The study of food intake is a prominent field of research in ecology. Many hypotheses have postulated about the selective forces operating on the evolution of foraging strategies of mammalian herbivores and on the coevolution between plants and animals. Small rodents are continuously faced with the choice of selecting appropriate food. Feeding behaviors direct them to when, where, what, and how much to eat. Selection involves the choice of food and can be affected by factors such as food availability, nutritional content, plant defense, foraging experience and physiological status. Many studies have focused on animals’ abilities to optimize their well-being and to reject food that is either poisonous or low in nutritional value. The physiological status of animals has been largely ignored in previous studies on food selection. The objective of this study was to test the influence of hunger and plant secondary compounds on the food selection of foraging behavior. From June to July, 2001, experiments were performed in Microtus fortis to determine the effect of huger and plant secondary compounds on their food selection and foraging behavior. The voles were captured in Dongting Lake area, Hunan province in May, 2006. The voles were first offered food ad libitum for a period of four days. Food intake was recorded daily for calculation of average food intake by each vole. To determine the amount of food to be provided during a following 3-d starvation period, the calculated average food intake was multiplied by a hunger index ranging from 0, 25, 50, 75, 100. The index 0 represented a complete deprivation of food and index 100 an ad libitum food supply. The voles were kept individually in fiberglass boxes with the lid removed in a dark room and behavior observation were made with the aid of an infrared night vision system. When the feeding bout ended, the animals were removed and the amount of food eaten was determined. Measurements were made for 2-4 feeding bouts per animal per night over 4 consecutive nights. The results indicated that hunger increased food intake, but had no significant effects on food selection. Ingesting rate and biting size of voles increased with severity of hunger, but the feeding frequency was not significant affected by hunger, and the time of feeding bout increased slowly. When the food vole had is as more 25% times as that of the food they had when they freely accessing to the food, the time of feeding bout of hunger voles were significantly increased. These results suggested that voles increased their food intake mainly by increasing bite size when they were in hunger. The changes of foraging behavior indicated that herbivores increased their bite sizes and food intake rate to satisfy their nutritional demands rather than prolonged their foraging time, decreasing the time for defending or reproductive activities.