Sperm whale

The sperm whale (Physeter macrocephalus), or cachalot, is the largest of the toothed whales. It is the only living member of genus Physeter, and one of three extant species in the sperm whale family, along with the pygmy sperm whale and dwarf sperm whale of the genus Kogia. Mature males average at 16 metres (52 ft) in length but some may reach 20.5 metres (67 ft), with the head representing up to one-third of the animal's length.

The sperm whale feeds primarily on giant and colossal squid. Plunging to 3 kilometres (9,800 ft) for prey, it is the deepest diving mammal. Its clicking vocalization, a form of echolocation and communication, may be as loud as 230 decibels (re 1 µPa at 1 m) underwater, making it the loudest sound produced by any animal. It has the largest brain of any animal on Earth, more than five times heavier than a human's. Sperm whales can live for more than 60 years.

The sperm whale can be found anywhere in the open ocean. Females and young males live together in groups while mature males live solitary lives outside of the mating season. The females cooperate to protect and nurse their young. Females give birth every four to twenty years, and care for the calves for more than a decade. A mature sperm whale has few natural predators. Calves and weakened adults are taken by pods of orcas.

From the early eighteenth century through the late 20th the species was a prime target of whalers. The head of the whale contains a liquid wax called spermaceti, from which the whale derives its name. Spermaceti was used in lubricants, oil lamps, and candles. Ambergris, a waste product from its digestive system, is still used as a fixative in perfumes. Occasionally the sperm whale's great size allowed it to defend itself effectively against whalers.

The species is now protected by a whaling moratorium, and is currently listed as vulnerable by the IUCN. The sperm whale is the largest toothed whale, with adult males measuring up to 20.5 metres (67 ft) long and weighing up to 57,000 kilograms (56 long tons; 63 short tons). By contrast, the second largest toothed whale, Baird's Beaked Whale measures 12.8 metres (42 ft) and weighs up to 15 short tons (14,000 kg). The Nantucket Whaling Museum has a 5.5 metres (18 ft)-long jawbone.

Source: http://en.wikipedia.org/wiki/Sperm_whale

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Blue whale

The blue whale (Balaenoptera musculus) is a marine mammal belonging to the baleen whales (Mysticeti). At 30 metres (98 ft)[4] in length and 170 tonnes (190 short tons) or more in weight, it is the largest known animal ever to have 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. 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 blue whale is the largest animal ever known to have lived. The largest known dinosaur of the Mesozoic Era was Argentinosaurus, which is estimated to have weighed up to 90 metric tons (99 short tons). Blue whales are difficult to weigh because of their size.

 

Source: http://en.wikipedia.org/wiki/Blue_whale

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