How do mice hibernate in nature? - briefly
Mice do not undergo true hibernation; instead, they enter short periods of torpor, reducing body temperature and metabolic rate while remaining in insulated burrows or nests. This physiological adjustment conserves energy during cold weather but requires periodic arousals to feed and maintain vital functions.
How do mice hibernate in nature? - in detail
Mice enter a state of prolonged torpor during the cold season, reducing body temperature, heart rate, and respiration to minimal levels. This metabolic depression conserves energy when food is scarce and ambient temperatures drop below the species’ thermal tolerance.
The transition is triggered by decreasing photoperiod and ambient temperature. As daylight shortens, the hypothalamus detects changes in melatonin secretion, initiating endocrine cascades that lower thyroid hormone activity and suppress metabolic processes. Simultaneously, the sympathetic nervous system reduces brown‑fat thermogenesis, allowing core temperature to fall close to ambient conditions.
Physiological adjustments include:
- Body temperature: declines from ~37 °C to 5–10 °C, depending on ambient conditions.
- Metabolic rate: drops to 2–5 % of the active-state basal rate.
- Heart rate: falls from 600–700 beats min⁻¹ to 50–100 beats min⁻¹.
- Respiratory frequency: reduces from 150–200 breaths min⁻¹ to 10–20 breaths min⁻¹.
- Energy utilization: primarily fatty acids stored in white adipose tissue; glycogen reserves are spared.
During torpor, mice periodically arouse briefly, a process called interbout arousal. These episodes, lasting 30 minutes to several hours, restore normal temperature and allow waste elimination, immune function maintenance, and replenishment of depleted substrates. The frequency of arousals varies with species and environmental severity; colder climates produce longer torpor bouts with fewer interruptions.
Species differences affect hibernation patterns. The common house mouse (Mus musculus) typically employs short, daily torpor rather than true multi‑month hibernation, whereas the Siberian hamster (Phodopus sibiricus) and certain wood mouse (Apodemus sylvaticus) populations exhibit extended multi‑week torpor periods. Genetic adaptations, such as upregulated uncoupling protein 1 (UCP‑1) in brown fat and altered expression of clock genes, support these divergent strategies.
Energy balance calculations demonstrate that a mouse can survive several months on stored lipids alone. Assuming an average fat reserve of 2 g and an energy yield of 39 kJ g⁻¹, the total available energy (~78 kJ) exceeds the reduced metabolic demand of ~0.5 kJ day⁻¹ during deep torpor, providing a safety margin for unpredictable environmental fluctuations.
In summary, the winter survival strategy of mice involves precise neuroendocrine signaling, extensive metabolic suppression, periodic thermoregulatory arousals, and species‑specific physiological adaptations that collectively enable prolonged inactivity in cold habitats.