Learning is differentially preserved across seasonal brain size change in the common shrew

Spatial learning was robust: all groups improved across trials and converged by the final trial, and neither season nor captivity reliably predicted strategy adoption. Visual associative learning was consistently inefficient but showed no winter decline; instead, shrews were most likely to adopt the high-performance strategy during spring regrowth. Path integration was the task most clearly impaired in winter, and efficiency declined across trials in all groups, suggesting that exploration is prioritised over navigational precision once a route becomes familiar.

Captivity acted as a task-dependent filter, depressing associative learning while leaving spatial learning unaffected and increasing return-path straightness. Seasonal brain shrinkage therefore does not impair cognition uniformly: ecologically critical functions are preserved while less urgent ones are allowed to decline, and brain size alone cannot serve as a proxy for learning ability.