Optimization of Diets through Food Preferences by Heteromyid Rodents

The number of seeds requiring per day by four species of Sonoran Desert rodents (Dipodomys merriami, Perognathus amplus, Perognathus baileyi, and Perognathus intermedius), and the average energy content/seeds of the species the rodents ingested, were determined from information on the rodent daily energy requirement, proportions of seeds in the diets and cheek pouches of the rodents and the soil near their capture sites, and the energy content per seed of the important seed species. All rodent species except P. amplus gather seeds which are energetically superior to those randomly available in the soil, and all species choose to ingest, from the seeds they have gathered, those seeds which are richest in energy. The data indicate that the rodents primarily base their dietary preferences on energy considerations. The rodents do not, however, maximize energy intake, but rather optimize their diets by also ingesting a number of seed species which are relatively low in energy content, but which apparently provide some undefined value (e.g . nutrition, moisture).