Sex and species differences in spatial memory in food-storing kangaroo rats

Abstract

Scatter-hoarding birds show superior performance in many spatial memory tasks and appear to relocate sites using different cues than nonscatter hoarders. However, there have not been similar studies of cue use and memory for locations by mammals that differ in their reliance on scatter hoards for survival. Here we report differences in spatial memory in two species of kangaroo rats that are predicted by foraging ecology. Merriam's kangaroo rat, Dipodomys merriami, a scatter hoarder that hoards intensively, showed accurate memory on a cache simulation task, which required the rat to find four predetermined locations after a 24-h delay. In contrast, the leaf-eating specialist Great Basin kangaroo rat, D. microps, which relies less on scatter hoarding, showed poorer accuracy under the same experimental conditions. The presence of local landmarks did not differentially affect recovery in the two species of kangaroo rats, unlike previous studies in birds. We did find a significant interaction between the presence of local landmarks and sex on target recovery. Female performance was significantly impaired by the absence of local landmarks, while male performance was unaltered. Spatial ecology predicted both species and sex differences in spatial memory in kangaroo rats.