Animal Info - Notes on the IUCN Red List Categories

 

IUCN Categories 

1960's, 1970's, 1980's, 1994, 1996, 2000, 2001, 2002, 2003

1960's - These ratings are based on the looseleaf IUCN Red Data Book sheets published in 1966 through 1969. The rating system used by IUCN at that time was substantially different from that which has been used more recently; therefore, for comparison purposes, the original ratings have been converted to the more familiar ones used in the 1994 IUCN Red List of Threatened Animals, as described below.

The first IUCN Red Data Book - Volume 1 - Mammalia published in 1966, did not use the categories "Endangered" (E), "Vulnerable" (V), "Rare" (R), etc. which were utilized to categorize threatened species in the 1970's, 1980's and early 1990's. Rather, it used a system combining "Categories", "Symbols", and "'Star'" listings:

Categories:

1 - Very rare and believed to be decreasing in numbers.
2 - Less rare but believed to be threatened - requires watching.
3 - Very rare but believed to be stable or increasing.
4 - Status inadequately known - survey required or data sought.

Symbols:

(a) - Full species.
(b) - Subspecies.
E - Exotic, introduced or captive populations believed more numerous than indigenous stock.
M - Under active management in a national park or other reserve.
P - Legally protected, at least in some parts of its range.
R - Included because of its restricted range.
S - Secrecy still desirable.
T - Subject to substantial export trade.

'Star' Listings (Species or subspecies of special importance):

*** - Giving cause for very grave anxiety
** - Giving cause for considerable anxiety
* - Giving cause for some anxiety

In addition, information concerning "three-star" (***) species was shown on pink sheets, and information concerning species which formerly were rare but had recovered to an extent that they were no longer endangered, were shown on green sheets.

For example, the hispid hare (Caprolagus hispidus) was rated 4(a)*** and listed on a pink sheet published in June 1967, while the cape mountain zebra (Equus zebra zebra) was rated 3(b)*MP on a sheet published in January 1966.

In January, 1969 the definitions for the Categories were completely revised and two of the 'Star' listings were dropped as follows:

Categories:

1 - Endangered. In immediate danger of extinction: continued survival unlikely without the implementation of special protective measures.
2 - Rare. Not under immediate threat of extinction, but occurring in such small numbers and/or in such a restricted or specialized habitat that it could quickly disappear. Requires careful watching.
3 - Depleted. Although still occurring in numbers adequate for survival, the species has been heavily depleted and continues to decline at a rate which gives cause for serious concern.
4 - Indeterminate. Apparently in danger, but insufficient data currently available on which to base a reliable assessment of status. Needs further study.

Symbols:

Same as above.

'Star' Listing:

*** - Critically endangered

In addition, pink sheets were still used for critically endangered species (***) and green sheets were used to denote species that were formerly endangered but had since recovered to the extent that their names had been withdrawn from the Red Data Book.

For comparison purposes, we have established the rough equivalency between the rating systems described above and those used more recently (see "1994" below):

Prior to January 1969

  • *** = E
  • 1,2 or ** = V
  • 3 = R
  • 4 = K

January 1969 and Thereafter

  • 1 or *** = E
  • 2 = R
  • 3 = V
  • 4 = I

1970's - Categories are those listed in Walker's Mammals of the World - 4th Edition (Nowak & Paradiso 1983) (taken from various individual data sheets in the IUCN Red Data Book issued through 1978).

1980's - Categories are those reported in The Collins Guide to the Rare Mammals of the World (Burton & Pearson 1987); which were taken from the IUCN Red Data Books current at the time and defined as follows:

  • Ext. - Extinct. Species that are possibly extinct, or near extinction.
  • E - Endangered. Species in danger of extinction, and whose survival is unlikely if the causal factors continue operating.
  • V - Vulnerable. Species believed likely to move into the 'Endangered' category in the near future, if the causal factors continue operating.
  • R - Rare. Species with small world populations that are not at present 'Endangered' or 'Vulnerable' but are at risk.
  • I - Indeterminate. Species known to be 'Endangered', 'Vulnerable' or 'Rare', but where there is not enough information to say which of the three categories is appropriate.
  • K - Insufficiently known. Species that are suspected, but not definitely known, to belong to any of the above categories, because of lack of information.

1994 - Categories are those used in the 1994 IUCN Red List of Threatened Animals and defined as follows:

  • Ex - Extinct. Species not definitely located in the wild during the past 50 years. On a few occasions, the category Ex? has been assigned; this denotes that it is virtually certain that the species has recently become extinct.
  • E - Endangered. Species in danger of extinction and whose survival is unlikely if the causal factors continue operating. Included are species whose numbers have been reduced to a critical level or whose habitats have been so drastically reduced that they are deemed to be in immediate danger of extinction. Also included are species that may be extinct but have definitely been seen in the wild in the past 50 years.
  • V - Vulnerable. Species believed likely to move into the 'Endangered' category in the near future if the causal factors continue operating. Included are species of which most or all the populations are decreasing because of over-exploitation, extensive destruction of habitat or other environmental disturbance; species with populations that have been seriously depleted and whose ultimate security has not yet been assured; and species with populations that are still abundant but are under threat from severe adverse factors throughout their range.
  • R - Rare. Species with small world populations that are not at present 'Endangered' or 'Vulnerable', but are at risk. These species are usually localised within restricted geographical areas or habitats or are thinly scattered over a more extensive range.
  • I - Indeterminate. Species known to be 'Endangered', 'Vulnerable' or 'Rare' but where there is not enough information to say which of the three categories is appropriate.
  • K - Insufficiently known. Species that are suspected but not definitely known to belong to any of the above categories, because of lack of information.

1996 - Categories are those used in the 1996 IUCN Red List of Threatened Animals. Listed below are the definitions for the categories and the criteria that were used to place each species in the three categories of highest degree of threat, "Critically Endangered" (CR), "Endangered" (EN) and "Vulnerable" (VU) (Species in any of these three categories are termed "Threatened"). (Note: These three categories are considered to correspond loosely with the three categories: Endangered (E), Vulnerable (V) and Rare (R), respectively, used in the 1994 IUCN Red List (1996 IUCN Red List of Threatened Animals, p. Intro 40)):

Categories:

  • EX - Extinct. A species is Extinct when there is no reasonable doubt that the last individual has died.
  • EW - Extinct in the Wild. A species is Extinct in the Wild when it is known only to survive in cultivation, in captivity or as a naturalised population (or populations) well outside the past range. A species is presumed extinct in the wild when exhaustive surveys in known and/or expected habitat, 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.
  • CR - Critically Endangered. 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) listed below.
  • EN - Endangered. 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) listed below.
  • VU - Vulnerable. 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 D) listed below.
  • LR - Lower Risk. A species is Lower Risk when it has been evaluated and 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:
    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. Near Threatened (nt). Species which do not qualify for Conservation Dependent, but which are close to qualifying for Vulnerable.
    3. Least Concern (lc). Species which do not qualify for Conservation Dependent or Near Threatened.
  • DD - Data Deficient. 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.
  • NE - Not Evaluated. A species is Not Evaluated when it has not yet been assessed against the criteria.

Criteria for Critically Endangered (CR), Endangered (EN) and Vulnerable (V):

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 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 ten 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, 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 sq km (39 sq mi) or area of occupancy estimated to be less than 10 sq km (3.9 sq mi), 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 three 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 ten years or three 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 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 50% over the last ten 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, hybridisation, 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 sq km (1930 sq mi) or area of occupancy estimated to be less than 500 sq km (193 sq mi), and estimates indicating any two of the following:

  1. Severely fragmented or known to exist at no more than five locations.
  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 2500 mature individuals and either:

  1. An estimated continuing decline of at least 20% within five years or two 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 twenty years or five 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 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 20% over the last ten 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, hybridisation, 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 sq km (7720 sq mi) or area of occupancy estimated to be less than 2000 sq km (772 sq mi), and estimates indicating any two of the following:

  1. Severely fragmented or known to exist at no more than ten locations.
  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 10,000 mature individuals and either:

    1. An estimated continuing decline of at least 10% within ten years or three 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 sq km (39 sq mi)) 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.

2000 - Same as 1996Revised criteria came into effect in 2001.

Weight

Information on body weights was compiled from a number of sources. See especially:

Values listed could be maximum weight, average weight, or whatever was available. The weights listed here should be considered only as approximate indicators of species' weights, frequently only accurate to within a factor of two at best (despite the fact that they may be listed with two significant figures).


Home | Rarest Mammals | Species Index | Species Groups Index | Country Index | Links


Last modified: July 28, 2004;

1999 - 2014 Animal Info. Endangered animals of the world. SJ Contact Us.