The whales of today evolved from four legged, hairy land mammals around 50 million years ago. They began their transition back into the oceans by feeding on the abundant food present in the shallows around the waters’ edge. This quickly led to an amphibious life, much like that of the fur seal or otter of today.
Gradually cetaceans adapted to their marine environment in many different ways. The tail became adapted for vertical beating. Insulating blubber developed. The hair was mostly lost. The eyes and kidneys adapted to the different salt balance, and the ears became sealed over and developed to function under water. Although they returned to inhabit the oceans, whales still had to breathe air. They developed nasal plugs to close the nostrils when diving.
The most primitive whale discovered to date, is a 50-53 million year old fossil from Pakistan known as Pakicetus. This creature did not seem to be that far removed from land mammals, but a distinct ear bone indicated it was adapted for underwater hearing.
A later fossil known as Protocetus and found in Egypt is 50 million years old. It was similar to modern cetaceans because it had a long slender upper jaw with a blow hole behind the tip, simple cheek teeth, widely -separated eyes, and a low brain case. It also had the distinct ear bone associated with underwater hearing. From findings so far it is impossible to know exactly how the body of Protocetus was formed. It could have had external hind limbs. Both Pakicetus and Protocetus are known as archaeocetes or archaic whales, and all of the earliest fossils are from northern locations. These animals did not reach southern waters until about 40 million years ago, where they developed into the advanced archaeocetes.
By about 30 million years ago, the archaeocetes began to disappear. Two new groups of whales began to evolve rapidly. These were: the odontocetes, which became the toothed whales, and the mysticetes, which developed into the baleen whales. The decline of the archaeocetes is unclear, but it may be they could not compete with the odontocetes, which ate similar food. Odontocetes were more efficient hunters, as they could hunt and navigate using echolocation. The mysticetes, on the other hand, developed baleen. They could feed on the abundant micro organisms, such as krill and plankton, present in the seas. This allowed them to reach the gigantic size they have attained today. In addition to this, archaeocetes were probably not totally aquatic and still had to haul themselves up on land to give birth to their young. Unlike the archeocetes, the odontocetes and mysticetes are likely to have been wholly aquatic, giving birth in the water.
Today’s odontocetes and the mysticetes contain smaller groups or families. Thirteen families of cetaceans contain around 80 different species of whales. These not only include the great whales, which are immense in size, but also includes all the smaller whale species such as dolphins and porpoises.
The Mysticetes family, filter feeders otherwise known as the baleen whales, include the largest species of whales and are sometimes referred to as the “great whales.” They can be found in all the world’s oceans. At times they will undertake extensive migrations. There are 3 families in this group.
Right whales (Balaenidae)
Balaenidae The distinguishing features of Right whales are their highly arched upper jaw and their long narrow plates of baleen. Their heads are large when compared to total body length, and they have huge lower lips. They do not have a dorsal fin. The skin over their throats is smooth, and the neck vertebrae are fused.
Gray whales (Eschrichtiidae)
Eschrichtiidae Like the Right whales, Gray whales also have no throat grooves, but there are two to four furrows present. Again they have no dorsal fin. Instead, there are several humps on the upper surface of the tail stock. The neck vertebrae of Gray whales is not fused together like that of the Right whales.
Balaenopteridae This group of whales have shorter and narrower baleen plates compared to the right whales. Their most distinguishing feature is the numerous throat grooves which extend from the chin to mid abdomen. Although a dorsal fin is present it is generally small. Like the Gray whales, Rorquals’ neck vertebrae are not fused. This family includes humpback whales: Megaptera novaeangliae. Humpbacks are well-known for their preference to migrate near coastlines and to breed close to tropical islands, and blue whales: Balaenoptera musculus Hunted virtually to extinction in the Southern Hemisphere, less than 2000 remain of the original 200,000 in Antartica in the early 1900’s.
OdontocetesOdontocetes or toothed whales are comprised of nine families. Apart from the large sperm whales, this group is generally comprised of the smaller whale species. It includes the dolphins and porpoises. They can be found in a variety of habitats including rivers.
Sperm whales (Physeteridae)
This family includes the largest of the toothed whales. They all have very large heads which contain a structure known as the Spermaceti organ. Only their lower jaws contain functional teeth.
White whales (Monodontidae)
The White whale family including beluga whales and narwhals has no beak, and although some species have retained a small dorsal fin, generally it is absent. Interestingly the neck vertebrate are all separated which provides the animals with a little flexibility in that area. The male narwhals’ tooth develops into an enormous, long tusk.
Beaked whales (Ziphiidae)
A long snout has become the distinguishing feature of beaked whales. Their throats have a pair or grooves running the length of it. One species of beaked whales has no teeth at all. Others only have two in the lower jaw, and these only break through the gums in the males of the species.
This group includes such species as the killer whales or Orcas, Pilot whales, as well as the Bottlenose dolphin, Common dolphin, Hector’s dolphin, Spinner dolphin, and Dusky dolphin, to name a few. Delphinidae are the most varied of all the whale species and are found in all oceans, from the tropics to the polar regions, including both coastal and offshore populations. Dolphins have cone shaped teeth.
Unlike dolphins, porpoises do not have a beak. Generally they are small usually less than 2.45m long and have more than 15 teeth in the back row of the upper jaw. Porpoises have spade shaped teeth different to dolphins.
River dolphins (Platanistidae, Iniidae, Lipotidae, Pontoporiidae)
This group includes four families. Three of them inhabit fresh water rivers in South America and Asia. The fourth, Pontoporiidae, is a rare coastal species that inhabits the shallow waters of South America. River dolphins are distinguished by their very long beaks and a low, long dorsal fins.
What is a whale?
Whales are mammals. They are more closely related to humans than to the many fish and creatures which they share the oceans with. Like us, they are warm blooded, give birth to live young and they suckle their young. In their behaviour we see echoes of our own humanity.
Bones and Skin
Whales shape and size differ radically from land mammals. Much of this is due to the buoyant nature of water that has allowed them to attain enormous size.
Perfectly adapted for life in the oceans whales have radically changed their shape to one that is more efficient for moving through a denser medium such as water. They have become streamlined and the forelimbs have turned into rigid paddles (pectoral fins) which help with their balancing and steering. Whales have no hind limbs and, therefore, no hip or leg bones. The dorsal fins prevent whales from rolling. Part of their streamlining means that their skin is smooth and almost hairless, except for some hair around the mouth and chin, the external ear has been lost and the genitals and mammary glands are retracted within the body.
Although we may know the basics there is far less known about whale anatomy than any other group of mammals. This has partly been due to the difficulty of studying them in the wild making it impossible to understand the function of certain structures they possess.
There are several creatures that attach to the skin of whales. They are referred to as parasites. However, they are not “true” parasites and gain no direct nourishment from the whale itself. Often the whale will provide scraps from their own meals that the parasite can feed on or it gives its guest a free ride to nutrient rich waters which are plentiful in food. The most noticeable of whales’ parasites are barnacles. These will usually form encrustations that occur under the chin and along the leading edge of the flippers. The change in temperature, when whales migrate from the cool Arctic and Antarctic waters to the warm tropics, will cause the barnacles to die and drop off. But they are quickly replaced again. All of the great whales have their own specialised barnacle population.
Another parasite associated with whales are “whale lice.” These are actually little crustaceans similar to crabs. They are usually found in the folds around the eyes, on flippers, throat grooves and around the barnacle infestations. They too do not damage the whale. They are unaffected by changes in temperature.
How does a warm blooded mammal like us survive in an environment that can be extremely cold and cause them to rapidly lose body heat?
Temperature control provides a considerable challenge to the whale. Unlike land mammals, whales cannot use behavioural means, such as huddling together, to keep warm. That’s why they have developed blubber: a deep layer of fat under the whales’ skin that will not only store energy but act as an insulator. Blubber thickness varies between species but it has been measured at up to 50cm thick in Bowhead whales.
Blubber is great for keeping whales warm. But after prolonged activities, such as catching prey and swimming, whales could become extremely overheated. To prevent this whales have large arteries running through the blubber. The arteries pump blood to the outer skin where the surrounding water will cool it. When the whale has cooled down enough these same arteries will constrict and will not let as much blood flow through, allowing the blubber to become an insulator again.
The whales flippers, flukes and dorsal fins do not, however, have a layer of blubber. Therefore, whales have developed a temperature control system for these areas. This is known as counter current heat control and is also present in many land mammals including humans. The whale has modified it further.
The major arteries which supply the flipper, dorsal fin and tail are accompanied by two or more veins. Veins and arteries transfer heat between each other. As the blood flows to the extremities it is cooled so that no body heat will not be lost into the water, then as the blood flows back to the heart it will be reheated. Counter current heat exchange can also be used and controlled when the animal wants to cool off, allowing heat loss at the extremities.
For most people, their encounters with whales are not when they enter the oceans (the whales’ world) but rather when the whale momentarily enters their world in order to breathe. For, like us, whales have to breathe air. In whales, the nostrils have been modified into a blowhole on the top of the head. This forms a double blowhole in the baleen whales, which have two nostrils, and a single blowhole in the toothed whales. A series of valves and plugs closes the blowhole when the animal dives again.
It is during their short time at the surface that whales obtain all the oxygen they need for dives that can last up to two hours in some species. Although they breathe less often than land mammals, whales will compensate by taking deeper breaths and extracting more oxygen from the air they breathe. The whale will exchange a far greater volume of air from its lungs with each breath, 85-90%, almost completely exchanging the old air for new air unlike humans who only renew 10-20% of the air in the lungs. When a whale exhales, the air comes out of their blowholes between 300- 500 km per hour.
Whales do not have huge lungs. Proportionately, whales’ lungs are not significantly larger than land mammals. So to dive for minutes, maybe hours at a time, the whale has other adaptations, such as a modified circulatory system. They have a greater percentage of red blood cells. Red blood cells are responsible for transporting oxygen around the body. In addition, the heart rate of the animal will slow down when it is in a dive, the heart beating less times per minute. This condition is known as Bradycardia. Upon reaching the surface and breathing again, the heart rate rises sharply for a brief time. The length of time the whale is submerged will affect how high its heart rate rises when it breaths again. The blood circulatory system is modified as well. Blood flow becomes restricted when diving and it is only directed to the vital organs, almost stopping in other areas. However, whales can still remain very active because they are capable of storing large amounts of oxygen in their muscles before diving.
Diving and the Bends
All species of whales are remarkable divers, however, some are truly incredible, like the Sperm whale and Bottlenose whale who can stay submerged for up to 90 and 120 minutes. Not only that, but the Sperm whale dives down 2000m and possibly as deep as 3200m. The baleen whales will dive for about 40 minutes rarely longer, they are not as deeper divers (with the exception of the Grey whale which feeds by stirring up the bottom sediment and sieving out the small crustaceans, shellfish and worms) because their food source is more concentrated near the surface. Amongst the dolphins, the bottlenose will dive for about 15 minutes, the common dolphin will only dive for about 3 minutes.
When humans scuba dive, if they come to the surface too quickly, they can get a condition known as “the bends.” This can be fatal. Nitrogen gas in the air they are breathing dissolves into the bloodstream as they breathe at increasing depth and pressure. When coming back to the surface after a dive, the diver can get the bends if the nitrogen in the bloodstream comes out of liquid solution too quickly for the lungs to deal with it. It will then form small bubbles in the blood and tissue. This doesn’t happen to whales, why? The whale is a breath-hold diver, only taking down the air contained in its lungs and respiratory passages, so very little nitrogen will dissolve in their blood.
However, the whale still has to deal with immense changes in temperature and pressure. The routine dives made by Sperm whales takes them down as deep as 3000m to feed on giant squid. Therefore, if they are in tropical waters, the temperature will go from a warm 25oC in sunlight to total blackness and a temperature just above freezing point at depth. To deal with the great increase in pressure, the lungs of whales are elastic and are capable of collapsing without affecting the whale. This would be fatal in humans. When they do collapse, the air in them is forced into the nasal passages leading to the blowhole. The rest of the whale’s body adjusts to the increased pressure because a large proportion of the body is comprised of water, which is almost incompressible.
The evolution of land mammals saw the development of five main senses: sight; touch; taste; smell and hearing. These allowed them to receive clear and vital information through the air. When the ancestors of whales left the land to inhabit the oceans, their senses developed for air had to adapt and function underwater. Those senses which could not adapt, or were unnecessary, were lost, and in one case, an amazing new one developed.
This is what could be described as a sixth sense which is completely new, and can best be described as “seeing with ones ears.” This is exactly what the toothed whales are capable of doing.
When they returned to the marine environment, whales’ competitors, such as sharks, had already been evolving in the oceans for many millions of years. They had developed, and perfected, highly specialised senses such as smell and hearing. Whales were in competition with these sharks for food. They were also preyed upon by sharks. To compensate for this, whales had to develop quickly in a way that would let them compete successfully with the sharks. For the baleen whales, the problem was solved by living on small plankton that the sharks do not feed on. They also grew to enormous size, so the sharks could not attack them. But the toothed whales had a more interesting response to the problem when they developed echolocation.
Echolocation is used by whales to communicate, detect prey, navigate when sight isn’t adequate and get an acoustic picture of the underwater topography. When a whale echolocates, it emits sounds which radiate out from it. These sounds take the form of short broad-spectrum burst-pulses or clicks and are focused in a directional beam by the melon of oil in the whales head. The returning echoes from these sounds are received through the whales lower jaw and provide the whale with 3 dimensional information about their surrounding environment.
Information to date indicates that there are a series of events associated with a whale or dolphin’s echolocation pattern. When the animal is swimming along it will produce a general low frequency echolocation signal. This will provide it with information about the topography of the area such as water depth and the position of any coastal features or large animals in the area. If a new echo is received by the whale, it will want to collect more information about it, such as, is it predator or prey? To do this, the whale will produce a series of clicks with a broad frequency band. The echoes from these provide the whale with a series of bits of information. The higher the frequency of sound the more detailed the information is. The only draw back is that the whale needs to be close to the target when producing the high frequency sounds, or the echoes are quickly lost in the surrounding water. But once the whale or dolphin focuses on the target, its high frequency clicks will give a detailed picture of it. The details increase the closer the whale comes to the target and the clicks will be very close together and sound like a continuous “creaking.”
Not only is echolocation used to detect prey, it is believed that it can also be used to literally “stun” prey. Some species of whales no longer have functional teeth because they have developed echolocation to such an extent that they no longer need teeth. Sperm whales are a perfect example of this, they feed on the giant fast-swimming squid that are 12m long and longer. It is believed that they use intense sound to stun and disorient their prey. Their teeth in the lower jaw are much reduced in size and number. The same can be said of the Beaked whales, in this family the teeth of the female may never break through the gums, and in the males, often only two of the teeth will break through. Theories about these whales stunning their prey grew out of information from whaling times when large sperm whales were caught who had deformed or damaged jaws yet they had full stomachs and were very healthy.
Breeding and Reproduction
In order to streamline their bodies and allow ease of movement through water, the whales external genitalia had to be retracted into the body. Telling the difference between the sexes can at first appear quite difficult. But this is not the case and, in general, the technique for sexing whales is universal for all species. Basically, revealing a whale’s sex can be done by viewing the underbelly of the animal and noting the positioning of the slits, or genital opening, on the underside of the whale’s body. Although this is the most reliable and accurate way of sexing cetaceans, in some species there are other small differences among the sexes. For example, in most species of baleen whales, the females will tend to be about 10% larger than the males. However, this situation is reversed for the larger toothed whales, the males become the larger animals. For instance, Sperm whale females are 40% smaller than the males. These differences in size are not nearly as marked in the smaller whales such as dolphins and porpoises. Orcas have another characteristic which allows the sexes to be easily distinguishable. There is a difference in their dorsal fins. Male Orcas have long, straight, up and down dorsal fins that are somewhat larger than female Orcas’ which are quite curved.
To date, the majority of information about mating in whales has been gained by observing the dolphins and small whales which have been kept in captivity. Mating of whales in the wild has only been rarely observed. In migrating species, such as many of the baleen whales, breeding is seasonal, whereas in most of the other whale species it will occur throughout most, or all, of the year.
Being warm blooded mammals, whales give birth to live young. Gestation or pregnancy varies amongst whale species, but in general it takes approximately 10-12 months in baleen whales, and is timed to coincide with their annual migration patterns. They feed in the nutrient rich Arctic and Antarctic waters in the summer, moving to the tropical waters in the winter to breed and give birth. For the toothed whales gestation can be anywhere from nine months to 18 months. Twins are very rare. Usually a single young will be born fluke first rather than head first.
The calf is suckled by the mother close to the water’s surface so both of them can take time to breath. Feeding by the calf is different to that of land mammals. Because the mammary glands lie within the mother’s genital slit, the baby doesn’t actually latch on to a nipple. Instead strong muscles squirt the milk into the calf’s mouth. Whale milk is very concentrated with fat and protein and this enables the calf to grow very rapidly. Humpback whale calves will drink up to 600lt of milk a day from their mother.
The time a whale takes to suckle its young will also vary amongst species. In the rorquals of the baleen whales, lactation will last four to eleven months. After which the young calf is weaned and travels with other juveniles, leaving it’s mother. A year or more is the time taken by toothed whales for lactation. In fact, older female Pilot whales will lactate for longer than younger ones. In females less than 20 years old lactation will last for two to six years, but it can be up to 15 years in the older animals. This does not mean however, that the young whale will only feed on its mother’s milk for all that time. After approximately their first year of life, all young whales begin to take solid food.
The most obvious difference between the two major types of whales is the fact that some have teeth while the other group possess a structure that in the past was referred to as whalebone, but is correctly termed “baleen.” It is not bone at all but is comprised of keratin, which is similar to human finger nails or the outer portion of cows horns. This sets the whales into two vastly different feeding types, those with teeth that actively hunt and catch their prey. And those with baleen that entrap their food. Baleen plates are essentially modified teeth, they form in the whales mouth a giant sieve used to strain their food out of the water.
In the oceans microscopic plants called phytoplankton use the energy from the sun to produce their own food. These plants are then eaten by zooplankton which are themselves microscopic animals: a large portion of which are crustaceans. They are related to crabs, lobsters, crayfish and shrimps. The word plankton refers to the fact that these animals are carried about by the water currents rather than their own swimming abilities. They are so small that swimming does not move them far, some plankton cannot swim at all. These creatures are at the base of the marine food chain and other animals in the oceans will feed of them.
The size of the baleen determines the size of the food the whale will eat. For example, Humpback whales have quite coarse baleen, therefore they feed on larger schooling crustaceans and fish, consuming up to 2 tone per day. Fin whales, by comparison, have much finer baleen and prey on smaller organisms such as plankton.
By developing baleen which enabled them to feed at the base of the food chain, the mysticetes are feeding at the most productive end and gain a lot of nourishment out of their food. This in turn is probably one of the reasons they were able to reach the enormous sizes they have attained today.
Even though the all mysticetes have baleen in common, their methods of feeding still vary among the different families. The Rorquals, to which the Blue, Fin, Bryde’s, Sei, Minke and Humpback whales belong, are “gulpers.” They have massive throat grooves which greatly expand as the animal takes a huge gulp of water and food. They then close their mouth and push up their tongue which expels the water out through the baleen and leaves all the food entrapped on the inside. The Right whales, and this includes the Bowhead, are “skimmers”. They have extremely long baleen (in the Bowhead whale it can be over 4m long). When feeding they plough through the water, allowing it to flow in through the front and out the baleen at the sides. This then traps the tiny animals on the baleen which they use their tongue to remove. The Grey whales are termed as “right-sided feeders”. They will swim to the bottom and stir up the sediment. They then suck the disturbed water into their mouths and sieve out any of the small bottom dwelling organisms that are in it. Because they use predominantly their right side to stir up the bottom, the baleen on this side can get quite worn down. They will also at times take mouthfuls of kelp and strain the small crustaceans off them.
The ondontocetes, the toothed whales, are not as large as their baleen relatives because they feed further up the food chain on fish and squid. They are active hunters in the ocean, using echolocation. This allows them to easily detect prey, and the intense sounds they produce are thought to actually stun and disorient their prey. The shape of the teeth does not allow them to chew their prey. They are adapted only to seize and hold it. The size and number of the teeth vary by species. Some, such as the Common dolphin, have over one hundred in each jaw. Others, such as the Sperm whale or Risso’s dolphin, do not have any in their upper jaws. Because they emerge from the gums several weeks after birth and remain for the animal’s entire life, the teeth have been used to find out whales’ ages.
Besides the physiological differences of feeding with baleen or teeth, certain species of whales have developed some very interesting and ingenious techniques to catch their prey.
One of the most intriguing of these techniques are the “bubblenets” used by Humpback whales in the northern hemisphere. When they come into contact with a large concentration of food the Humpback will move below the food and begin to circle it. As it then begins to move towards the surface, the whale will gently expel air from its blowhole. This air forms bubbles that rise in a circle around the food source. This forms a screen, or net, that will act as a barrier on the organisms, forcing them closer together and tightening their formation. The Humpback will then emerge vertically within the grouped animals, its mouth wide open, engulfing everything in its path. When making bubblenets, one whale might work alone or in cooperation with several others. The bubbles themselves can be as small as pearls or as big as basketballs.
A behaviour exhibited by Orcas is not as subtle as the Humpbacks’ bubblenets, but very spectacular. They will literally strand themselves in order to catch and eat fur seals from a sandy beach. The young Orcas learn how to do this by watching the older animals.
A behaviour similar to the Orca strandings has been exhibited in Bottlenose dolphins. They will herd schools of fish up onto a mud bank. Then they will intentionally strand themselves to feed on the trapped fish, before sliding back into the water. This behaviour has been used by fishermen in West Africa. They will beat sticks against the water to attract schools of dolphins who drive the fish up the shore. The fishermen entrap the fish in gill nets and the dolphins take their share before swimming away.
Mammals are animals which prefer to live in groups or communities. Whales are no exception. They are highly social animals and every aspect of their behaviour is influenced by this fact. In order for a community of any animals to live together the individuals within that community need to be able to communicate with each other. Whales have developed complex communication systems using sight, sound and touch cues.
The groups in which whales live are referred to as pods. Many advantages are to be gained by living together. There is protection from predators. Its easy to find a mate. And they can cooperate to catch prey and feed.
Association patterns exhibited by the various species of whales are as diverse as the species themselves. Orcas found throughout the world’s oceans in both offshore and coastal populations will tend to form matriarchal family groups which are stable for life. These pods form communities with certain other pods, but not all the pods in an area will be part of the same community. As a result, each pod has its own distinct dialect or language. These dialects are similar for pods that form a community together, but are very different from those in different communities. This sort of information only became available through long term research following populations of Orcas for over twenty years. Family structure in the large whales is less well understood, but with improvements in techniques for studying them, we are beginning to be capable of interpreting the structure of their communities. Family groups in Sperm whales are, in part, defined by migration patterns. Apart from the breeding season, the sexes live almost separately. Adult male Sperm whales migrate to polar waters to feed, leaving behind nursery groups which are comprised of adult females, juveniles and calves. Nursery groups can be comprised of anywhere between two and 50 animals. The immature male Sperm whales form “bachelor” schools that can also have as many as 50 animals in them. These school sizes decrease as the animals mature. Then adult bulls fight for access to the adult females in the nursery groups.
The social behaviour of baleen whales is even less well understood than that of toothed whales.
In the tropical waters of Humpback whales’ winter breeding grounds, they can be found either individually or in groups of up to 20 animals. During this time the male Humpbacks compete for the right to escort the females in the hope that they may mate with her that season.
The behaviour of Humpbacks at their summer feeding grounds is vastly different. In the summer they are found in groups from one to 10 animals, and these show no stability over time. The only stable groups form between mothers and calves, an association of around 1 year. The size of a prey patch will to some extent determine the size of the feeding group. Non feeding whales can form “short-term” companionships when they are traveling together, but these usually last less than a day.
Sometimes the social structure and behaviour patterns exhibited by whales can be influenced by ecological factors. Such is the case with Spinner dolphins. Because they feed at night and rest during the day, they can often be found associating with spotted dolphins who rest at night and feed during the day. This works to both species’ advantage. When one group is resting, the other is alert and watchful for predators.
Breeding and Giving Birth
Courtship in cetaceans appears to be a very complex series of behaviours of which little is known. It is probably a combination of sight, sound and touch cues exchanged between individuals. Reproduction may not always be the result of courtship rituals displayed by whales. It may also be expressed as a way of greeting or bonding with individuals, or a group, who have been separated from each other.
During the Sperm whales’ breeding season, the largest males will fight for access to the females. Those which are successful in their battles take on the rights to an entire nursery school. The breeding females in it become part of their harem.
Similar battles take place during the Humpbacks’ breeding season. Courtship displays take place both below and above the water. With fluke slapping, rolling and head butting in ritualised displays between males. However, in addition to this, male Humpbacks will woo their mates with song. It has been documented that Humpbacks do not mate for life. When calves from one female had DNA tests performed on them, it was found they had different fathers.
Often when giving birth, a whale will be accompanied be another whale who is referred to as the “aunt.” They will assist in the birth and, if necessary, help the newborn to the surface for its first breath.
Do whales sleep?
This simple behaviour that is quite well understood in other animals is still almost a complete mystery in cetaceans. Breathing in whales is not an automatic reflex such as in humans. Because of this they will rest one side of the brain at a time. When slowly swimming along they will close one eye for a short time before swapping over and closing the other eye. This still allows them to control their breathing. The fact that a lot of whale species are negatively buoyant (they sink in the water) means that they have to keep moving while resting.
Breeching, Spy-hopping, Fluke Slapping Apart from feeding and courtship behaviours, whales exhibit other behaviours for communication and navigation.
At times, whales leap clear of the water. Reasons why they breech may vary. There is speculation that it could be for pure enjoyment. But others have suggested that it could be to have a look around, as a form of long distance communication between pods. Perhaps letting the others know of its presence.
Spy-hopping is the term given to the position whales take when they sit vertically in the water with their eyes above the surface. This is usually to have a look around. In species such as Orca, it is associated with their hunting techniques.
Reasons why whales slap their flukes is mostly for communication. It could be an aggressive display between males, an attempt to defend calves against aggression, or a signal alerting the group to predators or a danger nearby.
Play forms an integral part in the life of whales. Young whales are not the only ones to participate in play behaviour, but adult whales will invent their own games that have no specific purpose except to amuse themselves. However, just like us, the young are the ones who spend the most time playing. And just like humans, adult whales can become a little aggravated with an overzealous juvenile. This has been observed in a Right whale calf, who tormented its resting mother by repeatedly wriggling up onto her back, covering her blowhole, then sliding down her flukes and butting against her. This went on for some time until the mother rolled onto her back and held the calf between her flippers, completely immobilising it until it calmed down.
All whales probably produce sounds. However, the extent of that sound varies between species. The Grey and Humpback whales provide the best examples of the extremes of the sound producing scale. The Grey whale is almost silent but the Humpback produces the longest and most complex of all whale songs.
In general, the bigger the whale the lower the frequency of sound it produces, and the greater distance the sound will travel. For example, the low frequency moans of the Blue whale will travel over longer distances (maybe over hundreds of kilometers) than the high frequency clicks that dolphins make (which may travel only a few meters).
The loudest sounds produced by any animal in the world are those produced by Bottlenose dolphins. Their clicks have been recorded at 217-228dB. This is louder than a jet airplane which produces a sound of 170dB. Most of the sounds cetaceans will make are inaudible to the human ear. We only hear up to 20kHz. Whales produce sounds up to 200kHz.
It seems that the production of whale sounds is predominantly for communication between individuals. This may be during courtship or when defending territory.
The songs produced by Humpback whales are the most famous of any whale. They are a distinct series of different sounds that vary from moans, groans, roars and sighs to high pitched squeaks and chirps. Ten minutes can pass before a whole song is completed. These may then be repeated for many hours at a time.
The connection between Humpback song and reproductive behaviour is that there is more singing during the breeding season than the feeding season. Also, only male Humpbacks have ever been recorded singing, presumably to attract a mate.
Although a song sequence may change with the seasons, at any one time all the animals in the same area will produce the same song. But this will differ to the songs produced by animals in different areas.
Being able to identify different whales individually, by the songs they sing, is proving to be a great asset to whale researchers as they track populations through migration routes.