The greater frequency of trees that persists in the higher elevations (appx. 5,000 ft.) around the Great Basin area of northern Nevada and in Sonoran Desert of northern Arizona

Introduction The optimal foraging theory is an evolutionary model based on the predictability of animal foraging. This model is based on various adaptive principles such as: (1) the next generation depends upon the ability for the current generation to forage and prosper; (2) there is a genetic component to foraging that may be inherited; (3) finally, rate of foraging is related to the fitness of the organism (Pyke, 1977). The optimal foraging theory implies that foraging animals will leave a quantity of resources, or what is known as “give up density” (GUD), after the amount of energy gained from the nutrients is less than the amount of energy lost in attempts to obtain the nutrients (Wellborn 2002). Based on this concept it is hypothesized that food patches varying in density will be diminished to the same degree regardless of beginning density. This prediction from optimal foraging theory will be the main focus of the study. By testing both low and high density food patches at high and low elevations this study will examine if elevation has an impact upon nocturnal rodent foraging habits in two different desert environments.