Niche separation was documented in a year-long study of Varecia variegata rubra and Eulemur fulvus albifrons on the Masoala Peninsula, Madagascar. Feeding trees were measured, and diet, forest height, and forest site were recorded at 5-min time points on focal animals. For time point data, multivariate and bivariate analysis of frequencies was employed to examine how niche dimensions vary between species according to sex, season, and reproductive stage. V. v. rubra feeds in larger trees than E. f. albifrons. V. v. rubra has a diet consisting mainly of fruit, whereas E. f. lbifrons has a more varied diet. V. v. ubra ranges mainly above 15 m in tree crowns, whereas E. f. albifrons ranges mainly below 15 m in a wide array of forest sites. Both species are largely frugivorous, but they harvest fruit in different-sized trees, in different quantities, and in different forest strata. Niche partitioning varies in tandem with seasonal shifts in climate and food availability and with reproductive stages. Seasonal shifts in forest site and forest height use are largely attributed to species-specific tactics for behavioral thermoregulation and predator avoidance. The diet of E. f. albifrons is diverse whether examined by season or reproductive stage. However, females of both species diversify their diets with more low-fiber protein than males during gestation, lactation, and the hot seasons. This pattern is most pronounced for V. v. rubra females and may be directly attributed to high energetic investment in reproduction. These results suggest that niche partitioning may be driven more by the energetic requirements of reproductive females than males.