I just got two babies and I have kept them communal but may separate them. Both of mine did this but together under the same cork bark, actually one did most of the excavating and the other guarded the entrance and would charge at me when I opened the enclosure, now they both are underground sharing the tunnel, with the most aggressive baby still guarding the entrance. I’m no expert but maybe the babies do this until they are adults and more able to protect themselves. Are yours still currently underground?
