Zen has what looks liks a peice of dead skin hanging off the back of her head. Not very big...just a little peice. I don't think she's dehydrated, I soak her every other day.
desert tortoises especially shed skin. I had several yearlings and they shed from the back of their necks regularly. Don't pull it off...it will fall off naturally but it takes a while...it has nothing to do with being dehydrated...