King penguins ( Aptenodytes patagonicus )
|Scientific name of the order|
|Sharpe , 1891|
|Scientific name of the family|
|Bonaparte , 1831|
The penguins (Spheniscidae) are a group of flightless seabirds from the southern hemisphere and form the only family in the order Sphenisciformes. Their tribal sister group are probably the loons (Gaviiformes) and tubular noses (Procellariiformes). Penguins are easy to distinguish from all other birds and are extremely well adapted to life in the sea and in the sometimes extreme cold zones of the earth.
The German word penguin comes directly from the English word penguin . This designation probably originally referred to the flightless giant aalk (formerly Pinguinus impennis ), native to the northern hemisphere in the Atlantic, which was exterminated around 1850 . The first records of penguins from the late 15th century in Africa and the early 16th century in South America do not yet use the name penguin . Although not closely related to the giant alk, the name was probably transferred to the superficially similar-looking penguins by seafarers in the second half of the 16th century.
The origin of the English word penguin is disputed. It is probably derived from the Welsh pen gwyn "white head". In contrast to penguins, the giant alkes have two white spots on their heads. It was also speculated that the term “white head” could not refer to the predominantly dark head of the giant alke, but to the islands with breeding colonies of birds, colored white by guano.
Another theory derives the name from the Latin pinguis "fat", which would refer to the body structure of animals. (In Dutch , vetgans , literally “fat goose”, is a synonym for pinguïn .) English pin-wing and languages of native Americans were also discussed as possible origins. So far, none of the theories has been conclusively proven. The term fat goose was also common in German before the 20th century .
Anatomy and appearance
The size and weight difference of the different penguin species is considerable, but body structure and plumage are very homogeneous in the family.
height and weight
The little penguin ( Eudyptula minor ) only reaches a size of 30 centimeters and a weight of one to one and a half kilograms, whereas the emperor penguin ( Aptenodytes forsteri ) with a size of up to 1.20 meters and a weight of up to 40 kilograms is one of the largest new pine birds ever. This difference in size is explained by Bergmann's rule , of which the penguins are a frequently cited example. Bergmann's rule states that animals are larger in colder regions, as this leads to a more favorable ratio of volume to surface of the animal and thus less heat loss. Most species are only slightly lighter than the water they displace, so diving is comparatively easy for them.
The sturdy body of the animals is clearly adapted to a life in the sea due to its streamlined shape and the wings that have been redesigned to narrow but powerful fins. Unlike the flightless ratites , penguins have a sternum with a well-developed keel to which the powerful wing muscles attach. Since, unlike flying in air, when swimming underwater, due to the higher water resistance, the upward movement of the wing costs as much energy as the downward movement, the shoulder blades have a larger surface area than other birds on which the muscles responsible for the upward movement can attach. The humerus and forearm bones are straight and rigidly connected at the elbow, which gives the fins great strength. The bones, which are otherwise hollow in birds, are dense and heavy in penguins, as weight loss is not necessary for swimming.
The thighs are very short, the knee joint rigid and the legs set back a lot, which causes the unusual upright gait on land. The large webbed feet are relatively short - on land the animals often rest on their heels, with their comparatively rigid tail feathers providing additional support. The tail is usually greatly reduced, its much more pronounced function as a rudder in other diving seabirds is primarily taken over by the legs.
In most species the beak is not very long, but strong; An exception are the great penguins ( Aptenodytes ), whose beak is probably long, slender and slightly curved in adaptation to their prey - fast swimming fish.
Penguins are sometimes exposed to extreme climatic conditions in their habitat and have adapted to them through various anatomical features.
A pronounced layer of fat, often two to three centimeters thick, is initially used for thermal insulation, over which there are three waterproof layers of short, tightly packed feathers evenly distributed over the entire body. In contrast to almost all other birds, penguins do not have apteries , skin regions in which no feathers grow; The facial skin is an exception in some tropical species. The air trapped in the feather layers also protects very effectively against heat loss in the water.
In addition, penguins have highly developed heat exchangers in their fins and legs: the arterial blood flowing into these limbs gives off a large part of its heat to the cooler venous blood flowing back into the body, so that heat losses are minimized. This is known as the "countercurrent principle".
On the other hand, some species of penguin native to tropical waters are more likely to struggle with overheating. To prevent this, their fins are wider than their body size, so that the area over which heat can be given off is enlarged. In some species, the facial skin is not covered by feathers, so that accumulated heat can be released more quickly in the actively sought shadow. Some penguin species shift their activity time completely to the evening or night.
The color of the plumage, which consists of numerous small, undifferentiated, almost hair-like feathers , is a blue-gray on the reverse side of almost all species, while the underside is white. Males and females look very similar, although the former are usually slightly larger. Most crested penguins ( Eudyptes ) have a particularly striking orange-yellow headdress .
In young animals, the plumage is usually uniformly gray to brown, in some species the flanks and the belly side are colored white.
Usually shortly after the end of the breeding season, after the young have been reared, penguins moult , the exchange of plumage. During this time, which can last between two and six weeks depending on the species, the birds use up their fat reserves about twice as quickly as before. In the case of gentoo penguins ( Pygoscelis papua ) and Galápagos penguins ( Spheniscus mendiculus ), however, the moulting time is not fixed and can take place at any time between the breeding seasons. Non-breeding birds almost always molt earlier than their breeding counterparts.
Sight and hearing
The eyes of the penguins are focused on sharp underwater vision; their cornea is extremely flat, so that the birds are slightly nearsighted on land. The pupils of the eyes, especially in deep-diving emperor penguins, are also extremely capable of expansion and contraction, so that the eyes can quickly adjust to different light conditions such as those on the surface of the water or at a depth of 100 meters. From the pigment composition one concludes that penguins can see better in the blue than in the red part of the spectrum and possibly perceive ultraviolet light. Since red light is already filtered out in the uppermost water layers, this suggests an evolutionary adaptation.
As with most birds, the ears have no externally perceptible structures. They are sealed watertight by particularly strong springs when diving. In the case of large penguins, the edge of the outer ear is enlarged so that it can be closed, so that the middle and inner ear are protected from pressure damage caused by diving.
Under water - unlike on land, where they communicate with each other through trumpet-like calls and loud snarling - penguins do not make any noticeable noises. It is not known whether, conversely, they use their hearing to track down prey or to detect predators.
Penguins live in the open seas of the southern hemisphere. There they found especially in the coastal waters of Antarctica , in New Zealand , southern Australia , South Africa , Namibia ( Penguin Island ), southern Angola , on the front of South America located Falkland Islands and on the west coast up as far as Peru and on the equator located Galápagos Islands . As cold-loving birds, they only appear in tropical areas when cold water currents exist; this is the case on the west coast of South America with the Humboldt Current or around South Africa with the Benguela Current on the Cape Peninsula .
Most species live between 45 and 60 degrees south latitude; the largest number of individuals can be found around Antarctica and on nearby islands. In the northern hemisphere, with the exception of zoo animals and part of the population of the Galápagos penguin, there are no penguins on the equatorial Galápagos island of Isabela .
The real habitat of the penguins is the open sea, to which they are anatomically perfectly adapted. They only return to land for breeding and changing feathers; there they live on the rocky coasts of the southern continents, in cool forests of the temperate zones, on subtropical sandy beaches, on largely vegetation-free lava fields, sub-Antarctic grasslands or on the ice of the Antarctic. While the tropical species are true to their location, others sometimes move several hundred kilometers away from the ocean in winter to get to their breeding grounds.
According to measurements, the average speed achieved by penguins when swimming is around five to ten kilometers per hour, although higher speeds are also conceivable in short sprints. A particularly fast type of locomotion is "dolphin swimming"; like a dolphin, the animal suddenly leaves the water for a short time. The reasons for this behavior are still unknown: it may use the lower flow resistance in the air, but it may also serve to confuse predators.
When diving, some penguins show astonishing achievements: While the smaller species such as the gentoo penguin ( Pygoscelis papua ) usually only dive for about one, rarely more than two minutes and then "only" reach depths of about 20 meters, emperor penguins are Documented dives lasting more than 18 minutes, during which depths of more than 530 meters were measured. Although the extreme performance of the great penguins in particular cannot be properly explained to this day, it is known that the heartbeat of the animals can be reduced to up to a fifth of the normal resting value during diving, which reduces oxygen consumption and thus the diving time possible with the same amount of breathing air multiplied. The pressure and temperature regulation during deep dives, however, is still a challenge for research at the beginning of the 21st century.
When leaving the water, penguins can jump heights of up to 1.80 meters. Due to their relatively short legs, they usually waddle around on land, a form of locomotion that, as biomechanical studies have shown, is surprisingly energy-efficient. On the other hand, they can move very quickly on the ice by sliding downhill on their stomachs. Some species travel kilometers between their breeding colonies and the sea.
Depending on their size, penguins feed on fish , often, for example, the Antarctic silverfish ( Pleuragramma antarctica ), anchovies (Engraulidae) or sardines (in Clupeidae), crustaceans such as krill or small squid that are actively hunted by sight and swallowed while underwater become. If different species share the same habitat, they usually have different food preferences: Adelie penguins and chinstrap penguins eat krill of different sizes.
The species that specialize in small crustaceans are much more dependent on regular prey than the fish-hunting penguins, but they also require less energy to catch: While the latter can often be successful in ten attempts, the former have to track down up to 16 small crabs per dive - the equivalent of one catch in six seconds - to meet her and her youngsters' energy needs. The number of dives per hunting expedition depends on the species and the season: during the breeding season it is more than 190 for chinstrap penguins ( Pygoscelis antarctica ), while emperor penguins can undertake more than 860 dives on their extensive day-long expeditions.
During the moult and with large penguins ( Aptenodytes ), Adelie penguins ( Pygoscelis adeliae ), chinstrap penguins ( Pygoscelis antarctica ) and crested penguins ( Eudyptes ) also in the breeding season, many penguins have to forego food entirely. The length of the fasting period varies for the individual species and is around one month for the Adelia and Crested penguins, but it can last more than three and a half months for male emperor penguins. During this time they can lose up to half their body weight, as the birds then have to draw their metabolic energy from the fat reserves built up before the moulting or breeding season. In gentoo penguins ( Pygoscelis papua ), yellow-eyed penguins ( Megadyptes antipodes ), little penguins ( Eudyptula minor ) or black-footed penguins ( Spheniscus demersus ) males and females, however alternate in brooding, so they rely only during moulting their fat reserves must.
Penguins mainly get their water needs from the sea. Excess salt is excreted by special salt glands located above the eyes.
The age at which penguins first attempt to reproduce depends on the one hand on the species and on the other hand on their gender. Little penguins, yellow-eyed penguins, donkey and spectacled penguins breed for the first time at the age of two; the females of Adelia, Chinstrap, King and Emperor penguins usually begin the first attempt at breeding a year later, while the males of these species wait another twelve months to reproduce. Crested penguins do not breed until they are five years old.
The above data are statistical mean values: In practice, with increasing age the stays in the breeding colony become longer and longer until the breeding behavior itself finally sets in. For example, only a few annuals visit the colony of the king penguins; even in their second year of life, the animals often only appear there for a few days. In the following years, however, the first appearance in the colony not only shifts forward from time to time, but also the length of stay increases significantly with increasing age. It is not uncommon for males of the great penguins to start breeding only from the age of eight.
The seasonal start of the breeding season is primarily dependent on climatic factors. While the Galápagos, Little Penguins and African Penguins living further north can breed throughout the year and Little Penguins raise two broods per year in individual cases, almost all penguins living in sub-Antarctic to Arctic climates generally begin to lay eggs in spring or summer. A notable exception to this rule are the emperor penguins, where the breeding season begins in autumn. The young are then raised during the Antarctic winter at temperatures as low as –40 degrees Celsius - unique adaptations to life in the cold are therefore vital for them. The young of the king penguins also overwinter in the breeding colonies (further north). During this time, however, they are rarely fed by their parents, so that they experience considerable weight loss in the first winter.
Penguins are very sociable animals not only in the water, but also on land. In particular, the laying of eggs, hatching and the further rearing of the young take place synchronously in large breeding colonies in many species, which in extreme cases can contain up to five million animals.
In the case of the non-permanently settling species, it is usually the males who enter the colony first during the breeding season and, in almost all species, try to secure a small territory, which, however, rarely covers more than one square meter. Your social behavior is therefore nest-bound. The only exception are the large penguins, who do not create nests for their eggs and only show conspicuous behavior towards their partners and their offspring.
The males then try to win a female by shouting like a trumpet. If it is not the first attempt at breeding, this is often the partner from last year. The “divorce rate” for penguins varies depending on the species: The percentage of yellow-eyed penguins who chose another partner after one year is very low at 14; Their loyalty to partners is also underlined by the fact that twelve percent of partnerships last longer than seven years. In contrast, the annual separation rate for Adelie penguins is more than 50 percent, so no partnerships are known that have lasted longer than six years. It is known that the breeding success of the previous year plays an important role in the question of partner choice.
There is a close connection between the complexity of social behavior and the mechanisms for partner identification on the one hand and the colony size on the other hand: The mating rituals of the Adelie, bridle, donkey and crested penguins, which live close together in huge colonies, are particularly noticeable both visually and acoustically; the yellow-eyed penguins that live in dense vegetation or the little penguins that breed in widely spaced nests are much more cautious.
Egg laying and brood reduction
After copulation, for which the male has to balance on the partner's back, the eggs are laid. While emperor and king penguins hatch their only egg on their feet, in all other species the female penguins lay two eggs every three to five days in a simple nest that is made from the materials available in the area, such as grass or small pebbles . The egg color is white or greenish.
Not all eggs are hatched successfully: especially with young couples, the young often do not even hatch; For example, hatching rates of less than 33 percent were found in two-year-old parents. The breeding success then increases rapidly with increasing age and reaches values of over 90 percent; only in very old penguin pairs does it slowly fall back to around 75 percent because of the then decreasing fertility.
Usually the first egg is slightly larger than the second, so that the first chick hatches a little earlier than its sibling chick. The incubation period is between one and two months, depending on the species. The first-born young animal is preferred by its parents and, for example, regularly receives more food than the second hatched, which usually dies quickly. This so-called brood reduction is an evolutionary adaptation to a limited food supply: The rapid death of the second chick ensures that the chances of survival of the first are not reduced by distributing the scarce resources between two offspring. Conversely, the parents have “reinsured” themselves through the second egg in case the first chick should perish prematurely.
While in most species brood reduction occurs only when food is scarce and the thick-billed penguins ( E. pachyrhynchus ) almost always raise both chicks, brood reduction is the rule for all crested penguins. Interestingly, in this genus, the second egg is the larger (the percentage difference is between 20 and 70 percent) from which the first young animal hatches.
The rearing of the young can be divided into two phases:
- In the first two to three weeks - in the case of large penguins even six - the chick (s) are permanently supervised by one of the parents while the partner goes foraging.
- As soon as the young animals have grown up, the “kindergarten” period begins, in which the youngsters form groups while both adults try to get food. Depending on the species, such groups, also known as crèches , may only include a few animals from neighboring nests, such as rein or spectacle penguins, or consist of thousands of individuals such as adelie, donkey or great penguins.
The feeding times are very dependent on the species: Gentoo penguins feed their offspring every day, Adelia or chinstrap penguins only every two days, the great penguins often only every four days or less. However, with the latter, the meals are all the larger. The amount of food is usually adapted to the developmental stage of the young, but always enormous in relation to body weight: Even young chicks of small penguin species can easily receive 500 g of food per feeding; Big penguins even pass on up to one kilogram of fish to their young in one fell swoop. King penguin cubs can be heavier than their parents after twelve months.
In the case of species that are not permanently living in a colony, the colony is quickly abandoned after the parental moult, in the case of the crested penguins, for example, within a week. In all likelihood, parental care has ended - so far, feeding at sea has not been reported, and it is also difficult to imagine. Gentoo penguins, who spend the whole year near their colony, regularly return to their parents for two to three weeks and receive additional food there; after that they too are on their own.
Your chances of survival are slim in the first twelve months. In the case of Adelie penguins, for example, it is estimated that just under half of all young live after the tough first year. An important factor that has a decisive influence on their prospects for life is the amount of fat reserves set up in the breeding colony, which in turn depends on the feeding by the old animals and thus on their hunting success.
The survival probability of adult animals, on the other hand, is much higher: it is 70 to 80 percent for the small Adelie penguins and more than 90 percent for the large penguins. Penguins can live to be more than 25 years old.
Due to the mostly isolated breeding sites, adult penguins have almost no enemies on land; However, mammals introduced by humans, such as dogs and cats, pose a serious regional threat. Penguins can use both their beak and their fins as effective weapons for defense. Chicks, on the other hand, quickly become prey for the Subantarctic kuas ( Catharacta antarctica ) if left unattended . These birds and some gulls take every opportunity to steal eggs.
Leopard seals ( Hydrurga leptonyx ), southern fur seals ( Arctocephalus ), Australian ( Neophoca cinerea ) and New Zealand sea lions ( Phocarctos hookeri ) as well as orcas ( Orcinus orca ) and sharks (Selachii) often hunt penguins in the sea, especially the specified seal species patrol in the shallow water the breeding colonies, where penguins cannot make good use of their high maneuverability. It is estimated that around five percent of all Adelie penguins are killed this way each year.
This is probably the reason for the birds' fear of going into the water, which at first glance seems strange, to which they are so well adapted. Before swimming, penguins often hesitantly approach the shore in smaller groups, obviously each with the wish not to have to be the first to enter the sea ( penguin effect ); this procedure often takes up to half an hour. As soon as one person has finally taken courage and jumps into the water, all the others follow suit.
Three species, the crowned penguin ( Eudyptes sclateri ), the yellow-eyed penguin ( Megadyptes antipodes ) and the Galápagos penguin ( Spheniscus mendiculus ) are classified as critically endangered at the beginning of the 21st century, and seven others are considered endangered.
The reasons include the loss of habitat, such as the yellow-eyed penguin, whose populations are threatened by increasing land use and human interference in New Zealand's dune system. Wild mammals are also a threat, such as the Galápagos penguin, whose breeding colonies, which are confined to two islands, have been decimated by stray dogs. In addition, climate changes play a role: The populations of Galapagos penguins were decimated in the 1980s and 1990s by a collapse of fish stocks, on the climate change brought in connection El Niño can be attributed phenomenon.
Rockhopper penguins ( Eudyptes chrysochome ), Magellanic penguins ( Spheniscus magellanicus ) or Humboldt penguins ( Spheniscus humboldti ) repeatedly come into conflict with commercial fisheries , some of which have specialized in the same species , on their extensive forays for anchovies and sardines in sub-Antarctic waters . While the fishermen are complaining about lost income, many penguins are losing their food supply. However, efforts are being made to defuse this competitive conflict while taking the interests of the fishermen into account.
African penguins and Magellanic penguins, whose colonies are on the Cape of Good Hope in South Africa or on the Strait of Magellan off South America, suffer particularly from the oil pollution caused by the shipping and especially tanker routes there. Oily penguins can be caught, cleaned and released again; however, this is a very time consuming and costly process. They also often get caught in fishing nets.
On the other hand, the intensive hunting of the baleen whales (Mysticeti) and the resulting krill reproduction has led to a considerable increase in bridle and king penguins; most Antarctic species are considered stable because of the remoteness of their habitat.
Penguins as Research Objects - Danger from Marking and False Conclusions
For some excitement among zoologists and climatologists , the realization that a method that is very common for migration studies , the attachment of flipper bands to the fins , is a considerable threat to penguins living in the wild and has a negative impact on their way of life. A ten-year study of a colony of king penguins shows that tagged animals have a 16% lower chance of survival and produce 39% fewer chicks than non-tagged penguins. One explanation for this is that the marking strips can lead to injuries to the fins and the surrounding body parts due to the constant friction , since the flapping frequency of a medium-sized penguin is around three beats per second while swimming. In addition, penguins marked with flippers have to use approx. 24% more force to swim than unmarked animals. As a result of this impairment, their foraging takes considerably longer, and they arrive at the breeding sites on average 16 days later than the other animals.
Penguins, like other predators at the top of the food chain , are widely used as integrative indicator species to study the impact of climate change on the marine ecosystem of the southern polar ocean. However, the ten-year study clearly shows that tagged animals react differently to environmental changes - for example as a result of the warmer climate - than unmarked animals . This leaves considerable doubts as to the validity of data obtained with the help of marking tapes. In the opinion of the researchers, the reliability of penguins marked with ribs as indicators of climate change and its consequences for the southern polar ecosystem should be reconsidered.
Penguins and man
The first encounter between humans and penguins is attested from Australia: Archaeological bone finds in Aboriginal deposits show that penguins formed part of the diet of these Australian natives in prehistoric times.
In Europe, penguins did not become known until the end of the 15th and beginning of the 16th century through the exploratory trips of the Portuguese navigators under Vasco da Gama and Ferdinand Magellan . The first known reference to the birds comes from Vasco da Gama's diary of November 25, 1497, when he was anchored in Mossel Bay on the coast of South Africa. There he met the birds known today as the African penguin ( Spheniscus demersus ). The African penguin is also the first scientifically described species from which the Latin family and ordinal name is derived - it was treated as early as 1758 by the Swedish systematist Carl von Linné in his work Systema Naturae . Almost all other species, however, were not discovered until the exploration of the southern ocean in the late 18th and 19th centuries.
In the past, whole colonies were wiped out from the rich layer of fat by collecting eggs for food and slaughtering the adults for oil. In addition, penguins were used as fuel for the production of oil .
Penguins are very curious birds and are largely fearless on land. Unlike tamed animals, which have only lost their fear through frequent contact with humans, most penguins are naturally not afraid of humans. Although the view can naturally not be scientifically confirmed, Antarctic travelers have often assumed the assumption that the birds themselves thought they were merely oddly built penguins.
In Central Europe, penguins can only be seen in zoological gardens . For this purpose, some offer so-called penguin marches, during which the birds are usually released from their enclosures on weekends and can take a short tour of their home under the supervision and observation of the zoo keepers. Penguin marches are offered in the zoological gardens of Münster and Munich , in Switzerland at the Zurich Zoo and Basel Zoo ; the penguin march at Edinburgh Zoo is well worth seeing.
Penguins are very popular animals that can trigger passionate encouragement. Refrigerators are named after them, as are ice hockey teams, and a large English book publisher also appears under their English name, Penguin . To this day, this charm does not seem to have faded: When Linus Torvalds , the author of the free software operating system Linux , was looking for a mascot, he decided with Tux for a penguin (albeit with certain influences of a duck).
Conversely, it was perhaps precisely the peaceful, charming image that prompted the creators of the Batman comic series to give the sinister figure of the top villain the name penguin of all things. Danny DeVito played this role in the 1992 film Batman Returns . In contrast, penguins encounter the viewer in a friendly and peaceful manner in the children's cartoon character Pingu on Swiss television.
The involuntary comedy caused by the seeming awkwardness of the animals is often cited as a reason for human sympathy: the hopping, sliding and waddling birds have an amusing effect on many viewers. The plumage, remotely reminiscent of a white shirt and black tuxedo, in other words very formal men's clothing, reinforces this impression; In some idioms , the word “penguin” is a joking name for a man wearing tails.
But the cause of the affection may also lie deeper: Accordingly, people in birds recognize themselves not least - which is certainly also due to the fact that penguins are one of the few animal species that walk upright on two legs like humans.
The penguins belong to a group of sea and water birds, which probably separated from the other bird groups in the early Cretaceous period and to which among others the loons (Gaviiformes) and tube noses (Procellariiformes) belong. The group was determined by comparing DNA and was given the scientific name Aequorlithornithes in 2015.
Cladogram according to Prum et al .:
The fossils known since the early Tertiary give little insight into the phylogenetic relationships, as the early penguins already stand out very clearly from all other birds. However, the wing bone (pterygoid) of the extinct genus Paraptenodytes is reminiscent of the corresponding bones of the tubular noses, and the long, pointed beak of the genus Palaeeudyptes has similarities with the beaks of the loons. The latter can dive underwater like penguins, but get their propulsion from their feet and not from fins. However, there is fossil evidence that the ancestors of the loons used their wings to move underwater, like today's penguins.
How the appearance of the penguins came about is unknown: The first penguin fossils come from the Paleocene 61 to 58 million years ago and were described under the generic name Waimanu . Fossils from the Eocene have survived 55 million years ago, and on the front of Antarctica lying island Seymour were found, already show the typical Penguin features.
It is clear that the penguins descend from flying birds, which, like today's loons, could already hunt underwater. Flying in the air and swimming underwater, however, place very different demands on the wings of a bird - as a result, the flying and diving ancestors of the penguins may have been a little larger than today's pygmy or African penguins. This results in a - hypothetical - scenario, according to which the penguins are descended from a population of small marine birds that are true to their location and that lived in coastal waters of the subtropical or temperate zones at water temperatures above about 15 degrees Celsius, and such as the Galápagos penguins on isolated islands nested. In the course of an ever better adaptation to the sea, their wings continued to develop into fins, while the legs moved backwards in order to reduce the flow resistance when swimming. With the specialization in the marine habitat and increasing body size, there was at the same time a loss of the ability to fly and the waddling walk on land, forced by the recessed legs, theoretically endangered the animals on land; however, in the absence of predators, this was not an evolutionary disadvantage.
The exact area in which the penguins developed cannot be reconstructed today, but hypothetically both New Zealand and the then much warmer Antarctica are considered. It is only undisputed that the penguins originated in the southern hemisphere, as not a single fossil could be found north of the equator. In the following period, warm equatorial ocean currents apparently represented an insurmountable barrier for the birds; In addition, the high number of fast predatory fish in tropical latitudes, such as sharks, is considered to be the reason why the penguins never crossed the equator.
The further development of the phylogenetic history can only be roughly traced, even if at least 17 fossil genera were described by the beginning of the 21st century. No complete skeleton has survived, and most of the fossils come from large birds; this is probably only a selection effect , which can be explained by the much better fossilization of their bones and probably has no systematic significance.
The highest biodiversity of the penguins was reached in the Tertiary , especially in the geological epochs of the Oligocene and early Miocene . The largest penguins, which reached a body length of up to 1.70 meters, also lived at this time. One such species was, for example, Pachydyptes ponderosus . Why the giant penguins eventually became extinct in the Miocene is unknown; The increasing competition from seals (Pinnipedia) and whales (Cetacea) is speculatively cited: The giant penguins needed very large legs and feet to carry their body weight on their regular shore leave, which had to be uselessly dragged along in the sea - unlike the completely marine mammals, who could transform their hind limbs into fins or give up completely.
Somewhat earlier, around 25 million years ago, at the turning point of the Oligocene and Miocene, the formation of the cold circumpolar current , triggered by the opening of the Drake Passage between Antarctica and South America, began , which climatically insulated Antarctica and thus a lowering of water temperatures by more than ten degrees. As animals already living in water and therefore well insulated from heat, the penguins were relatively well prepared for this drop in temperature, so that one can speak of exaptation , in this case the utilization of a combination of characteristics developed for a certain ecological niche for another niche.
The modern penguin genera did not appear until the Pliocene three million years ago.
- The long-tailed penguins ( Pygoscelis ) have black and white plumage without exception and molt at the end of the respective breeding season. A distinction is made between three species, the gentoo penguin ( P. papua ), the Adelie penguin ( P. adeliae ) and the chinstrap penguin ( P. antarctica ), which is also known as the throated penguin . All species are very social, the chinstrap penguin forms the largest penguin colony on Deception Island with an estimated five million breeding pairs.
- The great penguins ( Aptenodytes ), which include the king penguin ( A. patagonicus ) and the emperor penguin ( A. forsteri ), comprise the two largest penguin species. They have a long, slender, slightly curved bill and each have a characteristic orange-colored spot on their necks. Great penguins do not build nests; the only egg is hatched on the feet instead.
- The crested penguins ( Eudyptes ) comprise the greatest biodiversity. The group is quite diverse, but is characterized by yellow-orange feather headdresses. Crested penguins live mainly in the waters around New Zealand, their colonies only exist during the breeding season. In all species there is an obligatory brood reduction: Although two eggs are always laid, only one young animal is raised in order to avoid an unfavorable distribution of food, in which none of the young animals receive enough food in the end.
- The genus of the yellow-eyed penguins ( Megadyptes ) is monotypical, i.e. it only includes one species, the yellow-eyed penguin ( M. antipodes ), which breeds in southern New Zealand. Yellow feathers indicate its close relationship with the crested penguins.
- The genus of the little penguins ( Eudyptula ) contains only one species, the little penguin ( E. minor ), but some taxonomists are of the opinion that the populations of Australia and New Zealand are separate species and lead the Australian population under the name Eudyptula novaehollandiae .
- African penguins ( Spheniscus ) form a very homogeneous genus, which is probably of very recent origin. The four species are characterized by black stripes on the flanks, a characteristic black and white head pattern and bare skin on the head. African penguins are the furthest north living penguins and are at home in tropical regions. The birds stay with their colonies all year round; The breeding season and moult are usually very variable and quite independent of the season. Little penguins and the young of the African penguins look very similar, a finding that is taken as an indication of the close relationship between the two genera.
The relationships between the genera and species are expressed in the following cladogram , which is based on the analysis of the genome of all penguin species:
Quick overview by genre
The habitat and the external characteristics are also given
- Long-tailed penguins , Antarctica, black and white pinnate
- Great penguins , Antarctica, largest penguins
- Crested penguins , Australia / New Zealand, yellow-orange feather headdress
- Yellow- eyed penguins , Australia / New Zealand, yellow feathers on the eye
- Fairy penguins , Australia / New Zealand (the smallest penguins)
- African penguins , tropical regions, black stripes on the flanks, black and white head patterns, bare skin on the head
World Penguin Day is celebrated internationally on April 25th.
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