Every fall, when the painted turtle senses winter coming, she dives to the bottom of her pond, burying herself in the muck and mud. She pulls into her shell and goes still: her heart rate slows, almost stopping. Her body temperature drops, staying just above freezing. She stops breathing, and she waits. For six months, she stays buried, and her body releases calcium from her bones into her bloodstream, so that she slowly begins even to lose her shape.