Taxonomically, there is no such thing as a whale: whales are a diverse group of mammals within the infraorder Cetacea
GREATEST SIZE DIFFERENCE BETWEEN PREDATOR AND PREY
Blue whales are the largest mammals and the largest animals [see above right). Their prey is minuscule, however: they feed on krill, tiny shrimp-like crustaceans around 50 mm [2 in) long. To feed, a blue whale gulps in vast quantities of kriN-fiNed seawater. It expels the water by lifting the world’s heaviest tongue [typically weighing 4 tonnes, or 8,818 lb) to the roof of its mouth, leaving the krill trapped in the strands of baleen [bristle-like protein) that , hang from its upper jaw.
Then they are swallowed.
▼ GREATEST WEIGHT LOSS IN AN ANIMAL
During her seven-month lactation period, a 120-tonne [264,555-lb) female blue whale can lose 25% of her weight while nursing her calf. Blue whale calves weigh around
2,500 kg [5,511 lb 9 oz) at birth, but thereafter add some 80-100 kg [176-220 lb) per day during the lactation period.
The mother eats very little during these seven months, relying almost entirely on her body reserves for energy.
Basilosaurids were prehistoric whales that existed 34-40 million years ago, during the late Mid- to early Late Eocene epoch. Most were characterized by lengthy, serpentine or eel-like bodies, and some grew to immense sizes. The longest basilosaurid species presently known from fossils is Basilosaurus cetoides, which grew to 18 m [59 ft) and possibly longer. Its great length was due to a marked elongation of the central portion [centrum) of the thoracic and anterior caudal vertebrae in its backbone.
The blue whale might be the world’s largest animal [see above) but it doesn’t have the biggest mouth. That honour belongs to the bowhead whale [Balaena mysticetus), which has a mouth measuring 5 m [16 ft 4 in) long,
4 m [13 ft 1 in) high and 2.5 m [8 ft 2 in) wide.
Its tongue weighs approximately 1 tonne [2,200 lb) – about the same as a dairy cow.
Owing to its relatively small size, low oil yield and a distribution mainly in the southern hemisphere, the Antarctic or southern minke whale [Balaenoptera [aka Rorqualus] bonaerensis) was generally ignored by the whaling industry during the pre-modern age, so its numbers have remained high. In 2006, a scientific report detailing three completed circumpolar sets of Antarctic minke whale surveys, spanning 1978-79 to 2003-04, estimated that it numbered in the hundreds of thousands – far more than the number estimated for any other baleen whale.
The largest taxonomic family of baleen whales is Balaenopteridae, containing the rorquals, which consists of nine currently recognized species. These include the blue whale, the sei whale [Balaenoptera [aka Rorqualus] borealis) and the humpback whale [Megaptera novaeangliae). Like all baleen whales, rorquals feed mainly on tiny marine
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organisms that they strain from seawater via large comb- or sieve-like baleen plates, but some will also gulp down larger fishes.
Adult male short-finned pilot whales [Globicephala macrorhynchus) have a maximum recorded body length of 7.2 m [23 ft 7.4 in), the largest pilot whale. Adult females grow to
5.5 m (18 ft). The species inhabits the Pacific Ocean’s warm temperate and tropical waters.
Largest beaked whale
Baird’s beaked whale [Berardius bairdii) is one of three species categorized as giant beaked whales. Native to cold temperate waters in the
North Pacific, it attains a maximum confirmed length of 13 m [42 ft 7.8 in) and weighs up to 14 tonnes [30,864 lb).
The smallest species of beaked whale is the
pygmy or Peruvian beaked whale [Mesoplodon peruvianus). It measures some 4 m [13 ft) long when adult and is around 1.6 m [5 ft 3 in) long when newborn. It has been recorded in eastern tropical Pacific waters stretching south from California in the USA and Baja California in Mexico to Peru and Chile in north-western South America.
As of Oct 2016, the newest species of
beaked whale was a recently recognized species from Japan, known colloquially by local Japanese fishermen as the karasu but still awaiting formal scientific description and naming. Much smaller and darker in colour than its closest relatives, the giant beaked whales [genus Berardius), the karasu inhabits shallow waters off Japan and the Korean Peninsula and also in the Bering Sea off Alaska.
The deepest dive by a mammal was made by a Cuvier’s beaked whale [Ziphius cavirostris) off the coast of southern California, USA, in 2013. During a three-month study of eight individuals, marine scientists used satellite-linked tags to record the whales’ dives, the deepest of which reached 2,992 m [9,816 ft)
– equivalent to more than three-and-a-half times the height of the Burj Khalifa, the world’s tallest building [see pp.36-37).
Shepherd’s beaked whale [Tasmacetus shepherdi) has been recorded off New Zealand, Australia and Argentina. With as many as 27 pairs of functional teeth in each jaw, plus a pair of short tusks at the tip of the lower jaw in males, it has the most teeth for a beaked whale species. All other beaked whales possess only a handful of teeth at most. Indeed the paucity of teeth is a characteristic feature of these whales.