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Density-dependent negative feedback relationships between populations and the forage available to them have long served as a foundation for large ungulate population ecology and habitat management in North America. However, increasing evidence suggests that density-independent relationships between large ungulates and nutrition also exist during summer, that these may significantly limit reproduction and population growth, and that these limitations may be more common than often believed. We consider our data collected on elk in the western US and on caribou in Canada, along with findings from a variety of studies, to discuss ecological attributes that may contribute to density-independent, nutrition-based limitations in summer. Density-independent limitations are increasingly documented in arid, highly stochastic environments but our data suggests they may also occur in forest ecosystems where nutrient content (mainly digestible energy) and/or forage abundance (through instantaneous and daily intake rates) fail to satisfy nutrition requirements of lactating females. Although the data remain indirect, we conclude that ecological characteristics in some settings can be responsible for inadequate forage quality or quantity, regardless of ungulate population density (i.e., density-independent nutritional limitations), and that greater understanding of relationships between ecological conditions, forage quality and quantity, and ungulate population dynamics should lead to better management of habitat on behalf of large ungulate populations in many areas of North America.