Basking and sunlight a sperm whale rests after its journey from the black depths of the ocean.
Sperm whales are the deepest diving of all mammals and can spend up to ninety minutes on the sea floor hunting giant squid and other bottom dwellers.
Like mammals on land all whales and their dolphins cousins are warm-blooded and need to breathe air.
So, how have whales adapted terrestrial organs to a life at sea so successfully?
And what prompted their ancestors to move from the land to the oceans?
The blue whale is the largest animal ever to have inhabited the planet. Growing up to one hundred feet and weighing as much as one hundred and ninety tons or three hundreds eighty thousand pounds. It is also extremely rare. Only its need to breathe allows us a fleeting glimpse of its legendary bulk.
The blue whale belong to the order Cetacea which includes the great whales and their much smaller relations porpoises and dolphins.
The smallest of dolphins is a fraction of the size of a blue whale’s fluke. At a little over four feet Hector’s dolphins are also rare. Their range is limited to a few coastal areas of New Zealand.
Where they hunt for fish near the surface. As mammals whales use lungs to breathe air rather than gills to breathe water. Whale’s lungs are relatively small but they are remarkably efficient.
When a whale surfaces it can replace up to ninety percent of the air in its lungs in just a few seconds. But this efficiency alone cannot account for its ability to stay underwater in some species, for as long as two hours. A diving whale descends with almost half its total oxygen stored in the muscles where it is slowly released overtime. The whale uses this oxygen with great economy. Only essential organs, such as the brain are supplied while others go into oxygen debt until the animal returns to the surface.
But the deep diving sperm whale needs more than these adaptations. Its bulbous head contains the so called spermaceti organ. Filled with a complex mixture of fats and waxes one of organ’s functions is almost certainly to act as a biological ballast tank. When water is drawn into the huge nasal passages the mixture cools and hardens helping the whale to descend rapidly. The process is reversed by ejecting the water and pumping warm blood through the organ to liquefy the wax.
All whales have bones that are light and filled with oil which acts as an aid to buoyancy. It’s also a vital energy reserve during periods of fasting. Whales are powerful swimmers with tail flukes that are horizontal rather than vertical, as in fish. The flukes are boneless and consists of strong, fibrous tissue.
Powered by a pair of massive muscle blocks forward of the flukes whales cruise at six miles an hour with the fastest reported speed in excess of forty miles an hour. Unlike cold-blooded fish whales need to stay warm in frigid waters.
Blubber, a layer of fat up to twenty inches thick acts as thermal insulation. But whales can also actively conserve heat using warm blood pumped from the heart. Areas with little or no blubber such as the head and flukes operate a heat exchange system. Cooled blood in the extremities is partly heated as it passes by the warmer blood.
A vital adaptation because heat from a body immersed in water is lost around twenty-five times faster than in air. The very cold water, thousands of feet below the surface are the natural hunting grounds of the sperm whale
Sperm whales are the largest of the toothed whales part of the group that includes the orca or killer whale. With up to ten or twelve pairs of cone-shaped teeth orcas can threaten even the largest prey. And it’s the only whale that can kill other whales.
Dolphins also belong to the toothed whale group and feed on fast moving fish and squid. Dolphins have even moved into some large rivers where they have become highly specialized. Primitive river dolphins like the Amazon Buto have limited eyesight and use echolocation to find their prey in murky waters.