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COSEWIC Annual Report - 2005

Appendix VI : COSEWIC Assessment Process, Categories and Guidelines (COSEWIC O&P Manual –Appendix E3)

 Approved by COSEWIC in May 2004

Approved by CESCC in September 2004

Modifications approved by COSEWIC May 2005 [1]

Table 1.  Determining eligibility of species for status assessment.

A) Taxonomic validity

COSEWIC would normally only consider species and subspecies or varieties that have been established as valid in published taxonomic works or in peer reviewed communications from taxonomic specialists.  COSEWIC would not normally consider other designatable units unless they can be shown to be genetically distinct, separated by a major range disjunction, or biogeographically distinct (refer to Guidelines for Designatable Units Below the Species Level, Appendix F5). Justification for considering designatable units below the species level must be provided.

B)  Native species

COSEWIC would normally only consider native species.  A native species is a wild species that occurs in Canada naturally, or that has expanded its range into Canada without human intervention from a region where it naturally occurred, has produced viable populations, and has persisted in Canada for at least 50 years.

C)  Regularity of occurrence

COSEWIC would normally only consider species which occur or formerly have occurred regularly in Canada, excluding vagrants.

D)  Requires habitat in Canada

COSEWIC considers species that are year-round residents in Canada.  COSEWIC also considers a species which, although not a full‑time residents in Canada, meet the other eligibility criteria and require habitat in Canada for a key life history stage.

E)   Special cases

Notwithstanding the above guidelines, a taxon may be considered eligible if there are clear conservation reasons for consideration (for example high risk of extinction).  In particular, a species which does not meet the eligibility criteria but which is at risk in its primary range outside of Canada could be considered for designation.

Reasons for considering a special case must be presented and supporting information must be provided; this should normally be reviewed and agreed to by COSEWIC before a status report is prepared.

Table 2. COSEWIC quantitative criteria and guidelines for the status assessment of species.

COSEWIC’s revised criteria to guide the status assessment of species.  These were in use by COSEWIC by November 2001, and are based on the revised IUCN Red List categories (IUCN 2001 [2]).  An earlier version of the quantitative criteria was used by COSEWIC from October 1999 to May 2001. For definitions of terms marked in bold italics, see COSEWIC’s Glossary of Definitions and Abbreviations (Appendix C).

A. Declining Total Population
Reduction in population size based on any of the following 4 options and specifying a-e as appropriate:
>70 %>50 %
                       (1) population size reduction that is observed, estimated, inferred, or suspected in the past 10 years or 3 generations, whichever is longer, where the causes of the reduction are clearly reversible AND understood AND ceased, based on (and specifying) one or more of a-e below.
>50 %>30 %
                       (2) population size reduction that is observed, estimated, inferred or suspected over the last 10 years or 3 generations, whichever is longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) one or more of  a-e below.  
                      (3) population size reduction that is projected or suspected to be met within in the next 10 years or 3 generations, whichever is longer (up to a maximum of 100 years), based on (and specifying) one or more of b-e  below.
                    (4) population size reduction that is observed, estimated, inferred, projected or suspected over any 10 year or 3 generation period, whichever is longer (up to a maximum of 100 years in the future), where the time period includes both the past and the future, AND where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) one or more of a-e below.
  1. direct observation
  2. an index of abundance appropriate for the taxon
  3. a decline in area of occupancy, extent of occurrence and/or quality of habitat
  4. actual or potential levels of exploitation
  5. the effects of introduced taxa, hybridisation, pathogens, pollutants, competitors or parasites

B. Small Distribution, and Decline or Fluctuation 
     1.  Extent of occurrence < 5,000 km P2 P< 20,000 km P2 P
     2.   Area of occupancy< 500 km P2 P< 2,000 km P2 P
For either of the above, specify at least two of a-c: 
          (a)  either severely fragmented or known to exist at # locations <5<10
           (b) continuing decline observed, inferred or projected in one or more of the following:
  1. extent of occurrence
  2. area of occupancy
  3. area, extent and/or quality of habitat
  4. number of locations or populations
  5. number of mature individuals 
           (c) extreme fluctuations in one or more of the following:> 1 order of magnitude> 1 order of magnitude
  1. extent of occurrence
  2. area of occupancy
  3. number of locations or populations
  4. number of mature individuals 
C. Small Total Population Size and Decline  
Number of mature individuals< 2,500< 10,000
and 1 of the following 2:  
     (1)  an estimated continuing decline rate of at least:20% in 5 years or 2 generations whichever is longer (up to a maximum of 100 years in the future)10% in 10 years or 3 generations whichever is longer (up to a maximum of 100 years in the future)

      (2)  continuing decline, observed, projected, or inferred, in numbers of mature individuals and at least one of the     

             following (a-b):

            (a) population structure in  the form of one of the following: (i) no population estimated to contain >250 mature individuals(i) no population estimated to contain >1,000 mature individuals
 (ii)  at least 95 % of mature individuals in one population(ii) all mature individuals are in one population 
            (b)  extreme fluctuations in the number of mature individuals 

D. Very Small Population or Restricted Distribution 
       (1) number of mature individuals estimated to be< 250< 1,000
(2) Applies only to threatened:  Population with a very restricted area of occupancy (area of occupancy typically < 20 km²) or number of locations (typically 5 or fewer) such that it is prone to the effects of human activities or stochastic events within a very short time period in an uncertain future, and thus is capable of becoming highly endangered or even extinct in a very short time period.
E. Quantitative Analysis  

Indicating the probability of extinction in the wild to be

at least:

20% in 20 years or 5 generations, whichever is longer (up to a maximum of 100 years)10% in 100 years


Special Concern:  
those species that are particularly sensitive to human activities or natural events but are not endangered or threatened species.

Species may be classified as being of Special Concern if: 

  1. the species has declined to a level of abundance at which its persistence is increasingly threatened by genetic, demographic or environmental stochasticity, but the decline is not  sufficient to qualify the species as Threatened; or
  2. the species is likely to become Threatened if factors suspected of negatively influencing the persistence of the species are neither reversed nor managed with demonstrable effectiveness; or
  3. the species is near to qualifying, under any criterion, for Threatened status; or
  4. the species qualifies for Threatened status but there is clear indication of rescue effect from extra-limital populations.

Examples of reasons why a species may qualify for “Special Concern”:

  • a species that is particularly susceptible to a catastrophic event (e.g., a seabird population near an oil tanker route); or
  • a species with very restricted habitat or food requirements for which a threat to that habitat or food supply has been identified (e.g., a bird that forages primarily in old-growth forest, a plant that grows primarily on undisturbed sand dunes, a fish that spawns primarily in estuaries, a snake that feeds primarily on a crayfish whose habitat is threatened by siltation; or
  • a recovering species no longer considered to be Threatened or Endangered but not yet clearly secure.

Examples of reasons why a species may not qualify for “Special Concern”:

  • a species existing at low density in the absence of recognized threat (e.g., a large predatory animal defending a large home range or territory); or
  • a species existing at low density that does not qualify for Threatened status for which there is a clear indication of rescue effect.

Guidelines for use of Extinct or Extirpated

A species may be assessed as extinct or extirpated from Canada if:

  • there exists no remaining habitat for the species and there have been no records of the species despite recent surveys; or
  • 50 years have passed since the last credible record of the species, despite surveys in the interim; or
  • there is sufficient information to document that no individuals of the species remain alive.

Guidelines for use of Data Deficient

Data Deficient should be used for cases where the status report has fully investigated all best available information yet that information is insufficient to: a) satisfy any criteria or assign any status, or b) resolve the species’ eligibility for assessment.


  • Records of occurrence are too infrequent or too widespread to make any conclusions about extent of occurrence, population size, threats, or trends.
  • Surveys to verify occurrences, when undertaken, have not been sufficiently intensive or extensive or have not been conducted at the appropriate time of the year or under suitable conditions to ensure the reliability of the conclusions drawn from the data gathered.
  • The species’ occurrence in Canada cannot be confirmed or denied with assurance.

Data Deficient should not be used if: a)  the choice between two status designations is difficult to resolve by COSEWIC, or b) the status report is inadequate and has not fully investigated all best available information (in which case the report should be rejected), or c) the information available is minimally sufficient to assign status but inadequate for recovery planning or other such use.

Table 3. Guidelines for modifying status assessment based on rescue effect.

COSEWIC’s approach to assigning status is, first, to examine the Canadian status of a species or other Designatable Unit in isolation and then, if deemed appropriate, to consider the potential for “rescue” from extra-regional populations (e.g., from across an international boundary or from another Designatable Unit within Canada). The potential for “rescue” is then considered. The rescue effect is the immigration of gametes or individuals that have a high probability of reproducing successfully, such that extirpation or decline of a population, or some other Designatable Unit, can be mitigated. If the potential for rescue is high, the risk of extirpation may be reduced, and the status may be downgraded. COSEWIC addresses this by applying the following guidelines developed by IUCN for this purpose (Gardenfors et al. 1999 [3]).

  •  Likelihood of propagule migration: Are there any extra-regional populations within a distance from which propagules could reach the region?  Are there any effective barriers preventing dispersal to and from extra-regional populations?  Is the species capable of long-distance dispersal?  Is it known to do so?
  • Evidence for the existence of local adaptations: Are there any known differences in local adaptation between regional and extra-regional populations, i.e. is it probable that individuals from extra-regional populations are adapted to survive within the region?
  • Availability of suitable habitat: Are current conditions of habitats and/or other environmental (including climatological) requirements of the taxon in the region such that immigrating propagules are able to successfully establish themselves (i.e. are there inhabitable patches), or has the taxon disappeared from the region because conditions were not favourable?
  • Status of extra-regional populations: How abundant is the taxon in neighbouring regions?  Are the populations there stable, increasing or decreasing?  Are there any important threats to those populations?  Is it probable that they produce an appreciable amount of emigrants, and will continue to do so for the forseeable future?
  • Degree of dependence on extra-regional sources: Are extant regional populations self-sustaining (i.e. have they shown a positive reproductive rate over the years) or are they dependent on immigration for long-term survival (i.e. are the regional populations sinks)?
  • If there are no extra-regional populations or propagules are not able to disperse to the region, the regional population behaves as an endemic and the status category should be left unchanged.
  • If it is unlikely that individuals from extra-regional populations would be able to survive within the region, the status category should be left unchanged.
  • If there is not enough suitable habitat and current conservation measures are not leading to an improvement of the habitat within a foreseeable future, immigration from outside the region will not decrease extinction risk and the status category should be left unchanged.
  • If the taxon is more or less common outside the region and there are no signs of population decline, and if the taxon is capable of dispersing to the region and there is (or soon will be) available habitat, downgrading the category is appropriate. If the population size of extra-regional populations is declining, the ‘rescue effect’ is less likely to occur, hence downgrading the status category may not be appropriate.
  • If there is evidence that a substantial number of propagules regularly reach the region and the population still has a poor survival, the regional population may be a sink.  If so, and there are indications that the immigration will soon cease, upgrading the status category may be appropriate.

Table 4: Policy for modifying status assessment based on quantitative criteria 

COSEWIC, IUCN and other groups recognize the need for additional assessment tools. Specifically, there is a need to consider life‑history variation amongst species and other taxa. COSEWIC has developed the following guideline:

In addition to the quantitative guidelines, COSEWIC will base its assessment on the degree to which various life-history characteristics (e.g., age & size at maturity, dispersal strategy, longevity) affect extinction probability and the likelihood that the species is vulnerable to the Allee effects of density dependence.

All else being equal:

  • species with delayed age at maturity tend to be at greater risk of extinction than species with early age at maturity;
  • for indeterminately growing organisms (species that continue to grow after attaining maturity), larger species tend to be at greater risk of extinction than smaller species;
  • species with low dispersal tend to be at greater risk of extinction than species with high dispersal; and
  • species with non-overlapping generations tend to be at greater risk of extinction than species with overlapping generations.

Table 5.  COSEWIC status categories.

Extinct (X):
A wildlife species that no longer exists
Extirpated (XT):
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere
Endangered (E):
A wildlife species facing imminent extirpation or extinction
Threatened (T):
A wildlife species likely to become Endangered if limiting factors are not reversed
Special Concern (SC):
A wildlife species that may become a Threatened or an Endangered species because of a combination of biological characteristics and identified threats
Not at Risk (NAR):
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances
Data Deficient (DD):
A wildlife species for which there is inadequate information to make a direct, or indirect, assessment of its risk of extinction.

[1]In Table 1, Part C, wording was added to clarify that COSEWIC would consider species that have formerly occurred regularly in Canada.

In Table 2, Criteria 4a was modified slightly to correct a minor transcription error when the IUCN criteria was adapted by COSEWIC.

In Table 2, Criteria C2a was modified slightly to correct a minor transcription error when the IUCN criteria was adapted by COSEWIC.

In Table 3, the introductory text was modified to reflect the use of the term "Designatable Unit", which supersedes (but is not equivalent to) the older term "Population of National Significance".  Minor changes in the body of the table were made for clarity to more consistency use the term “extra-regional population”

[2]IUCN 2001. IUCN Red List Categories and Criteria: Version 3.1. Prepared by the IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, UK.

[3]Gardenfors, U.,  J.P.Rodriquez, C. Hilton‑Taylor, C. Hyslop, G. Mace, S. Molur and S. Poss. 1999.  Draft guidelines for the application of Red List criteria at national and regional levels. Species 31-32:58-70.