Is larger better: Effects of resource quality on grazer energy utilization

Body size and grazing efficiency are closely linked: larger grazers typically exhibit higher feeding rates and faster growth rates than smaller grazers. However, independent of body size, grazers differ in their response to shifting resource qualities. Thus, grazers can be adapted to their resource quality environment suggesting that body size alone may not always explain the outcome of grazer interactions. We studied resource acquisition and energy utilization in several Daphnia species feeding on a range of algae of different resource qualities. We found that larger grazers were better than smaller grazers in utilizing energy from all food sources. Overall, body size explained a considerable proportion of the species specific variation in resource utilization.