An endangered species is a population of an organism which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters. An endangered species is usually a taxonomic species, but may be another evolutionary significant unit. The World Conservation Union (IUCN) has calculated the percentage of endangered species as 40 percent of all organisms based on the sample of species that have been evaluated through 2006.IUCN Red-list statistics (2006) (Note: the IUCN groups all threatened species for their summary purposes.) Many nations have laws offering protection to these species: for example, forbidding hunting, restricting land development or creating preserves. Only a few of the many species at risk of extinction actually make it to the lists and obtain legal protection. Many more species become extinct, or potentially will become extinct, without gaining public notice.

Conservation status

main: Conservation status

The conservation status of a species is an indicator of the likelihood of that endangered species not living. Many factors are taken into account when assessing the conservation status of a species; not simply the number remaining, but the overall increase or decrease in the population over time, breeding success rates, known threats, and so on. The IUCN Red List is the best known conservation status listing.

Internationally, 190 countries have signed an accord agreeing to create Biodiversity Action Plans to protect endangered and other threatened species. In the United States this plan is usually called a species Recovery Plan.

IUCN Red List Endangered species

IUCN Red List of Threatened Species uses the term endangered species as a specific category of imperilment, rather than as a general term. Under the IUCN Categories and Criteria, endangered species is between critically endangered and vulnerable. Also critically endangered species may also be counted as endangered species and fill all the criteria

The more general term used by the IUCN for species at risk of extinction is threatened species, which also includes the less-at-risk category of vulnerable species together with endangered and critically endangered.

IUCN categories include:

• Extinct: the last remaining member of the species has died, or is presumed beyond reasonable doubt to have died. Examples: Thylacine, Dodo, Passenger Pigeon
• Extinct in the wild: captive individuals survive, but there is no free-living, natural population. Examples:South China Tiger, Alagoas Curassow
• Critically endangered: faces an extremely high risk of extinction in the immediate future. Examples: Arakan Forest Turtle, Javan Rhino, Brazilian Merganser
• Endangered: faces a very high risk of extinction in the near future. Examples: Blue Whale, Snow Leopard, African Wild dog, Tiger, Albatross, Crowned Solitary Eagle
• Vulnerable: faces a high risk of extinction in the medium-term. Examples: Cheetah, Gaur, Lion, Wolverine
• Conservation Dependent: The following animal is not severely threatened, but the animal must depend on conservation programs. Examples: Spotted Hyena, Leopard Shark, Black Caiman
• Near Threatened: may be considered threatened in the near future. Examples: Blue-billed Duck, Solitary Eagle, Small-clawed Otter , Maned Wolf
• Least Concern: no immediate threat to the survival of the species. Examples: Brown Rat, Nootka Cypress, Wood Pigeon