Blue whale

| status = EN | status_system = IUCN3.1 | status_ref = | status2 = CITES_A1 | status2_system = CITES | status2_ref = | image = Anim1754 - Flickr - NOAA Photo Library.jpg | image_caption = | image2 = blue whale size.svg | image2_caption = | genus = Balaenoptera | species = musculus | authority = (Linnaeus, 1758) | subdivision_ranks = Subspecies | subdivision = * ''B. m. brevicauda'' Ichihara, 1966 * ?''B. m. indica'' Blyth, 1859 * ''B. m. intermedia'' Burmeister, 1871 * ''B. m. musculus'' Linnaeus, 1758 | range_map = Cypron-Range Balaenoptera musculus.svg | range_map_caption = Blue whale range (in blue) | synonyms = * ''Balaena musculus'' * ''Balaenoptera gibbar'' Scoresby 1820 * ''Pterobalaena gigas'' Van Beneden 1861 * ''Physalus latirostris'' Flower 1864 * ''Sibbaldius borealis'' Gray 1866 * ''Flowerius gigas'' Lilljeborg 1867 * ''Sibbaldius sulfureus'' Cope 1869 * ''Balaenoptera sibbaldii'' Sars 1875 }}

The blue whale (''Balaenoptera musculus'') is a marine mammal and a baleen whale. Reaching a maximum confirmed length of and weighing up to , it is the largest animal known ever to have existed. however, this was later disputed in 2024. Several extinct dinosaurs may also have reached a similar mass to the blue whale.}} The blue whale's long and slender body can be of various shades of greyish-blue on its upper surface and somewhat lighter underneath. Four subspecies are recognized: ''B. m. musculus'' in the North Atlantic and North Pacific, ''B. m. intermedia'' in the Southern Ocean, ''B. m. brevicauda'' (the pygmy blue whale) in the Indian Ocean and South Pacific Ocean, and ''B. m. indica'' in the Northern Indian Ocean. There is a population in the waters off Chile that may constitute a fifth subspecies.

In general, blue whale populations migrate between their summer feeding areas near the poles and their winter breeding grounds near the tropics. There is also evidence of year-round residencies, and partial or age/sex-based migration. Blue whales are filter feeders; their diet consists almost exclusively of krill. They are generally solitary or gather in small groups, and have no well-defined social structure other than mother–calf bonds. Blue whales vocalize, with a fundamental frequency ranging from 8 to 25 Hz; their vocalizations may vary by region, season, behavior, and time of day. Orcas are their only natural predators.

The blue whale was abundant in nearly all the Earth's oceans until the end of the 19th century. It was hunted almost to the point of extinction by whalers until the International Whaling Commission banned all blue whale hunting in 1966. The International Union for Conservation of Nature has listed blue whales as Endangered as of 2018. It continues to face numerous man-made threats such as ship strikes, pollution, ocean noise, and climate change. Provided by Wikipedia