Reseach ArticleMule deer (Odocoileus hemionus), elk (Cervus elaphus), and cattle share rangelands throughout much of interior western North America. Considerable debate exists about the degree to which facilitation or competition occurs for forage between these three species (Nelson 1982, Wisdom and Thomas 1996, Miller 2002). Prior cattle grazing can have beneficial effects on elk nutrition. The removal of forage by cattle can improve forage quality by enhancing regrowth of forage or by changing ratios of live to dead plant material (Cook 2002), and forage quality on elk winter ranges in the interior Northwest can be improved by cattle grazing in the spring (Anderson and Scherzinger 1975, Clark 1996). To date, however, studies have not shown enhancement of forage quality in the summer following late spring or early summer grazing by elk or cattle. Competition for forage between mule deer, elk, and cattle is probably greatest on winter and spring/autumn ranges (Nelson 1982, Wisdom and Thomas 1996), and minimal between wild ungulates and cattle during summer (Miller 2002). Most summer ranges for mule deer and elk are on large areas of public land containing a diversity of habitats and high potential for forage production (Miller 2002). On some summer ranges, however, competition for forage may exist in late summer and early fall because forage quality can be poor and not meet nutritional requirements of wild ungulates and cattle (Torbit 1985, Hanley et al. 1989, Cook 2002). This is especially evident in regions where summer drought is the normal part of the climatic regime (Vavra and Phillips 1980, Svejcar and Vavra 1985). On the Starkey Experimental Forest and Range (Starkey), northeast Oregon, competition for forage may occur in late summer among all three species, especially between elk and cattle (Coe et al. 2001, Stewart et al. 2002). Conditions at Starkey typify those on summer ranges shared by mule deer, elk, and cattle in forests of the interior western United States. Consequently, we conducted a manipulative experiment on Starkey summer range to evaluate the potential for competition or facilitation for forage among mule deer, elk, and cattle in grand fir (Abies grandis) forests. Our specific objectives were to determine diet composition, dry matter intake rates, and percent dietary overlap of all three species in response to prior grazing by elk and cattle. In this paper we focus on results obtained from the bite count data. A detailed analysis of the nutritional consequences of previous grazing by elk or cattle on subsequent diets of mule deer, elk, or cattle will be presented elsewhere (Damiran in prep.). Results from our study could improve range management for mule deer, elk and cattle on public land, especially with regards to allocating forage among these three species when ranges are shared in forested habitats (Ager et al. 2004).