It is clear to anyone that has watched astronauts being carried from their rockets that microgravity and disuse play havoc with our bones. But hibernating animals routinely experience months of immobility during every winter, and yet resume normal activity within hours of waking up in spring. Curious to find out how hibernating animals' bones fare during months of winter disuse, Frank van Breukelen and his colleagues from the University of Nevada tested hibernating golden-mantled ground squirrels' bones to see how well they stood up to months of inactivity(p. 2746).

Comparing the strength and stiffness of the bones of hibernating inactive and active ground squirrels, the team found that the dormant ground squirrels'bones were in fine condition. They were as strong and stiff as those of the active animals'. So months of winter inactivity did not affect the ground squirrels' bones.

However, when van Breukelen and his colleagues compared the strength of active summer squirrels and squirrels that had been inactive during the summer, they were surprised to see that the inactive squirrels had suffered bone loss, much like inactive humans and other mammals.

van Breukelen is now keen to understand how hibernating ground squirrels maintain their bones during months of inactivity and is curious to find out whether the cool winter conditions play a role in protecting the animals'bones from atrophy.

Utz, J. C., Nelson, S., O'Toole, B. J. and van Breukelen, F.(
). Bone strength is maintained after 8 months of inactivity in hibernating golden-mantled ground squirrels, Spermophilus lateralis.
J. Exp. Biol.