Blue Whale

The blue whale (Balaenoptera musculus) is a marine mammal belonging to the baleen whales (Mysticeti). At 30 metres (98 ft) in length and 190 tonnes (210 short tons) or more in weight, it is the largest existing animal and the heaviest that has ever existed.

Long and slender, the blue whale's body can be various shades of bluish-grey dorsally and somewhat lighter underneath. There are at least three distinct subspecies: B. m. musculus of the North Atlantic and North Pacific, B. m. intermedia of the Southern Ocean and B. m. brevicauda (also known as the pygmy blue whale) found in the Indian Ocean and South Pacific Ocean. B. m. indica, found in the Indian Ocean, may be another subspecies. As with other baleen whales, its diet consists almost exclusively of small crustaceans known as krill.

Blue whales were abundant in nearly all the oceans on Earth until the beginning of the twentieth century. For over a century, they were hunted almost to extinction by whalers until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 blue whales worldwide, located in at least five groups. More recent research into the Pygmy subspecies suggests this may be an underestimate. Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (range 202,000 to 311,000). There remain only much smaller (around 2,000) concentrations in each of the eastern North Pacific, Antarctic, and Indian Ocean groups. There are two more groups in the North Atlantic, and at least two in the Southern Hemisphere. As of 2014, the Californian blue whale population has rebounded to nearly its pre-hunting population.

The blue whale has a long tapering body that appears stretched in comparison with the stockier build of other whales. The head is flat,U-shaped and has a prominent ridge running from the blowhole to the top of the upper lip. The front part of the mouth is thick with baleen plates; around 300 plates (each around one metre (3.2 ft) long) hang from the upper jaw, running 0.5 m (1.6 ft) back into the mouth. Between 70 and 118 grooves (called ventral pleats) run along the throat parallel to the body length. These pleats assist with evacuating water from the mouth after lunge feeding (see feeding below).

The dorsal fin is small, ranging in height from 8–70 centimeters (3.1–27.6 in) (usually 20–40 centimeters (7.9–15.7 in)) and averaging about 28 centimetres (11 in). It is visible only briefly during the dive sequence. Located around three-quarters of the way along the length of the body, it varies in shape from one individual to another; some only have a barely perceptible lump, but others may have prominent and falcate (sickle-shaped) dorsals. When surfacing to breathe, the blue whale raises its shoulder and blowhole out of the water to a greater extent than other large whales, such as the fin or sei whales. Observers can use this trait to differentiate between species at sea. Some blue whales in the North Atlantic and North Pacific raise their tail fluke when diving. When breathing, the whale emits a spectacular vertical single-column spout up to 12 metres (39 ft), typically 9 metres (30 ft). Its lung capacity is 5,000 litres (1320 U.S. gallons). Blue whales have twin blowholes shielded by a large splashguard.

The flippers are 3–4 metres (9.8–13.1 ft) long. The upper sides are grey with a thin white border; the lower sides are white. The head and tail fluke are generally uniformly grey. The whale's upper parts, and sometimes the flippers, are usually mottled. The degree of mottling varies substantially from individual to individual. Some may have a uniform slate-grey color, but others demonstrate a considerable variation of dark blues, greys and blacks, all tightly mottled.

Blue whales can reach speeds of 50 kilometres per hour (31 mph) over short bursts, usually when interacting with other whales, but 20 kilometres per hour (12 mph) is a more typical traveling speed. When feeding, they slow down to 5 kilometres per hour (3.1 mph).

Blue whales most commonly live alone or with one other individual. It is not known how long traveling pairs stay together. In locations where there is a high concentration of food, as many as 50 blue whales have been seen scattered over a small area. They do not form the large, close-knit groups seen in other baleen species.

The blue whale is the largest animal ever known to have lived. By comparison, one of the largest known dinosaurs of the Mesozoic Era was Argentinosaurus, which is estimated to have weighed up to 90 tonnes (99 short tons), comparable to the average of blue whale. Amphicoelias fragillimus, at an estimated 122 tonnes (134 short tons) is still lighter than the largest blue whales, despite being 200 feet (61 m) in length.

Blue whales are difficult to weigh because of their size. As is the case with most large whales targeted by whalers, adult blue whales have never been weighed whole, but cut up into manageable pieces first. This caused an underestimate of the total weight of the whale, due to the loss of blood and other fluids. As a whole, blue whales from the Northern Atlantic and Pacific appear to be smaller on average than those from sub-Antarctic waters. Nevertheless, measurements between 150–170 tonnes (170–190 short tons) were recorded of animals up to 27 metres (89 ft) in length. The weight of an individual 30 metres (98 ft) long is believed by the American National Marine Mammal Laboratory (NMML) to be in excess of 180 tonnes (200 short tons). The largest blue whale accurately weighed by NMML scientists to date was a female that weighed 177 tonnes (195 short tons).

There is some uncertainty about the biggest blue whale ever found, as most data came from blue whales killed in Antarctic waters during the first half of the twentieth century, which were collected by whalers not well-versed in standard zoological measurement techniques. The heaviest whale ever recorded weighed in at approximately 190 metric tons (210 short tons). The longest whales ever recorded were two females measuring 33.6 and 33.3 metres (110 and 109 ft), although in neither of these cases was the piecemeal weight gathered. The longest whale measured by scientists at the NMML was a 29.9 metres (98 ft), female caught in the Antarctic by Japanese whalers in 1946–47. Lieut. Quentin R. Walsh, USCG, while acting as whaling inspector of the factory ship Ulysses, verified the measurement of a 30 m (98 ft) pregnant blue whale caught in the Antarctic in the 1937–38 season. The longest reported in the North Pacific was a 27.1 metres (89 ft) female taken by Japanese whalers in 1959, and the longest reported in the North Atlantic was a 28.1 metres (92 ft) female caught in the Davis Strait.

Due to its large size, several organs of the blue whale are the largest in the animal kingdom. A blue whale's tongue weighs around 2.7 tonnes (3.0 short tons) and, when fully expanded, its mouth is large enough to hold up to 90 tonnes (99 short tons) of food and water. Despite the size of its mouth, the dimensions of its throat are such that a blue whale cannot swallow an object wider than a beach ball. Its heart weighs 1,000 pounds (450 kg) and is 6 feet (1.8 m) wide, with a thoracic aorta estimated to be 9 inches (23 cm) in diameter. During the first seven months of its life, a blue whale calf drinks approximately 400 litres (110 US gal) of milk every day. Blue whale calves gain weight quickly, as much as 90 kilograms (200 lb) every 24 hours. Even at birth, they weigh up to 2,700 kilograms (6,000 lb)—the same as a fully grown hippopotamus. Blue whales have relatively small brains, only about 6.92 kilograms (15.26 lb) , about 0.007% of its body weight. The blue whale penis is the largest penis of any living organism and also set the Guinness World Record as the longest of any animal's. The reported average length varies but is usually mentioned to have an average length of 2.4 m (8 ft) to 3.0 m (10 ft).

The Natural History Museum in London contains a famous mounted skeleton and life-size model of a blue whale, which were both the first of their kind in the world, but have since been replicated at the University of California, Santa Cruz. Similarly, the American Museum of Natural History in New York City has a full-size model in its Milstein Family Hall of Ocean Life. A juvenile blue whale skeleton is installed at the New Bedford Whaling Museum in New Bedford, Massachusetts.

The Aquarium of the Pacific in Long Beach, California features a life-size model of a mother blue whale with her calf suspended from the ceiling of its main hall. The Beaty Biodiversity Museum at the University of British Columbia, Canada, houses a display of a blue whale skeleton (skull is cast replica) directly on the main campus boulevard. A real skeleton of a blue whale at the Canadian Museum of Nature in Ottawa was also unveiled in May 2010.

The Museum of Natural History in Gothenburg, Sweden contains the only stuffed blue whale in the world. There one can also find the skeleton of the whale mounted beside the whale.

The Melbourne Museum features a skeleton of the pygmy blue whale.

The North Carolina Museum of Natural Sciences in Raleigh, North Carolina features a mounted skeleton of a blue whale which visitors can view from both the first and second floors.

The South African Museum in Cape Town, South Africa, features a considerable hall devoted to Whales and natural history known as the Whale Well. The centrepiece of the exhibit is a suspended mounted Blue Whale skeleton, gleaned from the carcass of a partially mature specimen which washed ashore in the mid 1980s. The skeleton's jaw bones are mounted on the floor of Whale Well to permit visitors a direct contact with them, and to walk between them so as to appreciate the size of the animal. Other mounted skeletons include that of a Humpback Whale and a Right Whale, together with in-scale composite models of other whales, dolphins and porpoises.

The Tokyo National Museum in Ueno Park displays a life-sized model of a blue whale in the front. Several other institutions such as Tokai University and Taiji Whale Museum hold skeleton of skeleton model of Pygmy blue whales, while several churches and buildings in western Japan including Nagasaki Prefecture display jawbone of captured animals as a gate.