Study
Freeze avoidance in a mammal: body temperatures below 0 °C in an Arctic hibernator
Barnes, Brian M.
Science, 1989
Implanted temperature-sensitive transmitters in Arctic ground squirrels and recorded abdominal temperature through the winter in animals hibernating in natural burrows in Alaska.
- Studied in
- Urocitellus parryii
- Sample size
- implanted free-living ground squirrels over a winter
Body temperature fell below freezing — to around −3 °C — and was held there for weeks without the animal freezing, in a supercooled state, while the squirrel remained alive and periodically rewarmed.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
A mammal can maintain a supercooled body temperature below 0 °C for extended periods, which had not previously been shown.
How NatureHQ reads it
The cleanest single demonstration that avoiding freezing and tolerating freezing are different solutions. The squirrel is below zero and unfrozen; the wood frog at the same temperature is frozen and alive. Both survive; almost nothing else about them is the same.
- A small number of animals, and the supercooled state is fragile — an ice nucleus would end it.
- How the squirrel avoids nucleation over weeks is still not fully explained.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: American Association for the Advancement of SciencePublished in Science or Science Advances (AAAS).
doi.org/10.1126/science.2740905
Checked against Crossref on 2026-09-28, and they agree on the title, the authors and the year.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-09-03.