Visual and auditory cues facilitate cache pilferage of Siberian chipmunks(Tamias sibiricus)under indoor conditions

In the struggle for survival,scatter-hoarding rodents are known to cache food and pilfer the caches of others.The extent to which rodents utilize auditory/visual cues from conspecifics to improve cache-pilfering is un­known.Here,Siberian chipmunks(Tamias sibiricus)were allowed to search for caches of Corylus heterophyl­la seeds(man-made caches and animal-made caches)after experiencing cues from a conspecific’s cache-search­ing events.For each type of cache,3 experimental scenarios were presented:(1)alone(control);(2)auditory/visual(hearing and seeing conspecific’s cache-searching events);and(3)auditory only(hearing conspecific’s cache-searching events only)with random orders.The subjects located man-made caches faster,harvested more caches,and hoarded more seeds both in the auditory/visual and the auditory only treatments compared to the control,while scatter-hoarding more seeds in the auditory/visual treatment but larder-hoarding more seeds in the auditory only treatment.Compared to the control,the animals spent less time locating animal-made caches,har­vested more caches,ate fewer seeds,larder-hoarded more seeds and hoarded more seeds in total both in the au­ditory/visual and the auditory only treatments,while eating more seeds and hoarded fewer seeds in total in the auditory only treatment than in the auditory/visual treatment.The results also show that females spent less time locating the animal-made caches,but they scatter-hoarded fewer seeds than males in the auditory/visual treat­ment.To the best of our knowledge,this is the first report that visual and/or auditory cues of conspecifics im­prove cache-pilfering and hoarding in rodents.

Olfaction alters spatial memory strategy of scatter-hoarding animals

Although it has been suggested that olfaction is closely interconnected with hippocampal systems,whether olfaction regulates spatial memory strategy remains never known.Furthermore,no study has examined how olfaction mediates spatial memory established on the external objects,for example,caches made by scatter-hoarding animals.Here,we experimentally induced nondestructive and reversible olfaction loss of a scatter-hoarding animal Leopoldamys edwardsi,to test whether and how olfaction regulates spatial memory to mediate cache recovery and pilferage.Our results showed that the normal L.edwardsi preferred to pilfer caches of others rather than to recover their own using accurate spatial memory(35.7%vs.18.6%).Anosmic L.edwardsi preferred to recover the caches they made prior to olfaction loss rather than to pilfer from others relied on spatial memory(54.2%vs.36.0%).However,L.edwardsi with anosmia showed no preference either to the caches they established after olfaction loss or caches made by others(25.8%vs.29.1%).These collectively indicate that olfaction loss has a potential to affect new memory formation but not previously established spatial memory on caches.Our study first showed that olfaction modified spatial memory strategy in cache recovery and pilferage behaviors of scatter-hoarding animals.We suggest that future studies pay more attention to the evolution of olfaction and its relationship with spatial memory strategy.