Blue whale

Description

The blue whale (Balaenoptera musculus) is a marine mammal and a baleen whale. Reaching a maximum confirmed length of 29.9 meters (98 ft) and weighing up to 199 metric tons (196 long tons; 219 short tons), it is the largest animal known to have ever existed. The blue whale's long and slender body can be of various shades of greyish-blue dorsally 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, B. m. indica in the Northern Indian Ocean. There is also 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 polars and their winter breeding ground 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. The fundamental frequency for blue whale vocalizations ranges from 8 to 25 Hz and the production of vocalizations may vary by region, season, behavior, and time of day. Orcas are their only natural predators. The blue whale was once 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. Blue whales have long, slender mottled grayish-blue bodies, although they appear blue underwater. The mottling pattern is highly variable. Individuals have a unique pigmentation pattern along the back in the region of the dorsal fin which can be used for the purpose of identification. Additional distinguishing features of the blue whale include a broad, flat head, which appears U shaped from above; 270-395 entirely black baleen plates on each side of their upper jaw; 60-88 expandable throat pleats; long, slender flippers; a small up to 33 centimeters (13 in) falcate dorsal fin positioned far back toward the tail; a thick tail stock; and a massive, slender fluke.