セミクジラ
, the International Union for Conservation of Nature (IUCN) recognized 86 cetacean species, 40 of which are considered whales. , six are considered at risk, as they are ranked "Critically Endangered" (North Atlantic right whale), "Endangered" (blue whale, North Pacific right whale, and sei whale), and "Vulnerable" (fin whale and sperm whale). Twenty-one species have a "Data Deficient" ranking. Species that live in polar habitats are vulnerable to the effects of recent and ongoing climate change, particularly the time when pack ice forms and melts.