Core areas are thought to be critical parts of animal home ranges for sustaining the population, but few studies have tested this important assumption. We examined whether core areas of spider monkeys Ateles geoffroyi had better habitat quality than the rest of their home range (non-core areas). Habitat quality parameters, including density and diversity of food trees, degree of forest maturity and density of sleeping trees in core and non-core areas were analyzed using Moran eigenvector generalized linear model (GLM) filtering using spatial eigenvector mapping to control for spatial autocorrelation. The best fitting GLM revealed that spider monkeys' core areas had higher habitat quality than non-core areas. This study provides quantitative evidence supporting the concept of core areas including the most critical resources for an animal population. In this respect, spider monkeys' core areas are a key to understand their movement ecology and habitat preferences.