Whales – Giants of the deep

by Hu Berry

Man’s relationship with whales began with merciless harpooning and then changed to one of concern when it was realised that these giants of the deep were close to extinction. Since then whale watching has become a growing tourist attraction.

The pages of history reveal an appalling sequence of slaughter when whales were butchered without consideration for their future existence.

Walvis (whale) Bay was so named when the Dutch West India Company sent commercial whalers to the area in 1726, following reports of large numbers of whales in these waters.

While we are spared the details of the massacre, whaling off the Southern African coast was the highest in the world, except for Antarctica.

The total of these gentle giants destroyed between 1908 and 1930 reached a shocking 73 500, with twice as many killed off the west coast than the east coast.

Blue, fin, sei, Bryde’s, humpback, right and sperm whales had explosive harpoons fired into their great bodies, followed by flaying on factory ships that accompanied the chase boats.

The scene on a factory ship may have portrayed man’s pitiless nature at its worst. Previously graceful, streamlined carcasses were reduced to a bloodied mix of blubber, gut and bone by the unfeeling blades of curved flaying knives.

Each animal so taken diminished the populations until, in the 1960s, there remained less than 10% of the original numbers of species, such as the blue and humpback whales.

Not only large leviathans suffered under human assault; small whale species like long-finned pilot whales were driven ashore in entire schools. In the 1950s about 10 000 of these marine mammals were intentionally beached annually on Newfoundland for dismembering.

Ten years later the same effort resulted in only 100 being stranded, a stark indicator of their demise.

The smallest whales, namely dolphins and porpoises, became ‘non-target’ victims when nets were trawled for tuna, with which dolphins associate.

The resultant ‘by-catch’ of dolphins in the tropical eastern Pacific during the 1960s was horrendous, with between 200 000 and 500 000 of these air-breathing mammals drowned in tuna nets.

This has decreased, yet several thousand dolphins still drown yearly by the hands of man.

The differences between a dolphin, a porpoise and a whale are not easily pinpointed.

Dolphins and porpoises, as well as whales, are scientifically classified as Cetaceans, originating from the Greek word for sea monster.

Moreover, Cetaceans are either toothed or baleened; the latter possessing up to 400 fibrous plates on either side of the upper jaw. Resembling coarse, splayed brushes, they form part of an elaborate filtering system, sieving out tiny creatures called ‘krill’ from large volumes of seawater.

Toothed whales hunt individual prey and swallow it whole. Dolphins and porpoises are all toothed whales, and porpoises are much smaller than dolphins, seldom exceeding two metres in length.

When separated at the family level, however, dolphins and porpoises are as physically different as cats and dogs. Whereas porpoises are chubby and robust, dolphins are sleek and streamlined. Porpoises display a shark-like, triangular fin.

In dolphins this fin is wave-shaped. Porpoises lack a rostrum or a beak, which is present in dolphins. Shy by nature, porpoises are seldom seen, unlike dolphins that confidently rise to the occasion and ride the bow wave of boats.

Strikingly coloured black and white, killer whales or orcas are the largest dolphin, males weighing nine tonnes, with a length of nearly 10 metres.

Known as ‘sea wolves’, orcas can be fierce hunters, having well-organised hunting techniques.

Their attack is ruthless and often fatal for sea lions, elephant seals, porpoises, sharks and penguins.

There are no documented cases of killer whales attacking a human in the open sea. Found in all the oceans of the world, they are more abundant in cooler waters. They are one of the few species of whales that move freely between hemispheres.

Moreover, most toothed whales are smaller in size than baleen whales. The heaviest living animal on earth is the blue whale, weighing up to 190 tonnes, with a length of 33 metres.

Hippos and whales have a common ancestor.

There are 78 species of Cetaceans, a Sub-order of the parent Order Whippomorpha, which holds an unlikely relative of whales – the hippopotamus.

This strange relationship becomes clearer when we consider that the DNA of hippos and whales prove a common ancestor; also that hippos are amphibious, whereas whales are totally aquatic.

Fresh and salt waters form their common bond.

Most highly modified of all mammals

We must credit Cetaceans with the attributes of being the most highly modified and specialised of all mammals. Lungs, warm blood and milk distinguish them from the gills, coldness and egg-laying of fish.

Furthermore, the forelimbs have fused into flippers, while only vestigial remains of hind-leg bones float loose from the skeleton.

The massive body is coated with a layer of blubber up to 13 centimetres thick, serving as reserve food source, insulation against polar cold, and giving buoyancy to surface for breathing.

Beached whales that are exposed to the sun risk the likelihood of being metabolically boiled by their own blubber. Similar to their large, land-locked counterparts, they possess a network of heat-controlling systems that conserve the temperature of hot arterial blood before it is pumped into flippers and tail flukes where heat loss occurs.

The final touch to this array of survival strategies in Cetaceans is the dorsal positioning of the nostrils or ‘blowhole’– a feat made possible by evolutionary elongation of the jaws, which make it appear that they are located on top of the head. This allows whales to breathe with a minimum of the surface of the head above water.

Deep-diving whales, like the mighty sperm whale, spend much of their time in depths that are more hostile and difficult for humans to survive in than outer space.

To accompany a hunting sperm whale, be prepared to go down to a world where cold, crushing darkness prevails; then inhale enough oxygen to stay submerged for an hour.

Gliding vertically at a fast walking pace, we reach the human limit of 500 metres at 50 bars (5 000 Kilopascals). Without a pressurised diving suit, our rib cage will have collapsed and our brain starved of oxygen.

After only four minutes at this tremendous pressure, human scuba divers are obliged to spend 14 days slowly decompressing to allow nitrogen in their blood and fatty tissues to release slowly enough to avoid nitrogen narcosis (the bends), which can be fatal.

At 1 km down, water presses on the whale’s body with 100 bars at a temperature of 2ºC.

Marvellously, under these pressures an obliquely set diaphragm allows the whale’s lungs to empty into its air passages, thereby stopping absorption of nitrogen into the blood.

Moreover, some Cetaceans have 60% more blood volume per kilogram of body mass than humans, permitting large amounts of oxygen to be stored in the haemoglobin during prolonged dives.

Two-and-a-half kilometres beneath the surface is where the sperm whale hunts fish and squid for 30 minutes before beginning the long swim to the surface.

To provide a comparison, the water pressure at 2 500 metres depth is 250 bar, which is 100 times more than a car tyre pumped very hard.

Whales ‘sing’ at three different frequencies – low-frequency ‘moans’, grunt-like thumps and knocks, and complex signals emitted as screams, roars, growls, chirps, cries, whistles and clicks.

These sounds are audible to our ears only when their energy pulses are speeded up or slowed down. None of these ‘songs’ will be heard by tourists who take the popular, daily boat cruises in Walvis Bay.

They may sight one of the great whales blowing or breaching, but more likely they will find and become fascinated by the second smallest Cetaceans in the world – endemic Heaviside’s dolphins – as they cruise and surface just ahead of the bow wave.

Their distinctive tri-coloured coat of blue-black with a grey cape and whitish underside render them unmistakable. If a great whale is sighted, the historical and infamous cry of the harpooner’s ‘Tha’r she blows’, instead gives way to the excited chatter of tourists and the digital clicks of high-resolution cameras as they capture, not kill, these giants of the ocean.

This article appeared in the 2009/10 edition of Conservation and the Environment in Namibia.

Hu Berry was a scientist, conservationist and specialist tour guide. He was one of Venture Publications' most valued authors. Sadly he passed away in July 2011. To read more about him click here.