I have a 6.5" tort and a 6" tort both females. The bigger one will put her front legs on the back of the smaller one or ram her head into the smaller ones side. The smaller one is minding her own business and allows the other one to do this without even walking away. It does not appear to be a sexual mounting or an actual fight or anything. Is it a show of dominance? We seperate them when we catch it but we are not with 24 hours a day. They have a 10' x 10' space so I doubt it is frustration from being too close. Any thoughts?