Solitary and slow-moving, the marbled electric ray may remain motionless for several days at a time. It is more active at night and spends much of the day buried in sediment with only the eyes and spiracles showing. Consistent with its sluggish nature, the marbled electric ray has a low blood oxygen carrying capacity and heart rate (10–15 beats/min), and consumes less oxygen than other sharks and rays of similar size. It is highly tolerant of being deprived of oxygen (hypoxia), allowing it to cope with deoxygenated bottom waters or being stranded in small pools by the falling tide. The ray stops breathing entirely when the oxygen partial pressure in the water drops below 10–15 Torr, and can survive such a state for at least five hours. It deals with extreme hypoxia by coupling anaerobic glycolysis to additional energy-producing pathways in its mitochondria, which serves to slow down the accumulation of potentially harmful lactate within its cells.