Blue Whale Totally Explained

Everything about Blue Whale totally explained

The Blue Whale (Balaenoptera musculus) is a marine mammal belonging to the suborder of baleen whales (called Mysticeti).
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 mainly of small crustaceans known as krill, as well as small fish and sometimes squid.
Blue Whales were abundant in nearly all oceans until the beginning of the twentieth century. For over 40 years 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 North-East Pacific, Antarctic, and Indian Ocean groups. There are two more groups in the North Atlantic and at least two in the Southern Hemisphere.

Taxonomy

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. but this wasn't accepted elsewhere. Blue Whale/Humpback Whale hybrids are also known.
   The specific name musculus is Latin and could mean "muscular", but it can also be interpreted as "little mouse". Linnaeus, who named the species in his seminal Systema Naturae of 1758, would have known this and may have intended the ironic double meaning. The species was called Sulphur-bottom by Herman Melville in his novel Moby-Dick due to an orangish-brown or yellow tinge on the underparts from diatom films on the skin. Other common names for the Blue Whale have included the Sibbald's Rorqual (after Sir Robert Sibbald), the Great Blue Whale and the Great Northern Rorqual. These names have fallen into disuse in recent decades.
   Authorities classify the species into three or four subspecies: B. m. musculus, the Northern Blue Whale consisting of the north Atlantic and north Pacific populations, B. m. intermedia, the Southern Blue Whale of the Southern Ocean, B. m. brevicauda, the Pygmy Blue Whale found in the Indian Ocean and South Pacific, and the more problematic B. m. indica, the Great Indian Rorqual, which is also found in the Indian Ocean and although described earlier may be the same subspecies as B. m. brevicauda.
   Blue Whales can reach speeds of 50 km/h (30 mph) over short bursts, usually when interacting with other whales, but 20 km/h (12 mph) is a more typical travelling speed. The largest known dinosaur of the Mesozoic era was the Argentinosaurus, which is estimated to have weighed up to 90 tonnes (100 short tons), though a controversial vertebra of Amphicoelias fragillimus may indicate an animal of up to 122 tonnes (135 short tons) and 40–60 meters (130–200 ft). There is some uncertainty about the biggest Blue Whale ever found as most data comes from Blue Whales killed in Antarctic waters during the first half of the twentieth century and was collected by whalers not well-versed in standard zoological measurement techniques. The longest whales ever recorded were two females measuring 33.6 m and 33.3 m (110 ft 3 in and 109 ft 3 in) respectively. However, the reliability of these measurements is disputed. The longest whale measured by scientists at the NMML was 29.9 m (98 ft). and when fully expanded its mouth is large enough to hold up to 90 tonnes (100 short tons) of food and water. Despite the size of its mouth, the dimensions of its throat are such that a Blue Whale can't swallow an object wider than a beach ball. Its heart weighs 600 kg (1,320 lb) and is the largest known in any animal. During the first 7 months of its life, a Blue Whale calf drinks approximately 400 litres (100 US gallons) of milk every day. Blue Whale calves gain weight quickly, as much as 90 kg (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. 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; in the Antarctic Euphausia superba, Euphausia crystallorophias and Euphausia valentin.
   The whales always feed in the areas with the highest concentration of krill, sometimes eating up to 3,600 kg (8,000 lb) of krill in a single day.

Life history

Mating starts in late autumn, and continues to the end of winter. Little is known about mating behaviour or breeding grounds. Females typically give birth once every two to three years at the start of the winter after a gestation period of ten to twelve months. Studies report that as many as 25% of mature Blue Whales have scars resulting from Orca attacks. However when strandings do occur they can become the focus of public interest. In 1920, a Blue Whale washed up near Bragar on the Isle of Lewis in the Outer Hebrides of Scotland. It had been shot in the head 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.

Vocalizations

Note that the whale calls have been sped up 10x from their original speed.

Estimates made by Cummings and Thompson (1971) suggest that source level of sounds made by Blue Whales are between 155 and 188 decibels when measured relative to a reference pressure of one micropascal at one metre. All Blue Whale groups make calls at a fundamental frequency of between 10 and 40 Hz, and the lowest frequency sound a human can typically perceive is 20 Hz. Blue Whale calls last between ten and thirty seconds. Additionally Blue Whales off the coast of Sri Lanka have been recorded repeatedly making "songs" of four notes duration lasting about two minutes each, reminiscent of the well-known Humpback Whale songs. Researchers believe that as this phenomenon hasn't been seen in any other populations, it may be unique to the B. m. brevicauda (Pygmy) subspecies. The reason for vocalization is unknown. Richardson et al (1995) discuss six possible reasons:

Maintenance of inter-individual distance

Species and individual recognition,

Contextual information transmission (for example, feeding, alarm, courtship)

Maintenance of social organization (for example, contact calls between females and males)

Location of topographic features

Location of prey resources

Population and whaling

Hunting era

Blue Whales are not easy to catch or kill. Their speed and power meant that they were rarely pursued by early whalers who instead targeted Sperm and Right Whales. In 1864 the Norwegian Svend Foyn equipped a steamboat with harpoons specifically designed for catching large whales. and illegal whaling by the USSR finally halted in the 1970s, by which time 330,000 Blue Whales had been killed in the Antarctic, 33,000 in the rest of the Southern Hemisphere, 8,200 in the North Pacific, and 7,000 in the North Atlantic. The largest original population, in the Antarctic, had been reduced to 0.15% of their initial numbers. to 1700. thus it's likely that numbers in the entire Indian Ocean are in the thousands. If this is true, the global numbers would be much higher than estimates predict.
Migratory patterns of these subspecies are not well known. For example, Pygmy Blue Whales have been recorded in the northern Indian Ocean (Oman, Maldives, Sri Lanka) where they may form a distinct resident population.

Threats other than hunting

Blue Whales may be wounded, sometimes fatally, after colliding with ocean vessels as well as becoming trapped or entangled in fishing gear. The whales summer in the cool, high latitudes, where they feed in krill-abundant waters; they winter in warmer, low latitudes, where they mate and give birth. The change in ocean temperature would also affect the Blue Whale’s food supply. The warming trend and decreased salinity levels would cause a significant shift in krill location and abundance.

In popular culture

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 has 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. Living Blue Whales may be encountered on whale-watching cruises in the Gulf of Maine, and are the main attractions along the north shore of the Gulf of Saint Lawrence and in the Saint Lawrence estuary. The Blue Whale has been represented in children's popular culture in the 1967 movie Doctor Dolittle, where it appears as a symbol of size and strength when it's employed to move an island.

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