Coprophagic behavior and cecal function were examined for the meadow vole (Microtus pennsylvanicus) and the pine vole (Microtus pinetorum) as diet quality was manipulated. The nutritional response of the voles to a high and low quality diet was measured after the coprophagic or cecal component was eliminated from the digestive process. The nature of the nutritional response was determined by measuring food consumption, fecal production, diet digestibility, energy intake, body weight dynamics, and reingestion frequency. The prevention of coprophagy lead to lower d!et digestibility and body weight loss as compared to controls, but did not reduce energy intake by pine or meadow voles. The deleterious effects of coprophagy prevention were similar in magnitude for both quality diets. It was concluded that coprophagy provided select dietary nutrients but was not critical for maximum energy or protein intake under these dietary conditions. Cecum removal decreased diet digestibility but did not significantly influence body weight dynamics since food consumption and passage rate increased to compensate for the digestibility perturbations induced by cecectomy. However, the effects of cecum removal on diet digestibility were more severe on the low quality diet. This suggested that cecal function became more important as diet quality decreased. The removal of the cecum probably disrupted existing mechanisms for internal digesta separation and selective retention that serve to improve fibrous forage digestibility. Consequently, cecectomized voles on the low quality diet reingested a smaller proportion of feces than did intact voles on the same diet. / Master of Science