Abstract: Much of the social behavior and organization of ungulates can be related to ecological parameters such as fiber content of forage, plant productivity, plant biomass, plant species diversity, productivity gradients, temporal and spatial fluctuations in productivity, habitat stability, food dispersion, three-dimensional structure of habitat, colonization, and predator density and diversity. These ecological variables can be linked via individual natural selection with the species' anti-predator strategies, emphasis on different channels of communication, relative frequency of damaging and non-damaging overt aggression, gregariousness and group structure, juvenile dispersal, home-range traditions, monogamy and polygamy, sexual dimorphism, territoriality, hierarchical rank structure, and plasticity of social structures. The ecological variables have primary manifestations which are behavior or which affect behavior, as well as secondary manifestations affecting behavior. There are logical links between the hypothesis linking ecology and behavior discussed here with some principles from bioenergetics, zoogeography, and paleontology. Although links do exist between ecology and behavior, they nevertheless represent distinct realms of natural selection in which social behavior appears as the more conservative element. The theoretical basis for this is discussed.