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" but not "extinct". Designation of a rare species may be made by an official body such as a national government, state or province. However, the term is used more commonly without reference to a specific criteria. The IUCN does not normally make such designations but may use the term in its scientific discussions.[1]
The concept of rarity is established from having a very small number of organisms worldwide, usually a number less than 10,000; however, the concept is also influenced by having a very narrow endemic range and/or fragmented habitat.[2]
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 simply because the inability of small population sizes to recover from stochastic events, and the potential for a rapid decline in population.