How do mice enter hibernation? - briefly
As ambient temperature falls, mice build up fat reserves, retreat to insulated burrows, and their hypothalamic signals lower body temperature and metabolic rate. Reduced thyroid hormone and elevated melatonin trigger torpor cycles that constitute hibernation.
How do mice enter hibernation? - in detail
Mice initiate hibernation when ambient temperature drops below a critical threshold and food availability declines. Photoperiod shortening signals the hypothalamus to adjust hormonal output, primarily reducing thyroid‑stimulating hormone and increasing melatonin. These endocrine changes trigger a cascade that lowers the set point for body temperature regulation.
Metabolic reprogramming follows:
- Suppression of thermogenesis: Brown adipose tissue activity diminishes, reducing non‑shivering heat production.
- Shift to lipid oxidation: Stored triglycerides are mobilized, providing fatty acids that fuel mitochondria with a high respiratory quotient, conserving glucose.
- Reduced cardiac output: Heart rate falls from 500–600 beats min⁻¹ to 50–80 beats min⁻¹, decreasing oxygen demand.
- Neurotransmitter modulation: Increased GABAergic signaling and decreased glutamatergic activity depress central nervous system arousal, promoting torpor entry.
Behaviorally, mice seek insulated microhabitats—burrows lined with nesting material—that buffer temperature fluctuations. Within the shelter, they undergo a gradual decline in core temperature, reaching 2–5 °C, and a concomitant drop in metabolic rate to 1–5 % of basal levels. Periodic arousals occur every 2–3 days, lasting 15–30 minutes, during which body temperature rebounds to near‑normothermic values to restore cellular homeostasis.
The transition unfolds over several days, beginning with a pre‑hibernation phase of reduced activity and increased food intake to build fat reserves, followed by the torpor induction phase characterized by the physiological adjustments listed above. Successful completion of these stages ensures survival throughout the winter months.