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A rare species is a group of organisms that are very uncommon or scarce. This designation may be applied to either a plant or animal taxon, and may be distinct from the term endangered or threatened species. Designation of a rare species may be made by an official body, such as a national government, state, or province. However, the term more commonly appears without reference to specific criteria. The IUCN does not normally make such designations, but may use the term in scientific discussion. Rarity rests on a specific species being represented by a small number of organisms worldwide, usually fewer than 10,000. However, a species having a very narrow endemic range or fragmented habitat also influences the concept. A species may be endangered or vulnerable, but not considered rare if—for example—it has a large, dispersed population, but its numbers are declining rapidly or predicted to do so. Rare species are generally considered threatened because a small population size is more likely to not recover from stochastic events. (via Freebase)