When out of burrow, does Mochi sit upright, or pancake out a lot? Are there very many vocalizations at night. If the answer to those questions is yes (sits upright mostly and croaks a lot), think male.
There is another indicator of gender, and that is the appearance of the front feet. In your photo, this indicator is impossible to see either way but with clean feet, you might be able to use the guidance below to make a determination.