Besides growth, their center of mass may also shift when one side becomes damper or dryer faster than the rest, due to sunlight, wind, or the wet ground.
The curved upper/exposed surface could act as an airfoil,
allowing gusts of wind to lift the moss-mouse, and move it a bit, and/or rotate it around it’s vertical axis.
Besides growth, their center of mass may also shift when one side becomes damper or dryer faster than the rest, due to sunlight, wind, or the wet ground.