Crocodiles
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Top left: Saltwater crocodile ( Crocodylus porosus ) |
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| Crocodylia | ||||||||||||
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The crocodiles (Crocodylia; ancient Greek κροκόδειλος , "crocodile") are an order of amniotic land vertebrates . Today a distinction is made between about 25 species , which are divided into 8 to 9 genera in the three families of real crocodiles , alligators (including caimans ) and gavials . In a more specific sense, the term “crocodiles” is also applied to real crocodiles.
Crocodiles live in rivers and lakes in the tropics and subtropics , only the saltwater crocodile can also live in the sea and is common on the coasts of Australia and various islands in Southeast Asia. Their lizard-like, primeval appearance is just one of many adaptations to their way of life as lurker hunters living in water. They have a laterally flattened tail that allows them to swim quickly. They also have their eyes and nostrils set up so that they are almost completely submerged, but can still breathe and look out of the water.
In addition to the birds , the crocodiles are one of the two still living ( recent ) taxa of the archosaurs , which also include the extinct pterosaurs and the dinosaurs (see external systematics ). However, today's crocodiles have only a fraction of the species diversity of birds. The relatively close relationship between birds and crocodiles can be demonstrated on the basis of a number of characteristics, especially the structure of the cardiovascular system .
Due to a back armor made of bone plates lying in the skin, the crocodiles are also known colloquially as armored lizards .
features
General
The body structure of today's crocodiles and their physiology are very much influenced by the way they live in the water. These features include the flat body with the mostly wide and flat muzzle and the tail, which is formed into a rudder and flattened at the side. Compared to most other recent “ reptiles ”, crocodiles are very large animals and, depending on the species, reach body lengths of 1.20 to 6.70 meters. The body weight is roughly related to the body length with the power of three, so that the small species weigh significantly less than 100 kilograms, while the large species can weigh more than 1000 kilograms. Fossil species even reached body lengths of over twelve meters and a correspondingly significantly higher weight (possibly more than 10 tons). Crocodiles grow for almost a lifetime, but the rate of growth decreases significantly with age, so that the annual increase in length in older crocodiles is only a few centimeters.
skull
The skull is the crocodiles, compared with many other reptiles, relatively elongated, even extremely extended in some forms. The majority of the skull (usually more than two thirds) is occupied by the snout. Depending on the diet, the snouts of the different species differ in length and width. Most species have a rather unspecialized, relatively broad snout, which allows them to use a wide range of food. Species such as the gharial ( Gavialis gangeticus ) and the sunda gavial ( Tomistoma schlegelii ) that specialize in fishing, on the other hand, have a very narrow, elongated snout.
The eye sockets of the crocodiles have moved up the skull in the course of evolution and the eyes of the living animal stand out clearly from the forehead. As in mammals, the bony outer nostrils are fused into a single opening. This is oval, lies far in front of the snout and is connected to the throat by a long canal system, which is separated from the oral cavity by a secondary roof of the mouth , so that the animals can breathe easily with a full mouth or immersed in water. The front part of the secondary roof of the mouth is formed by the maxillary bones. This is also a parallel to the anatomy of mammals.
As with the other representatives of the archosaurs and the diapsids in general, the skull has two temple windows on both sides . In crocodiles, unlike many other diapsids, the upper rear skull roof is flat, table-like and consists of thick-walled bone. The upper temple windows form round openings in this "skull table" and are not, as is the case with B. in lizards, separated by narrow bone bridges from the lower temple windows, but clearly separated from them. The lower temple window is located behind the eye opening (orbit) in the side wall of the skull, slightly hidden by the laterally overhanging "skull table". Overall, the skull is rather compact. Apart from the temporomandibular joint, it has no mutually movable parts ( akinetic skull ). On the upper side of the snout, on the upper posterior roof of the skull and on the outside of the lower jaw, the bone surface is sculptured like a honeycomb, which is related to the fact that the bone is firmly attached to the overlying skin (integument) at these points .
The rear area of the outer side wall of the lower jaw is also characterized by a conspicuous oval opening, the so-called mandibular window. The rear end of the lower jaw has an outgrowth, the retroarticular process, through which the lower jaw is overall longer than the upper part of the skull (cranium) and clearly protrudes beyond the back of the head (occiput). The retroarticular process serves as a lever and attachment for the muscles to open (lower) the lower jaw.
denture
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The fastening of the cone-shaped, single-pointed teeth in the jawbone is thecodont, that is, the tooth “roots” sit, like in mammals, in tooth sockets (alveoli) and are attached by connective tissue.
There are significant differences in the organization of the teeth, especially between the three crocodile families. The crocodile's dentition is, as is common for “lower” tetrapods and unlike almost all mammals, principally homodontic, that is, all teeth have the same shape. In real crocodiles (Crocodylidae) and alligators (Alligatoridae), however, the teeth are not all of the same size. That is why the teeth of these two groups are called pseudoheterodonts. The edges of the upper jaw are wavy, both in the longitudinal vertical plane (sagittal plane) and in the horizontal plane (frontal plane), which is known as festooning. The largest teeth sit on the “wave crests”, which additionally emphasizes the pseudoheterodontics. The edges of the lower jaw are also festooned. "Wave peaks" and the largest teeth are located where the "wave troughs" are in the upper jaw. One of these largest teeth is the fourth lower tooth. In the real alligators (Alligatorinae) the festooning is less pronounced than in the real crocodiles and all lower jaw teeth lie within (on the tongue side) of the upper jaw teeth when the mouth is closed and cannot be seen from the outside. The crown of the fourth lower tooth lies in a pit in the upper jaw bone. With the real crocodiles, due to the horizontal festooning, the teeth of the lower jaw are partly on the tongue side and partly on the cheek side of the teeth of the upper jaw when the mouth is closed and are therefore partly visible from the outside. The fourth lower tooth engages in a particularly deep, notch-like “wave valley” of the upper jaw. In the caimans (Caimaninae) the festooning is less pronounced than in the crocodiles, but more pronounced than in real alligators. In the Gaviale (Gavialidae) the snout is very narrow, strongly elongated and not festooned except for the foremost part. The teeth are relatively long and thin, roughly all the same size (homodontics in the true sense) and inclined on the cheek side. This is known as a trap bite.
Crocodile bites, like the bites of most vertebrates, experience multiple, regular tooth changes (polyphyodontics), with the replacement teeth developing in the sockets of the functional (“active”) teeth. In older animals, each tooth is replaced once a year, in younger animals more often. It is estimated that over the life of a four-meter-long individual, each tooth is changed up to 50 times. With increasing age, however, the change of teeth takes place less and less and finally stops completely, so that in very old animals the tooth crowns can be worn down to the jaw.
Bone armor
The name crocodilians owe the crocodiles her hard scales armor that extends over the entire fuselage, tail and extremities. The top layer of skin, the cornea (stratum corneum), consists of a varying number of layers of collagen fibers . Crocodile embryos have two to three of these layers. With increasing age, further layers accumulate underneath, so that in an adult Mississippi alligator ( Alligator mississippiensis ) up to 24 layers can lie on top of each other. Crocodiles do not molt, new layers are compensated by abrasion of the outer layers.
The scales on the back are particularly large and strongly developed and are therefore also called back shields. They are keeled and reinforced by bony plates ( osteoderms ) that are also keeled. Depending on the species, four to ten adjacent plates form a transverse row, and each transverse row corresponds to a vertebra of the spine . The shields in the neck of the animals, the nuchal plates, are underlaid with osteoderms and form species-typical patterns. The ventral shields of most species are keeled, flat and square, and only in a few species are reinforced by osteoderms. The transverse rows of the back and abdominal shields touch each other on the tail and thus form transverse rings. The top of the tail has a pair of scalloped combs that merge into a single scalloped comb towards the tip of the tail. Especially in smaller species, such as the smooth-forehead caimans (genus Paleosuchus ), the stump crocodile ( Osteolaemus tetraspis ) and the black caiman ( Melanosuchus niger ), the scales on the extremities, on the neck and even on the eyelids are provided with osteoderms. On the eyelids, these are called palpebralia. Larger species such as the saltwater crocodile ( Crocodylus porosus ) protect themselves primarily through their size and their scales have significantly fewer osteoderms.
Axial skeleton and extremities
The spine of all crocodiles consists of nine cervical and 17 trunk vertebrae, to which the tail is connected with 35 to 37 individual vertebrae. The trunk vertebrae can in turn be divided into eight thoracic , seven lumbar and two sacral vertebrae . All vertebrae are so-called "procoele vertebrae", ie vertebral bodies that have a cavity at the front end into which the next vertebrae reaches. The atlas , the Epistropheus as well as the central sacral vertebra and the first caudal vertebra are an exception . Crocodiles have ribs along the entire trunk spine up to the first caudal vertebrae, in addition one can find abdominal ribs (gastralia) with them without attachment to the spine. The breastbone (sternum) is cartilaginous .
The shoulder girdle has a simple structure and essentially corresponds to the basic construction plan of the tetrapods . The collarbones (clavicles) are missing, which means that there is greater freedom of movement. Interesting is the pelvis , which has a similar structure to that of mammals and, due to the alignment of the pubic and ischial bones, indicates an originally two-legged mode of locomotion. The forelimbs end in a five- fingered hand, of which only the medial three fingers have claws. Webbed feet are formed between the four toes of the hind limbs. The outermost ( lateral ) toe also lacks the claw.
Breathing and circulation
Various organ systems, especially the respiratory and circulatory systems , are specially adapted to the amphibious way of life. This affects, among other things, the structure of the nose: the nostrils are far forward and raised on the muzzle, the nasal cavity is almost completely isolated from the oral cavity by the bony secondary roof of the mouth, and the inner nostrils ( choanas ) are far back and open into the pharynx . This nasal structure allows crocodiles to breathe even though they are almost completely submerged by just keeping the tip of their snout out of the water. A fleshy soft palate closes the pharynx against the oral cavity when the mouth is open under water and prevents water from entering the windpipe. The secondary canopy also allows crocodiles to breathe while they hold a larger prey with their jaws and wait for it to give up its resistance. The lungs are very voluminous, divided into several pocket-like individual chambers and are ventilated by muscular movement of the chest cavity and by a septum similar to the diaphragm .
Like all amniotes , crocodiles have a four- chamber heart with two main and two antechambers. The heart septum (ventricular septum) completely separates both main chambers (ventricles), just as it does in birds and mammals. In contrast to mammals and birds, crocodiles, like all other reptiles, have two aortas (arteries), one on the right and one on the left. The left aorta arises together with the pulmonary artery from the right ventricle. The right aorta, from which the arteries to supply the head region (carotids) branch off, originates from the left ventricle. Above the aortic root is the so-called foramen panizzae , a small opening between the left and right aorta.
This breakthrough serves two main functions. On the one hand, it ensures that the left aorta also receives oxygen-rich blood during normal breathing and thus leads mixed blood into the trunk to the organs (so-called right-left shunt ), and on the other hand it takes over the pressure equalization between the right and left ventricles during longer dives or left and right aortic root ( left-right shunt ), because in the right ventricle or left aortic trunk there is a higher pressure despite the greatly reduced heart rate during these periods because the pulmonary artery is severely narrowed. Since the lungs are filled with air before the dive, the pulmonary circulation continues to transport relatively oxygen-rich blood to the left half of the heart and from there to the right aorta, so that the brain and the sensory organs in the head region are adequately supplied with oxygen. while only oxygen-deficient blood is transported via the left aorta.
The four-chamber structure of the heart with a completely closed ventricular septum is an important indication that crocodiles are more closely related to birds than to all other reptiles.
Way of life
Habitats
All crocodiles living today are adapted in their physique and their way of life to an amphibious way of life, whereby they spend most of the time in the water. With one exception, the estuarine crocodile, they all live mainly in fresh water , but can also be found in brackish water or in coastal salt water . There are both species that prefer open waters such as lakes and larger rivers, as well as species that live in streams and undergrowth. Their range is limited to the tropical areas, only the two alligator species live in their northern range in areas with light winters. In addition to these properties, the occurrence also depends on the food supply, the supply of breeding sites, the competitive situation and hunting by the local population.
Hunting behavior
All crocodiles are primarily carnivores. Most of the species hunt any type of prey, which they can overwhelm with their size, very unspecifically. The very narrow-snouted species with fish- like teeth (gharial, sunda gavial, australian crocodile ), which mainly prey on fish, specialize in a range of prey. Young animals and smaller species mainly hunt insects , frogs and small mammals , while the adult representatives of the large species attack everything they can reach. Even cannibalism , especially in young animals is not uncommon. Despite their sluggish appearance, crocodiles react extremely quickly and are also very skillful on land.
Crocodiles are effective hunters who spend most of their hunting, often at night, largely submerged in the water ( ambulance hunters ). They are able to silently approach the bank and whiz out of the water. They use their extremely powerful tail to propel them. When the prey is held, the conical teeth bore into the victim, when biting, the extremely strong jaw muscles develop enormous biting force, which usually makes escape impossible. When they have captured a victim, they drag it underwater to drown it. According to extrapolations from extensive stomach analyzes, an adult Nile crocodile probably only consumes 50 full meals a year, i.e. only about one prey per week . Mississippi alligators, on the other hand, hunt more often, but usually only capture smaller prey.
To tear off pieces of meat, they grab the victim with their teeth and turn themselves several times around their own axis. In doing so, they tear up their prey at the places where they have left a perforation with their teeth . To make it easier to dismember the prey, they often hide the carcass for a few days so that it becomes softer. Crocodiles are unable to chew food, so they swallow torn pieces of meat completely. They often have gastroliths , but their function has not yet been fully clarified. According to the two best-known hypotheses, these stones are used in the stomach either to crush food or as ballast to reduce buoyancy in the water.
As a scientific study published in July 2013 found, 13 of 18 examined crocodile species, including the Nile crocodile and the Mississippi alligator, also regularly consumed fruit, nuts and seeds.
Reproduction and Social Behavior
Crocodiles lay between 20 and 80 eggs in nests , depending on the species and nest size . Two nest types can be distinguished:
- Nests of hills are piled up from plant material, in which the necessary heat is generated through fermentation.
- Pit nests are self-dug depressions in which the eggs are covered with soil material or a mixture of soil and plants.
Crocodile eggs have a relatively firm, calcareous shell and in this respect resemble the eggs of birds more than the eggs of most scalp reptiles . You are thus well protected against water absorption from the outside as well as against excessive water loss.
The development of the crocodiles depends on the temperature in the nest ( temperature-dependent sex determination ). They do not have sex chromosomes, so the eggs can potentially develop into either sex. If the eggs are hatched below about 30 ° C, females will hatch, at a temperature of about 34 ° C only males will hatch. If the eggs are buried at different depths, there is a high chance that both sexes will emerge.
As adult animals, crocodiles have no natural enemies, but their young are stalked by birds, monitor lizards or even members of their own species. It is assumed that around 90 percent of crocodiles are captured by nest robbers or predators as embryos or as young animals. Nest predators include monitor lizards, mammals such as raccoons and pigs, as well as birds such as the African marabou . In addition, embryos can die from climatic conditions such as the cold or from fungus in the eggs. Young animals can be captured by birds of prey and herons .
In many species, eggs and young are guarded by the mother to protect them from predators. This can also help its young when they hatch as soon as they are acoustically noticeable. Afterwards, the mother often even carries her young into the water and fends off potential predators.
Life expectancy
The knowledge of how old crocodiles can get is currently very limited. Data on crocodiles that certainly died of natural causes come exclusively from zoological gardens, although the exact year of birth of only a few animals was known. In addition, it is unclear whether crocodiles in zoos are getting older than their wild counterparts due to medical care and permanently provided food, or whether they die earlier due to visitor stress and living in an artificial habitat. Wild crocodiles are dated using the growth lamellae on their long bones or osteoderms ( skeletochronology ), but this method is subject to certain uncertainties.
For smaller species (e.g. caimans) in captivity, a maximum age of 20 to 30 years is given. Larger species, like the saltwater crocodile, can live up to 70 years. The oldest crocodile in the world to have died in human care is believed to have been 115 years old.
Systematics
External system
The (recent) crocodiles (Crocodylia) living today are, besides birds, the only recent representatives of the archosaurs and thus close relatives of the great land and flight reptiles of the Mesozoic Era. This means that the birds are also the closest recent relatives of the crocodiles. Birds and crocodiles, however, have each gone through completely different developments, which is why their relatively close relationship is not immediately apparent today. The birds, highly active warm-blooded animals , emerged from the theropod dinosaurs, an archosaur line that comprised purely land-living forms. The dinosaurs had adopted this way of life from the common ancestral species of the dinosaur and crocodile lines. With the ancestors of the recent crocodiles, on the other hand, there was a development from land-living forms to amphibious forms with the typical, primeval, lizard-like habit (see also → Tribal history of crocodiles ).
The archosaurs are traditionally considered to be the sister group of the scaled lizards , the common group of the bridge lizards , double creeps , " lizards " and snakes . Scale lizards and archosaurs are grouped together under the group name Diapsida . The turtles have also been considered diapsids since the beginning of the 21st century. Their currently uncertain position within the group leaves open whether the crocodiles and birds are more closely related to the turtles than to the scaled lizards. However, it is undisputed that the crocodiles are more closely related to the birds, a warm-blooded group of animals, than to any other recent reptile. The following cladogram shows the position of the crocodiles within the modern land vertebrates:
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Internal system
The recent crocodiles are usually divided into three families: real crocodiles (Crocodylidae), alligators (Alligatoridae) and gavials (Gavialidae). Alternatively, they are also considered as one family, Crocodylidae, and divided into three subfamilies, sometimes plus a fourth, the false gavials (Tomistominae). According to the traditional view of many biologists, the family Gavialidae includes only one recent species, the Ganges gavial ( Gavialias gangeticus ). However, this has been doubted for many years, because the Sunda Gavial ( Tomistoma schlegelii ) also has characteristics that could make it part of the Gavialidae family. The close relationship between Ganges and Sunda gavials is also supported by molecular genetic analyzes and is widely recognized today. Both species are notable for their extremely long and narrow snouts. The Crocodylidae or real crocodiles are recognizable by their mostly strongly wavy (festooned) jaw edges, whereby the largest tooth of the lower jaw lies in a lateral indentation of the upper jaw when the mouth is closed and is visible from the outside. In the real alligators , the jaw edges are markedly less firm, the snout is much wider than in the Crocodylidae and the fourth lower tooth is not visible from the outside when the mouth is closed. The following list contains all recent genera and species, divided into three families according to the most common view.
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Gaviale (Gavialidae)
- Genus: Gavialis
- Gharial ( Gavialis gangeticus )
- ? Genus: Tomistoma
- Sunda gavial or false gavial ( Tomistoma schlegelii )
- Genus: Gavialis
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Real crocodiles (Crocodylidae)
- Genus: Crocodylus
- New Guinea crocodile ( Crocodylus novaeguineae )
- Saltwater crocodile or estuarine crocodile ( Crocodylus porosus )
- Freshwater crocodile or Australian crocodile ( Crocodylus johnsoni )
- "Bornean crocodile" ( Crocodylus raninus )
- Philippines crocodile ( Crocodylus mindorensis )
- Siamese crocodile ( Crocodylus siamensis )
- Marsh crocodile ( Crocodylus palustris )
- Nile crocodile ( Crocodylus niloticus )
- West African crocodile ( Crocodylus suchus )
- Bumpy crocodile ( Crocodylus moreletii )
- Cuban or diamond crocodile ( Crocodylus rhombifer )
- Orinoco crocodile ( Crocodylus intermedius )
- American crocodile ( Crocodylus acutus )
- Genus: Mecistops
- West African armored crocodile ( Mecistops cataphractus )
- Central African armored crocodile ( Mecistops leptorhynchus )
- Genus: Osteolaemus
- Common crocodile ( Osteolaemus tetraspis )
- "Osborn's stump crocodile" ( Osteolaemus osborni )
- ? Genus: Tomistoma
- Sunda gavial or false gavial ( Tomistoma schlegelii )
- Genus: Crocodylus
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Alligators (Alligatoridae)
- Genus: Alligator
- Mississippi alligator ( Alligator mississippiensis )
- China alligator ( Alligator sinensis )
- Genus: Caiman
- Broad- snouted caiman ( Caiman latirostris )
- Spectacled caiman ( Caiman yacare ) (status controversial)
- Crocodile caiman ( Caiman crocodilus )
- Genus: Melanosuchus
- Black caiman ( Melanosuchus niger )
- Genus: Paleosuchus
- Brow-fronted caiman ( Paleosuchus palpebrosus )
- Wedge-headed caiman ( Paleosuchus trigonatus )
- Genus: Alligator
The exact relationships between the recent crocodiles have not yet been fully clarified. Not only the position of the Sunda gavials is controversial, but also the position of the gavials as a sister group of the common clade of real crocodiles and alligators ( Brevirostres ). Above all, kinship analyzes based on morphological data (that is, on features of the body structure) support the position of the Sunda Gavial as a representative of the real crocodiles and the Brevirostres hypothesis, while analyzes based on molecular genetic data support a close relationship between Sunda and Ganges gavial as well as a position of the gavial as a sister group of the real crocodiles suggest.
Morphological tree with Brevirostres hypothesis (after Brochu, 1999, 2003):
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Molecular tree with alternative arrangement (after Oaks, 2011):
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Crocodiles in human history
Crocodiles play a major role in the cultural history of a large number of peoples, which is mainly characterized by fear, awe and admiration. In all parts of the world where crocodiles live, they have found their way into the mythology of the peoples living there. The fascination for these animals extends into modern times, when crocodiles are used as motifs in literature and in films.
CrocBITE, the database for crocodile attacks from Charles Darwin University , has registered 2150 attacks on humans worldwide (as of Jan. 2014), 1128 of which were fatal. Saltwater crocodiles are responsible for about half of the fatal and total attacks. The second most common Nile crocodile causes only a quarter of all global incidents, but two-thirds were fatal to the victim. Mississippi alligator and marsh crocodile are registered with around 150 attacks, with half of those attacked in the marsh crocodile died, in the Mississippi alligator only 17. The American crocodile is registered with 115 attacks (24 of them fatal), the other species are assigned significantly fewer attacks.
Crocodiles in ancient Egypt
The Egyptians only knew the native Nile crocodile and the West African crocodile ( Crocodylus suchus ), which is no longer found in Egypt . In ancient Egypt these crocodiles were revered as sacred animals and idolized in the form of the crocodile-headed god Sobek (also Souchos). Sobek was regarded by the Egyptians as a god of eternity. It is unknown whether the animals were sanctified out of fear or whether this only happened after the emergence of the deity Sobek in order to appease the god. Numerous temples with ponds for the sacred animals were dedicated to Sobek, the most important of which were found at Kom Ombo in Upper Egypt , at Tebtunis and at Krokodilopolis in Fajum . Crocodiles who died in these sacred temples were embalmed like humans and buried as mummies . Thousands of these crocodile mummies, especially young animals , were found at Kom-Ombo and in the Maabdah caves . The largest specimens were over five meters long.
Other African countries
Similar to Egypt, crocodiles were worshiped in other parts of Africa, especially along the Nile and its headwaters, the Volta and in the vicinity of the Great Lakes . In the area of the Bwaba in Burkina Faso, crocodiles were kept in ponds and given food offerings. The Akan and Twi in Ghana believed that crocodiles, as well as tse-tse flies or snakes , could be used by witches for malicious errands.
The island of Damba in Lake Victoria was dedicated to the crocodiles, who were occasionally thrown from the body parts of the enemies of the Bagandas living here as sacrifices to eat. In the temple that stood on the island, missionaries reported that a medium made contact with the crocodile spirits and spoke to the people by opening and closing their mouths like a crocodile. The Nuer on the Nile respected the crocodiles as a totem , but also hunted them as a source of food. When they injured or killed a crocodile, they made sacrifices to the spirits.
In Madagascar there was a belief that crocodiles only kill people if they had previously killed a crocodile. The same rule applied that a human being could kill a crocodile if it had previously killed an innocent person. If someone was suspected of killing a crocodile, they were taken to a river with crocodiles and had to cross it unscathed to prove their innocence.
The Chinese dragon
The alligators and crocodiles that live in the rivers and on the coasts of China were probably the model for the double-tailed dragon Long in Chinese mythology . Its story originated around 2200 BC. In the regions on the Yangtze River , the "Long River". He was considered the "master of all scaled reptiles" and during the following generations this dragon was decorated more and more and given the characteristics and properties of other animal species.
During the Tang Dynasty (around 618 to 906) crocodiles and alligators first appeared separately in descriptions of different books. Because of the call of the alligators, the "southern barbarians" were supposed to predict rain and distribute their meat at weddings. Due to the armored skin, the alligator was also considered a harbinger of war.
South East Asia
In Southeast Asia, the mythological meaning usually goes hand in hand with the belief in deceased rulers or ancestors who were reborn as crocodiles. It is mostly the dreaded saltwater crocodile that has become a believer.
For some traditional peoples of the Philippines , such as the Panay , the crocodile was considered divine and was not allowed to be killed. A British major named G. B. Bowers reported in the early 20th century about a crocodile on the coast of Luzon , who was viewed by local residents as the reincarnation of an old mountain chief.
In East Timor the saltwater crocodile is revered as the “grandfather crocodile”. The origin of this is the legend “ the good crocodile ”, according to which the island of Timor emerged from a crocodile. From what is now Indonesian West Timor , in 1884 the rulers of Kupang reported sacrifices of young girls to crocodiles : The crocodiles were considered the ancestors of the dynasty, the girls were sent to them as wives.
The Kayan in Borneo saw the crocodiles as guardian angels who, as blood brothers , could drive away evil spirits. The killing of crocodiles was forbidden in the whole of Borneo, even among the otherwise very bellicose Dayak . They told a fairy tale according to which a Dayak warrior named Bantangnorang, dressed in a tiger skin and the feathers of a hornbill , entered a crocodile's cave in search of gold. The crocodile offered him human meat as a test, and Bantangnorang ate it, but later killed the crocodile and stole its treasures.
Australia
Crocodiles play a huge role in the Aboriginal mythology of Northern Australia. There are very different meanings of animals. A crocodile ancestor, the Gunwinggu in Arnhem Land, is considered to be the creator of today's Liverpool River by chewing through the ground as it crossed the country. The grooves filled with water and formed the river. The Murinbata have a story of cheating on food and killing a totem being. The crocodile as the totem creature Yagpa represents the figure who would bring the murderer and deceiver. In less concrete stories it happens that people are devoured by crocodiles while hunting or traveling.
The oldest known representations of crocodiles also come from Australia. For example, scratch drawings with crocodiles were found in Panaramittee in South Australia, which are estimated to be 30,000 years old. These finds also raise the question of whether the crocodiles also lived in the south at the time or were only known through stories. Artful bark paintings with crocodile motifs are still widespread among the Manggalilis in Northern Australia and in the Oenpelli area . Crocodiles also became a motif in art among European immigrants, for example in a painting by Thomas Baines from 1856. One of the most modern depictions of Australian crocodiles in culture is the film series " Crocodile Dundee " with Paul Hogan in the lead role, who is depicted as a crocodile hunter and ranger of Australia and contrasted with the city dwellers of New York.
Melanesian islands
Especially from the Sepik region and its tributaries in New Guinea , numerous sculptures and wood carvings depicting crocodiles are known. On the Karawari, for example, there are slender and legless crocodile carvings that are decorated with tattoos . The tails of these bodies turn into snake heads. Crocodile-shaped mouthpieces for wind instruments are also quite common, and figures that partly represent people and partly crocodiles are used as additions to funerals in this region.
Among the Iatmul on the middle Sepik, the saltwater crocodile is considered to be the creator deity. This created the world from water by raising land. It also created a crevice in the earth that it mated with, creating living things. The crocodile's upper jaw became the sky, while the lower jaw formed the mountains of the earth. The same people also have stories of ancient crocodiles who colonized the land and founded settlements. The myth that the boy is swallowed by a crocodile and strangled again as a man plays a role in the initiation rites of the men of the Iatmul. To demonstrate this, wounds are cut in the body and above all in the shoulders of the initiates in the manhood ritual, the scars of which are later to represent the bite scars of the crocodile ( see scarification on the central sepic ).
A very well known figure in New Guinea is Yali from Sor, the founder of the Mandang cult. His comrade killed his totem animal, the crocodile, in a fight, whereupon Yali got lost in the jungle and was no longer seen. According to the Elema on the Gulf of Papua , wizards in the form of crocodiles could go into the water and attack their enemies by surprise, on land they should take the form of cassowaries and penetrate inland.
North and South America
Very little is known about the role of crocodiles and alligators in American mythology and popular belief. The Maya of the 10th century and the Aztecs of the 14th century believed that the world rests on the back of a large crocodile-like reptile in a lily pond . The god Ah ouh puc was similar to a crocodile and was depicted with the back of a crocodile.
The only evidence that the North American Indians dealt with alligators is shown in an etching by Theodore de Bryce Le Moin from 1565, on which Indians from today's Florida hunt alligators with long spears. In the 19th century, the anthropologist William Holmes was able to show the relationship between the Chiriquí Indians of Panama and the crocodiles of their homeland. For this he looked for the roots of stylized drawings on the people's clay pots and found that they come from easily recognizable images of crocodiles.
Western culture and modern times
In 58 BC Chr. Were in Rome first shown five crocodiles. Augustus had 36 crocodiles killed in the Circus Flaminius. Elagabal kept a crocodile as a pet . The Greeks knew and described crocodiles in the Nile , the length of which was given as up to 8 or 11 m. Crocodiles were hunted with fishing rods, nets and harpoons .
In Western art and literature, crocodiles were almost unknown for a very long time, so they were also missing in Henri Rousseau's descriptions of the jungle . You can find mentions of crocodiles in the work " Antony and Cleopatra " by William Shakespeare , and Edmund Spenser , who lived at the same time, coined the term crocodile tears in his poem " The Elf Queen " .
"Doth meet a cruell craftie Crocodile, Which in false griefe hyding his harmefull guile, Doth weepe full sore, and sheddeth tender teares"
"A brutal, cunning crocodile hides its harmful malice in false grief, weeps full of misery and secretes tender tears."
The term was later picked up by Robert Burton and Francis Bacon , who applied it to the cunning and cunning of the man who weeps before the setback in war. The crocodile itself became a symbol of brutality, cunning and cunning at that time. The novel " Peter Pan ", in which James M. Barrie used the crocodile with the swallowed alarm clock to kill the even more evil Captain Hook, did nothing to change that. In the depictions of animals you can almost always see them fighting with people. Around 1830, the French sculptor Antoine-Louis Barye depicted crocodiles fighting with other animals. In puppet theater , the crocodile is a permanent figure who stands for greed, undisguised urges and danger.
The symbolic character increased through the new media of film and television in the 20th century, in which crocodiles became brutal and calculating monsters alongside sharks , such as in the film adaptation of the 1977 book "Alligator" by Shelley Katz or the film Der Horror -Alligator . Crocodiles are also featured in the Australian horror films Rogue and Black Water .
Today's picture is shaped by these representations as well as stories circulating according to which crocodiles live in the sewage systems of larger cities (see crocodile in the canal ). There is also another, often belittling, view of animals, which becomes clear in the use of them as trademarks (e.g. by the clothing company Lacoste ) and consumer products ( e.g. Schnappi, the little crocodile ) and as the mascot of a football team.
Economic use
General
The human use of crocodiles has been passed down from relatively early civilizations that arose and existed in areas where crocodiles were naturally occurring. Crocodiles were hunted there mainly for their meat. In Southeast Asia and China, the offal, the skin bones of the back shields and other parts were also used for medical purposes (see Traditional Chinese Medicine ). The powdered teeth and claws were also added to potions, which were used as magic potions, especially in Indonesia . Skulls and tooth chains were used as decorative elements or as religious symbols.
It was only in the last few centuries that crocodiles were hunted with firearms on a large scale for their skins and meat. The first mentions of the use of crocodile skins come from the end of the 18th century. According to the lore of John James Audubon , the skins of the Mississippi alligator could be used to make boots, saddlebags and shoes. The hunt, however, had no commercial background, at that time the animals were regarded as pests and were always killed when they were encountered. That changed until the American Civil War in the 1860s. The demand for products made from crocodile skin , especially shoes, belts and bags, increased sharply. From 1888 there are numbers of a single hunting group of ten hunters who had killed over 5,000 alligators in one year; in some parts of Florida daily quotas of over 200 animals were normal. The catch of young alligators and their sale, live or groomed, were also very lucrative. By around 1900, the Mississippi alligator population collapsed and alternatives began to be sought in Mexico and other parts of Central and South America. These were found mainly in the pointed crocodiles, while the crocodile caiman was classified as inferior. When the other American species became rarer around 1930, alternatives were found in the Nile crocodile in Africa and in the Asian species.
The Mississippi alligator population continued to decline. While the number of hides sold in Florida was 190,000 in 1929, it had dropped to only 6,800 by 1943. In 1944, the alligator was placed under protection during the breeding season and up to a height of 1.20 meters so that the population could recover. In 1947 this measure increased the volume of trade again to 25,000 hides.
In addition to the Mississippi alligator, it was mainly the Nile crocodile that was hunted for the leather industry. The numbers of crocodiles shot in Africa are very patchy. The earliest reports of crocodile hunts in Africa date from the second half of the 19th century. Hunting around 1850 was limited to just a few animals for meat and fat production. On July 2, 1869 , an article appeared in a local newspaper, the Natal Herald , which stated that crocodile leather was in great demand for the manufacture of leather goods. This report led the first hunters to make a living killing crocodiles. Around 1913 the incentive was increased, as in some areas of Africa shooting quotas were paid for animals considered pests. The shooting rates rose until the 1950s, with individual hunters killing hundreds of the animals each year. The sales figures were some 100,000 animals, exact figures are not known. It was not until 1970 that the Nile crocodiles were placed under protection in most African countries.
While the Mississippi alligators and Nile crocodiles were most affected by overexploitation by hunting, the hunt affected all crocodile species in the world. It was not always about the skin, in India the Ganges gaviale were hunted by the locals (despite religious prohibitions) mainly as fish catchers and by the British with sporty motivation. In Asia, South America, and Oceania, commercial hunting began primarily in the 1960s, with commercial hunters often looking for local hunters to help them find and hunt the crocodiles. In this way, many species have been almost completely exterminated, including the endemic crocodiles of the Philippines and the Australian islands and the black caiman in South America. Since these stocks also declined, all crocodiles have been placed under international protection and the trade in crocodile products has been massively restricted. Today most of the products come from crocodile farms or from the crocodile caiman, which may be hunted to a limited extent, but which supplies “inferior” leather.
Crocodile farms
Crocodile farms were set up primarily as a result of efforts by the leather processing industry when the populations of many commercially usable crocodile species threatened to dwindle. These differ from pure show systems in that the animals can not only be kept there, but can also be used. Today there are breeding facilities for different species, which, in addition to their use, primarily serve to preserve the species and increase the number of wild animals. The main source of income for these farms is no longer the leather industry - the farms mainly serve as tourist attractions.
In the southern USA in particular, the crocodile ranch has established itself alongside crocodile farms, which takes eggs and young animals from the wild and uses them commercially. This is possible because the Mississippi alligator population has largely stabilized. In this way, commercial crocodile ranchers can market both the leather and the meat, with gatorburgers and lard made from alligator fat being among the main products. Crocodile farms and ranches are subject to constant controls and trade restrictions by the Convention on International Trade in Endangered Species of the Wild Fauna and Flora (CITES). In order to be able to use crocodiles commercially, the farms must always be able to prove that they are keeping a viable generation in the breed.
Poison from crocodile bile
The bile from crocodiles is considered to be very poisonous in sub-Saharan Africa and is said to have been used, among other things, to produce arrow poison and, with the help of “witches”, to kill people. However, doubts have been raised as early as the first half of the 20th century about the severe toxicity of crocodile bile, which does not differ significantly from the bile sap of other vertebrates, and it has been suggested that it was only used in the manufacture of arrow poison because of its sticky consistency Carrier for the actual toxin was used, which z. B. was obtained from Strophanthus . Animal experiments on mice and baboons with the bile of Nile crocodiles in Zimbabwe have confirmed that at least the bile of this species is not highly toxic.
Terrarium keeping
The keeping of crocodiles as terrarium animals plays only a very minor role, but has been increasing for several years. It is mainly the smaller species that are kept as pets, including the crocodile or the smaller caiman species. As with the trade in crocodile products, living crocodiles are also subject to strict trade restrictions and may only be passed on with CITES approval papers. In addition, there are keeping regulations, which mainly concern the size and equipment of the terrarium, as well as regional requirements for keeping "dangerous animals".
The keeping of the animals is only suitable for terrarium experts.
origin of the name
The name "crocodiles" goes back to the ancient Greek word "κροκόδῑλος" [krokódῑlos], the origin of which is probably to be found in "κροκ-δριλος" [krokó-drilos], "stone worm", a combination of κρόκη [króke] κροκάλη [krokále], "beach pebbles", with δρῖλος [drílos], "worm".
literature
- Charles A. Ross (Ed.): Crocodiles and Alligators - Evolution, Biology and Distribution. 2nd Edition. Orbis, Niedernhausen 2002, ISBN 3-572-01319-4 .
- Wolfgang Böhme: Crocodylia, crocodiles. In: Wilfried Westheide, Gunde Rieger (Ed.): Special Zoology. Part 2: vertebrates or skulls. 2nd Edition. Spektrum Akademischer Verlag, Heidelberg 2010, ISBN 978-3-8274-2039-8 , pp. 402-409.
- Joachim Brock: Crocodiles - A life with armored lizards. Natur und Tier, Münster 1998, ISBN 3-931587-11-8 .
- Albert Reese: The Alligator and its Allies. The Knickerbocker Press (GP Putnam's Sons), New York 1915, doi: 10.5962 / bhl.title.1548
- Gordon Grigg, Carl Gans: Morphology & Physiology of the Crocodylia. In: CG Glasby, GJB Ross, PL Beesley: Fauna of Australia. Volume 2A: Amphibia and Reptilia. Australian Government Publishing Service, Canberra 1993, ISBN 0-644-32429-5 , pp. 326-336. (online ; alternatively: "online-only version" with color photos )
- Reinhard Radke: Crocodiles - Expeditions to the heirs of the dinosaurs. Lübbe, Bergisch Gladbach 2002, ISBN 3-7857-2105-6 . (narrative illustrated book)
- H. Jes, H.-G. Petzold: order crocodiles, armored lizards (Crocodylia). In: Wolf-Eberhard Engelmann (Hrsg.): Zoo animal keeping - animals in human care. Reptiles and amphibians. Harri Deutsch, Frankfurt am Main 2006, ISBN 3-8171-1743-4 , pp. 177-191.
- Gordon Grigg, David Kirshner: Biology and Evolution of the Crocodylians. Cornell University Press, 2015, ISBN 978-0-8014-5410-3 . [Simultaneous Australian publication by CSIRO Publishing; ISBN 978-1-4863-0066-2 ]
Extensive, albeit not up-to-date, bibliographies can be found under The Bibliography of Crocodilian Biology ( Memento of September 8, 2007 in the Internet Archive ) and Crocodile Library ( Memento of January 2, 2007 in the Internet Archive )
Web links
- The Crocodile Specialist Group (English)
- Crocodilians Natural History & Conservation (English)
- Crocodilian, Tuatara, and Turtles Species of the World ( Memento from May 31, 2008 in the Internet Archive )
- Crocodylomorpha: Overview (English)
- Jumping crocodiles in Australia (German)
- Careless behavior of bathers and their deadly consequences (English)
- Link list of the Crocodile Specialist Group ( Memento from June 3, 2008 in the Internet Archive ) (further links, English)
- Angelika Lohwasser : The power of the crocodile. In: Martin Fitzenreiter: Animal cults in Pharaonic Egypt and in a cultural comparison. Internet articles on Egyptology and Sudan archeology Vol. 4, Humboldt University Berlin, 2003 (PDF file; 15 kB)
Individual evidence
- ^ The Reptile Database : Species Numbers (as of Feb 2014) .
- ^ A b c Gordon Grigg, David Kirshner: Biology and Evolution of Crocodylians. CSIRO Publishing, Clayton South (VIC) 2015, ISBN 978-1-4863-0067-9 , pp. 24-37.
- ↑ Gregory M. Erickson, Paul M. Gignac, Scott J. Steppan, A. Kristopher Lappin, Kent A. Vliet, John D. Brueggen, Brian D. Inouye, David Kledzik, Grahame JW Webb: Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation . In: PLoS ONE . tape 7 , 3, e31781, 2012, doi : 10.1371 / journal.pone.0031781 .
- ↑ Heinz Wermuth: Systematics of the recent crocodiles. In: Messages from the Zoological Museum in Berlin. Volume 29, No. 2, 1953, pp. 375-514, doi: 10.1002 / mmnz . 19530290203 , p. 380.
- ^ Richard J. Gross: The Physiology of Growth. Academic Press, 1978, ISBN 0-12-293055-X , p. 38.
- ^ Gordon Grigg, Carl Gans: Morphology & Physiology of the Crocodylia. In: CG Glasby, GJB Ross, PL Beesley: Fauna of Australia. Volume 2A: Amphibia and Reptilia. Australian Government Publishing Service, Canberra 1993, ISBN 0-644-32429-5 , p. 11 and plate 9.3. ( "Online-only version" )
- ↑ Steven F. Perry: Heart and Blood Vascular System. In: Wilfried Westheide, Gunde Rieger (Ed.): Special Zoology. Part 2: vertebrates or skulls. 2nd Edition. Spektrum Akademischer Verlag, Heidelberg 2010, ISBN 978-3-8274-2039-8 , pp. 103-119.
- ↑ SG Platt, RM Elsey, H. Liu, TR Rainwater, JC Nifong, AE Rosenblatt, MR Heithaus, FJ Mazzotti: Frugivory and seed dispersal by crocodilians: an overlooked form of saurochory? In: Journal of Zoology. Volume 291, No. 2, 2013, pp. 87-99, doi: 10.1111 / jzo.12052
- ↑ Knut Schmidt-Nielsen: Animal Physiology: Adaptation and Environment. 5th edition. Cambridge University Press, Cambridge (UK) 1997, ISBN 0-521-57098-0 , p. 49.
- ↑ see e.g. BJM Hutton: Age Determination of Living Nile Crocodiles from the Cortical Stratification of Bone. In: Copeia. Jhrg. 1986, No. 2, 1986, pp. 332-341, doi: 10.2307 / 1444994
- ^ Frank Slavens: Reptiles and Amphibians in Captivity - Logevity: Crocodylia Frank & Kate's Web Page. 1995-2003
- ^ Adam Britton: How long do crocodiles live for? Crocodilian Biology Database. 1995-2012
- ^ Tyler R. Lyson, Erik A. Sperling, Alysha M. Heimberg, Jacques A. Gauthier, Benjamin L. King, Kevin J. Peterson: Phylogenomic analyzes support the position of turtles as the sister group of birds and crocodiles (Archosauria). In: Biology Letters. Volume 8, No. 1, 2012, pp. 104–107, doi: 10.1098 / rsbl.2011.0477 , PMC 3259949 (free full text) ( Open Access )
- ↑ Ylenia Chiari, Vincent Cahais, Nicolas Galtier, Frédéric Delsuc: Phylogenomic analyzes support the position of turtles as the sister group of birds and crocodiles (Archosauria). In: BMC Biology. 10, 2012, p. 65, doi: 10.1186 / 1741-7007-10-65 ( Open Access )
- ↑ Ludwig Trutnau, Ralf Sommerlad: Crocodilians: their natural history & captive husbandry. Edition Chimaira, Frankfurt am Main 2006, ISBN 3-930612-97-6 , p. 361 ff.
- ↑ For a brief overview, see Ralph E. Molnar: Biogeography and Phylogeny of the Crocodylia. In: CG Glasby, GJB Ross, PL Beesley (Eds.): Fauna of Australia. Volume 2A: Amphibia and Reptilia. AGPS Canberra, 1993, "online only" version (PDF)
- ↑ a b Jamie R. Oaks: A time-calibrated species tree of Crocodylia reveals a recent radiation of the true crocodiles. In: evolution. Volume 65, No. 11, 2011, pp. 3285-3297, doi: 10.1111 / j.1558-5646.2011.01373.x
- ↑ Often regarded as identical to the saltwater crocodile, but see Charles A. Ross: Crocodylus raninus S. Müller and Schlegel, a valid species of crocodile (Reptilia: Crocodylidae) from Borneo. In: Proceedings of the Biological Society of Washington. Volume 103, No. 4, 1990, pp. 955-961 (full text on BHL ).
- ↑ For a long time regarded as identical to the Nile crocodile, but now elevated to a separate species based on DNA analyzes, see E. Hekkala, MH Shirley, G. Amato, JD Austin, S. Charter, J. Thorbjarnarson, KA Vliet , ML Houck, R. Desalle, MJ Blum: An ancient icon reveals new mysteries: Mummy DNA resurrects a cryptic species within the Nile crocodile. In: Molecular Ecology. Volume 20, 2011, pp. 4199-4215, doi: 10.1111 / j.1365-294X.2011.05245.x
- ↑ Has long been classified under the genus Crocodylus . Based on molecular data, it is now again regarded as an independent genus, see A. Schmitz, P. Mausfeld, E. Hekkala, T. Shine, H. Nickel, G. Amato, W. Böhme: Molecular evidence for species level divergence in African Nile Crocodiles Crocodylus niloticus (Laurenti, 1786). In: Comptes Rendus Pale. Volume 2, 2003, pp. 703-712, doi: 10.1016 / j.crpv.2003.07.002
- ↑ For a long time it was regarded as the Central African population of M. cataphractus , but in 2018 it was raised to the rank of an independent species again due to molecular data and some morphological and ecological peculiarities, see Matthew H. Shirley, Amanda N. Carr, Jennifer H. Nestler, Kent A. Vliet, Christopher A. Brochu: Systematic revision of the living African Slender-snouted Crocodiles (Mecistops Gray, 1844). In: Zootaxa. 4504, 2018, p. 151, doi: 10.11646 / zootaxa.4504.2.1 .
- ↑ Often regarded as identical to O. tetraspis (sometimes in the form of a subspecies, sometimes not even that). More recent studies of the morphology as well as DNA analyzes show that a position as a separate species could be justified, see MJ Eaton: Dwarf Crocodile Osteolaemus tetraspis. In: SC Manolis, C. Stevenson: Crocodiles. Status Survey and Conservation Action Plan. 3. Edition. Crocodile Specialist Group, Darwin 2010, pp. 127-132 ( PDF 2.0 MB).
- ↑ Christopher A. Brochu: Phylogenetics, Taxonomy, and Historical Biogeography of Alligatoroidea. In: Society of Vertebrate Paleontology Memoir. Volume 6 (Journal of Vertebrate Paleontology, Volume 19, Supplementum No. 2), 1999, pp. 9-100, doi: 10.1080 / 02724634.1999.10011201
- ↑ Christopher A. Brochu: Phylogenetic Approaches Toward Crocodylian History. In: Annual Review of Earth and Planetary Sciences. Volume 31, 2003, pp. 357-397, doi: 10.1146 / annurev.earth.31.100901.141308
- ^ CrocBITE - Worldwide Crocodilian Attack Database , accessed January 26, 2014.
- ^ Nile crocodile is two species , Nature.com
- ^ E. Hekkala, MH Shirley, G. Amato, JD Austin, S. Charter, J. Thorbjarnarson, KA Vliet, ML Houck, R. Desalle, MJ Blum: An ancient icon reveals new mysteries: Mummy DNA resurrects a cryptic species within the Nile crocodile . In: Molecular Ecology . 2011, doi : 10.1111 / j.1365-294X.2011.05245.x .
- ^ A b Louis Lewin: Die Pfeilgifte - According to our own toxicological and ethnological studies. Johann Ambrosius Barth, Leipzig 1923 ( archive.org ), pp. 199 , 214 , 351 .
- ↑ a b N. Z. Nyazema: Crocodile bile, a poison: myth or reality? In: Central African Journal of Medicine. Volume 30, No. 6, 1984, pp. 102-103 (online)
Remarks
- ↑ Note: The birds (Aves) also belong to the archosaurs or diapsids, but due to significant evolutionary modifications to the skull, they no longer have any obvious temple windows.
