In case you check back here, after a month, it is something that does indeed happen and does involve dominance and courtship. I don't THINK it is courtship. Where I work we have a slider tank for people who want to get rid of their pet sliders. River Cooters go in our outdoor pond and YBS and RES in our indoor tank. We have a Cooter-RES Hybrid male that will flutter his claws in a smaller YBS male's face. It is a sign of trying to exert dominance. The other turtle didn't mind this behavior too much at first and now just ignores it. If the other turtle stops getting enough food I would advise separation. Otherwise it doesn't matter much. The nails are soft and the fluttering isn't very rough, it's to only make contact not assault, sort of like brushing through a wall of hanging vines or beads, not enough force to put an eye out.