Study
Warming up for sleep? Ground squirrels sleep during arousals from hibernation
Daan, Serge; Barnes, Brian M.; Strijkstra, Arjen M.
Neuroscience Letters, 1991
Brain activity was recorded in hibernating ground squirrels through the periodic arousals that interrupt hibernation every week or two, when an animal rewarms to normal body temperature for a few hours at very large energetic cost before cooling again.
- Studied in
- Spermophilus
- Sample size
- hibernating ground squirrels with implanted electrodes
The electroencephalogram during arousals showed the signature of slow-wave sleep, and the amount of it was greatest after the longest torpor bouts — the pattern expected if sleep pressure had accumulated during torpor rather than being discharged by it.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Hibernating animals may arouse in order to sleep, implying that torpor does not fulfil the function sleep serves despite superficially resembling it.
How NatureHQ reads it
This is the cleanest available demonstration that hibernation is not sleep. An animal spends a substantial fraction of its winter fat budget rewarming from torpor, and what it does with that expensive time is sleep. Whatever sleep is for, being cold and motionless for a week does not supply it. The interpretation is not universally accepted and it remains the most striking finding in the area.
- One genus, in the laboratory, with implanted electrodes.
- Interpreting the electroencephalogram at low body temperatures is contested.
- Correlation between torpor bout length and subsequent sleep does not establish that sleep pressure is the cause of arousal.
Recording a hibernator during the hours it wakes up
Hibernators rewarm every week or two at enormous energetic cost, then cool again. What is worth that much of a winter fat budget?
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: Elsevier journalsPublished in an Elsevier journal.
doi.org/10.1016/0304-3940(91)90276-y
This reference was resolved automatically against Crossref on 2026-08-11.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-08-10.