Assessing spatial learning and working memory in plateau zokors in comparison with plateau pikas and laboratory rats

Abstract

Spatial learning and memory skills are imperative for the survival and fitness of subterranean rodents because of the harsh underground niche in which they live that necessitates the avoidance of higher energy expenditures or probable conflicts with conspecifics or predators. Our study aims to assess the spatial learning and working memory performance of a subterranean rodent species, plateau zokors (Eospalax baileyi), compared to that of the surface-dwelling plateau pikas (Ochotona curzoniae) and laboratory rats (Rattus norvegicus) which spend a considerable time of their lives above ground. Animals were tested with a spatial delayed alternation task in a T-maze for six consecutive days. Plateau zokors showed less efficient learning and working memory capacity in the T-maze compared to plateau pikas and laboratory rats, which maintained accurate and consistent increased spatial learning rates and working memory performances. The three species did not show bias towards a certain arm of the maze. Additionally, clear sex-specific differences were observed in the laboratory rats regarding spatial learning and working memory functions, while in pikas and zokors, no sex-specific variations were detected. The latency to accomplish the task was significantly lower in rats than in pikas and zokors, but no sex-specific differences were detected in all the species. The inferior performance of plateau zokors, compared to pikas and rats, in the T-maze might imply that although the functional significance of working memory may overlap in diverse taxonomic groups, the adaptive value thereof may differ considerably across taxa on account of the divergence in environmental stability, domestication, habitat structure, behavioural needs and the available sensory cues between species.