The CSG is the official IUCN Red List Authority responsible for conducting Red List assessments for cetacean species. The CSG works closely with the IUCN Red List Programme to assess, evaluate, and determine the appropriate extinction risk category for each species. The CSG attempts to update all species assessments at least once every ten years, applying the Red List criteria to do so, and more frequently for species assessed in a threatened category. Members of the CSG with expertise on a particular species are recruited to draft the Red List assessments, and these are reviewed by members of the CSG Red List Authority before being submitted to IUCN for checking and publication.
Cetacean Species and Taxonomy
The number of recognized cetacean species and subspecies is continually being revised and re-examined on the basis of new scientific data.
The Society for Marine Mammalogy’s (SMM) Committee on Taxonomy, chaired by Ana Costa (who took over from Patty Rosel in 2024), produces the official list of marine mammal species and subspecies. The IUCN Cetacean Specialist Group follows the SMM list including when identifying taxonomic units to be assessed for the Red List. The SMM list of marine mammal species is revised at least annually to reflect the continuing flux in marine mammal taxonomy.
Subspecies and Subpopulation Red List Assessments
Most cetacean species have very large distributions with multiple subpopulations that are demographically independent, and hence, could face different levels of threat and would be assigned to different listing categories. The global species distributions often span multiple countries with many stakeholders, which makes conservation planning at the species level difficult if not impossible. Therefore, most effective conservation planning and action for most cetaceans is at the subpopulation level. Red List assessments have the power to stimulate needed conservation attention and it is therefore beneficial to conduct assessments of a larger number of subspecies and subpopulations than are currently listed. However, as Red List assessments are undertaken on a volunteer basis by a small group of qualified and trained individuals, it is not feasible, or useful for conservation, to assess all subpopulations and subspecies.
Subspecies Assessments
Given the nature of cetacean biology, distribution and threats, the Cetacean Specialist Group has decided to prioritize future assessments below the species level primarily on the basis of which populations are likely to warrant listing as CR, EN or VU. As a general rule, where a subspecies would be assessed as LC or in the same threatened category as the species, or where there is considerable taxonomic uncertainty, it is not deemed necessary to conduct a specific subspecies assessment at this time. The document below provides a brief rationale as to why some baleen whale subspecies have not been and are not planned to be assessed. This was based on the guidelines for selecting cetacean subspecies and subpopulations for assessment developed by the CSG.
CSG Evaluation of Baleen Whale Subspecies for the Red List – Final
