ABSTRACT
Competition can affect species assemblages, population dynamics of competitors, and ecosystem processes. Understanding interspecific competition involves considering multidimensional factors that relate directly to the niche of competitors. For coexistence of species to occur, overlap on an important niche axis, such as diet, habitat, or space, must be accompanied by avoidance on another axis. Observed patterns of resource partitioning may have resulted from past competitive interactions, which reflect the realized rather than fundamental niches of competitors. Moreover, niche space and resultant overlap in resource use by competitors may differ seasonally, thereby leading to variation in competitive outcomes. This chapter describes interactions of black-tailed and mule deer (i.e., deer) with American bison; collared peccary; domestic livestock; elk; exotic animals, feral burros, horses, and pigs; moose; mountain sheep; pronghorn; and white-tailed deer. A changing climate holds potential to adversely affect deer across their distribution. Negative effects on forage quality and patterns of green-up may affect productivity of populations and alter migratory patterns. Drought in summer and amount and timing of spring rainfall may influence the distribution of deer and affect survival, especially in desert ecosystems. How such changes affect competitive interactions of mule deer with other ungulates is uncertain, and requires further research.
