When do mice hibernate? - briefly
Mice do not hibernate; they stay active throughout the year, finding insulated nests and stored food to survive cold periods. In severe temperatures they may briefly reduce metabolism, but they never undergo true hibernation.
When do mice hibernate? - in detail
Mice enter a period of reduced metabolic activity rather than true hibernation. This state, often termed torpor, begins when ambient temperatures fall below approximately 5 °C (41 °F) and food supplies become scarce. Laboratory studies show that house mice (Mus musculus) initiate torpor after several consecutive days of cold exposure combined with limited caloric intake.
Physiological changes during torpor include a drop in body temperature from the normal 35–37 °C to as low as 10–15 °C, heart rate reduction from 600–800 beats per minute to under 100, and a metabolic rate decline of up to 95 %. These adjustments conserve energy until conditions improve.
Geographic variation influences the timing and duration of the torpid phase. In temperate regions, wild field mice (Apodemus sylvaticus) may experience multiple torpor bouts throughout autumn and winter, each lasting from a few hours to several days. In contrast, populations in milder climates exhibit only occasional short torpor episodes during unusually cold spells.
Key factors that trigger the onset of this energy‑saving state are:
- Sustained ambient temperature below the thermal neutral zone.
- Decrease in available high‑energy food sources.
- Photoperiod shortening, which reinforces hormonal signals such as reduced melatonin and altered thyroid hormone levels.
Recovery from torpor occurs rapidly once temperatures rise above the threshold and food becomes abundant. Core body temperature and metabolic processes return to normal within 30–60 minutes, allowing the animal to resume normal activity.
Overall, mice do not hibernate in the classic sense; they employ torpor as a flexible response to cold and starvation, with onset determined by temperature, food availability, and seasonal light cues.