He really likes to dig. They call him a "Ground-Type" so I think that has something to do with it. He also sticks his head out like a bear trap when he finishes-- there, see? [Anthos pokes his head up out of the hole he dug, in the classic antlion pose.] It must be how his species hunts.

It doesn't take much convincing. Most seem more than happy to join a trainer after they're captured.