As most naked mole-rats scurry off to work, some continue to lie on their backs for a while in the sleeping chamber. It’s not laziness that keeps these animals from fulfilling their duties in the eusocial community structure of the mole-rats – it’s ventilation. 100 naked mole-rats may sleep together in a mound, and last night they were stuck in the middle. „The air can get very stuffy in these underground burrows,” says Professor Gary Lewin, a researcher at the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC). Oxygen levels can drop to conditions that would be life-threatening for other species.