The traveling speed for blue whales ranges 5–30 kilometers per hour (3.1–18.6 mph). Some whales have been recorded feeding in breeding grounds. There is evidence of alternative strategies, such as year-round residency, and partial (where only some individuals migrate) or age/sex-based migration. The animals appear to use memory to locate the best feeding areas. Populations may go on long migrations, traveling to their summer feeding grounds towards the poles and then heading to their winter breeding grounds in more equatorial waters. When productivity is high enough, blue whales can be seen in gatherings of more than 50 individuals. The blue whale is usually solitary, but can be found in pairs. In a female pygmy blue whale, one corpus albicans is formed on average every 2.6 years. In addition, female blue whales develop scars or corpora albicantia on their ovaries every time they ovulate. The maximum age of a pygmy blue whale determined this way is 73 years. The oldest blue whale determined using this method was 110 years old. Each year, a light and dark layer of wax is laid corresponding with fasting during migration and feeding time. Scientists look at a blue whale's earwax or ear plug to estimate its age. Life spanīlue whales live around 80–90 years or more. The record-holder blue whale was recorded at 173 tonnes (190 short tons), with estimates of up to 199 tonnes (220 short tons). The weight measured of the heart from a stranded North Atlantic blue whale was 180 kg (400 lb), the largest known in any animal. Eastern North Pacific blue whale males average 88.5 tonnes (195,000 lb) and females 100 tonnes (220,000 lb). In the Northern Hemisphere, males weigh an average 100 metric tons (220,000 lb) and females 112 metric tons (247,000 lb). The average length of sexually mature female blue whales is 22.0 meters (72.1 ft) for Eastern North Pacific blue whales, 24 meters (79 ft) for central and western North Pacific blue whales, 21–24 meters (68–78 ft) for North Atlantic blue whales, 25.4–26.3 meters (83.4–86.3 ft) for Antarctic blue whales, 23.5 meters (77.1 ft) for Chilean blue whales, and 21.3 meters (69.9 ft) for pygmy blue whales. It continues to face numerous man-made threats such as ship strikes, pollution, ocean noise and climate change. The International Union for Conservation of Nature has listed blue whales as Endangered as of 2018. It was hunted almost to the point of extinction by whalers until the International Whaling Commission banned all blue whale hunting in 1966. The blue whale was once abundant in nearly all the Earth's oceans until the end of the 19th century. 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. They are generally solitary or gather in small groups, and have no well-defined social structure other than mother-calf bonds. Blue whales are filter feeders their diet consists almost exclusively of krill. There is also evidence of year-round residencies, and partial or age/sex-based migration. 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 a population in the waters off Chile that may constitute a fifth subspecies. brevicauda (the pygmy blue whale) in the Indian Ocean and South Pacific Ocean, B. musculus in the North Atlantic and North Pacific, B. The blue whale's long and slender body can be of various shades of greyish-blue dorsally and somewhat lighter underneath. Reaching a maximum confirmed length of 29.9 meters (98 ft) and weighing up to 199 tonnes (196 long tons 219 short tons), it is the largest animal known ever to have existed. The blue whale ( Balaenoptera musculus) is a marine mammal and a baleen whale.

Are blue whales predators