Daily hoarding opportunity entrains the pacemaker for hamster activity rhythms

The effects on activity rhythms of a daily 30 min opportunity to leave the home cage and hoard seeds from an open field were assessed in Syrian hamsters housed in continuous dim illumination. Six of ten hamsters responded with clear entrainment of their activity rhythms to the hoarding opportunity, as demonstrated by responses to phase shifts and by the onset phase of subsequent freerunning rhythms. No entrainable component separate from the …