Whales have breasts

Whales

The order of the Whales (Cetacea), which roughly reside in baleen whales (Mysticeti) and toothed whales (Odontoceti) belongs within the class of mammals (Mammalia) to the subclass of higher mammals (Eutheria).

evolution

The beginning

Where exactly the origins of the whales lie is largely unknown. Since life in the water went hand in hand with extensive adaptations in the area of ​​anatomy, no conclusions can be drawn about the relationship. Genetic and biochemical studies suggest that whales are related to ungulates. Fossil finds that support this assumption date back to the early Eocene and are therefore between 55 and 52 million years old. How far back the relationship actually goes is not known. Until now it was believed that representatives of the order of Mesonychia, especially the Mesonyx come into question as a forerunner. To the order of the Mesonychia unanimously agreed that they were the only carnivores among ungulates. This thesis is now considered outdated. Molecular biological studies can today prove the relationship with the hippos. The rolling leg in the foot skeleton, which has been proven in fossil primeval whales, also supports these studies. Due to many similarities, whales and artifacts are therefore in the form of taxons Cetartiodactyla summarized.

But what made the forerunners of the whales adapt to life in such a way in the course of evolution? The first contact with the water was probably made while searching for food. In the shallow water of the bank surf, the animals found a rich supply of food. In this nutritional niche, the aquatic way of life developed over the course of millions of years. In the beginning, aquatic life probably looked similar to that of today Sea otters (Enhydra lutris) out. In the further course, the forelegs transformed into pectoral fins, the rear extremities receded almost completely and the tail gradually flattened out. The birth of the offspring also takes place on land. In the next evolutionary steps, the fur receded and a thick, insulating layer of fat formed under the skin.

The earliest animals, roughly reminiscent of today's whales, belong to the family of Protocetidae. This representative was for example Pakicetus. Pakicetus lived about 53 million years ago in the early Eocene. The fossil finds come from Pakistan and were found in 1977 by the paleontologist Philipp Gingerich. It was one of the most primitive of the ancient whales, as its skull is very similar to that of land animals. Another representative of the archaic primeval whales was Protocetus, the fossil finds come mainly from the Mediterranean, especially from northeast Africa. It was relatively small and only 250 centimeters long. About the body shape of Protocetus nothing is known as only one skull was found. It is also interesting that all fossil whales were found in the northern hemisphere. This fact limits the beginning of the evolution of the whales to the Tethys Sea. The Tethys Sea stretched from what is now the Mediterranean Sea to India.

The further development

As a result, the specialization continued. An important link to today's whales is the Zeuglodon. It lived about 45 to 38 million years ago in the mid to late Eocene. Originally, the Zeuglodon was called Basilosaurus because it was assumed to be a reptile. The first finds in the form of some vertebrae were found in 1832 by James Harlan in Louisiana, USA. However, the first determination quickly turned out to be a misjudgment. In 1839 further fragments of the skull and some teeth were found. Richard Owen determined that it had to be an ancient whale. The teeth had multiple points and the sinus arches in the skull were significantly enlarged. These characteristics can also be found in today's toothed and baleen whales. Zeuglodon was extremely large. Scientifically proven is a length of a good 21 meters with a weight of around 5 tons. The head was extremely small and made up only 7 percent of the total length. The external appearance should be reminiscent of modern whales. The pelvis, however, had not yet receded significantly. The zeuglodon was also one of the first representatives to be found in the southern hemisphere. Among the relatively well developed species of the primeval whales were the first representatives of the Dorudontinaefrom which the modern toothed and baleen whales ultimately developed. The splitting off of the toothed and humpback whales probably occurred towards the end of the Eocene or the beginning of the Oligocene some 38 million years ago. One of the last species that can be called a primeval whale Kakenodeonwhich probably died out around 30 million ago. The oldest fossils of porpoise-like animals come from the Miocene. They are therefore around 10 to 12 million years old and were found in the northern Pacific. It is believed that porpoises originated here. Many fossil finds come from late Miocene layers in California. At the same time as the porpoises (Phocoenidae) the first dolphins also appeared (Delphinidae) and gudgeon whales (Monodontidae) on. The common ancestor of the 3 families is Kentriodontidae. The unanimous opinion that the three families split off took place around 10 million years ago. The line of Kentriodontidae died out in the late Miocene. The extinction of the primeval whales was accompanied by an explosive development of modern toothed and baleen whales.

The first toothed and baleen whales

The first more or less primitive toothed whales appeared between 40 and 30 million years ago and began the triumphal march. Baleen whales did not appear until much later, around 30 to 24 million years ago. Overall, the toothed whales show a greater diversity and variety of shapes. The variety of shapes mainly relates to the shape of the skull. The teeth were of very different shapes. So there were toothed and smooth, coarse and fine structures. Depending on the species, the upper jaw was quite long or short, narrow or wide. The diversity was able to develop numerous species over the course of 25 million years. There was also a wide variety of sizes. Squalodon lived 25 to 6 million years ago and had roughly the shape of a modern one Great Killer Whale (Orcinus orca) on. It had sharp, shark-like teeth and, despite its rather small size, was a dangerous predator. The first baleen whales still had primitive teeth. One of the best-known types is, for example Mammalodonwho lived about 24 million years ago. However, the skull already showed the distinctive features of today's baleen whale. One of these features is the fact that the bones of the upper jaw could shift towards each other. The immediate successors of Mammalodon reminded of today's furrow whales (Balaenopteridae). Most of them died out 6 million years ago for reasons unknown.

Today's toothed and baleen whales

Today's baleen whales emerged around 15 million years ago. Even at this point in time, all baleen whales had the characteristic folds of skin around their throat and abdomen. Through these folds the mouth can be opened extremely wide and a large amount of water can be absorbed, which is then filtered. The deepened frontal bone above the eyes also appeared in the species 15 million years ago. This fact supports the thesis that these species were already filter feeders. The Humpback whale (Megaptera novaeangliae) is one of the youngest baleen whales in terms of development. Today’s form a special position Gray whale (Eschrichtius robustus). It does not appear to be closely related to any other recent baleen whale. The historical relationships are still largely in the dark. The same applies to the right whales (Balaenidae), whose development history has not yet been conclusively researched. What is certain is that right whales originated around 22 million years ago in the Merenocetus to have.

The toothed whales use echolocation to track down prey. Toothed whales have taken a completely different path than the baleen whales. Fossil toothed whale has been found worldwide. The peak of their development probably began 22 to 20 million years ago and culminated in today's biodiversity. Most of the prehistoric species were dolphin-like shapes and sizes. At the same time the first sperm whales appeared (Physeteridae), which, contrary to the great diversity of species, were already enormous. The sperm whale (Physeter catodon) has existed for a good 20 million years. There is also some fossil evidence of the sperm whale, of the dwarf sperm whale (Kogia breviceps), on the other hand, there is no fossil evidence. Today's dolphins (Delphinidae) evolved around 12 million years ago from the Kentriodontidae developed. The same goes for porpoises (Phocoenidae) and gudgeon whales (Monodontidae). Today dolphins belong to the most species-rich family within the toothed whale. Porpoises (Phocoenidae) split off from the dolphins around 10 million years ago. The detachment of the gudgeon whales (Monodontidae) occurs 12 to 10 million years ago. River dolphins such as the Amazon dolphins (Iniidae) are not closely related to the dolphins that live in the sea today. However, their similar physique can be explained by convergent evolution. One suspects a relationship with the river dolphins Squalodon.

description

General

In the course of a very long development period of more than 40 million years, whales have fully adapted to marine life. Despite extensive adaptations, whales share many characteristics with land-based mammals (Mammalia) on. These include the rudimentary hair, a heart consisting of four chambers, mammary glands and a placenta in female whales, as well as the three tiny auricles in the middle ear, which are individually designed as a hammer (Malleus), Anvil (Incus) and stirrups (Stapes) are designated. The presence of these traits always indicates a close relationship with mammals. Other features such as the streamlined body shape are not historical, but a functional inevitability. The question arises, however, why did some whales get so big? The largest whale on earth and at the same time the largest animal that ever lived on earth is the blue whale (Balaenoptera musculus). With its enormous length of up to 33 meters and a weight of 180 tons or more, the blue whale could not exist on land. His own weight would literally crush him. In the water, however, the size only plays a subordinate role. The main reason for the gigantic size is likely to be the reduction in the ratio of body surface area to body volume. The reasons are obvious. Due to its high body volume, a blue whale can maintain its body temperature in cold water.

Physique and shape

The body structure and the body shape are optimally adapted to life in the water. Whales, and especially dolphins, are quick and effective swimmers. Vertical movements of the caudal fin, also known as the fluke, provide propulsion. It is controlled via the pectoral fins, the so-called flippers. The shape of the whale's body allows the optimal flow of water. There are no external obstacles that could affect the flow of the water. Whales have no external extremities, no external lips and no external ears.

Head, body and fins

The individual families can be easily recognized by the shape of the head. Baleen whales can usually be recognized by their very elongated upper jaw. The head is usually kept flat and there are two blowholes. The upper jaw is the bearer of all representatives of this subordination. Toothed whales have a rather narrow and straight upper jaw. Another characteristic is the more or less pronounced melon, which is located above the eyes. In contrast to baleen whales, toothed whales only have one blowhole. The head of many dolphins ends like a beak. The lower jaw of baleen whales is significantly larger than that of toothed whales. Furrow whales have a peculiarity within the baleen whales. Your throat is marked by long furrows. Through these furrows, the throat can be greatly expanded and thus enables large amounts of water to be absorbed. Most whales have very small eyes for their head size. They are always on the side of the head. The internal ears are behind the eyes, usually halfway to the pectoral fins. The pectoral fins lie ventrolaterally just behind the head in the first third of the body. Have in the relationship between body length and the length of the pectoral fins Humpback whales (Megaptera novaeangliae) in the order of whales over the longest pectoral fins.
Dorsal fin of the humpback whale (Megaptera novaeangliae)
They reach a length of over 450 centimeters, i.e. around a third of the body length, and are considered to be the longest extremities within vertebrates. Most whale species have a more or less large dorsal fin dorsally, which can have a sickle-like, triangular or rounded shape. The dorsal fin is not kept in shape by a bony structure, but by hardened connective tissue. The skin is smooth and hairless in all species. There is a thick layer of fat under the skin, which is used to regulate the temperature. Below the layer of fat is the muscle mass in the form of the main muscles.

Skull and skeleton

The skeleton of individual whale species is sometimes very different from one another. The differences between baleen and toothed whales are most evident in the area of ​​the skull and the underlying tissue. Despite the great differences, the skulls of all whales can be traced back to a common type. In the course of evolution, the skulls have gone through a process that can be viewed as "pushing together". Some parts of the skull are superimposed on others. There are major differences between baleen and toothed whales, which are discussed below. In the toothed whales there was a clear shift of the main bones backwards and upwards. In all recent species, the main bones lie, mostly asymmetrically, across the front of the skull case. The assumption is that this shift is to be seen in connection with the development of the echo location. The jawbones that have migrated back support the large-volume facial muscles and converge in the area of ​​the nostril. Here they are in a number of Diverticula (Sacs) in the soft tissue of the nasal passages between the blowhole and the nasal openings of the skull. The ears show a strong enlargement of the middle ear cavity and bulges at the base of the skull. It is believed that these sinuses are used to equalize pressure while diving. The ear bones, hearing and the organ of equilibrium are controlled by the Periotic carried. The Periotic does not have a firm bond with the base of the skull, but rather lies movably on the connective tissue. The reason for this is obvious. In this way, sound waves are not transmitted from the ear into the bone structure and work, so to speak, as a silencer. How exactly the sound transmission works has not yet been adequately researched. It is believed that the transmission of sound waves to the bones of the ears occurs through fatty tissue and from there to the middle ear.

The jaws are distinctive in different ways, depending on the species. However, a common basis can be found in the straight construction. The name toothed whale says it all: all toothed whales have teeth. However, the teeth are fundamentally different from those of other mammals.
slightly open mouth of a humpback whale (Megaptera novaeangliae)
In most species, the teeth are conical in shape. The number of teeth is usually significantly higher than in mammals living on land. A tooth change does not take place in toothed whales. Another difference in the teeth of toothed whales is the homodontic construction, which is fundamentally different from the heterodontic construction of other mammals. You can't chew with these conical shaped teeth. They are essentially only used to grab and hold prey animals. Food is generally swallowed whole, if necessary torn into bite-sized pieces beforehand.

The baleen whale's upper jaw is usually flat and wide in shape. The main bones of the upper jaw carry the whiskers made of horn plates. With these whales, baleen whales filter microorganisms out of the water. Depending on the species, the beards can be very long. The beards are particularly long in the right whales (Balaenidae), her upper jaw also shows a significant bulge. The whale beards (Balaenopteridae) are significantly shorter and the upper jaw bones have a flat shape. The individual bones of the upper jaw are flexibly connected to one another.The same applies to the connection between the upper jaw and the skull. The lower jaw has no teeth or whiskers. Here, too, there is a flexible connection in the area of ​​the mandibular arches.

The cervical vertebrae of all whales are extremely short and partly fused together. This results in only limited head mobility. The skeleton of the whale does not essentially fulfill the support function of the body as it is the case in mammals living on land. Therefore, the ribs in particular are only weak and in some cases filigree. As a rule, there is also no firm connection between the ribs and the vertebrae or sternum. This fact also explains why whales suffocate and die under their own weight when stranded. The number of vertebrae in the spine varies greatly depending on the species. A pelvic belt is only rudimentary in all species and has no function at all. The shoulder blade, on the other hand, is strongly developed. This is where the well-developed pectoral fins sit. The fingers that are not visible from the outside are four or five fingers, depending on the species.

Internal organs

In all whales, the blowhole is on the top of the head. From here the windpipe runs to the lungs. The lungs are right next to the heart. In the baleen whales there are olfactory and sensory cells in the area of ​​the blowhole. However, they only have a minor function. Such sensory cells are completely absent in toothed whales. The brain in whales is extremely large when you put it in relation to body size. However, the brain is not supplied with blood via a carotid artery, as in other mammals, but via the so-called miracle network or else Retia mirabilia. The miracle network is a network of the finest arteries. The stomach can differ depending on the species and has several chambers in some species. This similarity with ungulates can be explained by a convergent evolution, since the various chambers fulfill a different function than the gastric chamber of a cow, for example. Internal organs such as the gallbladder and appendix are absent in all species.

Special features of the toothed whale

The teeth are very different in the individual toothed whale species. The teeth are simple, especially in the more highly developed species, and have a root and a conical crown. Other species have completely lost their teeth and only show horn-like thickenings in the jaws.
Ivory tusk: narwhal (Monodon monoceros)
Toothed whales have developed an extraordinarily wide variety of sizes, shapes, and ways of life. A large number of habitats are also settled. Some species live exclusively on the sea, others live closer to the coast, and still others have adapted to life in freshwater. A total of four families have adapted to life in fresh water or brackish water, to which the Amazon dolphins (Iniidae), the La Plata dolphins (Pontoporiidae), the Chinese river dolphins (Lipotidae) and the Ganges dolphins (Platanistidae) belong. Some of the species in these families can live in both salt and fresh water.

Toothed whales have undergone the greatest adaptation in terms of their diet. Numerous species have undergone diverse and specialized adaptation. This has not infrequently brought them into conflict with fishing, because many prey of toothed whales are also on man's wish list. However, the marine mammals themselves are often the focus of interest. Especially the sperm whale (Physeter catodon) was heavily hunted for centuries and brought to the brink of extinction. The oil was particularly popular. The meat was mostly processed into animal food. Many toothed whale species are still hunted today. The Japanese are among the most avid whale hunters who hunt with their fleets worldwide. Similar to the elephants one has it with the narwhal (Monodon monoceros) except for the horn, which is made of ivory. Today, however, many toothed whale species end up in the nets as bycatch. This is the case, for example, in the tuna fishery. Other species, such as those that live in rivers, are in some cases severely threatened by environmental influences or are on the verge of extinction. The Chinese river dolphin (Lipotes vexillifer) is considered to have already been eradicated.

Special features of the baleen whales

With their filter apparatus, baleen whales have especially adapted to a special food. In contrast to toothed whales, which have either teeth or horny jaws, the baleen whales use the whales, which are also known as whale legs, to obtain food. Baleen whales also come in different sizes and shapes. They include true giants like the blue whale (Balaenoptera musculus). It is all the more astonishing that even blue whales only feed on microorganisms, of which, however, they devour several tons a day.

The beards consist essentially of horn-like lamellas that hang down like a curtain in the area of ​​the upper jaw. The beards are heavily frayed on the inside, i.e. towards the throat. The fraying can vary greatly depending on the species and the preferred food. Beards, like hair and nails in humans, are made of keratin. Toothed whales sometimes hunt for individual prey. Of course, this does not work with baleen whales. They depend on large collections of prey. Baleen whales are on the lookout for large schools of plankton, some of which are home to billions of microorganisms. Such swarms are mainly found in the upper water layers, mostly even directly below the water surface. Baleen whales are nowhere near as diverse as toothed whales. These include the families of the right whale (Balaenidae), the minke right whale (Neobalaenidae) as well as the furrow whale (Balaenopteridae). Quite a few researchers see it Gray whale (Eschrichtius robustus) in a separate fourth family. Otherwise the gray whale is assigned to the furrow whales.

Right whales (Balaenidae) have the longest whales of all baleen whales. The beards are also extremely finely fringed. This fact points to the food: right whales feed on tiny copepods (Copepoda) and other very small crustaceans (Crustacea). This group includes the Atlantic northern right whale (Eubalaena glacialis) and the southern right whale (Eubalaena australis). When feeding, right whales swim through the water with their mouths only slightly open. When it flows out of the mouth, the food clings to the fine whiskers. This is the biggest difference to the furrow whales, which have to open their mouths wide to eat and therefore have deep furrows in the throat area that enable them to unlock. The second group are the furrow whales (Balaenopteridae). The most distinctive feature are the deep furrows in the throat and stomach area. These furrows make it possible to open the mouth very wide and to inflate the larynx. In terms of size, both the blue whale (Balaenoptera musculus) the largest recent whale as well as a smaller representative such as the northern minke whale (Balaenoptera acutorostrata) or the southern minke whale (Balaenoptera bonaerensis) represented. Another group of baleen whales is the minke right whale family (Neobalaenidae) to which only the pygmy right whale (Caperea marginata). He is monotypical in this family. With a length of only five to six meters, it remains significantly smaller than the representatives of the right whales (Balaenidae). Little is known about this species. Only a few years ago, among other things, research was carried out into the song of the minke right whale. In addition to size, another distinguishing feature is the dorsal fin, which the right whales lack. Some researchers put the gray whale into a separate family and equate it with the furrow whales. Other researchers classify the gray whale within the furrow whale.

Sense organs

sense of touch
The sense of touch occurs via nerve endings in the skin. From here, impulses reach the brain via the central nervous system and can be processed there. Some whale species have special nerve cells in their jaws that can be used to perceive low-frequency sounds and vibrations. The pressure is also measured via similar nerve cells. In the area of ​​the nostrils, special nerve cells are used to measure pressure. This is how a whale knows when the nostril is exposed and when it can be opened. Under water, the nostrils are always closed with the help of strong muscles.

Sense of sight
Not only the body, but also the sense of sight has undergone far-reaching adjustments in the course of evolution. Whales can see both under and over water. This is all the more astonishing since light spreads much more slowly underwater. However, this was not possible without a physiological adjustment. The eyes are surrounded by powerful muscles that can change the shape of the lens as required. In order to make effective use of the small amounts of light available at great depths, whales have very large pupils. You are able to collect and process this even when there is little light. At the surface of the water, the eyes narrow to a narrow slit to control the amount of light. The eyes of all whale species are on the side of the head. Therefore, it is not possible to see ahead. Objects are usually only examined with one eye. The eyes are able to focus on objects that are close as well as distant. It has been found that dolphins in particular have a wide range of colors and can recognize them. This is all the more astonishing since red and yellow in particular are absorbed by the environment after a few meters underwater. However, it is not known whether all whale species have this ability. It has only been proven in dolphins.

Sense of smell and taste
Chemical information that is dissolved in the water is evaluated via the sense of taste. Water is an excellent carrier for substances of all kinds. Even the smallest concentrations can be perceived through the sense of smell and taste. Both the sense of smell and taste play an extremely important role in prey acquisition and reproduction. Unlike the sense of sight, the sense of smell and taste no longer play a role on the surface of the water. The olfactory sensory cells (receptors) only fulfill their purpose under water. But there are also some big differences within the whales. Baleen whales have significantly more olfactory receptors than toothed whales. In the case of toothed whales, on the other hand, echolocation plays a much larger role. Toothed whales, especially dolphins, have numerous taste buds on their tongues that are likely to make them taste good. This is particularly evident from the fact that dolphins do not eat dead fish. They obviously use the sense of taste to check the palatability of food.

Hearing
Whales do not have external ears. All that is visible is a small hole directly behind the eyes. Depending on the type, such a hole is only a few millimeters in diameter. In baleen whales, the barely visible outer ear is closed with a horn-like wax plug. The toothed whales completely lack such a plug. The internal ear canal in toothed whales is open and therefore filled with water. To what extent the hearing process is managed is largely unexplored. There are various theories, some of which are very controversial. However, the loss of an external ear should not have any effect on hearing, as sound travels five times faster in water. Since sound can only travel to a very limited extent between water and air, it can be assumed that there is no air inside the ear.

Echolocation in toothed whales
Echolocation works in a similar way to bats (Microchiroptera) or the Egyptian bat (Rousettus aegyptiacus). The echo location is based on the active transmission of broadband impulses, which are also referred to as clicks. The echo that is thrown back by obstacles is evaluated. Natural obstacles can be rocks or stones, but of course the seabed can also be carnivores and prey. The broadband pulses can consist of both low-frequency and high-frequency tones. With the help of echolocation, a toothed whale, for example a dolphin, can orient itself even in absolute darkness or in cloudy water. The sound waves are emitted from the melon in the forehead area. Inside this melon there is fat tissue that bundles the sound waves and sends them out. The beams more or less form a directional beam. A toothed whale can use the echo to determine direction, distance, and even size. Even the composition can be recognized. Baleen whales have no echolocation facility.

Magnetic sense
In the case of whales, the question arises as to how they can orient themselves in the vastness of the world's oceans and sometimes always swim the same routes. It is believed that this is some kind of magnetic sense. Obviously, directional information from the earth's magnetic field is evaluated. The information is captured by tiny magnetite crystals in the outer tissue of the brain and evaluated by the brain itself. Together with geomagnetic anomalies, a toothed whale has a kind of map. Disturbances in this sensory performance can lead to stranding.

Way of life

Whales generally live in small to medium-sized schools. So they are considered to be extremely sociable. Of course, the way they live together differs depending on the species. Some species are very gregarious, others less so. Humpback whales, for example, are not very sociable marine mammals that live solitary or in small groups. In the feeding grounds, however, it is quite possible that larger groups are formed. The situation is similar with the Atlantic Northern Capeers, but their social system has only been little researched and much is still in the dark. What is known, however, is that they usually live in small schools of two to eight, rarely up to twelve, individuals. Older bulls can also be found solitary. The groups of whales are usually mixed-sex, but segregated-sex groups can also occur in some species. The killer whale is a very sociable and family-oriented marine mammal. He lives in large groups commonly known as schools. A school is headed by an older, dominant female. A school consists of a male, a large number of females and their not yet sexually mature offspring. The size of a school can easily consist of over 40 or 50 individuals. Common dolphins are also socially oriented marine mammals. They live in larger schools and are rarely found solitary. This also applies to foraging, which generally takes place in groups. The schools can range in size from 30 to 100 or even a few thousand animals. The size of a school can vary with the season and season.

Only a few whale species are extremely faithful to their location. Humpback whales are not sedentary animals. Every year they migrate back and forth between the feeding grounds and the reproductive habitats in the tropics. The birth and rearing of the calves also takes place in tropical waters. Here, humpback whales cover a few thousand kilometers. They are considered to be very fast swimmers who can easily reach a speed of over 25 km / h. The highest speeds are reached during the annual hikes. However, the average swimming speed is less than 10 km / h. But gray whales also migrate annually between the feeding grounds and the breeding habitats in the tropics. Here gray whales cover a few thousand kilometers.

The dive times are very different depending on the species. A humpback whale usually dives for 25 to 30 minutes while foraging, gray whales rarely dive for more than 15 minutes. Most whale species continue to be sociable when they forage. Large killer whales search for food in groups. To do this, they use different hunting strategies depending on the prey they have identified. This is dealt with separately in the chapter on food. Killer whales are among the most intelligent marine mammals in the world's oceans. This is not only expressed in the hunting methods, but also in social behavior. The playfulness of many dolphin species and some whale species is expressed in some high jumps in the air. Sometimes dolphins, for example, can jump a few meters out of the water. To this day, research has not yet figured out the meaning of these leaps in the air.

Toothed whales communicate with each other using the aforementioned clicks. Low-frequency sounds are used in baleen whales. Atlantic northern right whales produce tones in a frequency between 50 and 500 Hertz. The exclamations can extend over a period of one to six seconds. When they catch their prey, they emit sounds with a frequency of two to four kilohertz. Of all whales, the humpback whale has the most elaborate song.The multi-layered chants are heard mainly during the mating season and come mainly from the male. Scientists have found that the chants are particularly useful for pairing. The chants can vary greatly depending on the region. It is believed to be some kind of dialect. The chants mainly consist of low frequencies and can be heard for many kilometers due to the high conductivity of the water. Measurements have shown that the sounds of other whales can be heard over a distance of a few hundred kilometers. The chants of the northern and southern populations sound completely different.

distribution

Whales occur in all bodies of water and water zones around the world. Arctic, Antarctic, subarctic, subantarctic and temperate as well as warm temperate, subtropical and tropical waters are populated. In many species there are seasonal migrations, others are considered to be very sedentary. As a rule, whales are only found in salt water, but some species also live in fresh water inland. Still others can live in brackish water. Depending on the species, factors such as water temperature, salinity, water depth, the topography of the seabed and of course the availability of suitable food sources are particularly important for whales.

Baleen whales live in both arctic and tropical waters. In the tropics, whale cows give birth to their offspring. Their feeding grounds lie in the cold waters. There are sometimes 10,000 and more kilometers between the food and the breeding grounds. Only the Bryde's whale lives among the baleen whales (Balaenoptera brydei) only in tropical waters. Here he lives both on the high seas and near the coast. Other species such as the northern right whale (Eubalaena glacialis) live exclusively in cold waters. Toothed whales are also common worldwide. Some species are found in all bodies of water around the world, others live in a restricted manner in relatively small distribution areas. The killer whale, for example, is very widespread (Orcinus orca). It is at home in all oceans as well as in the larger seas such as the Mediterranean Sea. This includes arctic as well as tropical and subtropical regions. The same applies to the common dolphin (Delphinus delphis) or the round head dolphin (Grampus griseus). Both types occur worldwide.

Depending on the species, whales live in pelagic waters or near the coast. Some species definitely inhabit both habitats. Species like the Sotalia (Sotalia fluviatilis) have adapted to life in freshwater and brackish water. The Sotalia is widespread in South America with its two subspecies. The Amazon Sotalia (Sotalia fluviatilis fluviatilis) lives in the Amazon basin in particular in the rivers Amazonas, Rio Negro, Rio Madeira, Rio Xingu and Rio Tapajos. Guyana Dolphin (Sotalia fluviatilis guianensis) lives in the marine, coastal waters from Central America to north-eastern South America. Other species live exclusively in fresh water. These include, for example, ganges dolphins (Platanistidae) or Chinese river dolphins (Lipotidae).

The longest migrations within the order of the whales are undertaken by the representatives of the baleen whales (Mysticeti). On the one hand, the food supply and reproductive activity are decisive for the migration. Their main food is krill (Euphausiacea) occurs exclusively in the polar waters of the northern and southern hemispheres. The offspring cannot be born in the cold waters. Therefore, baleen whales move to subtropical or tropical waters to raise their offspring. The hikes always run in a north-south direction or vice versa. Between the feeding grounds and the mating areas, humpback whales migrate many thousands of kilometers back and forth every year. They cover up to 10,000, in rare cases up to 16,000 kilometers on one route. Humpback whales are among the mammals with the farthest migrations. Mating, the birth of the offspring and their rearing take place in tropical waters. <1>

Predators

Adult large whales basically have no natural enemies other than humans. Young animals as well as old, sick or weakened animals occasionally fall into great white sharks (Carcharodon carcharias) or killer whales (Orcinus orca) to the victim. Smaller whale species or dolphins are occasionally also referred to by the little killer whale (Pseudorca crassidens), the tiger shark (Galeocerdo cuvier) or a bull shark (Carcharhinus leucas) eaten.

Parasites

The parasites of the whales are differentiated according to the type of diet they eat. Some attach themselves to the skin of the whale and stay here for life, others follow the whales at a short distance and benefit from the whales' success as parasites. These companions are also called commensals, a whale is considered the host, although the whale does not experience any beneficial or disadvantageous effects. One can call this interspecific interrelation a probiosis. Most obvious is the correlation between a humpback whale and barnacles (Pollicipes pollicipes). They adhere almost to the entire body, but preferably in the head area around the mouth. Even if the name suggests, barnacles are not mussels, but belong within the barnacles (Cirripedia) to the barnacles family (Balanidae). Similar to the humpback whale, the barnacle also feeds on plankton, which it filters out of the water. Other parasites like wall lice (Cyamidae), which are particularly common in right whales (Balaenidae) occur, preferably settle in the calluses, as there is no water current here. They feed on algae, which they eat off the skin of the whales. Basically, the whale does not suffer any disadvantage when interacting with the Wallau. Here, too, the name belies the actual origin. Wall lice do not belong to the group of lice, but to the amphipods (Amphipoda). But endoparasites also play a major role, which can lead to illness or even death to a whale. These include numerous species such as tapeworms (Cestoda), Scratchworms (Acanthocephala) and tube worms (Nemathelminthes), which can affect the lungs and stomach as well as the intestines. Scratchworms live in the intestines, the liver and in and on the peritoneum folds of internal organs and lead to death if they are severely infected.

nutrition

In terms of diet, baleen whales and toothed whales differ considerably. Baleen whales feed mainly on microorganisms that are filtered out of the water. These include, for example, krill (Euphausiacea), Copepods (Copepoda), Multi-bristle (Polychaeta), Amphipods (Amphipoda), other higher crustaceans (Malacostraca) as well as small molluscs (Mollusca) and fish eggs. The humpback whale is also able to eat small fish in regions where there is a lack of microorganisms. Various species of mackerel such as Pacific mackerel (Cololabis saira), the sand eels (Ammodytidae) again Ammodytes americanus as well as the Atlantic herring (Clupea harengus) are high on the menu. Water enriched with food flows into the mouth and is pressed out through the beard. The food is held back and devoured by the beards. Different hunting strategies are used depending on the type of whale. For example, humpback whales dive under a school of fish and let air bubbles rise in a ring around the school. The frightened fish move closer together and are devoured in large portions by the humpback whale. Several whales always take part in this hunting method, some releasing air bubbles, others eating and vice versa. In schools that are just below the surface of the water, humpback whales swim in, lying on their sides with their mouths open. This hunting method can also be used successfully by solitary humpback whales. Another method of obtaining food for gray whales is "plowing through" the seabed. A gray whale lies on its side and picks up the sediments from the sea floor with its mouth. The whiskers are now used to filter the smallest life out of the mud.
The big feed: humpback whale (Megaptera novaeangliae)
Toothed whales target significantly larger prey and, in contrast to the baleen whales, also hunt individual prey. Prey animals are localized via echolocation. Toothed whales send out clicks and can thus determine where prey animals are. Most toothed whales are opportunistic carnivores. Porpoises (Phocoenidae) eat cephalopods, for example (Cephalopoda), Crustaceans (Crustacea) and smaller fish (Pisces). Depending on their occurrence and habitat, this includes mackerel (Scomber), Squids (Teuthida), Mullets (Mugilidae), Bill snapper (Nemipteridae), Real octopuses (Octopodidae), Cuttlefish (Sepiida), Cardinalfish (Apogonidae), Jacks (Carangidae), Herrings (Clupeidae), Conger eels (Congridae), Anchovies (Engraulidae), Pony fish (Leiognathidae), Umberfish (Sciaenidae), Perch (Serranidae), Sea bream (Sparidae) and medusa fish (Stromateidae). Larger toothed whales like the sperm whale mainly hunt squids (Teuthida) and here especially on giant squids (Architeuthis). This has been shown by analyzes of the stomach contents of sperm whales. Giant squids can be up to 15 meters long and weigh up to half a ton. Beluga whales also take mussels (Bivalvia) and snails (Gastropoda) to himself. The diving depths are very different depending on the species. Some species hunt in the area of ​​the water surface, other species such as the sperm whale dive to depths of a good 2,500 meters and more. Sperm whales stay under water for up to 80 minutes.

Beaked whales are also record-breaking (Ziphiidae). It is assumed that beaked whales dive to depths of 1,000 meters and more on average while foraging. It is proven that the Cuvier's beaked whale (Ziphius cavirostris) a record depth of 1,900 meters. With the Blainville beaked whale (Mesoplodon densirostris) a diving depth of about 1,200 meters could be proven. The average dive times for beaked whales are between 20 and 30 minutes. With a duck whale (Hyperoodon) a diving time of 80 minutes was detected and thus achieved a diving time similar to that of the sperm whale. Beaked whales (Ziphiidae) belong to the longest and deepest diving whale species.

Other species like the killer whale seem to have developed a nutritional preference for marine mammals. They hunt both small and large marine mammals. It has been observed that, depending on the distribution area, sea otters (Enhydra lutris), Whales (Cetacea) and dolphins (Delphinidae),, Dog seals (Phocidae), Ear seals (Otariidae), Walruses (Odobenidae) and even young blue whales. However, schools may specialize in other foods. That ranges from fish and cephalopods (Cephalopoda), about sea turtles (Cheloniidae) to seabirds and, in Antarctic waters, penguins (Spheniscidae). When hunting, killer whales always hunt for prey in groups. The hunting strategies are based on the preferred prey. For herrings (Clupeidae), for example, the swarms are pushed from below to the surface of the water. In doing so, they release air bubbles that form a real curtain around the fish. If a swarm is rounded up, the killer whales knock the fish unconscious with their huge tail fin and then swim into the swarm with their mouths open. This was particularly observed off the Norwegian coast. In the northwestern Pacific, on the other hand, cod (Gadus morhua), similar fish and cephalopods (Cephalopoda) prefers. Salmon, in particular, are eaten on the northeastern coast of North America. If a prey is small enough, it is devoured whole. Otherwise, the prey will be torn into pieces and eaten in bits and pieces. It has been observed that killer whales can play with larger prey for a while. A captured seal was thrown out of the water several times before it was finally killed and eaten. Near beaches it has been observed that killer whales swam at high speed all the way to the beach to pick up seals (Pinnipedia) or something similar. This is also usually done cooperatively in a group.

Reproduction

The sexes are not easy to distinguish. Due to the adaptations to the habitat water, the otherwise visible genitals are in a belly pocket, the so-called genital slit. The genital slit is more or less similar in both sexes. However, the distance between the genital and anus slit can be used as a distinguishing feature. The two slot-like openings are significantly further apart in the male. The mammary glands of the female can only be seen with a trained eye. They are also hidden in slits. Some species show a visible dimorphism in size, with a male becoming significantly larger. This is the case with sperm whales, for example. The male of the great killer whale can also be recognized by the significantly higher fin. In the body shape or in the color of the skin there are no differences between the sexes in any of the whale species.

The male's genitalia, the penis, lies curled up in a kind of pocket that is formed by a foreskin when at rest. A double-stranded retraction muscle holds the genitals in the pocket. The penis has a columnar shape and consists essentially of a more or less spongy tissue. Only in the course of the erection does the erectile tissue fill with blood and thereby stiffen. The retraction muscles loosen their "grip" and allow the erectile tissue to extend. The testicles are located inside the abdominal cavity, so there is no external scrotum (scrotum). As with all mammals, the sperm are produced in the testes and reach the genitals via the epididymis. The final maturity of the sperm takes place in the epididymis. The sexual organs of female whales are essentially similar to those of other mammals. The ovaries, two of which are present, are located in the area of ​​the stomach cavity. In the ovaries, the egg cells mature in an ovarian follicle (Folliculus ovaricus) approach. One speaks here of spherical follicles. The cervix, the so-called uterine neck, open towards the vagina. The vaginal wall is characterized by several ring-shaped folds near the cervix. During the mating season, a follicle breaks open and the egg cells migrate into the fallopian tube.

The reproduction cycle differs depending on the species. Due to the very long gestation and suckling period, most whale species have a mating cycle of two to four years. With increasing age, the pregnancy rate continues to decrease and, depending on the type, comes to a complete standstill between the ages of 20 and 40. Baleen whales in particular have a clear reproductive pattern. While they linger in the feeding grounds in the arctic waters in summer, they migrate to tropical waters during the mating season. This is also the case with many toothed whales. The sometimes very long reproduction cycles naturally also affect the stocks. A threatened population then only recovers very slowly.

Advertising behavior

Whales lead a polygamous way of life, there is no bond between the sexes that goes beyond the act of mating. In many species, courtship is accompanied by fierce courtship for a female. Among the bulls of the humpback whales, there are regular fierce rival fights that are fierce. The cops' fighting can last for several hours. They ram their skulls into the flanks of the opponent and deal violent blows with their fins. It is not uncommon for up to 20 males to pursue a female. <2> As in other mammals, the sense of smell plays only a subordinate role in advertising behavior. Rather, special behavior patterns come into play with the whales, especially to signal the willingness to mate. There is essentially no information available about the duration of a copulation, since matings could only be observed very rarely. It can be assumed that copulation lasts between a few seconds and a few minutes. What is best known today is the reproductive behavior of dolphins kept in captivity. In bottlenose dolphins, for example, copulation only lasts for a few seconds.

Embryonic development

Depending on the type of whale, the gestation period extends over an average of 10 to 12 months. Some toothed whales can be pregnant for up to 18 months. With the killer whale, for example, the gestation period is up to 16 months. The common porpoise has a very short gestation period of 9 to 10 months (Phocoena phocoena) on. The birthing process is similar in all whales.After the newborn has left the uterus and is placed in the water, the mother immediately pushes it to the surface of the water. As a rule, the offspring is born tail first, more rarely head first. The birth process takes a few minutes at most. Immediately after the umbilical cord is cut, the newborn has to go to the surface to breathe. As a rule, twin births are very rare. They are already documented, albeit rarely. The offspring is already far and fully developed at birth. He can swim independently and breathe on the surface of the water.

The birth weight and length of birth are very different depending on the species. The calf of a blue whale (Balaenoptera musculus) weighs a good 2,200 kilograms and is 7.5 meters long. The offspring of a common porpoise (Phocoena phocoena), on the other hand, only weighs 9 kilograms and is 70 centimeters long. A calf is suckled under water. The very fatty milk is actually pressed into the mouth of a calf through muscle contraction via the mammary gland. The suckling process usually takes place just below the surface of the water. Even if calves are already very developed, they are completely dependent on the protection of their mother. Incidentally, due to the polygamous way of life, the fathers play no role in the rearing of the offspring. Within a herd, however, close relatives of the mother help with the rearing. This behavior demonstrates the high level of social integrity within a herd. The suckling period extends over one to two years, depending on the type of whale. It is not uncommon for young animals to suckle from their mother until they are six years old, although they have not been dependent on milk for a long time.

ecology

whaling

Whaling is almost as old as mankind, or as seafaring mankind. Initially, due to the lack of ships, the only target was stranded whales and dolphins. Fossil finds indicate that whale bones and other products from whales were used in the Stone and Bronze Ages. The first active hunting will have taken place around 2,000 years ago. Whale hunting is most widespread among the Inuit, the natives around the arctic waters. They still hunt a wide variety of whale species today. Basically, however, without any commercial ulterior motives, but only for the purpose of obtaining food. Inuit hunt whales mostly with harpoons from kayaks. Large whales were probably hunted commercially by humans in Spain around 800 years ago. For centuries, whales were hunted with primitive harpoons. It is not uncommon for whales to be injured and escape. An agonizing bleeding to death was usually the result.

Almost all parts of the whales are recycled. The bacon, from which oil could be extracted, was particularly popular. The oil was mainly used to light oil lamps. But the whalebone and meat were and are also in demand. The sperm whale's whale oil was used in the manufacture of margarine, candles, polishes, lipsticks and other cosmetics, as well as soap. Teeth and bones were valued in handicrafts and made into all sorts of odds and ends. The very valuable ambergris, which was used in particular for perfume production, was extracted from the bowels of the sperm whales. Today most of the products are manufactured synthetically and one is no longer dependent on whale products. In the first half of the 20th century, hunting was massively expanded and reached its peak with new fishing methods. As a result, many species became rare and were facing extinction within a short time. Today whaling is largely prohibited. Whales are only caught under the guise of research. But the meat of these whales ultimately ends up on consumers' plates.

Further dangers

In the past few decades, water pollution, particularly that of the great oceans and seas and coastal waters, has increased dramatically. Not only is waste oil dumped, but PCB, DDT and other poisons are also discharged into the oceans via the rivers. It looks particularly bad in the areas with high population density on the coasts. The poisons either have a direct effect on the whales or indirectly through their food. The poisons and heavy metals are of course also ingested by fish, which form the foodstuff for the humpback whales. Overall, the northern populations are significantly more endangered than the populations in southern distribution areas. Today more and more voices are being raised that whales should be hunted more intensely, as one is of the opinion that the well-calculated populations of the whales are too high and would lead to overfishing of the world's oceans. However, the overfishing of the seas is solely due to man and his greed. For decades, fish species were fished unrestrainedly. Today almost 50 percent of all commercially used fish species are fished to their limits. Other species are considered already overfished or the stocks are even exhausted. Of course, the easiest way to blame whales is to admit their own mistakes. In fact, however, an increase in fish stocks should have been determined, since almost many whale species, especially the large whales, are on the verge of extinction. So the arguments of the fishing industry are by no means conclusive.

Today humans are penetrating ever further into the habitats of whales. Restlessness, stress and, last but not least, death are the inevitable consequences. In densely populated coastal areas, whales are injured by the propellers of ships and boats or they collide with ships. The mere presence of ships and boats in the home waters of the whales can cause unrest in the whale schools. Whales react nervously, are disoriented and profound interventions in social life cannot be ruled out either. It is not uncommon for these causes to lead to the death of the animals. Whale stranding is also a common phenomenon in densely populated habitats. It is believed that the stranding is triggered by a lack of orientation. When stranded, the animals, some of which weigh tons, suffocate due to their heavy weight outside of the water. The damage caused by engine and screw noises should be just as bad. This has a particular effect on hearing and orientation skills.

Keeping in captivity

The first whales were exhibited in England since 1870 and in the United States since 1913. Both of these were beluga whales. The first dolphins have been kept in captivity since 1913. The first aquariums include the Marineland of Florida and the Battery Aquarium in New York. Bottlenose dolphins were exhibited here as early as 1938. The Duisburg Zoo has also had bottlenose dolphins since 1965. A beluga whale has also been kept in Duisburg Zoo since 1969. Today a large number of marine mammals are kept worldwide. In addition to bottlenose dolphins, these include pilot whales, killer whales, beluga whales, killer whales, common porpoises and Amazon dolphins. The keeping of whales and dolphins is not without controversy. In general, aquariums only have limited space, so that it is not possible to keep them appropriately. The public interest is certainly great, but it is more linked to the greed for sensation than to the protection and conservation of the species. Public awareness of the threat to whales is mostly neglected. Research on captive whales only makes limited sense, as captive whales do not display their normal behavior.