a taxon is Critically Endangered when it is facing an
extremely high risk of extinction in the wild in the
immediate future, as defined by any of the following criteria (A to E):

A) Population reduction in the form of either of the
following:

1) An observed, estimated, inferred or suspected
reduction of at least 80% over the last 10 years or
three generations, whichever is the longer,
based on (and specifying) any of the following:

a) direct observation
b) an index of abundance appropriate for the
taxon
c) a decline in area of occupancy, extent of
occurrence and/or quality of habitat
d) actual or potential levels of exploitation
e) the effects of introduced taxa, hybridisation,
pathogens, pollutants, competitors or
parasites.

2) A reduction of at least 80%, projected or
suspected to be met within the next ten years or
three generations, whichever is the longer,
based on (and specifying) any of (b), (c), (d) or (e)
above.

B) Extent of occurrence estimated to be less than 100
km2 or area of occupancy estimated to be less than
10 km2, and estimates indicating any two of the
following:

1) Severely fragmented or known to exist at only a
single location.

2) Continuing decline, observed, inferred or
projected, in any of the following:

a) extent of occurrence
b) area of occupancy
c) area, extent and/or quality of habitat
d) number of locations or subpopulations
e) number of mature individuals.

3) Extreme fluctuations in any of the following:

a) extent of occurrence
b) area of occupancy
c) number of locations or subpopulations
d) number of mature individuals.

C) Population estimated to number less than 250
mature individuals and either:

1) An estimated continuing decline of at least 25%
within 3 years or one generation, whichever is
longer or

2) A continuing decline, observed, projected, or
inferred, in numbers of mature individuals and
population structure in the form of either:

a) severely fragmented (i.e. no subpopulation
estimated to contain more than 50 mature
individuals)
b) all individuals are in a single subpopulation.

D) Population estimated to number less than 50
mature individuals.

E) Quantitative analysis showing the probability of
extinction in the wild is at least 50% within 10
years or 3 generations, whichever is the longer.

[information taken from the IUCN homepage at http://www.iucn.org/themes/ssc/redlist/ redlist.htm]

Alternative form for Critically Endangered : CR.