Meadow voles (Microtus pennsylvanicus) utilized the sun for sun-compass orientation. Orientation was most predictable when food was utilized as a training goal. A delayed photoperiod shift altered orientation predictably in a clockwise direction. This orientation shift associated with the photoperiod change indicates an operative biological clock for sun-cued orientation. Also, females utilized this orientation mechanism predictably during homing studies; males responded nonpredictably. Reasons for this sexual difference are discussed.