What is a Whale ?
Fossil evidence suggests that primitive whales evolved about 50 million years ago. Possible links in whale ancestry comes from the shore-dwelling, hyena-like Mesonychid that returned to the sea roughly 50 million years ago and the otter-like Ambulocetus, a mammal the size of a sea lion, that had limbs which allowed it to swim and could support it on land.
However, scientists have linked a huge whale called Basilosaurus to modern-day whales. Living about 45-36 million years ago, Basilosaurus was the first whale to become truly enormous in size (about 25m long) and spend its days swimming slowly in water, watching for potential prey to keep it alive.
Minke Whales
Whales today, have streamlined, sleek bodies that move easily through the water and like all mammals:
- Whales are warm-blooded (they maintain a high body temperature)
- Whales breathe air into lungs and unlike fish, whales cannot breathe underwater.
- Whales have hair (although they have almost none as adults)
- Whales give birth to live young, which are fed with milk from their mothers.
- Whales have a four-chambered heart.
Blue Whale
The biggest whale is the blue whale, which grows to about 29m long. The blue whale is also the largest animal that has ever existed on Earth, as it is larger than any of the dinosaurs. To give you some idea of the sheer size of a blue whale, an adult giraffe is about 5m in height, while a Tyrannosaurs Rex would only have reached 6m!
Whales can be divided into two groups: baleen whales (Mysticeti) and toothed whales (Odontoceti).
Toothed whales, like the Sperm whale and Killer whale, use their peg-like teeth to catch marine mammals, fish and squid, swallowing them whole. In search of giant squid, Sperm whales dive regularly to 1,000m and have been tracked by sonar to nearly 3,000m. The name `killer’ for the distinctive Orca, is because they are predators of penguins, seals, fish and, on occasion, other whales. There are about 66 species of toothed whales.
Sperm whale
Baleen whales, like the Blue whale and Humpback Whale plough through concentrations of plankton, gulping huge quantities of water and expelling it through a comb-like structure of whalebone (instead of teeth) that filters the Baleen whales’ food from the water. Baleen whales then use their tongue to dislodge the food from the baleen and then swallow their catch of small krill and larval fish. Baleen is made of karatin, the same protein that our hair and nails are made of. In the Antarctic summer Blue whales feed on krill, taking over 8 tonnes in a day, which may amount to 8 million shrimps. There are about 10 species of Baleen whales.
Humpback whale
Many whales are quite acrobatic, breaching (jumping) high out of the water and then hitting the water hard as they come back down. Breaching may be used to loosen skin parasites, it may be for play or have some social meaning, but nobody is entirely sure of its meaning.
Some whales migrate over very long distances each year. Grey whales make the longest seasonal migration of any of the whales as it feeds in the northern polar region and then breeds and gives birth in the warmer waters of Baja, off Mexico. A Grey whale can make a yearly round trip of up to 20,100 km and in a lifetime, this distance is the equivalent of a return trip to the moon!
Fin whale
Whales and dolphins found in the Southern Ocean
| Length | Weight |
| Southern Right Whale | to 17m | to 100 tonnes |
| Blue Whale | to 30m | to 150 tonnes |
| Fin Whale | to 27m | to 90 tonnes |
| Minke Whale | to 10.7m | to 10 tonnes |
| Humpback Whale | to 16m | to 48 tonnes |
| Sperm Whale | to 15m | to 40 tonnes |
| Arnoux’s beaked Whale | to 9m | to 8 tonnes |
| Southern Bottlenose Whale | to 9m | to 4.5 tonnes |
| Hourglass Dolphin | to 1.7m | to 100kg |
| Killer Whale | to 9.5m | to 7 tonnes |
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What is a Whale <<
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