The International Union for the Conservation of Nature and Natural Resources (IUCN)/World Conservation Union red list categories.
The text below gives summary definitions of the categories (number of bats in each category).
EXTINCT
(EX) A species is Extinct when there is no reasonable doubt that
the last individual has died. (13)
EXTINCT IN THE WILD (EW) A
species is Extinct in the wild when it is known only to survive in cultivation,
in captivity or as a naturalized population (or populations) well outside its
past range. A species is presumed extinct in the wild when exhaustive surveys
in known and/or expected habitats, at appropriate times (diurnal, seasonal,
annual), throughout its historic range have failed to record an individual.
Surveys should be over a time frame appropriate to the species' life cycle and
life form. (0)
CRITICALLY ENDANGERED (CR) A species 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 criteria A to E.
(26)
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 species
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 species, hybridization, 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.
ENDANGERED (EN) A species is Endangered when
it is not Critically Endangered but is facing a very high risk of extinction in
the wild in the near future, as defined by any of the criteria A to E. (32)
A) Population reduction in the form of
either of the following:
1) An observed,
estimated, inferred or suspected reduction of at least 50% 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 species
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 species, hybridization, pathogens, pollutants, competitors or
parasites.
2) A reduction
of at least 50%, 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 5000 km2 or area of occupancy estimated to be less than 500 km2, and
estimates indicating any two of the following:
1) Severely fragmented or known to exist at no more than five locations.
2) Continuing decline, inferred, observed
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 2500 mature individuals and either:
1) An estimated continuing decline of at least 20% within 5 years or 2
generations, 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 250 mature
individuals)
b) all individuals are in a
single subpopulation.
D) Population estimated to number less
than 250 mature individuals.
E)
Quantitative
analysis showing the probability of extinction in the wild is at least 20%
within 20 years or 5 generations, whichever is the longer
VULNERABLE (VU) A species is Vulnerable when
it is not Critically Endangered or Endangered but is facing a high risk of
extinction in the wild in the medium-term future, as defined by any of the
criteria A to E. (173)
A) Population reduction in the form of
either of the following:
1) An observed,
estimated, inferred or suspected reduction of at least 20% 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 species
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 species, hybridization, pathogens, pollutants, competitors or
parasites.
2) A reduction
of at least 20%, 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 20,000 km2 or area of occupancy estimated to be less than 2000 km2,
and estimates indicating any two of the following:
1) Severely
fragmented or known to exist at no more than ten locations.
2) Continuing
decline, inferred, observed 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 10,000 mature individuals and either:
1) An estimated
continuing decline of at least 10% within 10 years or 3 generations, 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 1000 mature
individuals)
b) all individuals are in a
single subpopulation.
D)
Population very small or restricted in the form of either of the following:
1) Population estimated to number less than 1000 mature individuals.
2) Population is
characterized by an acute restriction in its area of occupancy (typically less
than 100 km2) or in the number of locations (typically less than 5). Such a
species would thus be prone to the effects of human activities (or stochastic
events whose impact is increased by human activities) within a very short
period of time in an unforeseeable future, and is thus capable of becoming
Critically Endangered or even Extinct in a very short period.
E) Quantitative analysis showing the
probability of extinction in the wild is at least 10% within 100 years.
LOWER RISK (LR) A species is Lower Risk when
it has been evaluated, but does not satisfy the criteria for any of the
categories Critically Endangered, Endangered or Vulnerable. Species included in
the Lower Risk category can be separated into three subcategories: (212)
1. Conservation Dependent (cd). Species
which are the focus of a continuing species-specific or habitat-specific
conservation program targeted towards the species in question, the cessation of
which would result in the species qualifying for one of the threatened
categories above within a period of five years. (2)
2. Near Threatened (nt). Species which
do not qualify for Conservation Dependent, but which are close to qualifying
for Vulnerable. (210)
3. Least Concern (lc). Species that do
not qualify for Conservation Dependent or Near Threatened. (0)
DATA DEFICIENT (DD) A
species is Data Deficient when there is inadequate information to make a
direct, or indirect, assessment of its risk of extinction based on its
distribution and/or population status. A species in this category may be well
studied, and its biology well known, but appropriate data on abundance and/or
distribution are lacking. Data Deficient is therefore not a category of threat
or Lower Risk. Listing of species in this category indicates that more
information is required and acknowledges the possibility that future research
will show that threatened classification is appropriate. It is important to
make positive use of whatever data are available. In many cases great care
should be exercised in choosing between DD and threatened status. If the range
of a species is suspected to be relatively circumscribed and if a considerable
period of time has elapsed since the last record of the species, threatened
status may well be justified. (43)
NOT EVALUATED (NE) A species is Not Evaluated
when it is has not yet been assessed against the criteria. (0)
Source: (http://www.wcmc.org.uk/species/animals/table1.html)