Ecotourism is increasing worldwide for financial, educational and social purposes. Organized viewing of wildlife, especially at feeding sites where wildlife is “ready-to-view”, increases the opportunities for tourists to observe animals in the wild. However, feeding sites might retain only a subsample of wild populations. We thus hypothesized that such human intervention could induce population subdivisions and alter random mating by artificially creating small groups. The endangered Yunnan snub-nosed monkey (Rhinopithecus bieti) is an emblematic example reflecting the contradictions between conservation and ecotourism. In Gehuaqing/Xiangguqing (Yunnan, China), some individuals are maintained at feeding sites, while the rest of the monkey subpopulation wanders in a large surrounding area. Using faecal sampling and molecular analyses, we showed that this subpopulation is genetically structured into two moderately differentiated subgroups. The fed subgroup exhibited lower genetic diversity and higher relatedness than the rest of the subpopulation. Simulation model results indicated that a single translocation probably would not restore genetic diversity in fed individuals. Thus, feeding sites implementation and associated management practices might rapidly induce founder effects. We discuss the possibilities of conciliating ecotourism and the conservation of endangered animal species from this viewpoint.