No reasonable doubt that the last individual has died.
EW
Extinct in the wild
Known only to survive in captivity or as a naturalized populations well outside its previous range.
CR
Critically endangered
The species is in imminent risk of extinction in the wild.
EN
Endangered
The species is facing an extremely high risk of extinction in the wild.
VU
Vulnerable
The species is facing a high risk of extinction in the wild.
NT
Near threatened
The species does not meet any of the criteria that would categorise it as risking extinction but it is likely to do so in the future.
LC
Least concern
There are no current identifiable risks to the species.
DD
Data deficient
There is inadequate information to make an assessment of the risks to this species.
Some species were assessed using an earlier set of criteria. Species assessed using this system have the following instead of near threatened and least concern categories:
LR/cd
Lower risk/conservation dependent
Species which were the focus of conservation programmes and may have moved into a higher risk category if that programme was discontinued.
LR/nt
Lower risk/near threatened
Species which are close to being classified as vulnerable but are not the subject of conservation programmes.
LR/lc
Lower risk/least concern
Species for which there are no identifiable risks.
The order Cetacea includes whales, dolphins and porpoises. They are the mammals most fully adapted to aquatic life with a spindle-shaped nearly hairless body, protected by a thick layer of blubber, and forelimbs and tail modified to provide propulsion underwater.
^This list is derived from the IUCN Red List which lists species of mammals and includes those mammals that have recently been classified as extinct (since 1500 AD). The taxonomy and naming of the individual species is based on those used in existing Wikipedia articles as of 21 May 2007 and supplemented by the common names and taxonomy from the IUCN, Smithsonian Institution, or University of Michigan where no Wikipedia article was available.