Evolution of cetaceans Blue whales are rorquals family Balaenopteridae , a family that includes the humpback whale , the fin whale , Bryde's whale , the sei whale , and the minke whale. The blue whale lineage diverged from the other rorquals during the Miocene, between 7.
Evolution of cetaceans Blue whales are rorquals family Balaenopteridae , a family that includes the humpback whale , the fin whale , Bryde's whale , the sei whale , and the minke whale.
The blue whale lineage diverged from the other rorquals during the Miocene, between 7. However, gene flow between the species appears to have continued beyond that date. The blue whale has the greatest genetic diversity of any baleen whale, and a higher than average diversity among mammals.
Arnason and Gullberg describe the genetic distance between a blue and a fin as about the same as that between a human and a gorilla. Other common names for the blue whale have included "Sibbald's rorqual" after Sibbald, who first described the species , the "great blue whale" and the "great northern rorqual". These names have now fallen into disuse. The first known usage of the term "blue whale" was in Melville's Moby-Dick, which only mentions it in passing and does not specifically attribute it to the species in question.
Sars adopted it as the Norwegian common name in This is likely because blue whales were driven north by expanding ice, and some have stayed there ever since. The pygmy blue whale's evolutionarily recent origins cause it to have a relatively low genetic diversity.
Between 70 and 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.
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. Blue whales have twin blowholes shielded by a large splashguard. 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 typically swim at a depth of about 13 meters 43 feet when migrating in order to eliminate drag from surface waves.
The deepest confirmed dive is meters 1, feet. 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. Size View of a blue whale and its bow wave, showing the blowhole The blow of a blue whale The small dorsal fin of this blue whale is just visible on the far left. The blue whale is the largest animal known to have ever lived.
They were never weighed whole, but cut into blocks 0. Adult weights typically range from 45— tonnes 50— short tons. 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. However, males may be slightly heavier on average than females of the same length, owing to heavier muscles and bones.
The longest measured by Macintosh and Wheeler was a female Walsh, USCG , while acting as whaling inspector of the factory ship Ulysses, verified the measurement of a A blue whale's tongue weighs around 2. In the North Atlantic, Meganyctiphanes norvegica , Thysanoessa raschii , Thysanoessa inermis and Thysanoessa longicaudata are the usual food; and in the Southern Hemisphere, Euphausia superba , Euphausia crystallorophias , Euphausia valentini , and Nyctiphanes australis.
Blue whales gorge on krill in the rich waters of the Antarctic before migrating to their breeding grounds in the warmer, less-rich waters nearer the equator. The blue whale can take in up to 90 times as much energy as it expends, allowing it to build up considerable energy reserves.
The whale feeds by lunging forward at groups of krill, taking the animals and a large quantity of water into its mouth. The water is then squeezed out through the baleen plates by pressure from the ventral pouch and tongue. Once the mouth is clear of water, the remaining krill, unable to pass through the plates, are swallowed.
The blue whale also incidentally consumes small fish, crustaceans and squid caught up with krill. In the fall, males will follow females for prolonged periods of time. This often causes the racing whales to breach, which is rare in blue whales.
This racing behavior may even escalate to physical violence between the males. Scientists have observed this behavior in multiple parts of the world, including the Gulf of St. The first video of a calf thought to be nursing was filmed on 5 February Strandings Blue whale strandings are extremely uncommon, and, because the species is largely solitary, mass strandings are unheard of. It had been shot by whalers, but the harpoon had failed to explode.
As with other mammals, the fundamental instinct of the whale was to try to carry on breathing at all costs, even though this meant beaching to prevent itself from drowning. Two of the whale's bones were erected just off a main road on Lewis and remain a tourist attraction. Despite efforts by the Albaug forest department and local fishermen, the whale died 10 hours after being stranded. The whale was towed to sea after 7 hours by a stronger boat. It is unknown whether it survived. Vocalizations Multimedia relating to the blue whale Note that the whale calls have been sped up 10x from their original speed.
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