Feeding Ecology of Valley Pocket Gophers (Thomomys bottae sanctidiegi) on a California Coastal Grassland

-San Diego valley pocket gophers (Thomomys bottae sanctidiegi) live on Mediterranean-climate coastal mesas where the growing season occurs during winter. I report seasonal food habits of these pocket gophers in a Mima mound and vernal pool habitat. Diets of 48 individuals collected over 1 yr were assessed by microhistological analysis of stomach contents. Shoots composed more than 70% dry mass of diets throughout the year, peaking at 99% during early spring. Pocket gophers consumed more than 60% dry mass forb shoots from late autumn until early spring, but shifted to 70% grass shoots during summer and early autumn. Belowground tissues and plants restricted to vernal pools were scarce in most diets. Pocket gophers in the genus Thomomys throughout the western United States exhibit striking dietary parallels when seasons are designated according to plant growth stage rather than time of year. Forb shoots appear to be the preferred food, particularly during reproduction; grass shoots, corms and roots increase in importance during plant dormancy.