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The Adélie penguin (''Pygoscelis adeliae'') is a species of
penguin Penguins (order Sphenisciformes , family Spheniscidae ) are a group of aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: only one species, the Galápagos penguin, is found north of the Equator. Highly adap ...
common along the entire coast of the Antarctic continent, which is the only place where it is found. It is the most widespread penguin species, and, along with the
emperor penguin The emperor penguin (''Aptenodytes forsteri'') is the tallest and heaviest of all living penguin species and is endemic to Antarctica. The male and female are similar in plumage and size, reaching in length and weighing from . Feathers of t ...
, is the most southerly distributed of all penguins. It is named after Adélie Land, in turn named for
Adèle Dumont d'Urville Adèle Dumont d'Urville (née Adèle Dorothée Pépin, also spelled as Adélie , 1798 – 8 May 1842) was the wife of French explorer Jules Dumont d'Urville, after whom Adélie Land, Adele Island, Adélie penguin and Cape Pepin are named. While ...
, who was married to French explorer
Jules Dumont d'Urville Jules Sébastien César Dumont d'Urville (; 23 May 1790 – 8 May 1842) was a French explorer and naval officer who explored the south and western Pacific, Australia, New Zealand, and Antarctica. As a botanist and cartographer, he gave his nam ...
, who first discovered this penguin in 1840. Adélie penguins obtain their food by both
predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
and foraging, with a diet of mainly krill and
fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...
.


Taxonomy and systematics

The first Adélie penguin specimens were collected by crew members of French explorer
Jules Dumont d'Urville Jules Sébastien César Dumont d'Urville (; 23 May 1790 – 8 May 1842) was a French explorer and naval officer who explored the south and western Pacific, Australia, New Zealand, and Antarctica. As a botanist and cartographer, he gave his nam ...
on his expedition to Antarctica in the late 1830s and early 1840s.
Jacques Bernard Hombron Jacques Bernard Hombron (1798–1852) was a French naval surgeon and natural history, naturalist. Hombron served on the French voyage of the ''French ship Astrolabe (1811), Astrolabe'' and ''Zélée'' between 1837 and 1840 to investigate the perim ...
and
Honoré Jacquinot Honoré Jacquinot (1 August 1815 in Moulins-Engilbert - 22 May 1887 in Nevers) was a French surgeon and zoologist. Jacquinot was the younger brother of the naval officer Charles Hector Jacquinot, and sailed with him as a surgeon and naturalist ...
, two French surgeons who doubled as naturalists on the journey, described the bird for science in 1841, giving it the scientific name ''Catarrhactes adeliæ''. They used specimens collected from an area of the continent which had been named "terre Adélie", French for Adélie Land, itself named for Dumont d'Urville's wife, Adèle. The bird was later placed in several other genera, including '' Eudyptes'', '' Pygoscelis'' and the now-defunct genus ''Dasyrhamphus'', and was also later inadvertently redescribed as ''Pygoscelis brevirostris''. The Adélie penguin is one of three species now assigned to the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
'' Pygoscelis''. DNA evidence suggests the ''Pygoscelis'' lineage diverged from that of other penguin species some 38 million years ago, roughly 2 million years after the ancestors of the genus ''
Aptenodytes The genus ''Aptenodytes'' contains two extant species of penguins collectively known as "the great penguins". Etymology The name "Aptenodytes" is a composite of Ancient Greek elements, "ἀ-πτηνο-δύτης" (without-wings-diver). Taxo ...
'' diverged. Adélie penguins
evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variati ...
about 19 million years ago, branching from the ancestor of the other two members of the genus ( chinstrap and gentoo penguins), both of which evolved some 5 million years later. Although it has no identifiable subspecies, the Adélie penguin has two distinct genetic lineages: one found primarily in the Ross Sea, and the other widespread throughout the Antarctic. The genus name ''Pygoscelis'' is a compound word, composed of the
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...
words ''pugē'', meaning "rump", and ''skelos'', meaning "leg". The members of this genus are often called "brush-tailed penguins", a reference to their long, stiff tail feathers. The birds regularly use their tails for support, and the stiff feathers sweep the ground as the penguins walk. The specific name ''adeliae'' indicates the location from which the
type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...
was collected.


Description

The Adélie penguin is a mid-sized bird, measuring in length and weighing . Although the sexes look the same, females have shorter wings and beaks, and weigh significantly less. The adult is black on the head, throat and upperparts, with snowy white underparts. It has a conspicuous white around a black iris. The
beak The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for fo ...
is largely covered with black feathers, leaving only the tip exposed; this is primarily black, though it can show indistinct reddish-brown markings. The upper surface of the wing is black with a white trailing edge, while the underside is white with a narrow black leading edge and a small black tip. The legs and feet, which are mostly unfeathered, are pinkish. Upon hatching, the chick is fully covered in down feathers. This coat of feathers is typically silvery-grey (darker on the head), though some birds are much darker overall. Within 10 days, the chick moults into another set of down feathers, this time all dark smoky-grey. Once they have moulted a third time, 7–9 weeks after hatching, the immature birds are similar to adults in appearance, though they tend to be smaller with a bluer tinge to their upperparts and white (rather than black) chins and throats. They lack the full white eye ring of the adult until they are at least a year old.


Similar species

The adult Adélie penguin is unlikely to be confused with any other species, but the white-throated immature bird can resemble the chinstrap penguin. However, the black on its face extends below its eyes, and it lacks a black line under the throat (the "chinstrap") that the chinstrap penguin has. In addition, the bill of the chinstrap penguin is longer, and lacks the feathering that covers most of the bill of the Adélie penguin.


Distribution and habitat

The Adélie penguin is a truly Antarctic creature – one of only four penguin species to nest on the continent itself. Breeding colonies are scattered along Antarctica's coasts and on a number of sub-Antarctic islands, including those in the South Orkneys, the South Shetlands, the South Sandwich Islands, the Balleny Islands,
Scott Island Scott Island is a small uninhabited island of volcanic origin in the Ross Sea, Southern Ocean, northeast of Cape Adare, the northeastern extremity of Victoria Land, Antarctica. It is long north–south, and between and wide, reaching a ...
and South Georgia. The penguins are much less common north of the 60th parallel south, but have occurred as vagrants in Australia, New Zealand and southern South America. During the breeding season, they need bare, rocky ground on which to build their nests. They will not nest on ice, and preferentially choose areas where wind or the angle of the sun (or both) helps to keep snow drifts from accumulating. At the start of the breeding seasons, colony sites may be up to from open water, though the distance decreases as summer progresses and the pack ice breaks up. Once they have finished breeding, adult Adélie penguins typically move to ice floes or ice shelves to moult, though some remain onshore. During the winter, the birds remain in the pack ice zone, with most moving north to reach areas where there is visible light for at least part of the day – thus north of roughly 73°S. While some remain near their breeding colonies, others may move hundreds or thousands of kilometres away. As long as there are breaks in the pack ice, they can survive hundreds of kilometres south of open water, and birds are known to forage in winter in areas with up to 80% pack ice cover.


Behaviour and ecology

Apsley Cherry-Garrard, a survivor of Robert Falcon Scott's ill-fated British Antarctic Expedition of 1910, documented details of penguin behaviour in his book '' The Worst Journey in the World''. "They are extraordinarily like children, these little people of the Antarctic world, either like children or like old men, full of their own importance..." George Murray Levick, a Royal Navy surgeon-lieutenant and scientist who also accompanied Scott, commented on displays of selfishness among the penguins during his surveying in the Antarctic: "At the place where they most often went in he water a long terrace of ice about six feet in height ran for some hundreds of yards along the edge of the water, and here, just as on the sea-ice, crowds would stand near the brink. When they had succeeded in pushing one of their number over, all would crane their necks over the edge, and when they saw the pioneer safe in the water, the rest followed." One writer observed how the penguin's curiosity could also endanger them, which Scott found a particular nuisance: Others on the mission to the South Pole were more receptive of this element of the Adélies' curiosity. Cherry-Garrard writes: Cherry-Garrard held the birds in great regard. "Whatever a penguin does has individuality, and he lays bare his whole life for all to see. He cannot fly away. And because he is quaint in all that he does, but still more because he is fighting against bigger odds than any other bird, and fighting always with the most gallant pluck, he comes to be considered as something apart from the ordinary bird..." Despite their size, Adélie penguins are known for their bold and boisterous personality, and will challenge other animals, including predators far larger than them. In footage shot for the 2018 BBC Earth documentary ''Spy in the Snow'', the boisterous behaviour of Adélie penguins was made especially apparent when an individual arrived to chase off a Southern giant petrel (''Macronectes giganteus'') that had landed to threaten a group of
emperor penguin The emperor penguin (''Aptenodytes forsteri'') is the tallest and heaviest of all living penguin species and is endemic to Antarctica. The male and female are similar in plumage and size, reaching in length and weighing from . Feathers of t ...
chicks, in spite of the species difference between them. Adélie penguins usually swim at around . They are able to leap some out of the water to land on rocks or ice.


Food and feeding

The Adélie penguin is known to feed mainly on
Antarctic krill Antarctic krill (''Euphausia superba'') is a species of krill found in the Antarctic waters of the Southern Ocean. It is a small, swimming crustacean that lives in large schools, called swarms, sometimes reaching densities of 10,000–30,000 ind ...
, ice krill, Antarctic silverfish, lanternfish, amphipods, sea krill, glacial squid and other
cephalopod A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...
s (diet varies depending on geographic location) during the chick-rearing season. The stable isotope record of fossil eggshell accumulated in colonies over the last 38,000 years reveals a sudden change from a fish-based diet to krill that began around 200 years ago. This is most likely due to the decline of the Antarctic fur seal since the late 18th century and baleen whales during the early 20th century. The reduction of competition from these predators has resulted in a surplus of krill, which the penguins now exploit as an easier source of food. Jellyfish including species in the genera ''
Chrysaora ''Chrysaora'' () is a genus of jellyfish, commonly called the sea nettles, in the family Pelagiidae. The origin of the genus name ''Chrysaora'' lies in Greek mythology with Chrysaor, brother of Pegasus and son of Poseidon and Medusa. Translated, ...
'' and '' Cyanea'' were found to be actively sought-out food items, while they previously had been thought to be only accidentally ingested. Similar preferences were found in the little penguin, yellow-eyed penguin and Magellanic penguin.


Breeding

Adélie penguins breed from October to February on shores around the Antarctic continent. Adélies build rough nests of stones. Two eggs are laid; these are incubated for 32 to 34 days by the parents taking turns (shifts typically last for 12 days). The chicks remain in the nest for 22 days before joining crèches. The chicks moult into their juvenile plumage and go out to sea after 50 to 60 days. Adélie penguins arrive at their breeding grounds in late October or November, after completing a migration that takes them away from the Antarctic continent for the dark, cold winter months. Their nests consist of stones piled together. In December, the warmest month in Antarctica (about /-19 °C or -2.2 °F), the parents take turns incubating the egg; one goes to feed and the other stays to warm the egg. The parent that is incubating does not eat and doesn't even leave to defecate but instead projects feces away from the nest. In March, the adults and their young return to the sea. The Adélie penguin lives on sea ice, but needs the ice-free land to breed. With a reduction in sea ice, populations of the Adélie penguin have dropped by 65% over the past 25 years in the Antarctic Peninsula. Young Adélie penguins which have no experience in social interaction may react to false cues when the penguins gather to breed. They may, for instance, attempt to mate with other males, with young chicks or with dead females. Levick was the first to record such behavior (1911–12), but his notes were deemed too indecent for publication at the time; they were rediscovered and published in 2012. "The pamphlet, declined for publication with the official Scott expedition reports, commented on the frequency of sexual activity, auto-erotic behaviour and seemingly aberrant behaviour of young unpaired males and females, including necrophilia, sexual coercion, sexual and physical abuse of chicks and homosexual behaviour," states the analysis written by Douglas Russell and colleagues William Sladen and David Ainley. "His observations were, however, accurate, valid and, with the benefit of hindsight, deserving of publication." Levick observed the Adélie penguins at Cape Adare, the site of the largest Adélie penguin rookery in the world. , he has been the only one to study this particular colony and he observed it for an entire breeding cycle. The discovery significantly illuminates the behaviour of the species whose population some researchers believe to be a bellwether of
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
.


Migration

Adélie penguins living in the Ross Sea region in Antarctica migrate an average of about each year as they follow the sun from their breeding colonies to winter foraging grounds and back again. During the winter, the sun does not rise south of the
Antarctic Circle The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. So ...
, but sea ice grows during the winter months and increases for hundreds of miles from the shoreline, and into more northern latitudes, all around Antarctica. As long as the penguins live at the edge of the fast ice, they will see sunlight. As the ice recedes in the spring, the penguins remain on the edge of it, until once again, they are on the shoreline during a sunnier season. The longest treks have been recorded at .


Osmoregulation

Adélie penguins are faced with extreme
osmotic Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (region ...
conditions, as their frozen habitats offer little fresh water. Such desert conditions mean that the vast majority of the available water is highly saline, causing the diets of Adélie penguins to be heavy in salt. They manage to circumvent this problem by eating krill with internal concentrations of salt at the lower end of their possible concentrations, helping to lower the amount of ingested salts. The amount of sodium imposed by this sort of diet is still relatively heavy and can create complications when considering the less tolerant chicks. Adult Adélie penguins feed their chicks by regurgitating the predigested krill, which can impose an excessive salt intake on the chicks. Adult birds address this problem by altering the ion concentrations while the food is still being held in their stomachs. By removing a portion of the sodium and potassium ions, adult Adélie penguins protect their chicks from ingesting excessive amounts of sodium. Adélie penguins also manage their salt intake by concentrating cloacal fluids to a much higher degree than most other birds are capable. This ability is present regardless of ontogeny in Adélie penguins, meaning that both adults and juveniles are capable of withstanding extreme levels of salt ion concentration. However, chicks do possess a greater ability to concentrate chloride ions in their cloacal fluids. Salt glands also play a major role in the excretion of excess salts. In aquatic birds such as the Adelie penguin, nasal salt glands excrete an extremely concentrated sodium chloride solution, reducing the load on their kidneys. These excretions are crucial in the maintenance of Antarctic ecosystems. Penguin rookeries can be home to thousands of penguins, all of which are concentrating waste products in their digestive tracts and nasal glands. These excretions inevitably drop to the ground. The concentration of salts and nitrogenous wastes helps to facilitate the flow of material from the sea to the land, serving to make it habitable for bacteria which live in the soils.


Threats

Adult Adélie penguins are regularly preyed upon by leopard seals. South polar skuas, in particular and Giant petrels kill many chicks and eat eggs as well. Giant petrels and
orca The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only extant species in the genus '' Orcinus'' and is recognizable by its black-and-white ...
s will occasionally kill adult Adelie penguins. Kelp gulls and snowy sheathbills also prey on chicks and eggs.


Status

Because of its very large and increasing population (estimated at more than 10 million mature individuals in 2020), and its unfragmented habitat, the Adélie penguin is considered by the
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
to be a species of
least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. ...
. A comprehensive census of the global Adélie penguin population was carried out in 2014 using analysis of high-resolution satellite images in combination with actual field surveys. The researchers looked for guano-discoloured coastal areas (red/brown patches in areas with no snow) in the satellite images, and augmented their findings with field surveys in areas where no good satellite images were available or where the presence of multiple penguins species was suspected. The results of field surveys were only used if they had been done within the previous four years. This census found an estimated 3.79 million breeding pairs in 251 distinct breeding colonies, including more than 40 that had never been surveyed before, a 53% increase over a census completed 20 years earlier. The colonies are distributed around the coastline of the Antarctic land and ocean. Colonies have declined on the Antarctic Peninsula since the early 1980s, but those declines have been more than offset by increases in East Antarctica. During the breeding season, they congregate in large breeding colonies, some over a quarter of a million pairs. Individual colonies can vary dramatically in size, and some may be particularly vulnerable to climate fluctuations. The Danger Islands have been identified as an "important bird area" by
BirdLife International BirdLife International is a global partnership of non-governmental organizations that strives to conserve birds and their habitats. BirdLife International's priorities include preventing extinction of bird species, identifying and safeguarding ...
largely because it supports Adélie penguin colonies, with 751,527 pairs recorded in at least five distinct colonies. In March 2018, a colony of 1.5 million was discovered.


See also

* Prostitution among animals#Penguins


Notes


Citations


References

* * * * * * * * * * * * * * * * *


External links


Adelie penguins at the Polar Conservation Organisation
* {{Authority control Pygoscelis Penguins Birds of Antarctica Birds described in 1841 Taxa named by Jacques Bernard Hombron Taxa named by Honoré Jacquinot Articles containing video clips