Influence of facultative hibernation on memory retention in two closely related hamster species.

Hibernation is characterized by repeated torpor-arousal cycles during which profound physiological suppression occurs, but its effect on memory retention remains controversial. This may be partly due to the fact that most previous studies have focused on obligatory hibernators, often examining only single species, which can limit comparability between studies. We investigated whether facultative hibernation affects memory retention in two closely related species: the Mongolian hamster (Allocricetulus curtatus) and Eversmann's hamster (Allocricetulus eversmanni), whose hibernation is characterized by short torpor bouts lasting up to 48 h. Animals were trained in the operant conditioning and spatial maze tasks before hibernation and retested after a three-month hibernation period. We found no significant effect of hibernation on general memory retention or species-specific differences in the operant conditioning task. In the spatial maze task, overall performance of the Firth penalized logistic regression model was not significant (p = 0.054), however, a species x hibernation interaction effect was significant, indicating hibernation affected spatial memory retention differently in the two studied species, with a positive effect in Mongolian hamsters and a likely different (negative or missing) effect in Eversmann's hamsters. These results suggest that the effect of hibernation on memory retention can be task-dependent and can vary between species with similar torpor-arousal patterns under the same environmental conditions for hibernation.