In the mountains across the world, different types of vegetation occur at different elevations creating distinct zones with well-defined borders between them. Each vegetation zone provides specific living conditions for animals. Therefore species that are adapted to habitats created in the specific zone occur only at the specific elevations and do not overlap with other species of similar ecology and behavior adapted to other vegetation zones at different elevations. This zonation is believed to be especially true for ecologically similar species that narrowly specialize to use specific resources and therefore compete with each other if they co-occur next to each other in the same habitat.