Whales

 

Whales

There are 90 species of whales and simply, there are two major classes – the toothed whales and the baleen whales. Baleen whales do not have teeth but plates of baleen made of keratin, the protein that forms human finger nails and hair. To feed, they take in enormous volumes of water which are sieved through the baleen sheets hanging from the upper jaw to extract krill and plankton.  

                                        Drawing showing baleen 

Image courtesy of Wikimedia Commons

Whales evolved from land-living animals related to prehistoric ancestors of hippos that lived more than 50 million years ago. The largest of these enormous mammals are the biggest living animals in the world. 

Chart showing whale sizes relative to man (top left)

Image courtesy of Wikimedia Commons

The blue whale is the greatest animal that has ever existed. The blue whale can reach 30 metres and weigh around 180 tons, though there have been reports of animals measuring 33 metres and weighing 200 tons. Its life span is about 90 years, though the oldest recorded survived an estimated 110 years. 

Blue whale skeleton, Natural History Museum, London

Image courtesy of Wikimedia Commons

This is outshone by the bowhead whale which can live for over 200 years. Australia’s national science body, CSIRO, estimates the bowhead’s maximum lifespan at 268 years. The bowhead has an enormous mouth, the largest of any animal, measuring almost one third of the length of its body. 

                                Drawing of bowhead whale
                                Image courtesy of Wikimedia Commons

Like the blue whale, it is a baleen whale, and its baleen plates are the longest of any whale, with a maximum length of 4 metres (13 feet)

The second largest whale is the Fin whale, also a baleen whale.

The third largest whale is the toothed Sperm whale, the largest toothed predator in the world. It has a huge head, roughly one third of its body length. There is a great size difference between the sexes - males are 30% to 50% longer than females and three times heavier.

Sperm whale and skeleton

Images courtesy of Wikimedia Commons

By contrast, the smallest whales, both toothed whales, are the dwarf sperm whale and the vaquita porpoise at around 2¾ metres (9 feet) and 1½ metres (5 feet) respectively.

As air-breathing mammals, whales must surface periodically to breathe in and out through the blow holes on top of their heads. The sperm whale, which dives deep to catch squid, can remain underwater for 90 minutes.

Scientists have discovered that the great baleen and sperm whales can capture carbon from the atmosphere equal to that of thousands of trees. When they die, their bodies sink to the ocean floor. When land animals die the carbon stored in their bodies is released almost immediately but the carbon at the bottom of the ocean can remain there for centuries – this is known as ‘blue carbon’. It may take up to 1000 years for the elements of a great whale carcase to return to the surface.

Each great whale can sequester 33 tons of carbon dioxide, compared to the 21 kilos a tree may appropriate in its lifespan. Before commercial whaling, there were 4 to 5 million whales in the oceans. Now there are 1.3 million and though they are protected by law, other factors threaten them, like noise pollution, which can disturb their communication, climate change, plastic waste, ship strikes and entanglement in fishing equipment. There are 13 great whale species, of which six are endangered or vulnerable.

Additionally, whales play a most important part in fertilising the marine ecosystem. Phytoplankton are microscopic organisms that form great carbon sinks. They sequester around 2 billion tons of carbon dioxide annually and produce at least 50% of all the oxygen in our atmosphere.

 Whales have some of the longest migratory journeys of any animal on this planet. As they swim, they stir up minerals from the depths and broadcast them across the seas. This is known as the ‘whale conveyor belt’ and gives the phytoplankton the nutrients they require for growth. Whales expel iron, phosphorus and nitrogen in their excrement, which also feeds the phytoplankton.

These magnificent, awe-inspiring animals are vital to our planet and to our survival.

I have tried to ensure that this post is as factually accurate as possible but there is conflicting information on some matters, so please don’t shoot me if I have unintentionally misrepresented facts. 

For example, one source stated that the bowhead whale was the second largest whale species; it was not at all clear if that meant it was numerically or physically large. As all other sources I looked at declared the Fin whale to be second in size only to the Blue whale, that is the information I have accepted as correct. 

As far as Bowhead whale numbers are concerned, there are 17,000 in the North Pacific and 1,300 in the North Atlantic and it is not considered vulnerable and is of least concern. Its numbers are increasing, but it hasn't got the largest population.

Numerically, the Minke whales have some of the greatest numbers - 515,000 in the Southern Hemisphere and 150,000 in the North Atlantic. Sperm whales have between 300,000 and 450,000 individuals. Compare this to the Blue whale population, estimated at between 10,000 and 25,000 animals. The Fin whale is estimated to be anything from under 100,000 to about 119,000.

The numbers are not huge. Whales do not reproduce rapidly and produce only singleton calves.. Pregnancy lasts from 9 to 18 months, depending on the species. Minke whales give birth every one to two years. Other species may only have one calf every few years. Whales also take many years to reach sexual maturity.