.