Utilization of non-native seeds by seed-eating rodents and ants was studied experimentally in the field. It was found that patterns of granivory in the Israeli deserts are very similar to those reported for the same groups in the deserts of North America. Rodents are more efficient than ants at finding and harvesting seeds. Only rodents can find and harvest seeds that occur below the soil surface. The two taxa appear to rank barley particles on the basis of size. Big seeds are utilized first and the shift to small seeds occurs only after most of the big seeds have been utilized. This result agrees with the prediction of optimal diet theory.