Blue whale

Appearance

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 long) hang from the upper jaw, running 0.5 m back into the mouth. Between 70 and 118 grooves run along the throat parallel to the body length. These pleats assist with evacuating water from the mouth after lunge feeding .

The dorsal fin is small, ranging in height from 8–70 centimeters ) and averaging about 28 centimetres . 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 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 , typically 9 metres . Its lung capacity is 5,000 litres . Blue whales have twin blowholes shielded by a large splashguard.

The flippers are 3–4 metres 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....hieroglyph snipped...

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

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.

Distribution

Since the introduction of the whaling ban, studies have failed to ascertain whether the conservation reliant global blue whale population is increasing or remaining stable. In the Antarctic, best estimates show a significant increase at 7.3% per year since the end of illegal Soviet whaling, but numbers remain at under 1% of their original levels. It has also been suggested that Icelandic and Californian populations are increasing but these increases are not statistically significant. The total world population was estimated to be between 5,000 and 12,000 in 2002, although there are high levels of uncertainty in available estimates for many areas.

The IUCN Red List counts the blue whale as "endangered" as it has since the list's inception. In the United States, the National Marine Fisheries Service lists them as endangered under the Endangered Species Act. The largest known concentration, consisting of about 2,800 individuals, is the northeast Pacific population of the northern blue whale subspecies that ranges from Alaska to Costa Rica, but is most commonly seen from California in summer. Infrequently, this population visits the northwest Pacific between Kamchatka and the northern tip of Japan.

In the North Atlantic, two stocks of ''B. m. musculus'' are recognised. The first is found off Greenland, Newfoundland, Nova Scotia and the Gulf of Saint Lawrence. This group is estimated to total about 500. The second, more easterly group is spotted from the Azores in spring to Iceland in July and August; it is presumed the whales follow the Mid-Atlantic Ridge between the two volcanic islands. Beyond Iceland, blue whales have been spotted as far north as Spitsbergen and Jan Mayen, though such sightings are rare. Scientists do not know where these whales spend their winters. The total North Atlantic population is estimated to be between 600 and 1,500.

In the Southern Hemisphere, there appear to be two distinct subspecies, ''B. m. intermedia'', the Antarctic blue whale, and the little-studied pygmy blue whale, ''B. m. brevicauda'', found in Indian Ocean waters. The most recent surveys provided an estimate of 2,280 blue whales in the Antarctic . Estimates from a 1996 survey show that 424 pygmy blue whales were in a small area south of Madagascar alone, thus it is 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.

A fourth subspecies, ''B. m. indica'', was identified by Blyth in 1859 in the northern Indian Ocean, but difficulties in identifying distinguishing features for this subspecies led to it being used a synonym for ''B. m. brevicauda'', the pygmy blue whale. Records for Soviet catches seem to indicate that the female adult size is closer to that of the Pygmy Blue than ''B. m. musculus'', although the populations of ''B. m. indica'' and ''B. m. brevicauda'' appear to be discrete, and the breeding seasons differ by almost six months.

Migratory patterns of these subspecies are not well known. For example, pygmy blue whales have been recorded in the northern Indian Ocean , where they may form a distinct resident population. In addition, the population of blue whales occurring off Chile and Peru may also be a distinct population. Some Antarctic blue whales approach the eastern South Atlantic coast in winter, and occasionally, their vocalizations are heard off Peru, Western Australia, and in the northern Indian Ocean. In Chile, the Cetacean Conservation Center, with support from the Chilean Navy, is undertaking extensive research and conservation work on a recently discovered feeding aggregation of the species off the coast of Chiloe Island in the Gulf of Corcovado, where 326 blue whales were spotted in 2007.

Efforts to calculate the blue whale population more accurately are supported by marine mammologists at Duke University, who maintain the Ocean Biogeographic Information System—Spatial Ecological Analysis of Megavertebrate Populations , a collation of marine mammal sighting data from around 130 sources.

Behavior

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 long) hang from the upper jaw, running 0.5 m back into the mouth. Between 70 and 118 grooves run along the throat parallel to the body length. These pleats assist with evacuating water from the mouth after lunge feeding .

The dorsal fin is small, ranging in height from 8–70 centimeters ) and averaging about 28 centimetres . 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 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 , typically 9 metres . Its lung capacity is 5,000 litres . Blue whales have twin blowholes shielded by a large splashguard.

The flippers are 3–4 metres 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....hieroglyph snipped...

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

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.

Food

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 Antarctic, ''Euphausia superba'', ''Euphausia crystallorophias'' and ''Euphausia valentini''.

An adult blue whale can eat up to 40 million krill in a day. The whales always feed in the areas with the highest concentration of krill, sometimes eating up to 3,600 kilograms of krill in a single day. The daily energy requirement of an adult blue whale is in the region of 1.5 million kilocalories. Their feeding habits are seasonal. 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.

Because krill move, blue whales typically feed at depths of more than 100 metres during the day and only surface-feed at night. Dive times are typically 10 minutes when feeding, though dives of up to 20 minutes are common. The longest recorded dive is 36 minutes. 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.


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. Although it was initially cumbersome and had a low success rate, Foyn perfected the harpoon gun, and soon several whaling stations were established on the coast of Finnmark in northern Norway. Because of disputes with the local fishermen, the last whaling station in Finnmark was closed down in 1904.

Soon, blue whales were being hunted off Iceland , the Faroe Islands , Newfoundland , and Spitsbergen . In 1904–05 the first blue whales were taken off South Georgia. By 1925, with the advent of the stern slipway in factory ships and the use of steam-driven whale catchers, the catch of blue whales, and baleen whales as a whole, in the Antarctic and sub-Antarctic began to increase dramatically. In the 1930–31 season, these ships caught 29,400 blue whales in the Antarctic alone. By the end of World War II, populations had been significantly depleted, and, in 1946, the first quotas restricting international trade in whales were introduced, but they were ineffective because of the lack of differentiation between species. Rare species could be hunted on an equal footing with those found in relative abundance.

Arthur C. Clarke, in his 1962 book ''Profiles of the Future'', was the first prominent intellectual to call attention to the plight of the blue whale. He mentioned its large brain and said, "we do not know the true nature of the entity we are destroying."

Blue whale hunting was banned in 1966 by the International Whaling Commission, and illegal whaling by the USSR finally halted in the 1970s, by which time 330,000 blue whales had been caught 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.

Due to their enormous size, power and speed, adult blue whales have virtually no natural predators. There is one documented case in ''National Geographic Magazine'' of a blue whale being attacked by orcas off the Baja California Peninsula; although the orcas were unable to kill the animal outright during their attack, the blue whale sustained serious wounds and probably died as a result of them shortly after the attack. Up to a quarter of the blue whales identified in Baja bear scars from orca attacks.

Blue whales may be wounded, sometimes fatally, after colliding with ocean vessels, as well as becoming trapped or entangled in fishing gear. The ever-increasing amount of ocean noise, including sonar, drowns out the vocalizations produced by whales, which makes it harder for them to communicate. Blue whales stop producing foraging D calls once a mid-frequency sonar is activated, even though the sonar frequency range far exceeds their sound production range . Human threats to the potential recovery of blue whale populations also include accumulation of polychlorinated biphenyl chemicals within the whale's body.

With global warming causing glaciers and permafrost to melt rapidly and allowing a large amount of fresh water to flow into the oceans, there are concerns that if the amount of fresh water in the oceans reaches a critical point, there will be a disruption in the thermohaline circulation. Considering the blue whale's migratory patterns are based on ocean temperature, a disruption in this circulation, which moves warm and cold water around the world, would be likely to have an effect on their migration. 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.

Predators

Due to their enormous size, power and speed, adult blue whales have virtually no natural predators. There is one documented case in ''National Geographic Magazine'' of a blue whale being attacked by orcas off the Baja California Peninsula; although the orcas were unable to kill the animal outright during their attack, the blue whale sustained serious wounds and probably died as a result of them shortly after the attack. Up to a quarter of the blue whales identified in Baja bear scars from orca attacks.

Blue whales may be wounded, sometimes fatally, after colliding with ocean vessels, as well as becoming trapped or entangled in fishing gear. The ever-increasing amount of ocean noise, including sonar, drowns out the vocalizations produced by whales, which makes it harder for them to communicate. Blue whales stop producing foraging D calls once a mid-frequency sonar is activated, even though the sonar frequency range far exceeds their sound production range . Human threats to the potential recovery of blue whale populations also include accumulation of polychlorinated biphenyl chemicals within the whale's body.

With global warming causing glaciers and permafrost to melt rapidly and allowing a large amount of fresh water to flow into the oceans, there are concerns that if the amount of fresh water in the oceans reaches a critical point, there will be a disruption in the thermohaline circulation. Considering the blue whale's migratory patterns are based on ocean temperature, a disruption in this circulation, which moves warm and cold water around the world, would be likely to have an effect on their migration. 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.

Evolution

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 10 to 12 months. The calf weighs about 2.5 metric tons and is around 7 metres in length. Blue whale calves drink 380–570 litres of milk a day. The calf is weaned after six months, by which time it has doubled in length. Sexual maturity is typically reached at five to ten years of age. In the Northern Hemisphere, whaling records show that males averaged 20–21 m and females 21–23 m at sexual maturity, while in the Southern Hemisphere it was 22.6 m and 24 m , respectively. In the Northern Hemisphere, as adults, males averaged 24 m and females 25 m , while in the Southern Hemisphere males averaged 25 m and females 26.5 m . In the North Pacific, photogrammetric studies have shown blue whale adults today average 21.6 m , with a maximum of over 24.4 m – although a 26.5 m female stranded near Pescadero, California in 1979.

Scientists estimate that blue whales can live for at least 80 years, but since individual records do not date back into the whaling era, this will not be known with certainty for many years. The longest recorded study of a single individual is 34 years, in the eastern North Pacific. The whales' only natural predator is the orca. Studies report that as many as 25% of mature blue whales have scars resulting from orca attacks. The mortality rate of such attacks is unknown.

Blue whale strandings are extremely uncommon, and, because of the species' social structure, mass strandings are unheard of. 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 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.