How many species of whale and dolphin are there? Where have they come from? How do they socialise and behave? Why do they migrate? Is it true they can sing? Why do we give them names? Are they special? Find out the answers to these questions and more.
‘Cetaceans’ is the collective name for all whales, dolphins and porpoises who between them form a single group, known as an order. It's a huge group, though, currently comprising around 90 whale, dolphin and porpoise species, so let's break it down.
To begin with, cetaceans can be divided into two categories; baleen whales, and toothed whales. Baleen whales have baleen plates in their mouths instead of teeth which allow them to filter feed. Their baleen, also known as whalebone, is not made of bone at all. It is made of keratin similar to our fingernails and grows downwards from the upper jaw of most large whales. When baleen whales open their mouths, water and prey, such as krill or small fish upon which they feed, pour in. The water floods back out but the baleen filters out the prey and traps it in the whale’s mouth, ready to swallow. Blue, fin, sei, minke, humpback, gray and right whales are all included in this group.
The vast majority of whales and dolphins, however, belong in the toothed category, and they feed on prey in a similar manner to most carnivores. These include the beaked whales, the dolphins and the porpoises. The sperm whale also sits here (the only large whale in this category) as do the beluga and narwhal.
With such a wide range of skills, feeding habits, behavioural patterns and more, there's a whale, dolphin or porpoise to suit virtually every aquatic environment on the planet.
So, a final group headcount for the species of whales, dolphins and porpoises currently known is: 15 baleen whales, 7 porpoises, 3 sperm whales, 23 beaked whales, 38 dolphins, 4 river dolphins and the beluga and narwhal.
The dolphins form the largest group, and (rather confusingly) include the orca, or killer whale, as well as the pilot whales. Marine dolphins can be found all around the world, varying in size and colouration, but rarely coming closer inland than bays or estuaries. There are a few species of freshwater dolphins, however, which are found in some of the largest of the world's rivers in South America and Asia. Sadly, one of them, the baiji ((Yangtze River dolphin), was declared functionally extinct in 2007.
The porpoises, seven species in all, are distinguished from dolphins by their stubbier beaks and flatter teeth.
Beaked whales are the least known of all cetaceans, as they principally lead their lives in deep waters and only visit the surface fleetingly. There are 23 different beaked whale species that have been discovered so far.
Back to the water
There are many mammals that spend time in the water. Seals, sea lions, walruses, water voles, the platypus and many more are capable of prolonged periods swimming above or below the surface, but all of them come onto the land. What makes whales, dolphins and porpoises different to all of these is that they live entirely in the water.
Unsurprisingly, therefore, scientists were rather baffled for centuries. Why on earth would a mammal, which needs to breathe air, and which has a bone structure, including vestigial limbs, that would suggest land-based movement, have evolved in an entirely aquatic environment?
The fossil record shows us that whales evolved from four-legged, even-toed hoofed mammal ancestors that lived on land 50 million years ago. Prehistoric whales that lived 40 to 35 million years ago are called ‘Basilosaurus’ because at first people thought the fossils were marine dinosaurs, but they are now known to be gigantic mammals and not reptiles.
Fossils have been discovered more recently that reveal the evolutionary steps between hoofed mammals and these ancient whales. These include a remarkable wolf-sized mammal called ‘Pakicetus’, who had similarly positioned and shaped ear bones to modern whales, as well as similarly arranged teeth. Pakicetus straddled two worlds of land and sea and ate both meat and fish and it is now thought that they were pre-whales and forerunners to Basilosaurus and then the whales and dolphins themselves. The fact that modern whales and dolphins are carnivorous suggests that their ancestors found an unchallenged niche in the water, and stayed there, steadily evolving until they no longer needed their land-based abilities.
Although whales and dolphins are social, air-breathing mammals, just like us, they had to undergo substantial changes to enable them to live their lives successfully in water. And it is the legacy of millions of years on land that still remain such as breathing air, feeding their babies with milk, finger skeletons inside their flippers, and hind limbs that disappear before birth. Various adaptions to their bodies, both inside and out, were necessary to feed, breed, dive, communicate, hear, navigate and travel in water. These adaptions were shaped initially through evolution, followed by cultural exchanges particular to individual species.
On the outside the body plan for all whales, dolphins and porpoises is similar. They all have streamlined bodies with flippers, horizontal tails, human-like eyes, obvious mouths, and blowholes (nostrils) on the top of the head. There are of course numerous variations when you look more closely at the different whale and dolphin species. The most obvious is the vast size differences; it would take about 20 New Zealand dolphins lined up end-to-end to equal the length of a single blue whale. Plus, some species have dorsal fins, some do not, some have beaks, others do not. They all have flippers but they vary hugely in size and shape; some are paddle-shaped, others are skinny, some are long and knobbly, and others are stubby and smooth. Some whales have smooth skin; others are covered in bumpy growths and callouses. Some are black or dark grey, others are white, some are pink, one is blue and most are multi-coloured.
Looking after baby
Whales, dolphins and porpoises are born already able to swim, with fully formed vision and hearing. However, the babies are small and a bit wrinkly, and they are vulnerable. At birth the mother, or fellow pod member, will immediately help the newborn to the surface to take their first breath of air. It takes the baby a few days to master surfacing smoothly for air at his or her mother’s side; at first they are a little clumsy and tend to push their heads too far out of the water. They stick to their mums like glue; and all mothers protect their babies from predators and nurse them with their own milk.
Young whales and dolphins need ongoing guidance and support from their mothers as they learn life skills and the cultural ways of their population and species. For many whales and dolphins, mothers and youngsters continue to stay close together long after the important early-life connection period. Family associations among whales and dolphins vary in terms of the kind or degree of closeness and the longevity of the relationships. The bond may be loose and temporary or it may be lifelong.
To give the well-known phrase a twist, no whale or dolphin is an island. These flippered, fully aquatic mammals are in fact highly social and seem to depend on, and very much enjoy each other’s company. Dolphins sometimes form superpods of 1000 individuals or more.
Whale and dolphin matrilines, communities, clans and societies, are not just for company either. They are built upon complex structures and levels of interdependence that can only be forged from the strongest of social bonds. In some dolphin societies, for example, groups will stay with injured or sick individuals, even physically supporting them to the surface if necessary so that they can breathe.
Individuals play very important roles in whale and dolphin societies. Older individuals often act as surrogate parents or as guardians of crèches, so that responsibilities can be shared around a group. Feeding systems, migratory patterns, group play and much more are all based on these strong social systems.
Communication is vital for smooth running social lives and high levels of cooperation, and whales and dolphins have developed some of the richest languages known. Clicks, grunts, whistles, squeals, squawks, calls, songs and more of extraordinary variety provide them with extensive vocabularies that cover all situations. In addition to their vocal repertoires, whales and dolphins are masters of body language too. Scientists are still trying to unravel the complexities of these languages, and it will be a long time before we are even close to understanding the full range.
One thing is certain: it is only within the heart of their communities that whales and dolphins can lead their lives to the full.
Migration is not only for birds and wildebeest; many baleen whales are impressive migrators too. The question is why do whales travel so far? Whales routinely migrate thousands of miles each year, commuting between northerly, cool, productive feeding areas, and much warmer waters closer to the equator, where they mate, give birth to their babies and nurture them. So the colder waters are ideal for finding plentiful food supplies but the warmer waters provide better protection for breeding and raising babies – and the only way to take advantage of both is to migrate annually between the two.
If you've ever watched whales or dolphins out at sea, on television, or even just seen photographs of them, you'll know that there's often much more to look at than just a fin poking out of the water. Heads, tails, flippers, sometimes entire bodies are thrust above the surface, in a glorious mixture of behaviours, each of which signifies or communicates something.
Perhaps you've seen dolphins swimming alongside a boat, riding a pressure wave; this is known as bow-riding, which seems to be great fun for them. At quieter times they might be seen 'logging', the term given to floating on the water's surface, a great energy saving, resting position.
Then there's lobtailing, sometimes known as tail-slapping, which is just what it describes: a hard smack of the water by a whale's fluke, or tail. One of the reasons this might be done is in order to cause a loud sound to stun or confuse prey. When the other end of the body appears - i.e. the head - for a good look around, then this is known as spyhopping. This is thrilling for whale watchers as everybody gets a good look at a whale’s face and eyes.
The most exciting sight to see above the waves, however, and the one that most people love to catch on camera if possible, is breaching. Breaching requires a great deal of whale power. Sometimes whales breach multiple times in a row. Humpback, right and sperm whales are particularly fond of leaping clear of the water in this way, and there are a number of theories as to why they do it. It could be to dislodge parasites, it could be to create a similar effect to lobtailing, it could be to convey messages to other members of their group, or it could, quite simply, be the sheer pleasure of exuberant play.
Some dolphins such as dusky, striped and spinner dolphins are particularly well known for their fast swimming, frequent jumping and boisterous behaviour. They are the acrobats of dolphin kind.
Whales and dolphins love to socialise and are often found in groups called pods. The foundation for whale and dolphin social lives is the mother-baby bond. Some of the large, baleen whales spend time alone, they may well be in acoustic contact with others and join together for group activities such as feeding, migrating and breeding.
Scientists working on long-term studies of whales and dolphins give names to individuals. They can tell them apart using a technique called photo-identification and sometimes differences they notice in character and behaviour. Recognising individuals is an important tool as it’s the key to finding out more and understanding whale and dolphin social lives, relationships, life histories, migration and habitat use.
Photo-identification catalogues can include hundreds or even thousands of individuals and names are so much easier to remember than numbers!
Wow…they are special
Why do so many of us love whales and dolphins? In their natural environments, wild and free they certainly enrich the lives of people who come into contact with them.
The feeling of kinship and sense of wonder we feel for whales and dolphins is undeniable, and that makes them very special. But what is it about these beautiful, stupendous, gregarious yet mysterious, other-worldly creatures that prompt so much feeling and empathy amongst us? Perhaps it’s because they are just like us in so many ways; they nurture, show intense affection, bond, play, demonstrate compassion, feel pain, express joy, grieve for their dead, are smart, and look after one another. It is plain to see that the most important thing in a whale or dolphin’s life is his or her relationships with others, they are unselfish and giving individuals, and that is inspiring.
Whales and dolphins are amazing creatures that keep surprising us; the more we discover, the more we are fascinated, moved and humbled. The more we learn about their extraordinary lives, the more we realise that we share our planet with the most remarkable of beings who still have so much more to teach us.
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