<P> Blue whales are difficult to weigh because of their size . They were never weighed whole, but cut into blocks 0.5--0.6 meters (1.6--2.0 ft) across and weighed by parts . This caused a considerable loss of blood and body fluids, estimated to be about 6% of the total weight . As a whole, blue whales from the Northern Atlantic and Pacific are smaller on average than those from Antarctic waters . Adult weights typically range from 45--136 tonnes (50--150 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 standard measuring technique is to measure in a straight line from the upper jaw to the notch in the tail flukes . This came about because the edges of the tail flukes were typically cut off, and the lower jaw often falls open upon death . Many of the larger whales in the whaling records (especially those over 100 ft (30.5 m)) were probably measured incorrectly or even deliberately exaggerated . The heaviest weight ever reported was 173 metric tons (190 short tons); for a southern hemisphere female in 1947, it is likely that the largest blue whales would have weighed over 200 short tons (181 t). The longest whales ever recorded were two females measuring 33.6 and 33.3 metres (110 and 109 ft), but in neither of these cases was the piecemeal weight gathered . Possibly the largest recorded male was killed near the South Shetland Islands in 1926 and was measured at 31.7 m (104 ft). </P> <P> Females are generally a few feet longer than males . However, males may be slightly heavier on average than females of the same length, owing to heavier muscles and bones . Verified measurements rarely exceed 28 metres (92 ft). The longest measured by Macintosh and Wheeler (1929) was a female 28.5 metres (94 ft), while the largest male was 26.45 metres (86.8 ft); one of the same authors later found a male of 26.65 metres (87.4 ft) and stated that those lengths may be exceeded . The longest whale measured by scientists was 29.9 metres (98 ft) long . Lieut . Quentin R. Walsh, USCG, while acting as whaling inspector of the factory ship Ulysses, verified the measurement of a 29.9 m (98 ft) pregnant blue whale caught in the Antarctic in the 1937--38 season . A 26.8 metres (88 ft) male was verified by Japanese scientists in the 1947--48 whaling 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 metres (92 ft) female caught in the Davis Strait . The average weight of the longest scientifically verified specimens (29.9 metres (98 ft)) would be calculated to be 176.5 tonnes (194.6 tons), varying from 141 tonnes (155.4 tons) to 211.5 tonnes (233.1 tons) depending on fat condition . One study found that a hypothetical 33 metres (108 ft) blue whale would be too large to exist in real life, due to metabolic and energy constraints . </P> <P> 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 . The heart of an average sized blue whale weighs 400 pounds (180 kg) and is the largest known in any animal . During the first seven months of its life, a blue whale calf drinks approximately 380 litres (100 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 (5,950 lb)--the same as a fully grown hippopotamus . Blue whales have proportionally small brains, only about 6.92 kilograms (15.26 lb), about 0.007% of its body weight, although with a highly convoluted cerebral cortex . 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 to 3.0 m (8 to 10 ft). </P> <P> Blue whales feed almost exclusively on krill, though they also take small numbers of copepods . The species of this zooplankton eaten by blue whales varies from ocean to ocean . In the North Atlantic, Meganyctiphanes norvegica, Thysanoessa raschii, Thysanoessa inermis and Thysanoessa longicaudata are the usual food; in the North Pacific, Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, Thysanoessa spinifera, Nyctiphanes symplex and Nematoscelis megalops; and in the Southern Hemisphere, Euphausia superba, Euphausia crystallorophias, Euphausia valentini, and Nyctiphanes australis . </P>

How big is the mouth of a blue whale