I have resently aquired three sugar gliders all three are females. i can only tell one apart from the others. This one is very gental with my daughter, so we named her sweet pea. the other two are so much alike i can't tell them apart. Is there some way to mark them? I would never consider any form that would hurt them. please help! they are also all 2 1/2 yrs old. thank you TONI