...they lose all tension and stop moving at all? My snake sleeps wrapped around my throat/shoulders. I know he's asleep because he stops tongue flicking, stops rhythmically massaging my neck, stops moving around, and breathes deeply and evenly. Seriously, total lack of tension, scenting the air, moving around at all, steady breathing.... He's either asleep or he's unconscious for some other reason. Once he started to slip and fall he was so out. He caught himself/tightened up again and resumed a normal amount of muscle tension but he was OUT.