Adélie penguin
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Adélie penguin
Temporal range: Pleistocene to recent[1]
Hope Bay-2016-Trinity Peninsula–Adélie penguin (Pygoscelis adeliae) 04.jpg
Hope Bay, Antarctica
Conservation status

Least Concern (IUCN 3.1)[2]
Scientific classificationedit
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Sphenisciformes
Family: Spheniscidae
Genus: Pygoscelis
Species: P. adeliae
Binomial name
Pygoscelis adeliae
(Hombron & Jacquinot, 1841)
Pygoscelis adeliae Distribuzione.jpg
Distribution of the Adélie penguin
Nesting sites in red
The Adélie penguin (Pygoscelis adeliae) is a species of penguin common along the entire coast of the Antarctic continent, which is its only habitat. It is the most widely spread penguin species,[3] as well as the most southerly distributed of all penguins, along with the emperor penguin. It is named after Adélie Land, in turn named for Adèle Dumont d'Urville, who was married to French explorer Jules Dumont d'Urville, who first discovered this penguin in 1840.[4] Adélie penguins obtain their food by both predation and foraging, with a diet of mainly krill and fish.[3]


Contents
1 Taxonomy
2 Description
3 Ecology
3.1 Diet
3.2 Predators
4 Distribution and habitat
5 Behaviour
5.1 Reproduction
5.2 Migration
6 Osmoregulation
7 Popular culture
8 See also
9 Notes and references
10 External links
Taxonomy
The Adélie penguin is one of three species in the genus Pygoscelis. Mitochondrial and nuclear DNA evidence suggests the genus split from other penguin species around 38 million years ago, about 2 million years after the ancestors of the genus Aptenodytes. In turn, the Adélie penguins split off from the other members of the genus around 19 million years ago.[5]

Description
These penguins are mid-sized, being 46 to 71 cm (18 to 28 in) in height and 3.6 to 6.0 kg (7.9 to 13.2 lb) in weight.[6][7] Distinctive marks are the white ring surrounding the eye and the feathers at the base of the bill. These long feathers hide most of the red bill. The tail is a little longer than other penguins' tails. The appearance looks somewhat like a tuxedo. They are a little smaller than most other penguin species.[8]

Adélie penguins usually swim at around 5 miles per hour (8.0 km/h).[9] They are able to leap some 3 metres (10 ft) out of the water to land on rocks or ice.[10]

Ecology
Diet
The Adélie penguin is known to feed mainly on Antarctic krill, ice krill, Antarctic silverfish, sea krill and glacial squid (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.[11]

Jellyfish including species in the genera Chrysaora 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.[12]

Predators
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 orcas will occasionally kill adult Adelie penguins. Kelp gulls and snowy sheathbills also prey on chicks and eggs.[13]

Distribution and habitat
On an iceberg in Antarctica
In Antarctica
Based on a 2014 satellite analysis of fresh guano-discoloured red/brown coastal areas, 3.79 million breeding pairs of Adélie penguins are in 251 breeding colonies,[14] 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,[15] but those declines have been more than offset by increases in East Antarctica[citation needed]. During the breeding season, they congregate in large breeding colonies, some over a quarter of a million pairs.[16] Individual colonies can vary dramatically in size, and some may be particularly vulnerable to climate fluctuations.[17] The Danger Islands have been identified as an "important bird area" by BirdLife International largely because it supports Adélie penguin colonies,[18] with 751,527 pairs recorded in at least five distinct colonies. In March 2018, a colony of 1.5 million was discovered.[19][20]

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.

Behaviour

Cape Adare
File:Manchots adelie.ogv
In Antarctica
Apsley Cherry-Garrard was a survivor of Robert Falcon Scott's ill-fated British Antarctic Expedition of 1910, and he 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."[21] 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 [the 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."[22]

One writer observed how the penguin's curiosity could also endanger them, which Scott found a particular nuisance:

The great trouble with [the dog teams] has been due to the fatuous conduct of the penguins. Groups of these have been constantly leaping onto our [ice] floe. From the moment of landing on their feet their whole attitude expressed devouring curiosity and a pig-headed disregard for their own safety. They waddle forward, poking their heads to and fro in their usually absurd way, in spite of a string of howling dogs straining to get at them. "Hulloa!" they seem to say, "here’s a game – what do all you ridiculous things want?" And they come a few steps nearer. The dogs make a rush as far as their harness or leashes allow. The penguins are not daunted in the least, but their ruffs go up and they squawk with semblance of anger.… Then the final fatal steps forward are taken and they come within reach. There is a spring, a squawk, a horrid red patch on the snow, and the incident is closed.[23]

Chicks in Antarctica, with MS Explorer and icebergs in the background
Chicks in Antarctica, with MS Explorer
Others on the mission to the South Pole were more receptive of this element of the Adélies' curiosity. Cherry-Garrard writes:

Meares and Dimitri exercised the dog-teams out upon the larger floes when we were held up for any length of time. One day, a team was tethered by the side of the ship, and a penguin sighted them and hurried from afar off. The dogs became frantic with excitement as he neared them: he supposed it was a greeting, and the louder they barked and the more they strained at their ropes, the faster he bustled to meet them. He was extremely angry with a man who went and saved him from a very sudden end, clinging to his trousers