Hibernation: The Metabolic Rate Plunge

Physiology

Q10 coefficient 2.5

Torpor set-point 4 °C

Burrow (ambient) temperature 2 °C

Cycle

Arousal interval 7 d

Time compression 24 h/s

Click the animal in the burrow to disturb it — a real cause of unscheduled, energetically costly arousal in hibernating mammals.

Live Readouts

Body temp

37.0 °C

Metabolic rate

100%

Day / state

0.0 — Euthermic

Arousals so far

Energy used (actual)

If never torpid

Net energy saved

Spent on arousals

The real physiology

Metabolic rate scales with body temperature through the Q10 relationship that governs biochemical reaction rates generally:

R(T) = R_37 · Q10^((T − 37)/10)

A hibernator such as a ground squirrel actively suppresses its own thermostat, letting core temperature fall to near the burrow temperature (sometimes within a degree or two of 0 °C) so that Q10 scaling collapses metabolic rate to roughly 1-2% of the awake baseline. But the animal cannot stay torpid indefinitely: every 1-3 weeks it spends several hours actively re-warming to 37 °C via shivering and brown-fat thermogenesis — a real, well-documented, and energetically expensive event that can burn as much fuel as many days of torpor combined, then holds euthermic for roughly a day before cooling back down. Despite that recurring cost, the net energy spent cycling through torpor and arousal is still a small fraction of what staying fully euthermic all winter would cost — the tracker on the left integrates both totals live so the trade-off is visible, not just asserted.

Euthermic

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