Columbian ground squirrels remember a maze after nine months of hibernation

Squirrels that had solved the maze before hibernation outperformed animals learning it for the first time.

Editorial illustration — not from the study.

Researchers tested 10 free-living Columbian ground squirrels on a maze during one active season and again after hibernation the following year. They compared their post-hibernation performance with that of eight squirrels that had not previously seen the maze.

The experienced squirrels were faster, took more efficient routes and made fewer navigation errors from their first post-hibernation trial. Their early performance was close to the level they reached at the end of their first set of trials, while the inexperienced squirrels needed at least five trials to match it.

Squirrels kept the map

Across measures of time to exit, route efficiency and navigational errors, squirrels that had previously completed the maze outperformed inexperienced squirrels by 41–98% after hibernation. Their initial post-hibernation performance was close to their earlier learned level, indicating that they retained useful information about the maze rather than having to learn it again. The experienced squirrels were about 93% faster and had about 36% less winding movement after hibernation than during their initial exposure, although their initial number of errors did not improve.

Why retained memory matters

The findings show that spatial memory can persist through a prolonged period of hibernation in a wild animal, despite the substantial changes in brain activity and neural structure associated with this state. For ground squirrels, retaining information about routes may help them quickly reuse or update important parts of their surroundings after returning to the active season. The results support the idea that changes in the brain during hibernation can preserve useful memories rather than simply causing memory loss.

Evidence and caveats

This was a field-based comparison involving 10 squirrels tested before and after hibernation and eight previously untested squirrels. Each animal completed up to 10 maze trials, and the researchers used statistical learning curves to distinguish retained performance from learning during the new trials. The squirrels were tested about 30 days after emerging from hibernation, so the study cannot determine whether memory could be retrieved immediately after emergence or whether recovery processes had already occurred. It tested one spatial maze task in one species, and 18 trials were excluded because of equipment problems or escapes.

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